U.S. patent application number 16/216944 was filed with the patent office on 2019-06-27 for wavelength combiner photonic integrated circuit with grating coupling of lasers.
The applicant listed for this patent is North Inc.. Invention is credited to Douglas R. Dykaar, Syed Moez Haque, Rony Jose James, Martin Joseph Kiik, Stefan Mohrdiek, Jorg Pierer.
Application Number | 20190196197 16/216944 |
Document ID | / |
Family ID | 66696695 |
Filed Date | 2019-06-27 |
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United States Patent
Application |
20190196197 |
Kind Code |
A1 |
Pierer; Jorg ; et
al. |
June 27, 2019 |
WAVELENGTH COMBINER PHOTONIC INTEGRATED CIRCUIT WITH GRATING
COUPLING OF LASERS
Abstract
Systems, devices, and methods of manufacturing optical engines
and laser projectors that are well-suited for use in wearable
heads-up displays (WHUDs) are described. Generally, the optical
engines of the present disclosure integrate a plurality of laser
diodes (e.g., 3 laser diodes, 4 laser diodes) within a single,
hermetically or partially hermetically sealed, encapsulated
package. Photonic integrated circuits having grating couplers
thereon may be used to wavelength multiplex beams of light emitted
by the plurality of laser diodes into a coaxially superimposed
aggregate beam. Such optical engines may have various advantages
over existing designs including, for example, smaller volumes,
better manufacturability, faster modulation speed, etc. WHUDs that
employ such optical engines and laser projectors are also
described.
Inventors: |
Pierer; Jorg; (Alpnach,
CH) ; James; Rony Jose; (Alpnach, CH) ;
Mohrdiek; Stefan; (Affoltern am Albis, CH) ; Dykaar;
Douglas R.; (Waterloo, CA) ; Kiik; Martin Joseph;
(Kitchener, CA) ; Haque; Syed Moez; (Kitchener,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
North Inc. |
Kitchener |
|
CA |
|
|
Family ID: |
66696695 |
Appl. No.: |
16/216944 |
Filed: |
December 11, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62597294 |
Dec 11, 2017 |
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62608749 |
Dec 21, 2017 |
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62609870 |
Dec 22, 2017 |
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62620600 |
Jan 23, 2018 |
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62760835 |
Nov 13, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/12004 20130101;
G03B 21/008 20130101; H04N 9/3161 20130101; G02B 27/102 20130101;
H01S 5/02272 20130101; G02B 2027/0178 20130101; H01S 5/02224
20130101; H04N 9/3129 20130101; G02B 6/4214 20130101; G02B 6/124
20130101; G02B 27/18 20130101; G02B 27/0101 20130101; H01S 5/02296
20130101; G02B 2027/011 20130101; G02B 2027/0116 20130101; G02B
6/4206 20130101; H01S 5/02292 20130101; G02B 2027/0134 20130101;
H01S 5/0071 20130101; G03B 21/2033 20130101; G02B 2027/0114
20130101; G02B 2027/014 20130101; G02B 27/1086 20130101; G02B
2006/12107 20130101; G02B 6/13 20130101; G03B 33/12 20130101; G02B
27/0172 20130101; H01S 5/02208 20130101; H01S 5/0226 20130101; G02B
2027/015 20130101; G03B 21/2066 20130101; H01S 5/4093 20130101;
H01S 5/02248 20130101; G02B 2006/12147 20130101; G02B 2006/12164
20130101; G02B 6/42 20130101; G02B 27/0176 20130101; H01S 5/02288
20130101; H01S 5/4012 20130101; G02B 27/4205 20130101; G02B 27/141
20130101 |
International
Class: |
G02B 27/01 20060101
G02B027/01; H01S 5/40 20060101 H01S005/40; H01S 5/022 20060101
H01S005/022; G02B 6/13 20060101 G02B006/13; G02B 6/124 20060101
G02B006/124; G02B 6/12 20060101 G02B006/12 |
Claims
1. A method of manufacturing an optical engine, the method
comprising: bonding a plurality of laser diodes directly or
indirectly to a base substrate; bonding a cap to the base
substrate, the cap comprising at least one wall that, with the base
substrate, defines an interior volume sized and dimensioned to
receive at least the plurality of laser diodes, the cap being
bonded to the base substrate to provide a hermetic or partially
hermetic seal between the interior volume of the cap and a volume
exterior to the cap; bonding writeable glass to the base substrate;
and after bonding the writeable glass to the base substrate,
writing a photonic integrated circuit into the writeable glass, the
photonic integrated circuit comprising a plurality of input facets
and at least one output facet, in operation, the photonic
integrated circuit receives a plurality of beams of light at the
plurality of input facets and wavelength multiplexes the plurality
of beams of light to provide an aggregated beam of light at the at
least one output facet.
2. The method of claim 1, further comprising: bonding each of the
laser diodes indirectly to the base substrate by bonding each laser
diode to a respective chip submount; and bonding each chip submount
to the base substrate.
3. The method of claim 2 wherein bonding each laser diode to a
respective chip submount comprises bonding each laser diode to a
respective chip submount using a eutectic gold tin (AuSn) solder
process.
4. The method of claim 2 wherein bonding each chip submount to the
base substrate comprises step-soldering each chip submount to the
base substrate.
5. The method of claim 2 wherein bonding each chip submount to the
base substrate comprises bonding each chip submount to the base
substrate using at least one of a reflow oven process, thermosonic
bonding, thermocompression bonding, transient liquid phase (TLP)
bonding, or laser soldering.
6. The method of claim 2 wherein bonding each chip submount to the
base substrate comprises bonding a chip submount that has a red
laser diode bonded thereto, bonding a chip submount that has a
green laser diode bonded thereto, bonding a chip submount that has
a blue laser diode bonded thereto, and bonding a chip submount that
has an infrared laser diode bonded thereto.
7. The method of claim 1, further comprising: bonding a plurality
of collimation lenses between the plurality of laser diodes and the
plurality of input facets of the photonic integrated circuit, each
of the plurality of collimation lenses positioned and oriented to
collimate light received from respective ones of the beams of light
emitted from the plurality of laser diodes, and to output the
collimated light toward the plurality of input facets of the
photonic integrated circuit.
8. The method of claim 1 wherein bonding the writeable glass to the
cap comprises bonding the writable glass against at least one
optical window in the cap positioned and oriented to allow beams of
light emitted from the plurality of laser diodes to exit the
interior volume.
9. The method of claim 1 wherein bonding the writeable glass to the
cap comprises bonding the writeable glass to the cap to form at
least one optical window in the writable glass positioned and
oriented to allow beams of light emitted from the plurality of
laser diodes to exit the interior volume.
10. The method of claim 1, further comprising: providing a coupling
between at least one laser diode driver circuit and the plurality
of laser diodes, in operation the at least one laser diode driver
circuit selectively drives current to the laser diodes.
11. The method of claim 10 wherein providing a coupling between at
least one laser diode driver circuit and the plurality of laser
diodes comprises: bonding a plurality of electrical connections to
the base substrate, each electrical connection coupled to a
respective laser diode in the plurality of laser diodes; providing
a coupling between each of the plurality of electrical connections
and the at least one laser diode driver circuit; and bonding an
electrically insulating cover to the base substrate over the
plurality of electrical connections, wherein bonding the cap to the
base substrate comprises bonding the cap to the base substrate and
the electrically insulating cover.
12. The method of claim 11 wherein providing a coupling between
each of the plurality of electrical connections and the at least
one laser diode driver circuit comprises: bonding a plurality of
electrical contacts to the base substrate, each electrical contact
coupled to a respective one of the plurality of electrical
connections; and providing a coupling between each of the
electrical contacts and the at least one laser diode driver
circuit.
13. The method of claim 10 wherein bonding the plurality of laser
diodes directly or indirectly to a base substrate comprises bonding
the laser diodes directly or indirectly to a first surface of the
base substrate, and bonding a cap to the base substrate comprises
bonding a cap to the first surface of the base substrate, the
method further comprising bonding the at least one laser diode
driver circuit to a second surface of the base substrate, the
second surface of the base substrate opposite the first surface of
the base substrate.
14. The method of claim 10 wherein bonding the plurality of laser
diodes directly or indirectly to a base substrate comprises bonding
the laser diodes directly or indirectly to a first surface of the
base substrate, and bonding a cap to the base substrate comprises
bonding a cap to the first surface of the base substrate, the
method further comprising bonding the at least one laser diode
driver circuit to the first surface of the base substrate.
15. The method of claim 1 wherein bonding a cap to the base
substrate comprises bonding a cap to the base substrate using at
least one of a seam welding process, a laser assisted soldering
process, or a diffusion bonding process.
16. The method of claim 1, further comprising: prior to bonding the
cap to the base substrate, flooding the interior volume with an
oxygen rich atmosphere.
17. The method of claim 1, further comprising: positioning and
orienting a collimation lens to receive and collimate the aggregate
beam of light from the at least one output facet of the photonic
integrated circuit.
18. The method of claim 1, wherein laser writing the photonic
integrated circuit into the writeable glass comprises laser writing
a plurality of waveguides into the writeable glass, each waveguide
of the plurality of waveguides being written for a respective one
laser diode of the plurality of laser diodes.
19. The method of claim 18, wherein laser writing a plurality of
waveguides into the writeable glass comprises writing a waveguide
combiner into the writeable glass.
20. The method of claim 19, wherein writing a waveguide combiner
into the writeable glass comprises writing at least one of: a
directional coupler, Y-branch, whispering gallery mode, or
multi-mode interface coupler.
21. The method of claim 18 wherein laser writing a plurality of
waveguides into the writeable glass comprises laser writing each
waveguide of the plurality of waveguides to have an input facet to
receive laser light from a respective laser diode of the plurality
of laser diodes and an output facet to output the received laser
light, a spacing between the output facets of each waveguide being
smaller than a spacing of the input facets of each waveguide.
22. The method of claim 1 wherein laser writing the photonic
integrated circuit into the writeable glass comprises writing each
input facet as a grating input coupler.
23. The method of claim 1 wherein laser writing the photonic
integrated circuit in the writeable glass comprises writing each
input facet as a planar region with an index of refraction lower
than an index of refraction of the writeable glass.
Description
BACKGROUND
Technical Field
[0001] The present disclosure is generally directed to systems,
devices, and methods relating to optical engines, for example,
optical engines for laser projectors used in wearable heads-up
displays or other applications.
Description of the Related Art
[0002] A projector is an optical device that projects or shines a
pattern of light onto another object (e.g., onto a surface of
another object, such as onto a projection screen) in order to
display an image or video on that other object. A projector
necessarily includes a light source, and a laser projector is a
projector for which the light source comprises at least one laser.
The at least one laser is temporally modulated to provide a pattern
of laser light and usually at least one controllable mirror is used
to spatially distribute the modulated pattern of laser light over a
two-dimensional area of another object. The spatial distribution of
the modulated pattern of laser light produces an image at or on the
other object. In conventional scanning laser projectors, at least
one controllable mirror may be used to control the spatial
distribution, and may include: a single digital micromirror (e.g.,
a microelectromechanical system ("MEMS") based digital micromirror)
that is controllably rotatable or deformable in two dimensions, or
two digital micromirrors that are each controllably rotatable or
deformable about a respective dimension, or a digital light
processing ("DLP") chip comprising an array of digital
micromirrors.
[0003] In a conventional laser projector comprising an RGB
(red/green/blue) laser module with a red laser diode, a green laser
diode, and a blue laser diode, each respective laser diode may have
a corresponding respective focusing lens. Each of the laser diodes
of a laser module are typically housed in a separate package (e.g.,
a TO-38 package or "can"). The relative positions of the laser
diodes, the focusing lenses, and the at least one controllable
mirror are all tuned and aligned so that each laser beam impinges
on the at least one controllable mirror with substantially the same
spot size and with substantially the same rate of convergence (so
that all laser beams will continue to have substantially the same
spot size as they propagate away from the laser projector towards,
e.g., a projection screen). In a conventional laser projector, it
is usually possible to come up with such a configuration for all
these elements because the overall form factor of the device is not
a primary design consideration. However, in applications for which
the form factor of the laser projector is an important design
element, it can be very challenging to find a configuration for the
laser diodes, the focusing lenses, and the at least one
controllable mirror that sufficiently aligns the laser beams (at
least in terms of spot size, spot position, and rate of
convergence) while satisfying the form factor constraints.
[0004] A head-mounted display is an electronic device that is worn
on a user's head and, when so worn, secures at least one electronic
display within a viewable field of at least one of the user's eyes,
regardless of the position or orientation of the user's head. A
wearable heads-up display is a head-mounted display that enables
the user to see displayed content but also does not prevent the
user from being able to see their external environment. The
"display" component of a wearable heads-up display is either
transparent or at a periphery of the user's field of view so that
it does not completely block the user from being able to see their
external environment. A "combiner" component of a wearable heads-up
display is the physical structure where display light and
environmental light merge as one within the user's field of view.
The combiner of a wearable heads-up display is typically
transparent to environmental light but includes some optical
routing mechanism to direct display light into the user's field of
view.
[0005] Examples of wearable heads-up displays include: the Google
Glass.RTM., the Optinvent Ora.RTM., the Epson Moverio.RTM., and the
Sony Glasstron.RTM., just to name a few.
[0006] The optical performance of a wearable heads-up display is an
important factor in its design. When it comes to face-worn devices,
users also care a lot about aesthetics and comfort. This is clearly
highlighted by the immensity of the eyeglass (including sunglass)
frame industry. Independent of their performance limitations, many
of the aforementioned examples of wearable heads-up displays have
struggled to find traction in consumer markets because, at least in
part, they lack fashion appeal or comfort. Most wearable heads-up
displays presented to date employ relatively large components and,
as a result, are considerably bulkier, less comfortable and less
stylish than conventional eyeglass frames.
Direct Laser Writing
[0007] Femtosecond laser micro-machining is a direct-laser-write
and rapid prototyping technique that provides great potential for
optical device fabrication. Strong focusing of femtosecond laser
light into transparent glass can induce positive refractive index
modifications up to 0.01 refractive index units (RIU) within the
material and without surface damage. Since then, ultrafast
(femto/pico-second) lasers have been shown to enable flexible 3D
structuring of various glasses, and has led to the demonstration of
many types of optical devices (waveguides, couplers, Bragg
gratings, waveplates, etc.) that serve as building blocks for 3D
optical circuits.
[0008] Direct-laser-writing uses ultrashort laser pulses to confine
strong nonlinear optical interactions that may induce, for example,
positive or negative refractive index changes in bulk transparent
materials for creating optical waveguides (WGs). The mechanisms by
which direct-laser-write modifications occur include, but are not
limited to, multiphoton ionization, avalanche ionization,
electron-atom collisions, plasma interactions, thermal effects
(e.g. diffusion, heat accumulation), energy dissipation, and
material cooling leading to inhomogeneous solidification. For
direct-laser-writing waveguides, waveguide performance can be tuned
and optimized by, but not limited to, the writing laser's
properties (pulse duration, pulse temporal shape, bandwidth and
shape, pulse repetition rate, wavelength, polarization, and beam
spatial shape) and the focusing conditions (lens numerical
aperture, air/liquid immersion, translation direction and
speeds).
BRIEF SUMMARY
[0009] An optical engine may be summarized as including a base
substrate; a plurality of laser diodes, each of the plurality of
laser diodes bonded directly or indirectly to the base substrate;
at least one laser diode driver circuit operatively coupled to the
plurality of laser diodes to selectively drive current to the
plurality of laser diodes; a cap comprising at least one wall and
at least one optical window that, together with the base substrate,
define an interior volume sized and dimensioned to receive at least
the plurality of laser diodes, the cap being bonded to the base
substrate to provide a hermetic or partially hermetic seal between
the interior volume of the cap and a volume exterior to the cap,
and the optical window positioned and oriented to allow beams of
light emitted from the plurality of laser diodes to exit the
interior volume; and a photonic integrated circuit comprising a
plurality of input facets and at least one output facet, in
operation, the photonic integrated circuit receives a plurality of
beams of light at the respective plurality of input facets and
wavelength multiplexes the plurality of beams of light to provide
an aggregated beam of light at the output facet.
[0010] The optical engine may further include a plurality of
collimation lenses, each of the plurality of collimation lenses
positioned and oriented to collimate light received from respective
ones of the beams of light emitted from the plurality of laser
diodes, and to output the collimated light toward to the plurality
of input facets of the photonic integrated circuit. Each of the
plurality of collimation lenses may be positioned within the
interior volume. Each of the plurality of collimation lenses may be
bonded to the optical window of the cap. The photonic integrated
circuit may be bonded to the optical window of the cap.
[0011] The optical engine may further include an optical director
element disposed within the interior volume, the optical director
element bonded to the base substrate proximate the plurality of
laser diodes, and positioned and oriented to reflect laser light
from the plurality of laser diodes toward the optical window of the
cap. The optical director element may include a mirror or a
prism.
[0012] The optical engine may further include a collimation lens
positioned and oriented to receive and collimate the aggregate beam
of light from the output facet of the photonic integrated circuit.
The collimation lens may include an achromatic lens. The
collimation lens may include an apochromatic lens.
[0013] The optical engine may further include at least one
diffractive optical element positioned and oriented to receive the
aggregate beam of light, in operation, the at least one diffractive
optical element provides wavelength dependent focus correction for
the aggregate beam of light.
[0014] The optical engine may further include a plurality of chip
submounts bonded to the base substrate, wherein each of the laser
diodes are bonded to a corresponding one of the plurality of chip
submounts. The plurality of laser diodes may include a red laser
diode to provide a red laser light, a green laser diode to provide
a green laser light, a blue laser diode to provide a blue laser
light, and an infrared laser diode to provide infrared laser light.
The base substrate may be formed from at least one of low
temperature co-fired ceramic (LTCC), aluminum nitride (AlN),
alumina, or Kovar.RTM.. The at least one laser diode driver circuit
may be bonded to a first surface of the base substrate, and the
plurality of laser diodes and the cap may be bonded to a second
surface of the base substrate, the second surface of the base
substrate opposite the first surface of the base substrate. The at
least one laser diode driver circuit, the plurality of laser
diodes, and the cap may be bonded to a first surface of the base
substrate. The plurality of laser diodes and the cap may be bonded
to the base substrate, and the at least one laser diode driver
circuit may be bonded to another substrate separate from the base
substrate. Each of the laser diodes may include one of an edge
emitter laser or a vertical-cavity surface-emitting laser (VCSEL).
The at least one wall of the cap may include at least one
continuous sidewall having a lower first end and an upper second
end, the lower first end bonded to the base substrate, and the
optical window may be hermetically or partially hermetically sealed
to the cap proximate the upper second end.
[0015] The photonic integrated circuit may include a plurality of
waveguides, each waveguide of the plurality of waveguides to
receive laser light from a respective laser diode of the plurality
of laser diodes. Each waveguide of the plurality of waveguides may
be optimized to receive and output laser light having a wavelength
corresponding to the wavelength of laser light received from the
respective laser diode. The plurality of waveguides may include a
waveguide combiner. The waveguide combiner may include at least one
of: a directional coupler, Y-branch, whispering gallery mode, or
multi-mode interface coupler. Each waveguide of the plurality of
waveguides may include an input facet to receive laser light from a
respective laser diode of the plurality of laser diodes and an
output facet to output the received laser light, a spacing between
the output facets of each waveguide being smaller than a spacing
between the input facets of each waveguide.
[0016] Each input facet of the plurality of input facets may be a
grating input coupler. Each input facet of the plurality of input
facets may be a planar region with an index of refraction lower
than an index of refraction of material from which the photonic
integrated circuit is formed.
[0017] A wearable heads-up display (WHUD) may be summarized as
including a support structure that in use is worn on the head of a
user; a laser projector carried by the support structure, the laser
projector including an optical engine, including a base substrate;
a plurality of laser diodes, each of the plurality of laser diodes
bonded directly or indirectly to the base substrate; at least one
laser diode driver circuit operatively coupled to the plurality of
laser diodes to selectively drive current to the plurality of laser
diodes; a cap comprising at least one wall and at least one optical
window that, together with the base substrate, define an interior
volume sized and dimensioned to receive at least the plurality of
laser diodes, the cap being bonded to the base substrate to provide
a hermetic or partially hermetic seal between the interior volume
of the cap and a volume exterior to the cap, and the optical window
positioned and oriented to allow beams of light emitted from the
plurality of laser diodes to exit the interior volume; and a
photonic integrated circuit comprising a plurality of input facets
and at least one output facet, in operation, the photonic
integrated circuit receives a plurality of beams of light at the
respective plurality of input facets and wavelength multiplexes the
plurality of beams of light to provide an aggregated beam of light
at the output facet; and at least one scan mirror positioned to
receive the aggregate beam of light output at the output facet of
the photonic integrated circuit, the at least one scan mirror
controllably orientable to redirect the aggregate beam of light
over a range of angles.
[0018] The WHUD may further include a processor communicatively
coupled to the laser projector to modulate the generation of light
signals.
[0019] The WHUD may further include a transparent combiner carried
by the support structure and positioned within a field of view of
the user, in operation the transparent combiner directs laser light
from an output of the laser projector into the field of view of the
user.
[0020] The optical engine of the WHUD may further include a
collimation lens positioned and oriented to receive and collimate
the aggregate beam of light from the output coupler of the photonic
integrated circuit. The collimation lens may include an achromatic
lens or an apochromatic lens.
[0021] The optical engine of the WHUD further may include at least
one diffractive optical element positioned and oriented to receive
the aggregate beam of light, in operation, the at least one
diffractive optical element provides wavelength dependent focus
correction for the aggregate beam of light.
[0022] The optical engine of the WHUD may further include a
plurality of collimation lenses, each of the plurality of
collimation lenses positioned and oriented to collimate light
received from respective ones of the beams of light emitted from
the plurality of laser diodes, and to output the collimated light
toward to the plurality of input facets of the photonic integrated
circuit. The photonic integrated circuit may be bonded to the
optical window of the cap.
[0023] The optical engine of the WHUD may further include an
optical director element disposed within the interior volume, the
optical director element bonded to the base substrate proximate the
plurality of laser diodes, and positioned and oriented to reflect
laser light from the plurality of laser diodes toward the optical
window of the cap. The optical engine of the WHUD may further
include a plurality of chip submounts bonded to the base substrate,
wherein each of the laser diodes are bonded to a corresponding one
of the plurality of chip submounts. The plurality of laser diodes
may include a red laser diode to provide a red laser light, a green
laser diode to provide a green laser light, a blue laser diode to
provide a blue laser light, and an infrared laser diode to provide
infrared laser light.
[0024] The at least one laser diode driver circuit may be bonded to
a first surface of the base substrate, and the plurality of laser
diodes and the cap may be bonded to a second surface of the base
substrate, the second surface of the base substrate opposite the
first surface of the base substrate. The at least one laser diode
driver circuit, the plurality of laser diodes, and the cap may be
bonded to a first surface of the base substrate. The plurality of
laser diodes and the cap may be bonded to a first surface of the
base substrate, and the at least one laser diode driver circuit may
be mounted to the support structure.
[0025] Each of the laser diodes may include one of an edge emitter
laser or a vertical-cavity surface-emitting laser (VCSEL). The at
least one wall of the cap may include at least one continuous
sidewall having a lower first end and an upper second end, the
lower first end bonded to the base substrate, and the optical
window may be hermetically or partially hermetically sealed to the
cap proximate the upper second end.
[0026] The photonic integrated circuit may include a plurality of
waveguides, each waveguide of the plurality of waveguides to
receive laser light from a respective laser diode of the plurality
of laser diodes. Each waveguide of the plurality of waveguides may
be optimized to receive and output laser light having a wavelength
corresponding to the wavelength of laser light received from the
respective laser diode. The plurality of waveguides may include a
waveguide combiner. The waveguide combiner may include at least one
of: a directional coupler, Y-branch, whispering gallery mode, or
multi-mode interface coupler. Each waveguide of the plurality of
waveguides may include an input facet to receive laser light from a
respective laser diode of the plurality of laser diodes and an
output facet to output the received laser light, a spacing between
the output facets of each waveguide being smaller than a spacing
between the input facets of each waveguide.
[0027] Each input facet of the plurality of input facets may be a
grating input coupler. Each input facet of the plurality of input
facets may be a planar region with an index of refraction lower
than an index of refraction of material from which the photonic
integrated circuit is formed.
[0028] A laser projector may be summarized as including an optical
engine, comprising: a base substrate; a plurality of laser diodes,
each of the plurality of laser diodes bonded directly or indirectly
to the base substrate; at least one laser diode driver circuit
operatively coupled to the plurality of laser diodes to selectively
drive current to the plurality of laser diodes; a cap comprising at
least one wall and at least one optical window that, together with
the base substrate, define an interior volume sized and dimensioned
to receive at least the plurality of laser diodes, the cap being
bonded to the base substrate to provide a hermetic or partially
hermetic seal between the interior volume of the cap and a volume
exterior to the cap, and the optical window positioned and oriented
to allow beams of light emitted from the plurality of laser diodes
to exit the interior volume; and a photonic integrated circuit
comprising a plurality of input facets and at least one output
facet, in operation, the photonic integrated circuit receives a
plurality of beams of light at the respective plurality of input
facets and wavelength multiplexes the plurality of beams of light
to provide an aggregated beam of light at the output facet; and at
least one scan mirror positioned to receive the aggregate beam of
light output at the output facet of the photonic integrated
circuit, the at least one scan mirror controllably orientable to
redirect the aggregate beam of light over a range of angles.
[0029] The laser projector may further include a processor
communicatively coupled to the optical engine to modulate the
generation of light signals.
[0030] The optical engine of the laser projector may further
include a plurality of collimation lenses, each of the plurality of
collimation lenses positioned and oriented to collimate light
received from respective ones of the beams of light emitted from
the plurality of laser diodes, and to output the collimated light
toward to the plurality of input facets of the photonic integrated
circuit. Each of the plurality of collimation lenses may be bonded
to the optical window of the cap. The photonic integrated circuit
may be bonded to the optical window of the cap.
[0031] The optical engine of the laser projector may further
include an optical director element disposed within the interior
volume, the optical director element bonded to the base substrate
proximate the plurality of laser diodes, and positioned and
oriented to reflect laser light from the plurality of laser diodes
toward the optical window of the cap. The optical engine of the
laser projector may further include a collimation lens positioned
and oriented to receive and collimate the aggregate beam of light
from the output facet of the photonic integrated circuit. The
optical engine of the laser projector may further include at least
one diffractive optical element positioned and oriented to receive
the aggregate beam of light, in operation, the at least one
diffractive optical element provides wavelength dependent focus
correction for the aggregate beam of light.
[0032] The optical engine of the laser projector may further
include a plurality of chip submounts bonded to the base substrate,
wherein each of the laser diodes are bonded to a corresponding one
of the plurality of chip submounts. The plurality of laser diodes
may include a red laser diode to provide a red laser light, a green
laser diode to provide a green laser light, a blue laser diode to
provide a blue laser light, and an infrared laser diode to provide
infrared laser light.
[0033] The at least one laser diode driver circuit may be bonded to
a first surface of the base substrate, and the plurality of laser
diodes and the cap may be bonded to a second surface of the base
substrate, the second surface of the base substrate opposite the
first surface of the base substrate. The at least one laser diode
driver circuit, the plurality of laser diodes, and the cap may be
bonded to a first surface of the base substrate. The plurality of
laser diodes and the cap may be bonded to the base substrate, and
the at least one laser diode driver circuit may be bonded to
another substrate separate from the base substrate.
[0034] Each of the laser diodes may include one of an edge emitter
laser or a vertical-cavity surface-emitting laser (VCSEL). The at
least one wall of the cap may include at least one continuous
sidewall having a lower first end and an upper second end, the
lower first end bonded to the base substrate, and the optical
window may be hermetically or partially hermetically sealed to the
cap proximate the upper second end.
[0035] The photonic integrated circuit may include a plurality of
waveguides, each waveguide of the plurality of waveguides to
receive laser light from a respective laser diode of the plurality
of laser diodes. Each waveguide of the plurality of waveguides may
be optimized to receive and output laser light having a wavelength
corresponding to the wavelength of laser light received from the
respective laser diode. The plurality of waveguides may include a
waveguide combiner. The waveguide combiner may include at least one
of: a directional coupler, Y-branch, whispering gallery mode, or
multi-mode interface coupler. Each waveguide of the plurality of
waveguides may include an input facet to receive laser light from a
respective laser diode of the plurality of laser diodes and an
output facet to output the received laser light, a spacing between
the output facets of each waveguide being smaller than a spacing
between the input facets of each waveguide.
[0036] Each input facet of the plurality of input facets may be a
grating input coupler. Each input facet of the plurality of input
facets may be a planar region with an index of refraction lower
than an index of refraction of material from which the photonic
integrated circuit is formed.
[0037] A method of operating an optical engine, the optical engine
including a plurality of laser diodes hermetically or partially
hermetically sealed in an encapsulated package, may be summarized
as including causing the plurality of laser diodes to generate a
corresponding plurality of beams of laser light through an optical
window in the encapsulated package; coupling the plurality of beams
of laser light into a respective plurality of input facets of a
photonic integrated circuit; and wavelength multiplexing, by the
photonic integrated circuit, the beams of laser light to generate
an aggregate beam of light at an output facet of the photonic
integrated circuit.
[0038] The method may further include collimating, by a collimation
lens, the aggregate beam of light that exits from the output facet
of the photonic integrated circuit. Collimating the aggregate beam
of light may include collimating the aggregate beam of light using
an achromatic lens or an apochromatic lens.
[0039] The method may further include correcting, by at least one
diffractive element, wavelength dependent focus for the aggregate
beam of light. Causing the plurality of laser diodes to generate
laser light may include causing a red laser diode to generate red
laser light, causing a green laser diode to generate green laser
light, causing a blue laser diode to generate blue laser light, and
causing an infrared laser diode to generate infrared laser light.
Coupling the plurality of beams of laser light into a respective
plurality of input facets of a photonic integrated circuit may
include coupling the plurality of beams of laser light into a
respective plurality of input facets of a photonic integrated
circuit via a plurality of collimation lenses.
[0040] Wavelength multiplexing, by the photonic integrated circuit,
the beams of laser light may include receiving, by each waveguide
of a plurality of waveguides, laser light from a respective laser
diode of the plurality of laser diodes, and outputting, by the
plurality of waveguides, an aggregate beam of light.
[0041] The photonic integrated circuit may include a waveguide
combiner which includes the plurality of input facets and the
output facet, and wavelength multiplexing, by the photonic
integrated circuit, the beams of laser light may include:
receiving, by each input facet of the plurality of input facets,
laser light from a respective laser diode of the plurality of laser
diodes; and outputting, by the output facet of the waveguide
combiner, a coaxially superimposed aggregate beam of light.
[0042] The photonic integrated circuit may include a plurality of
waveguides, each waveguide of the plurality of waveguides including
an input facet and an output facet, and wavelength multiplexing, by
the photonic integrated circuit, the beams of laser light may
include: receiving, by the respective input facet of each waveguide
of the plurality of waveguides, laser light from a respective laser
diode of the plurality of laser diodes; and outputting, by the
respective output facet of each waveguide of the plurality of
waveguides, a beam of light, a spacing between the output facet of
each waveguide being smaller than a spacing between the input
facets of each waveguide to produce an aggregate beam of light.
[0043] Coupling the plurality of beams of laser light into a
respective plurality of input facets of a photonic integrated
circuit may include coupling the plurality of beams of laser light
into a respective plurality of grating input couplers of the
photonic integrated circuit. Coupling the plurality of beams of
laser light into a respective plurality of input facets of a
photonic integrated circuit may include coupling the plurality of
beams of laser light into the photonic integrated circuit via a
plurality of planar regions with an index of refraction lower than
an index of refraction of material from which the photonic
integrated circuit is formed.
[0044] An optical engine may be summarized as including a base
substrate; a plurality of laser diodes, each of the plurality of
laser diodes bonded directly or indirectly to the base substrate; a
cap comprising at least one wall that, with the base substrate,
defines an interior volume sized and dimensioned to receive at
least the plurality of laser diodes, the cap being bonded to the
base substrate to provide a hermetic or partially hermetic seal
between the interior volume of the cap and a volume exterior to the
cap; and a photonic integrated circuit comprising a plurality of
input facets and at least one output facet, in operation, the
photonic integrated circuit receives a plurality of beams of light
at respective ones of the plurality of input facets and wavelength
multiplexes the plurality of beams of light to provide an
aggregated beam of light at the output facet. Each of the plurality
of laser diodes may be positioned immediately adjacent a respective
one of the plurality of input facets of the photonic integrated
circuit. Each of the plurality of input facets of the photonic
integrated circuit may be positioned inside the interior volume and
the at least one output facet of the photonic integrated circuit
may be positioned outside of the interior volume. The cap may
include at least one optical window positioned and oriented to
allow beams of light emitted from the plurality of laser diodes to
exit the interior volume.
[0045] The photonic integrated circuit may be bonded to the optical
window of the cap. The at least one wall of the cap may include at
least one continuous sidewall having a lower first end and an upper
second end, the lower first end bonded to the base substrate, and
the optical window may be hermetically or partially hermetically
sealed to the cap proximate the upper second end. The optical
engine may further include an optical director element disposed
within the interior volume, the optical director element bonded to
the base substrate proximate the plurality of laser diodes, and
positioned and oriented to reflect laser light from the plurality
of laser diodes toward the optical window of the cap.
[0046] The optical engine may further include a plurality of
collimation lenses, each of the plurality of collimation lenses
positioned and oriented to collimate light received from respective
ones of beams of light emitted from the plurality of laser diodes,
and to output the collimated light toward to the plurality of input
facets of the photonic integrated circuit. The optical engine may
further include a collimation lens positioned and oriented to
receive and collimate the aggregate beam of light from the output
facet of the photonic integrated circuit. The optical engine may
further include at least one diffractive optical element positioned
and oriented to receive the aggregate beam of light, in operation,
the at least one diffractive optical element provides wavelength
dependent focus correction for the aggregate beam of light.
[0047] The optical engine may further include a plurality of chip
submounts bonded to the base substrate, wherein each of the laser
diodes are bonded to a corresponding one of the plurality of chip
submounts. The plurality of laser diodes may include a red laser
diode to provide a red laser light, a green laser diode to provide
a green laser light, a blue laser diode to provide a blue laser
light, and an infrared laser diode to provide infrared laser
light.
[0048] The optical engine may further include at least one laser
diode driver circuit operatively coupled to the plurality of laser
diodes to selectively drive current to the plurality of laser
diodes. The at least one laser diode driver circuit may be bonded
to a first surface of the base substrate, and the plurality of
laser diodes and the cap may be bonded to a second surface of the
base substrate, the second surface of the base substrate opposite
the first surface of the base substrate. The at least one laser
diode driver circuit, the plurality of laser diodes, and the cap
may be bonded to a first surface of the base substrate. The
plurality of laser diodes and the cap may be bonded to the base
substrate, and the at least one laser diode driver circuit may be
bonded to another substrate separate from the base substrate. Each
of the laser diodes may include one of an edge emitter laser or a
vertical-cavity surface-emitting laser (VCSEL).
[0049] The photonic integrated circuit may include a plurality of
waveguides, each waveguide of the plurality of waveguides to
receive laser light from a respective laser diode of the plurality
of laser diodes. Each waveguide of the plurality of waveguides may
be optimized to receive and output laser light having a wavelength
corresponding to the wavelength of laser light received from the
respective laser diode. The plurality of waveguides may include a
waveguide combiner. The waveguide combiner may include at least one
of: a directional coupler, Y-branch, whispering gallery mode, or
multi-mode interface coupler. Each waveguide of the plurality of
waveguides may include an input facet to receive laser light from a
respective laser diode of the plurality of laser diodes and an
output facet to output the received laser light, a spacing between
the output couplers of each waveguide being smaller than a spacing
between the input facets of each waveguide. Each input facet of the
plurality of input facets may be a grating input coupler. Each
input facet of the plurality of input facets may be a planar region
with an index of refraction lower than an index of refraction of
material from which the photonic integrated circuit is formed.
[0050] A method of manufacturing an optical engine may be
summarized as including: bonding a plurality of laser diodes
directly or indirectly to a base substrate; bonding a cap to the
base substrate, the cap comprising at least one wall that, with the
base substrate, defines an interior volume sized and dimensioned to
receive at least the plurality of laser diodes, the cap being
bonded to the base substrate to provide a hermetic or partially
hermetic seal between the interior volume of the cap and a volume
exterior to the cap; and bonding a photonic integrated circuit
comprising a plurality of input facets and at least one output
facet to the cap, in operation, each input facet of the photonic
integrated circuit receives a respective beam of light of a
plurality of beams of light, and the photonic integrated circuit
wavelength multiplexes the plurality of beams of light to provide
an aggregated beam of light at the output facet.
[0051] The method may further include: bonding each of the laser
diodes indirectly to the base substrate by bonding each laser diode
to a respective chip submount; and bonding each chip submount to
the base substrate. Bonding each laser diode to a respective chip
submount may include bonding each laser diode to a respective chip
submount using a eutectic gold tin (AuSn) solder process. Bonding
each chip submount to the base substrate may include step-soldering
each chip submount to the base substrate. Bonding each chip
submount to the base substrate may include bonding each chip
submount to the base substrate using at least one of a reflow oven
process, thermosonic bonding, thermocompression bonding, transient
liquid phase (TLP) bonding, or laser soldering. Bonding each chip
submount to the base substrate may include bonding a chip submount
that has a red laser diode bonded thereto, bonding a chip submount
that has a green laser diode bonded thereto, bonding a chip
submount that has a blue laser diode bonded thereto, and bonding a
chip submount that has an infrared laser diode bonded thereto.
[0052] The method may further include bonding a plurality of
collimation lenses between the plurality of laser diodes and the
plurality of input facets of the photonic integrated circuit, each
of the plurality of collimation lenses positioned and oriented to
collimate light received from respective ones of the beams of light
emitted from the plurality of laser diodes, and to output the
collimated light toward the plurality of input facets of the
photonic integrated circuit. Bonding the photonic integrated
circuit to the cap may include bonding the plurality of input
facets of the photonic integrated circuit against at least one
optical window in the cap positioned and oriented to allow beams of
light emitted from the plurality of laser diodes to exit the
interior volume. Bonding the photonic integrated circuit to the cap
may include bonding the photonic integrated circuit to the cap to
form at least one optical window in the photonic integrated circuit
positioned and oriented to allow beams of light emitted from the
plurality of laser diodes to exit the interior volume.
[0053] The method may further include providing a coupling between
at least one laser diode driver circuit and the plurality of laser
diodes, in operation the at least one laser diode driver circuit
selectively drives current to the laser diodes. Providing a
coupling between at least one laser diode driver circuit and the
plurality of laser diodes may include: bonding a plurality of
electrical connections to the base substrate, each electrical
connection coupled to a respective laser diode in the plurality of
laser diodes; providing a coupling between each of the plurality of
electrical connections and the at least one laser diode driver
circuit; and bonding an electrically insulating cover to the base
substrate over the plurality of electrical connections, and bonding
the cap to the base substrate may include bonding the cap to the
base substrate and the electrically insulating cover. Providing a
coupling between each of the plurality of electrical connections
and the at least one laser diode driver circuit may include:
bonding a plurality of electrical contacts to the base substrate,
each electrical contact coupled to a respective one of the
plurality of electrical connections; and providing a coupling
between each of the electrical contacts and the at least one laser
diode driver circuit. Bonding the plurality of laser diodes
directly or indirectly to a base substrate may include bonding the
laser diodes directly or indirectly to a first surface of the base
substrate, and bonding a cap to the base substrate may include
bonding a cap to the first surface of the base substrate, and the
method may further include bonding the at least one laser diode
driver circuit to a second surface of the base substrate, the
second surface of the base substrate opposite the first surface of
the base substrate. Bonding the plurality of laser diodes directly
or indirectly to a base substrate may include bonding the laser
diodes directly or indirectly to a first surface of the base
substrate, and bonding a cap to the base substrate may include
bonding a cap to the first surface of the base substrate, and the
method may further include bonding the at least one laser diode
driver circuit to the first surface of the base substrate.
[0054] Bonding a cap to the base substrate may include bonding a
cap to the base substrate using at least one of a seam welding
process, a laser assisted soldering process, or a diffusion bonding
process. The method may further include prior to bonding the cap to
the base substrate, flooding the interior volume with an oxygen
rich atmosphere. The method may further include positioning and
orienting a collimation lens to receive and collimate the aggregate
beam of light from the output coupler of the photonic integrated
circuit.
[0055] The method may further include laser writing the photonic
integrated circuit into writeable glass before bonding the photonic
integrated circuit to the cap. Laser writing the photonic
integrated circuit into writeable glass may include laser writing a
plurality of waveguides into the writeable glass, each waveguide of
the plurality of waveguides being written for a respective one
laser diode of the plurality of laser diodes. Laser writing a
plurality of waveguides into the writeable glass may include
writing a waveguide combiner into the writeable glass. Writing a
waveguide combiner into the writeable glass may include writing at
least one of: a directional coupler, Y-branch, whispering gallery
mode, or multi-mode interface coupler. Laser writing a plurality of
waveguides into the writeable glass may include laser writing each
waveguide of the plurality of waveguide to have a input facet to
receive laser light from a respective laser diode of the plurality
of laser diodes and an output facet to output the received laser
light, a spacing between the output facets of each waveguide being
smaller than a spacing of the input facets of each waveguide. Laser
writing the photonic integrated circuit into writeable glass may
include writing each input facet as a grating input coupler. Laser
writing the photonic integrated circuit in writeable glass may
include writing each input facet as a planar region with an index
of refraction lower than an index of refraction of the writeable
glass.
[0056] A method of manufacturing an optical engine may be
summarized as including: bonding a plurality of laser diodes
directly or indirectly to a base substrate; bonding a cap to the
base substrate, the cap comprising at least one wall that, with the
base substrate, defines an interior volume sized and dimensioned to
receive at least the plurality of laser diodes, the cap being
bonded to the base substrate to provide a hermetic or partially
hermetic seal between the interior volume of the cap and a volume
exterior to the cap; bonding writeable glass to the base substrate;
and after bonding the writeable glass to the base substrate,
writing a photonic integrated circuit into the writeable glass, the
photonic integrated circuit comprising a plurality of input facets
and at least one output facet, in operation, the photonic
integrated circuit receives a plurality of beams of light at the
plurality of input facets and wavelength multiplexes the plurality
of beams of light to provide an aggregated beam of light at the at
least one output facet.
[0057] The method may further include: bonding each of the laser
diodes indirectly to the base substrate by bonding each laser diode
to a respective chip submount; and bonding each chip submount to
the base substrate. Bonding each laser diode to a respective chip
submount may include bonding each laser diode to a respective chip
submount using a eutectic gold tin (AuSn) solder process. Bonding
each chip submount to the base substrate may include step-soldering
each chip submount to the base substrate. Bonding each chip
submount to the base substrate may include bonding each chip
submount to the base substrate using at least one of a reflow oven
process, thermosonic bonding, thermocompression bonding, transient
liquid phase (TLP) bonding, or laser soldering. Bonding each chip
submount to the base substrate may include bonding a chip submount
that has a red laser diode bonded thereto, bonding a chip submount
that has a green laser diode bonded thereto, bonding a chip
submount that has a blue laser diode bonded thereto, and bonding a
chip submount that has an infrared laser diode bonded thereto.
[0058] The method may further include bonding a plurality of
collimation lenses between the plurality of laser diodes and the
plurality of input facets of the photonic integrated circuit, each
of the plurality of collimation lenses positioned and oriented to
collimate light received from respective ones of the beams of light
emitted from the plurality of laser diodes, and to output the
collimated light toward the plurality of input facets of the
photonic integrated circuit. Bonding the writeable glass to the cap
may include bonding the writable glass against at least one optical
window in the cap positioned and oriented to allow beams of light
emitted from the plurality of laser diodes to exit the interior
volume. Bonding the writeable glass to the cap may include bonding
the writeable glass to the cap to form at least one optical window
in the writable glass positioned and oriented to allow beams of
light emitted from the plurality of laser diodes to exit the
interior volume.
[0059] The method may further include providing a coupling between
at least one laser diode driver circuit and the plurality of laser
diodes, in operation the at least one laser diode driver circuit
selectively drives current to the laser diodes. Providing a
coupling between at least one laser diode driver circuit and the
plurality of laser diodes may include: bonding a plurality of
electrical connections to the base substrate, each electrical
connection coupled to a respective laser diode in the plurality of
laser diodes; providing a coupling between each of the plurality of
electrical connections and the at least one laser diode driver
circuit; and bonding an electrically insulating cover to the base
substrate over the plurality of electrical connections, and bonding
the cap to the base substrate may include bonding the cap to the
base substrate and the electrically insulating cover. Providing a
coupling between each of the plurality of electrical connections
and the at least one laser diode driver circuit may include:
bonding a plurality of electrical contacts to the base substrate,
each electrical contact coupled to a respective one of the
plurality of electrical connections; and providing a coupling
between each of the electrical contacts and the at least one laser
diode driver circuit.
[0060] Bonding the plurality of laser diodes directly or indirectly
to a base substrate may include bonding the laser diodes directly
or indirectly to a first surface of the base substrate, and bonding
a cap to the base substrate may include bonding a cap to the first
surface of the base substrate, the method may further include
bonding the at least one laser diode driver circuit to a second
surface of the base substrate, the second surface of the base
substrate opposite the first surface of the base substrate. Bonding
the plurality of laser diodes directly or indirectly to a base
substrate may include bonding the laser diodes directly or
indirectly to a first surface of the base substrate, and bonding a
cap to the base substrate may include bonding a cap to the first
surface of the base substrate, the method may further include
bonding the at least one laser diode driver circuit to the first
surface of the base substrate.
[0061] Bonding a cap to the base substrate may include bonding a
cap to the base substrate using at least one of a seam welding
process, a laser assisted soldering process, or a diffusion bonding
process. The method may further include prior to bonding the cap to
the base substrate, flooding the interior volume with an oxygen
rich atmosphere. The method may further include positioning and
orienting a collimation lens to receive and collimate the aggregate
beam of light from the at least one output facet of the photonic
integrated circuit.
[0062] Laser writing the photonic integrated circuit into the
writeable glass may include laser writing a plurality of waveguides
into the writeable glass, each waveguide of the plurality of
waveguides being written for a respective one laser diode of the
plurality of laser diodes. Laser writing a plurality of waveguides
into the writeable glass may include writing a waveguide combiner
into the writeable glass. Writing a waveguide combiner into the
writeable glass may include writing at least one of: a directional
coupler, Y-branch, whispering gallery mode, or multi-mode interface
coupler. Laser writing a plurality of waveguides into the writeable
glass may include laser writing each waveguide of the plurality of
waveguides to have an input facet to receive laser light from a
respective laser diode of the plurality of laser diodes and an
output facet to output the received laser light, a spacing between
the output facets of each waveguide being smaller than a spacing of
the input facets of each waveguide.
[0063] Laser writing the photonic integrated circuit into the
writeable glass may include writing each input facet as a grating
input coupler. Laser writing the photonic integrated circuit in the
writeable glass may include writing each input facet as a planar
region with an index of refraction lower than an index of
refraction of the writeable glass.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0064] In the drawings, identical reference numbers identify
similar elements or acts. The sizes and relative positions of
elements in the drawings are not necessarily drawn to scale. For
example, the shapes of various elements and angles are not
necessarily drawn to scale, and some of these elements may be
arbitrarily enlarged and positioned to improve drawing legibility.
Further, the particular shapes of the elements as drawn, are not
necessarily intended to convey any information regarding the actual
shape of the particular elements, and may have been solely selected
for ease of recognition in the drawings.
[0065] FIG. 1A is a left side, sectional elevational view of an
optical engine, in accordance with the present systems, devices,
and methods.
[0066] FIG. 1B is a front side, sectional elevational view of the
optical engine also shown in FIG. 1A, in accordance with the
present systems, devices, and methods.
[0067] FIG. 2 is a flow diagram of a method of operating an optical
engine, in accordance with the present systems, devices, and
methods.
[0068] FIG. 3 is a schematic diagram of a wearable heads-up display
with a laser projector that includes an optical engine, and a
transparent combiner in a field of view of an eye of a user, in
accordance with the present systems, devices, and methods.
[0069] FIG. 4 is an isometric view of a wearable heads-up display
with a laser projector that includes an optical engine, in
accordance with the present systems, devices, and methods.
[0070] FIG. 5 is a flow diagram of a method of manufacturing an
optical engine, in accordance with the present systems, devices,
and methods.
[0071] FIG. 6 is a top plan view of a photonic integrated circuit
for wavelength multiplexing that includes a plurality of grating
couplers on a surface thereof, the photonic integrated circuit
followed by a common collimation lens and an optional diffractive
optical element, in accordance with the present systems, devices,
and methods.
[0072] FIG. 7 is a left side sectional elevational view of an
optical engine that includes a plurality of laser diodes inside a
hermetically or partially hermetically sealed package coupled to
the photonic integrated circuit for wavelength multiplexing, and a
common collimation lens and an optional diffractive optical
element, in accordance with the present systems, devices, and
methods.
[0073] FIG. 8 is a schematic diagram of a laser writing system
which can be used to write photonic integrated circuits in
accordance with the present systems, devices, and methods.
[0074] FIG. 9 is a flow diagram of a method of manufacturing an
optical engine including writing a photonic integrated circuit, in
accordance with the present systems, devices, and methods.
[0075] FIGS. 10A and 10B are schematic diagrams of laser writing
systems which can be used to write photonic integrated circuits in
writeable glass already bonded to a substrate or circuit, according
to at least two illustrated implementations.
[0076] FIGS. 11A and 11B are isometric views of optical engines
including an insulating cover which prevents undesired electrical
signal transmission from electrical connections, and showing
implementations of optical engines having differing positions for a
laser diode driver circuit in accordance with the present systems,
devices, and methods.
[0077] FIG. 12A is a side sectional view of an optical engine that
includes a plurality of laser diodes which output beams of light to
a beam combiner which produces an aggregate beam.
[0078] FIG. 12B is a side sectional view of an optical engine
having collimation lenses which redirect beams to a beam combiner
which does not directly line up with outputs of laser diodes of the
optical engine.
[0079] FIG. 12C is a side sectional view of an optical engine
having a collimation lens which collimates an aggregate beam output
from a beam combiner.
[0080] FIG. 13 is an isometric view of a laser diode, showing a
fast axis and a slow axis of a light beam generated by the laser
diode, in accordance with the present systems, devices, and
methods.
[0081] FIG. 14A is a left side sectional view of a set of
collimation lenses for collimating a beam of light separately along
different axes.
[0082] FIG. 14B is a top side sectional elevational view of the set
of collimation lenses of FIG. 14A.
[0083] FIGS. 14C and 14D are isometric views of exemplary lens
shapes which could be used as lenses in the implementation of FIGS.
14A and 14B.
[0084] FIG. 15A is a left side sectional view of a set of
collimation lenses for circularizing and collimating a beam of
light.
[0085] FIG. 15B is a top side sectional elevational view of the set
of collimation lenses of FIG. 15A.
[0086] FIGS. 15C and 15D are isometric views of exemplary lens
shapes which could be used as a collimation lens in the
implementation of FIGS. 15A and 15B.
DETAILED DESCRIPTION
[0087] In the following description, certain specific details are
set forth in order to provide a thorough understanding of various
disclosed implementations. However, one skilled in the relevant art
will recognize that implementations may be practiced without one or
more of these specific details, or with other methods, components,
materials, etc. In other instances, well-known structures
associated with computer systems, server computers, and/or
communications networks have not been shown or described in detail
to avoid unnecessarily obscuring descriptions of the
implementations.
[0088] Unless the context requires otherwise, throughout the
specification and claims that follow, the word "comprising" is
synonymous with "including," and is inclusive or open-ended (i.e.,
does not exclude additional, unrecited elements or method
acts).
[0089] Reference throughout this specification to "one
implementation" or "an implementation" means that a particular
feature, structure or characteristic described in connection with
the implementation is included in at least one implementation.
Thus, the appearances of the phrases "in one implementation" or "in
an implementation" in various places throughout this specification
are not necessarily all referring to the same implementation.
Furthermore, the particular features, structures, or
characteristics may be combined in any suitable manner in one or
more implementations.
[0090] As used in this specification and the appended claims, the
singular forms "a," "an," and "the" include plural referents unless
the context clearly dictates otherwise. It should also be noted
that the term "or" is generally employed in its sense including
"and/or" unless the context clearly dictates otherwise.
[0091] The headings and Abstract of the Disclosure provided herein
are for convenience only and do not interpret the scope or meaning
of the implementations.
[0092] One or more implementations of the present disclosure
provide laser-based optical engines, for example, laser-based
optical engines for laser projectors used in wearable heads-up
displays or other applications. Generally, the optical engines
discussed herein integrate a plurality of laser dies or diodes
(e.g., 3 laser diodes, 4 laser diodes) within a single,
hermetically or partially hermetically sealed, encapsulated
package. As discussed further below with reference to FIGS. 6, 7,
and 10A, in at least some implementations, photonic integrated
circuits having grating couplers thereon may be used to wavelength
multiplex beams of light emitted by the plurality of laser diodes
into a coaxially superimposed aggregate beam. Alternatively, each
wavelength of light may be channeled individually through the
photonic integrated circuit. Such optical engines may have various
advantages over existing designs including, for example, smaller
volume, lower weight, better manufacturability, lower cost, faster
modulation speed, etc. The material used for the optical engines
discussed herein may be any suitable materials, e.g., ceramics with
advantageous thermal properties, etc. As noted above, such features
are particularly advantages in various applications including
WHUDs.
[0093] FIG. 1A is a left side, elevational sectional view of an
optical engine 100, which may also be referred to as a "multi-laser
diode module" or an "RGB laser module," in accordance with the
present systems, devices, and methods. FIG. 1B is a front side,
elevational sectional view of the optical engine 100. The optical
engine 100 includes a base substrate 102 having a top surface 104
and a bottom surface 106 opposite the top surface. The base
substrate 102 may be formed from a material that is radio frequency
(RF) compatible and is suitable for hermetic sealing. For example,
the base substrate 102 may be formed from low temperature co-fired
ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar.RTM., other
ceramics with suitable thermal properties, etc. The term Kovar.RTM.
generally refers to iron-nickel-cobalt alloys having similar
thermal expansion coefficients to glass and ceramics, thus making
Kovar.RTM. materials particularly suitable for forming hermetic
seals which remain functional in a wide range of temperatures.
[0094] The optical engine 100 also includes a plurality of chip
submounts 108a-108d (collectively 108) bonded (e.g., attached) to
the top surface 104 of the base substrate 102. The plurality of
chip submounts 108 are aligned in a row across a width of the
optical engine 100 between the left and right sides thereof. Each
of the plurality of chip submounts 108 includes a laser diode 110,
also referred to as a laser chip or laser die, bonded thereto. In
particular, an infrared chip submount 108a carries an infrared
laser diode 110a, a red chip submount 108b carries a red laser
diode 110b, a green chip submount 108c carries a green laser diode
110c, and a blue chip submount 108d carries a blue laser diode
110d. In operation, the infrared laser diode 110a provides infrared
laser light, the red laser diode 110b provides red laser light, the
green laser diode 110c provides green laser light, and the blue
laser diode 110d provides blue laser light. Each of the laser
diodes 110 may comprise one of an edge emitter laser or a
vertical-cavity surface-emitting laser (VCSEL), for example. Each
of the four laser diode/chip submount pairs may be referred to
collectively as a "laser chip on submount," or a laser CoS 112.
Thus, the optical engine 100 includes an infrared laser CoS 112a, a
red laser CoS 112b, a green laser CoS 112c, and a blue laser CoS
112d. In at least some implementations, one or more of the laser
diodes 110 may be bonded directly to the base substrate 102 without
use of a submount 108. It should be appreciated that although some
implementations discussed herein describe laser diodes as chips or
dies on submounts, other dies or types of devices, e.g., p-side
down devices, may be used as well.
[0095] The optical engine 100 also includes a laser diode driver
circuit 114 bonded to the bottom surface 106 of the base substrate
102. The laser diode driver circuit 114 is operatively coupled to
the plurality of laser diodes 110 via suitable electrical
connections 116 to selectively drive current to the plurality of
laser diodes. In at least some implementations, the laser diode
driver circuit 114 may be positioned relative to the CoSs 112 to
minimize the distance between the laser diode driver circuit 114
and the CoSs 112. Although not shown in FIGS. 1A and 1B, the laser
diode driver circuit 114 may be operatively coupleable to a
controller (e.g., microcontroller, microprocessor, ASIC) which
controls the operation of the laser diode driver circuit 114 to
selectively modulate laser light emitted by the laser diodes 110.
In at least some implementations, the laser diode driver circuit
114 may be bonded to another portion of the base substrate 102,
such as the top surface 104 of the base substrate. In at least some
implementations, the laser diode driver circuitry 114 may be
remotely located and operatively coupled to the laser diodes 110.
In order to not require the use of impedance matched transmission
lines, the size scale may be small compared to a wavelength (e.g.,
lumped element regime), where the electrical characteristics are
described by (lumped) elements like resistance, inductance, and
capacitance.
[0096] Proximate the laser diodes 110 there is positioned an
optical director element 118. Like the chip submounts 108, the
optical director element 118 is bonded to the top surface 104 of
the base substrate 102. In the illustrated example, the optical
director element 118 has a triangular prism shape that includes a
plurality of planar faces. In particular the optical director
element 118 includes an angled front face 118a that extends along
the width of the optical engine 100, a rear face 118b, a bottom
face 118c that is bonded to the top surface 104 of the base
substrate 102, a left face 118d, and a right face 118e opposite the
left face. The optical director element 118 may comprise a mirror
or a prism, for example.
[0097] The optical engine 100 also includes a cap 120 that includes
a vertical sidewall 122 having a lower first end 124 and an upper
second end 126 opposite the first end. A flange 128 may be disposed
around a perimeter of the sidewall 122 adjacent the lower first end
124. Proximate the upper second end 126 of the sidewall 122 there
is a horizontal optical window 130 that forms the "top" of the cap
120. The sidewall 122 and the optical window 130 together define an
interior volume 132 sized and dimensioned to receive the plurality
of chip submounts 108, the plurality of laser diodes 110, and the
optical director element 118. The lower first end 124 and the
flange 128 of the cap 120 are bonded to the base substrate 102 to
provide a hermetic or partially hermetic seal between the interior
volume 132 of the cap and a volume 134 exterior to the cap.
[0098] As shown best in FIG. 1A, the optical director element 118
is positioned and oriented to direct (e.g., reflect) laser light
received from each of the plurality of laser diodes 108 upward (as
shown) toward the optical window 130 of the cap 120, wherein the
laser light exits the interior volume 132.
[0099] The cap 120 may have a round shape, rectangular shape, or
other shape. Thus, the vertical sidewall 122 may comprise a
continuously curved sidewall, a plurality (e.g., four) of adjacent
planar portions, etc. The optical window 130 may comprise an entire
top of the cap 120, or may comprise only a portion thereof. In at
least some implementations, the optical window 130 may be located
on the sidewall 122 rather than positioned as a top of the cap 120,
and the laser diodes 110 and/or the optical director element 118
may be positioned and oriented to direct the laser light from the
laser diodes toward the optical window on the sidewall 122. At
least some implementations may not include optical director element
118 such that laser light from the laser diodes may be output
towards the optical window on the sidewall 122 without the need for
intervening optical elements. In at least some implementations, the
cap 120 may include a plurality of optical windows instead of a
single optical window.
[0100] The optical engine 100 also includes four
collimation/pointing lenses 136a-136d (collectively 136), one for
each of the four laser diodes 110a-110d, respectively, that are
bonded to a top surface 138 of the optical window 130. Each of the
plurality of collimation lenses 136 is positioned and oriented to
receive light from a corresponding one of the laser diodes 110
through the optical window 130. In particular, the collimation lens
136a receives light from the infrared laser diode 110a via the
optical director element 118 and the optical window 130, the
collimation lens 136b receives light from the red laser diode 110b
via the optical director element and the optical window, the
collimation lens 136c receives light from the green laser diode
110c via the optical director element and the optical window, and
the collimation lens 136d receives light from the blue laser diode
110d via the optical director element and the optical window.
[0101] Each of the collimation lenses 136 is operative to receive
laser light from a respective one of the laser diodes 110, and to
generate a single color beam. In particular, the collimation lens
136a receives infrared laser light from the infrared laser diode
110a and produces an infrared laser beam 138a, the collimation lens
136b receives red laser light from the red laser diode 110b and
produces a red laser beam 138b, the collimation lens 136c receives
green laser light from the green laser diode 110c and produces a
green laser beam 138c, and the collimation lens 136d receives blue
laser light from the blue laser diode 110d and produces a blue
laser beam 138d.
[0102] The optical engine 100 may also include, or may be
positioned proximate to, a beam combiner 140 that is positioned and
oriented to combine the light beams 138a-138d received from each of
the collimation lenses 136 into a single aggregate beam 142. As an
example, the beam combiner 140 may include one or more diffractive
optical elements (DOE) and/or refractive/reflective optical
elements that combine the different color beams 138a-138d in order
to achieve coaxial superposition. An example beam combiner is shown
in FIG. 3 and discussed below.
[0103] In at least some implementations, the laser CoSs 112, the
optical director element 118, and/or the collimation lenses 136 may
be positioned differently. As noted above, laser diode driver
circuit 114 may be mounted on the top surface 104 or the bottom
surface 106 of the base substrate 102, depending on the RF design
and other constraints (e.g., package size). In at least some
implementations, the optical engine 100 may not include the optical
director element 118, and the laser light may be directed from the
laser diodes 110 toward the collimation lenses 136 without
requiring an intermediate optical director element. Additionally,
in at least some implementations, one or more of the laser diodes
may be mounted directly on the base substrate 102 without use of a
submount. For the sake of a controlled atmosphere inside the
interior volume 132, it may be desirable to have no organic
compounds inside the interior volume 132. In at least some
implementations, the components of the optical engine 100 may be
bonded together using no adhesives. In other implementations, a low
amount of adhesives may be used to bond at least one of the
components, which may reduce cost while providing a relatively low
risk of organic contamination for a determined lifetime (e.g., 2 or
more years) of the optical engine 100. The use of adhesives may
result in a partial hermetic seal, but this partial hermetic seal
may be acceptable in certain applications, as detailed below.
[0104] Generally, "hermetic" refers to a seal which is airtight,
that is, a seal which excludes the passage of air, oxygen, and
other gases. "Hermetic" within the present specification carries
this meaning. Further, "partially hermetic" as used herein refers
to a seal which limits, but does not necessarily completely
prevent, the passage of gases such as air. "Partially hermetic" as
used herein may alternatively be stated as "reduced hermiticity".
In the example above, adhesives may be used to bond components.
Such adhesives may result in a seal being not completely hermetic,
in that some amount of gasses may slowly leak through the adhesive.
However, such a seal can still be considered "partially hermetic"
or as having "reduced hermiticity", because the seal reduces the
flow of gasses therethrough.
[0105] In one example application, even in an environment with only
partial hermiticity, the life of laser diodes 110 and transparency
of optical window 130 may be maintained longer than the life of a
battery of a device, such that partial hermiticity may be
acceptable for the devices. In some cases, even protecting interior
volume 132 from particulate with a dust cover may be sufficient to
maintain laser diodes 110 and transparency of optical window 130
for the intended lifespan of the device. In some cases, laser
diodes 110 and transparency of optical window 130 may last for the
intended lifespan of the device even without a protective cover.
Various bonding processes (e.g., attaching processes) for the
optical engine 100 are discussed below with reference to FIG.
5.
[0106] FIG. 2 is a flow diagram of a method 200 of operating an
optical engine, in accordance with the present systems, devices,
and methods. The method 200 may be implemented using the optical
engine 100 of FIGS. 1A-1B, for example. It should be appreciated
that methods of operating optical engines according to the present
disclosure may include fewer or additional acts than set forth in
the method 200. Further, the acts discussed below may be performed
in an order different than the order presented herein.
[0107] At 202, at least one controller may cause a plurality of
laser diodes of an optical engine to generate laser light. As
discussed above, the plurality of laser diodes may be hermetically
or partially hermetically sealed in an encapsulated package. The
laser diodes may produce light sequentially and/or simultaneously
with each other. At 204, at least one optical director element may
optionally receive the laser light from the laser diodes. The
optical director element may comprise a mirror or a prism, for
example. As discussed above, in at least some implementations the
optical engine may be designed such that laser light exits the
optical engine without use of an optical director element.
[0108] At 206, the at least one optical director element, if
included, may direct the received laser light toward an optical
window of the encapsulated package. For example, the optical
director element may reflect the received laser light toward the
optical window of the encapsulated package. In implementations
without at least one optical director element, the laser light
generated by the plurality of laser diodes may be output directly
toward the optical window of the encapsulated package.
[0109] At 208, a plurality of collimation lenses may collimate the
laser light from the laser diodes that exits the encapsulated
package via the optical window to generate a plurality of
differently colored laser light beams. The collimation lenses may
be positioned inside or outside of the encapsulated package. As an
example, the collimation lenses may be physically coupled to the
optical window of the encapsulated package.
[0110] At 210, a beam combiner may combine the plurality of laser
light beams received from each of the collimation lenses into a
single aggregate beam. The beam combiner may include one or more
diffractive optical elements (DOE) that combine different color
beams in order to achieve coaxial superposition, for example. The
beam combiner may include one or more DOEs and/or one or more
refractive/reflective optical elements. An example beam combiner is
shown in FIG. 3 and discussed below.
[0111] FIG. 3 is a schematic diagram of a wearable heads-up display
(WHUD) 300 with an exemplary laser projector 302, and a transparent
combiner 304 in a field of view of an eye 306 of a user of the
WHUD, in accordance with the present systems, devices, and methods.
The WHUD 300 includes a support structure (not shown), with the
general shape and appearance of an eyeglasses frame, carrying an
eyeglass lens 308 with the transparent combiner 304, and the laser
projector 302.
[0112] The laser projector 302 comprises a controller or processor
310, an optical engine 312 comprising four laser diodes 314a, 314b,
314c, 314d (collectively 314) communicatively coupled to the
processor 310, a beam combiner 316, and a scan mirror 318. The
optical engine 312 may be similar or identical to the optical
engine 100 discussed above with reference to FIGS. 1A and 1B.
Generally, the term "processor" refers to hardware circuitry, and
may include any of microprocessors, microcontrollers, application
specific integrated circuits (ASICs), digital signal processors
(DSPs), programmable gate arrays (PGAs), and/or programmable logic
controllers (PLCs), or any other integrated or non-integrated
circuit.
[0113] During operation of the WHUD 300, the processor 310
modulates light output from the laser diodes 314, which includes a
first red laser diode 314a (R), a second green laser diode 314b
(G), a third blue laser diode 314c (B), and a fourth infrared laser
diode 314d (IR). The first laser diode 314a emits a first (e.g.,
red) light signal 320, the second laser diode 314b emits a second
(e.g., green) light signal 322, the third laser diode 314c emits a
third (e.g., blue) light signal 324, and the fourth laser diode
314d emits a fourth (e.g., infrared) light signal 326. All four of
light signals 320, 322, 324, and 326 enter or impinge on the beam
combiner 316. Beam combiner 316 could for example be based on any
of the beam combiners described in U.S. Provisional Patent
Application Ser. No. 62/438,725, U.S. Non-Provisional patent
application Ser. No. 15/848,265 (U.S. Publication Number
2018/0180885), U.S. Non-Provisional patent application Ser. No.
15/848,388 (U.S. Publication Number 2018/0180886), U.S. Provisional
Patent Application Ser. No. 62/450,218, U.S. Non-Provisional patent
application Ser. No. 15/852,188 (U.S. Publication Number
2018/0210215), U.S. Non-Provisional patent application Ser. No.
15/852,282, (U.S. Publication Number 2018/0210213), and/or U.S.
Non-Provisional patent application Ser. No. 15/852,205 (U.S.
Publication Number 2018/0210216).
[0114] In the illustrated example, the beam combiner 316 includes
optical elements 328, 330, 332, and 334. The first light signal 320
is emitted towards the first optical element 328 and reflected by
the first optical element 328 of the beam combiner 316 towards the
second optical element 330 of the beam combiner 316. The second
light signal 322 is also directed towards the second optical
element 330. The second optical element 330 is formed of a dichroic
material that is transmissive of the red wavelength of the first
light signal 320 and reflective of the green wavelength of the
second light signal 322. Therefore, the second optical element 330
transmits the first light signal 320 and reflects the second light
signal 322. The second optical element 330 combines the first light
signal 320 and the second light signal 322 into a single aggregate
beam (shown as separate beams for illustrative purposes) and routes
the aggregate beam towards the third optical element 332 of the
beam combiner 316.
[0115] The third light signal 324 is also routed towards the third
optical element 332. The third optical element 332 is formed of a
dichroic material that is transmissive of the wavelengths of light
(e.g., red and green) in the aggregate beam comprising the first
light signal 320 and the second light signal 322 and reflective of
the blue wavelength of the third light signal 324. Accordingly, the
third optical element 332 transmits the aggregate beam comprising
the first light signal 320 and the second light signal 322 and
reflects the third light signal 324. In this way, the third optical
element 332 adds the third light signal 324 to the aggregate beam
such that the aggregate beam comprises the light signals 320, 322,
and 324 (shown as separate beams for illustrative purposes) and
routes the aggregate beam towards the fourth optical element 334 in
the beam combiner 316.
[0116] The fourth light signal 326 is also routed towards the
fourth optical element 334. The fourth optical element 334 is
formed of a dichroic material that is transmissive of the visible
wavelengths of light (e.g., red, green, and blue) in the aggregate
beam comprising the first light signal 320, the second light signal
322, and the third light signal 324 and reflective of the infrared
wavelength of the fourth light signal 326. Accordingly, the fourth
optical element 334 transmits the aggregate beam comprising the
first light signal 320, the second light signal 322, and the third
light signal 324 and reflects the fourth light signal 326. In this
way, the fourth optical element 334 adds the fourth light signal
326 to the aggregate beam such that the aggregate beam 336
comprises portions of the light signals 320, 322, 324, and 326. The
fourth optical element 334 routes the aggregate beam 336 towards
the controllable scan mirror 318.
[0117] The scan mirror 318 is controllably orientable and scans
(e.g. raster scans) the beam 336 to the eye 306 of the user of the
WHUD 300. In particular, the controllable scan mirror 318 scans the
laser light onto the transparent combiner 304 carried by the
eyeglass lens 308. The scan mirror 318 may be a single bi-axial
scan mirror or two single-axis scan mirrors may be used to scan the
laser light onto the transparent combiner 304, for example. In at
least some implementations, the transparent combiner 304 may be a
holographic combiner with at least one holographic optical element.
The transparent combiner 304 redirects the laser light towards a
field of view of the eye 306 of the user. The laser light
redirected towards the eye 306 of the user may be collimated by the
transparent combiner 304, wherein the spot at the transparent
combiner 304 is approximately the same size and shape as the spot
at the eye 306 of the user. The laser light may be converged by the
eye 306 to a focal point at the retina of eye 306 and creates an
image that is focused. The visible light may create display content
in the field of view of the user, and the infrared light may
illuminate the eye 306 of the user for the purpose of eye
tracking.
[0118] FIG. 4 is a schematic diagram of a wearable heads-up display
(WHUD) 400 with a laser projector 402 in accordance with the
present systems, devices, and methods. WHUD 400 includes a support
structure 404 with the shape and appearance of a pair of eyeglasses
that in use is worn on the head of the user. The support structure
404 carries multiple components, including eyeglass lens 406, a
transparent combiner 408, the laser projector 402, and a controller
or processor 410. The laser projector 402 may be similar or
identical to the laser projector 302 of FIG. 3. For example, the
laser projector 402 may include an optical engine, such as the
optical engine 100 or the optical engine 312. The laser projector
402 may be communicatively coupled to the controller 410 (e.g.,
microprocessor) which controls the operation of the projector 402,
as discussed above. The controller 410 may include or may be
communicatively coupled to a non-transitory processor-readable
storage medium (e.g., memory circuits such as ROM, RAM, FLASH,
EEPROM, memory registers, magnetic disks, optical disks, other
storage), and the controller may execute data and/or instruction
from the non-transitory processor readable storage medium to
control the operation of the laser projector 402.
[0119] In operation of the WHUD 400, the controller 410 controls
the laser projector 402 to emit laser light. As discussed above
with reference to FIG. 3, the laser projector 402 generates and
directs an aggregate beam (e.g., aggregate beam 336 of FIG. 3)
toward the transparent combiner 408 via at least one controllable
mirror (not shown in FIG. 4). The aggregate beam is directed
towards a field of view of an eye of a user by the transparent
combiner 408. The transparent combiner 408 may collimate the
aggregate beam such that the spot of the laser light incident on
the eye of the user is at least approximately the same size and
shape as the spot at transparent combiner 408. The transparent
combiner 408 may be a holographic combiner that includes at least
one holographic optical element.
[0120] FIG. 5 is a flow diagram of a method 500 of manufacturing an
optical engine, in accordance with the present systems, devices,
and methods. The method 500 may be implemented to manufacture the
optical engine 100 of FIGS. 1A-1B or the optical engine 312 of FIG.
3, for example. It should be appreciated that methods of
manufacturing optical engines according to the present disclosure
may include fewer or additional acts than set forth in the method
500. Further, the acts discussed below may be performed in an order
different than the order presented herein.
[0121] At 502, a plurality of laser diodes may be bonded to a
respective plurality of submounts. In at least some
implementations, this method may be performed by an entity
different than that manufacturing the optical engine. For example,
in at least some implementations, one or more of the plurality of
laser diodes (e.g., green laser diode, blue laser diode) may be
purchased as already assembled laser CoSs. For ease of handling and
simplification of the overall process, in at least some
implementations it may be advantageous to also bond laser diodes
that cannot be procured on submounts to a submount as well. As a
non-limiting example, in at least some implementations, one or more
of the laser diodes may be bonded to a corresponding submount using
an eutectic gold tin (AuSn) solder process, which is flux-free and
requires heating up top 280.degree. C.
[0122] At 504, the plurality of CoSs may be bonded to a base
substrate. Alternatively, act 502 could be skipped for at least one
or all of the laser diodes, and act 504 could comprise bonding the
at least one or all of the laser diodes directly to the base
substrate. The base substrate may be formed from a material that is
RF compatible and is suitable for hermetic sealing. For example,
the base substrate may be formed from low temperature co-fired
ceramic (LTCC), aluminum nitride (AlN), alumina, Kovar.RTM., etc.
Since several CoSs are bonded next to each other on the same base
substrate, it may be advantageous to either "step-solder" them
sequentially or to use a bonding technique that does not rely on
re-melting of solder materials. For step-soldering, each subsequent
soldering step utilizes a process temperature that is less than the
process temperatures of previous solder steps to prevent re-melting
of solder materials. It may also be important that the laser
diode-to-submount bonding does not re-melt during bonding of the
CoSs to the base substrate. Bonding technologies other than
step-soldering that may be used include parallel soldering of all
CoS in reflow oven process, thermosonic or thermocompression
bonding, transient liquid phase (TLP) bonding, laser soldering,
etc. Some of these example bonding technologies are discussed
below.
[0123] For parallel soldering of all CoSs in a reflow oven process,
appropriate tooling is required to assure proper bonding and
alignment during the process. An advantage of this process is the
parallel and hence time efficient bonding of all CoSs at once and
even many assemblies in parallel. A possible disadvantage of this
process is the potential loss of the alignment of components during
the reflow process. Generally, a soldering cycle ideally needs a
few minutes of dwell time. Preheating may be used to reduce the
soldering time, which requires a few minutes for such a process
depending on the thermal mass of the components being bonded. Thus,
a batch process may be used with regular soldering to reduce the
assembly costs with high throughput at the expense of alignment
tolerance.
[0124] For thermosonic or thermocompression bonding, thick gold
metallization may be used but no extra solder layer is required.
The temperatures for thermocompression bonding might be as high as
300 to 350.degree. C. to have a good bond with a good thermal
conductivity. Thermosonic bonding may be used to reduce the
pressure and temperature needed for bonding, which may be required
for at least some components that might not tolerate the
temperatures required for thermocompression bonding.
[0125] Transient liquid phase (TLP) bonding may also be used. There
are many different reaction couples that may be used, including
gold-tin, copper-tin, etc. With this method, a liquid phase is
formed during the bonding which will solidify at the same
temperature. The re-melting temperatures of the bond are much
higher than the soldering temperatures.
[0126] In at least some implementations, laser soldering may be
used to bond some or all of the components of the optical engine.
Generally, the thermal characteristic of the parts to be bonded may
be important when implementing a laser soldering process.
[0127] Subsequent reflows of solder are not recommended due to
liquid phase reaction or dissolution mechanisms which may reduce
the reliability of the joint. This could result in voiding at the
interface or a reduction in strength of the joint itself. In order
to mitigate potential reflow dissolution problems, other options
can be taken into consideration, which do not rely on extreme
heating of the device and can be favorable in terms of production
cost. For example, bonding of the base substrate with adhesives
(electrically conductive for common mass, or non-conductive for
floating) may be acceptable with respect to heat transfer and
out-gassing as discussed regarding partial hermetic sealing
above.
[0128] Further, in at least some implementations, a reactive
multi-layer foil material (e.g., NanoFoil.RTM.) or a similar
material may be used as a solder pre-form, which enables localized
heat transfer. A reactive multi-layer foil material is a metallic
material based on a plurality (e.g., hundreds, thousands) of
reactive foils (aluminum and nickel) that enables die-attach
soldering (e.g., silicon chip onto stainless steel part). In such
implementations, dedicated heat transfer support metallizations may
be deposited onto the two components being joined together. This
method may be more advantageous for CoS-to-base substrate mounting
compared to chip-to-submount bonding. Generally, bonding using
reactive multi-layer foil materials enables furnace-free,
low-temperature soldering of transparent or non-transparent
components, without reaching the bonding temperatures for solder
reflow processes. Reactive multi-layer foil materials can be
patterned with a ps-laser into exact preform shapes.
[0129] At 506, the optical director element, if included, may be
bonded to the base substrate proximate the laser CoSs. The optical
director element may be bonded to the base substrate using any
suitable bonding process, including the bonding processes discussed
above with reference to act 504.
[0130] At 508, the laser diode driver circuit may optionally be
bonded to the base substrate. As noted above, the laser diode
driver circuit may be bonded to the base substrate such that the
distance between the laser diode driver circuit and the laser CoSs
is minimized. This may also comprise positioning a plurality of
electrical connections which operatively couple the laser diode
driver circuit to the plurality of laser diodes as shown in FIGS.
11A and 11B. In alternative implementations, the laser diode driver
circuit may be bonded to a separate base substrate from the other
components mentioned above as shown in FIG. 11B. The process used
to bond the laser diode driver circuit to the base substrate may be
any suitable bonding process, such as bonding processes commonly
used to bond surface mount devices (SMD) to circuit boards. In
other alternative implementations, the laser diode driver circuit
may be mounted directly to a frame of a WHUD. For implementations
where the laser diode drive circuit is not bonded to the same base
substrate as the other components mentioned above, a plurality of
electrical contacts and electrical connections could be bonded to
the base substrate, each electrical connection operatively
connecting a respective electrical contact to a respective laser
diode. Subsequently, the at least one laser driver circuit could be
operatively coupled to the electrical contacts, which will then
electrically couple the laser diode drive circuit to the electrical
connections and consequently to the laser diodes. Exemplary
arrangements of electrical connections and electrical contacts is
discussed later with reference to FIG. 11B.
[0131] At 510, the cap may be bonded to the base substrate to form
a hermetic or partially hermetic seal between the interior volume
of the encapsulated package and an exterior environment. As noted
above, it may be desirable to maintain a specific atmosphere for
the laser diode chips for reliability reasons. In at least some
implementations, adhesive sealing may be undesirable because of the
high permeability of gases. This is especially the case for blue
laser diodes, which emit blue laser light that may bake
contamination on facets and windows, thereby reducing transparency
of the optical window. However, as detailed above regarding FIGS.
1A and 1B, partial hermeticity, a particulate dust cover, or even
no protective cover may be acceptable for certain applications. In
implementations where the cap would be bonded over electrical
connections which connect the at least one laser diode driver
circuit to the plurality of laser diodes, such as when the at least
one laser diode driver circuit is bonded to the same side of a base
substrate as the laser diodes, or when the at least one laser diode
driver circuit is coupled to electrical contacts bonded to the same
side of the base substrate as the laser diodes, an electrically
insulating cover can first be bonded to the base substrate over the
electrical connections. Subsequently, the cap can be bonded at
least partially to the electrically insulating cover, and
potentially to a portion of the base substrate if the insulating
cover does not fully encircle the intended interior volume. In this
way, at least a portion of the cap will be bonded to the base
substrate indirectly by being bonded to the electrically insulating
cover. In some implementations, the entire cap could be bonded to
the base substrate indirectly by being bonded to an electrically
insulating cover which encircles the intended interior volume.
Exemplary electrically insulating covers are discussed later with
reference to FIGS. 11A and 11B.
[0132] During the sealing process, the atmosphere may be defined by
flooding the package accordingly. For example, the interior volume
of the encapsulated package may be flooded with an oxygen enriched
atmosphere that burns off contaminants which tend to form on
interfaces where the laser beam is present. The sealing itself may
also be performed so as to prevent the exchange between the package
atmosphere and the environment. Due to limitations concerning the
allowed sealing temperature, e.g., the components inside the
package should not be influenced, in at least some implementations
seam welding or laser assisted soldering/diffusion bonding may be
used. In at least some implementations, localized sealing using a
combination of seam welding and laser soldering may be used.
[0133] At 512, the collimation lenses may be actively aligned. For
example, once the laser diode driver circuit has been bonded and
the cap has been sealed, the laser diodes can be turned on and the
collimations lenses for each laser diode can be actively aligned.
In at least some implementations, each of the collimation lenses
may be positioned to optimize spot as well as pointing for each of
the respective laser diodes.
[0134] At 514, the beam combiner may be positioned to receive and
combine individual laser beams into an aggregate beam. As discussed
above, the beam combiner may include one or more diffractive
optical elements and/or one or more refractive/reflective optical
elements that function to combine the different color beams into an
aggregate beam. The aggregate beam may be provided to other
components or modules, such as a scan mirror of a laser projector,
etc.
[0135] FIG. 6 is a top plan view of a photonic integrated circuit
600 for wavelength multiplexing followed by a common collimation
lens 602 and an optional diffractive optical element 604. The
photonic integrated circuit 600 may be a component in an optical
engine, such as an optical engine 700 of FIG. 7, an optical engine
1000a of FIG. 10A, or an optical engine 1000b of FIG. 10B discussed
further below. The photonic integrated circuit 600 includes a
plurality of input facets 612a-612d and at least one output facet
608 (e.g., output optical coupler or grating output coupler). In
FIG. 6, input facets 612a-612d are shown as grating couplers (also
referred to as "diffractive grating couplers" or "grating input
couplers") on a top surface 606 thereof, but other input facets are
possible such as illustrated in FIG. 10B discussed below. In
operation, the photonic integrated circuit 600 receives a plurality
of beams of light 610a-610d that are coupled to the photonic
integrated circuit via the input facets 612a-612d, respectively,
and wavelength multiplexes the plurality of beams to provide a
coaxially superimposed aggregate beam of light 614 that exits the
photonic integrated circuit at the output facet 608, output optical
coupler or grating output coupler. Compared to edge coupling, in at
least some applications using grating input couplers for input
facets 612a-612d may allow for relaxed tolerances for beam
alignment. Generally, the photonic integrated circuit 600 may
include one or more diffractive optical elements (DOE) and/or
refractive/reflective optical elements that combine the different
color beams 610a-610d in order to achieve coaxial
superposition.
[0136] Following out-coupling of the aggregate beam 614 from the
output facet 608 of the photonic integrated circuit 600, the
aggregated beam is collimated via the common collimation lens 602.
In at least some implementations, the collimation lens 602 may be
either an achromatic lens or an apochromatic lens (or lens
assemblies), depending on the particular optical design and
tolerances of the system. In at least some implementations, one or
more diffractive optical elements 604 may be used to provide
wavelength dependent focus correction.
[0137] FIG. 7 is a left side sectional elevational view of the
optical engine 700. The optical engine 700 includes several
components that may be similar or identical to the components of
the optical engine 100 of FIGS. 1A and 1B. Thus, some or all of the
discussion above may be applicable to the optical engine 700.
[0138] The optical engine 700 includes a base substrate 702 having
a top surface 704 and a bottom surface 706 opposite the top
surface. The base substrate 702 may be formed from a material that
is radio frequency (RF) compatible and is suitable for hermetic
sealing. For example, the base substrate 702 may be formed from low
temperature co-fired ceramic (LTCC), aluminum nitride (AlN),
alumina, Kovar.RTM., etc.
[0139] The optical engine 700 also includes a plurality of chip
submounts 708 (only one chip submount visible in the sectional view
of FIG. 7) that are bonded (e.g., attached) to the top surface 704
of the base substrate 702. The plurality of chip submounts 708 are
aligned in a row across a width of the optical engine 700 between
the left and right sides thereof. Each of the plurality of chip
submounts 708 includes a laser diode 710, also referred to as a
laser chip or laser die, bonded thereto. In particular, an infrared
chip submount carries an infrared laser diode, a red chip submount
carries a red laser diode, a green chip submount carries a green
laser diode, and a blue chip submount carries a blue laser diode.
In operation, the infrared laser diode provides infrared laser
light, the red laser diode provides red laser light, the green
laser diode provides green laser light, and the blue laser diode
provides blue laser light. Each of the laser diodes 710 may
comprise one of an edge emitter laser or a vertical-cavity
surface-emitting laser (VCSEL), for example. Each of the four laser
diode/chip submount pairs may be referred to collectively as a
"laser chip on submount," or a laser CoS 712. Thus, the optical
engine 700 includes an infrared laser CoS, a red laser CoS, a green
laser CoS, and a blue laser CoS. In at least some implementations,
one or more of the laser diodes 710 may be bonded directly to the
base substrate 702 without use of a submount 708.
[0140] The optical engine 700 also includes a laser diode driver
circuit 714 bonded to the bottom surface 706 of the base substrate
702. The laser diode driver circuit 714 is operatively coupled to
the plurality of laser diodes 710 via suitable electrical
connections 716 to selectively drive current to the plurality of
laser diodes. Generally, the laser diode driver circuit 714 may be
positioned relative to the CoSs 712 to minimize the distance
between the laser diode driver circuit 714 and the CoSs 712.
Although not shown in FIG. 7, the laser diode driver circuit 714
may be operatively coupleable to a controller (e.g.,
microcontroller, microprocessor, ASIC) that controls the operation
of the laser diode driver circuit 714 to selectively modulate laser
light emitted by the laser diodes 710. In at least some
implementations, the laser diode driver circuit 714 may be bonded
to another portion of the base substrate 702, such as the top
surface 704 of the base substrate, similar to the implementations
shown in FIGS. 11B and 11C. In at least some implementations, the
laser diode driver circuitry 714 may be remotely located and
operatively coupled to the laser diodes 710. In order to not
require the use of impedance matched transmission lines, the size
scale may be small compared to a wavelength (e.g., lumped element
regime), where the electrical characteristics are described by
(lumped) elements like resistance, inductance, and capacitance.
[0141] Proximate the laser diodes 710 there is positioned an
optical director element 718. Like the chip submounts 708, the
optical director element 718 is bonded to the top surface 704 of
the base substrate 702. In the illustrated example, the optical
director element 718 has a triangular prism shape that includes a
plurality of planar faces. In particular the optical director
element 718 includes an angled front face 718a that extends along
the width of the optical engine 700, a rear face 718b, a bottom
face 718c that is bonded to the top surface 704 of the base
substrate 702, a left face 718d, and a right face 718e opposite the
left face. The optical director element 718 may comprise a mirror
or a prism, for example. In at least some implementations, the
angled front face 718a may be curved to provide fast axis
collimation of the laser light from the laser diodes 710.
[0142] The optical engine 700 also includes a cap 720 that includes
a vertical sidewall 722 having a lower first end 724 and an upper
second end 726 opposite the first end. A flange 728 may be disposed
around a perimeter of the sidewall 722 adjacent the lower first end
724. Proximate the upper second end 726 there of the sidewall 722
there is a horizontal (as shown) optical window 730 that forms the
"top" of the cap 120. The sidewall 722 and the optical window 730,
along with a portion of the top surface 704 of the base substrate
702, together define an interior volume 732 sized and dimensioned
to receive the plurality of chip submounts 708, the plurality of
laser diodes 710, and the optical director element 717. The lower
first end 724 and the flange 728 of the cap 720 are bonded to the
base substrate 702 to provide a hermetic or partially hermetic seal
between the interior volume 732 of the cap and a volume 734
exterior to the cap.
[0143] The optical director element 718 is positioned and oriented
to direct (e.g., reflect) laser light received from each of the
plurality of laser diodes 710 upward (as shown) toward the optical
window 730 of the cap 720, wherein the laser light exits the
interior volume 732.
[0144] The cap 720 may have a round shape, rectangular shape, or
other shape. Thus, the vertical sidewall 722 may comprise a
continuously curved sidewall, a plurality (e.g., four) of adjacent
planar portions, etc. The optical window 730 may comprise an entire
top of the cap 720, or may comprise only a portion thereof. In at
least some implementations, the optical window 730 may be located
on the sidewall 722 rather than positioned as a top of the cap 720,
and the laser diodes 710 and/or the optical director element 718
(if present) may be positioned and oriented to direct the laser
light from the laser diodes toward the optical window on the
sidewall 722. In at least some implementations, the cap 720 may
include a plurality of optical windows instead of a single optical
window 730.
[0145] In at least some implementations, the optical engine 700
optionally includes four collimation lenses 736 (only one visible
in the sectional view of FIG. 7), one for each of the four laser
diodes 710. In other implementations, the collimation lenses 736
are omitted. In the illustrated implementation, the collimation
lenses 736 are bonded to a bottom surface of the optical window 730
in a row, although the collimation lenses may be positioned
differently in other implementations. For example, in at least some
implementations, the collimation lenses 736 may be positioned
outside of the package (e.g., outside of the interior volume 732)
rather than inside the package as shown in FIG. 7. Each of the
plurality of collimation lenses 736 may be positioned and oriented
to receive light from a corresponding one of the laser diodes 710,
and to direct collimated light upward (as shown) through the
optical window 730 toward the photonic integrated circuit 600,
which is shown "inverted" in FIG. 7 (relative to FIG. 6) so that
the input facets 612a-612d (collectively, 612) on the surface 606
of the photonic integrated circuit face a top surface 738 of the
optical window 730 of the cap 720.
[0146] The optical director element 718 and the collimation lenses
736 (when present) direct the beams of light 610a-610d (see FIG. 6)
into the photonic integrated circuit 600 via the input facets
612a-612d. The photonic integrated circuit 600 may be bonded to the
top surface of the optical window 730, as shown in FIG. 7. In at
least some implementations, the photonic integrated circuit 600 may
be bonded to the top surface 704 of the base substrate 702 instead.
As discussed above, in operation, the photonic integrated circuit
600 receives a plurality of beams of light 610a-610d via the inputs
facets 612a-612d (e.g. grating couplers), respectively, and
wavelength multiplexes the plurality of beams to provide a
coaxially superimposed aggregate beam of light 614 that exits the
photonic integrated circuit at the output optical coupler 608.
[0147] In at least some implementations, the laser diodes 710 may
be directly coupled to the photonic integrated circuit 600. In such
implementations, the laser diodes 710 may be positioned immediately
adjacent to a waveguide structure (e.g., photonic integrated
circuit or other waveguide structure) such that sufficient coupling
(e.g., acceptable insertion loss) is achieved. For example, in at
least some implementations, the photonic integrated circuit 600 may
function as the optical window of the package itself.
[0148] Following out-coupling of the aggregate beam 614 from the
output facet 608 of the photonic integrated circuit 600, the
aggregated beam may be collimated via the common collimation lens
602. In at least some implementations, the common collimation lens
602 may be bonded to the top surface 704 proximate the photonic
integrated circuit 600. In at least some implementations, the
collimation lens 602 may be either an achromatic lens or an
apochromatic lens, depending on the particular optical design and
tolerances of the system. In at least some implementations, the
optical engine 700 may include one or more diffractive optical
elements 604 to provide wavelength dependent focus correction.
[0149] In at least some implementations, at least some of the
components may be positioned differently. As noted above, the laser
diode driver circuit 714 may be mounted on the top surface 704 or
the bottom surface 706 of the base substrate 702, or may be
positioned remotely therefrom, depending on the RF design and other
constraints (e.g., package size), similarly to as discussed with
reference to FIGS. 11A and 11B below. In at least some
implementations, the optical engine 700 may not include an optical
director element (e.g., optical director element 718 of FIG. 7),
and the laser light may be directed from the laser diodes 710
toward the optical window 730 directly, such as if the laser diodes
are VCSEL laser diodes as discussed with reference to FIGS. 12A-12C
below, with our without collimation lenses 736. Additionally, in at
least some implementations, one or more of the laser diodes 710 may
be mounted directly on the base substrate 702 without use of a
submount. Further, in at least some implementations, in the case of
an inorganic or acceptably organic waveguide (e.g., photonic
integrated circuit), coupling may be accomplished inside the
encapsulated package. Such feature eliminates the requirement for a
separate window, as the waveguide 600 services as the window (e.g.,
optical window 730). In such implementations, the plurality of
grating couplers of the photonic integrated circuit may be
positioned inside the interior volume of the encapsulated package
and the at least one optical output coupler of the photonic
integrated circuit may be positioned outside of the interior
volume, for example.
[0150] For the sake of a controlled atmosphere inside the interior
volume 732, it may be desirable to have no organic compounds inside
the interior volume 732. In at least some implementations, the
components of the optical engine 700 may be bonded together using
no adhesives. In other implementations, a low amount of adhesives
may be used to bond at least one of the components, which may
reduce cost while providing a relatively low risk of organic
contamination for a determined lifetime (e.g., 2 or more years) of
the optical engine 700. Similarly to as detailed above regarding
FIGS. 1A and 1B, partial hermeticity, a particulate dust cover, or
even no protective cover may be acceptable for certain
applications. Various bonding processes (e.g., attaching processes)
for the optical engine 700 are discussed above with reference to
FIG. 5.
[0151] In at least some implementations, the collimation lenses 736
(when present) and the collimation lens 602 may be actively
aligned. In at least some implementations, the CoSs 712, the cap
720 (including optical window 730), and/or the photonic integrated
circuit 600 may be passively aligned. Further, depending on the
particular design, it may be advantageous to utilize a smaller base
substrate 702 and use an additional carrier substrate instead.
[0152] FIG. 8 is a schematic diagram of a laser writing system 800
in accordance with the present systems, designs and methods. Laser
writing system 800 comprises at least writing laser 810, focusing
optic 812, writeable glass 820 and translatable mount 830. Although
the term "glass" is used herein for convenience, any appropriate
laser-writable material could be used in place of writeable glass
820. Writing laser 810 emits laser light 811. Laser light 811
comprises short (femptosecond and/or picosecond length) pulses of
laser light; consequently, laser light 811 has extremely high peak
instantaneous power. Focusing optic 812 focuses laser light 811 to
focal point 813. Writeable glass 820 may comprise a contiguous
piece of glass or similar transparent material, which is typically
transparent to the laser light 811 emitted by the writing laser
810; in other words the light emitted by the writing laser
generally will not be absorbed by the glass via typical (linear)
optical processes. At the focal point 813, the intensity of laser
light 811 is very high due to the combination of spatial focusing
(focusing the beam of writing laser light 811 to a small point 813)
and temporal focusing (emitting the laser light 811 as extremely
short femptosecond or picosecond pulses). The high intensity of
light at the focal point 813 allows nonlinear optical processes
such as multiphoton absorption, avalanche ionization, Coulomb
collisions (causing lattice ionization and breakdown), and heat
conduction to occur in the writeable glass 820, absorbing the light
and changing the refractive index of the glass. The change in
refractive index may be a positive increase in refractive
index.
[0153] Writeable glass 820 can be physically coupled to
translatable mount 830, such as by using clamps 821, adhesive, or
any other appropriate coupling mechanism. Such coupling mechanism
is preferably removable, such that writeable glass 820 can be
detached from translatable mount 830 after laser writing is
complete. Translation of translatable mount 830 in the X, Y, and/or
Z direction will result in corresponding translation of writeable
glass 820, moving the location of focal point 813 within writeable
glass 820. Translating the writeable glass 820 relative to focal
point 813 can create a region of changed refractive index in the
writeable glass 820. An increased refractive index in this region
causes any light channeled therethrough to experience total
internal reflection, thus forming waveguide 822. In other words,
waveguide 822 can be formed as a continuous path of increased
refractive index within writeable glass 820 created by laser light
811 at focal point 813.
[0154] The technique of FIG. 8 can be used to laser write at least
one waveguide into writeable glass 820. For example, a photonic
integrated circuit could be written, such as photonic integrated
circuit 600 described with regards to FIG. 6. Inputs facets 612a,
612b, 612c, and 612d (such as grating couplers) could also be
written using this technique.
[0155] Writing at least one waveguide may include writing an
individual waveguide for each wavelength of light impinging on the
writeable glass 820, where each waveguide comprises a respective
input facet (such as an input grating coupler) and a respective
output facet. Each output facet may be positioned to provide light
to other components or modules, such as a scan mirror of a laser
projector, etc. In one implementation, four waveguides could be
written into writeable glass 820, one waveguide for each beam of
light 610a, 610b, 610c, and 610d. Four grating couplers could also
be written, one for each waveguide.
[0156] Writing at least one waveguide may include writing a
waveguide combiner, wherein the waveguide combiner combines
individual laser beams into a coaxially superimposed aggregate
beam. Writing a waveguide combiner may include writing at least
one: directional coupler (DC), Y-branch, whispering gallery mode
coupler, or multi-mode interference coupler. The aggregate beam may
be provided to other components or modules, such as a scan mirror
of a laser projector, etc.
[0157] In other implementations, the photonic integrated circuit
600 may include one or more diffractive optical elements (DOE)
and/or refractive/reflective optical elements that combine the
different color beams 610a-d in order to achieve coaxial
superposition.
[0158] Alternatively, instead of writing a waveguide combiner,
individual waveguides could be written which do not strictly
coaxially superimpose the beams of light, but instead bring each
beam of light close together. That is, the input facet (e.g.
grating coupler) for each waveguide in the photonic integrated
circuit can be positioned relatively far from the other input
facets, to receive laser light from a respective laser diode, but
the output facets for each of the waveguides can be positioned
relatively close together. In other words, a spacing between the
output facets of each waveguide can be smaller than a spacing of
the input facets of each waveguide. In such an implementation, each
waveguide can be optimized for performance with light of a
corresponding wavelength, for example to ensure that each
wavelength of light exits the photonic integrated circuit with the
same divergence angle as each other wavelength. The output of each
individual waveguide can be placed close enough together (on the
order of 10s of microns) such that that the light output by each
individual waveguide may still follow the same optical path through
the rest of a projector, display, or WHUD assembly where the
photonic integrated circuit is implemented.
[0159] FIG. 9 is a flow diagram of a method 900 of manufacturing an
optical engine, in accordance with the present systems, devices,
and methods. The method 900 may be implemented to manufacture the
optical engine 700 of FIG. 7, for example. It should be appreciated
that methods of manufacturing optical engines according to the
present disclosure may include fewer or additional acts than set
forth in the method 900. Further, the acts discussed below may be
performed in an order different than the order presented
herein.
[0160] Method 900 can include at least acts 902, 904, 906, 908,
910, 912, 914, and 916. Acts 902, 904, 906, 908, and 910
substantially correspond to acts 502, 504, 506, 508, and 510,
respectively, of method 500 in FIG. 5, such that the disclosure of
these acts with reference to FIG. 5 is also applicable to FIG. 9.
As such, the details of these acts in FIG. 9 will not be repeated
in the interests of brevity.
[0161] At 912, a photonic integrated circuit is laser written in
writeable glass, using for example the techniques described with
regards to FIG. 8. The photonic integrated circuit may be similar
to photonic integrated circuit 600 described with reference to FIG.
6. Specifically, the photonic integrated circuit can include at
least one input facet and at least one output facet. In operation,
the photonic integrated circuit can receive a plurality of beams of
light that are coupled to the photonic integrated circuit at a
plurality of input facets (e.g. grating couplers), and wavelength
multiplex the plurality of beams of light to provide a coaxially
superimposed aggregate beam of light that exits the photonic
integrated circuit at the output facet. Alternatively, in
operation, the photonic integrated circuit can receive a plurality
of beams of light that are coupled to the photonic integrated
circuit at a plurality of input facets (e.g. grating couplers),
redirect the plurality of beams of light to exit the photonic
integrated circuit at a plurality of spatially close output
facets.
[0162] At 914, the writeable glass including the photonic
integrated circuit is bonded to the cap. Any appropriate bonding
technique may be used, including those described with reference to
acts 502, 504, 506, 508, and 510 in FIG. 5. In some
implementations, the photonic integrated circuit may be positioned
against an optical window of the cap, such that laser light from
the laser diodes may pass through the optical window directly into
the input facets of the photonic integrated circuit. Alternatively,
the photonic integrated circuit may be positioned directly against
the cap, such that the photonic integrated circuit acts as the
optical window, and laser light from the laser diodes may directly
enter the input facets of the photonic integrated circuit.
[0163] In order for light to travel through a photonic integrated
circuit, the light emitted by each laser diode should preferably be
aligned with a respective input facet of the photonic integrated
circuit with high precision; mis-alignment of greater than 10
micrometers may significantly reduce the efficiency of the photonic
integrated circuit. An output facet of each laser diode may have
dimensions smaller than four square micrometers; aligning such
small components to such high precision presents a non-trivial
technical challenge.
[0164] In one implementation, each input facet of the photonic
integrate circuit could be written as a grating coupler as shown in
FIG. 6, which increases the tolerances for misalignment.
[0165] In act 916, a collimation lens may be provided such that a
coaxially superimposed beam of light from the output edge of the
photonic integrated circuit will be collimated by the collimation
lens. The collimation lens may optionally optimize the spot (e.g.,
circularize) the coaxially superimposed beam. In some
implementations, more than one collimation lens may be provided if
the light output from the photonic integrated circuit is not a
fully coaxially superimposed beam. The collimation lens or lenses
may be actively aligned after the other components are assembled,
or may be passively aligned such that appropriate alignment is
achieved during assembly.
[0166] As mentioned above, aligning a photonic integrated circuit
such that each input facet of the photonic integrated circuit lines
up with a beam of light emitted by each laser diode with
high-precision presents a non-trivial challenge. The present
systems, devices, and methods provide a solution to this challenge,
by producing photonic integrated circuits where the fabrication
process includes an alignment process, obviating the need for a
later mechanical alignment process, as discussed below with
reference to FIG. 10. Direct laser writing (DLW) as disclosed
herein is a process by which photonic integrated circuits may be
fabricated with high precision that allows for intrinsic
alignment.
[0167] FIG. 10A is a left side sectional view of photonic
integrated circuit writing system 1000a. Photonic integrated
circuit writing system 1000a includes components that may be
substantively similar to components of optical engine 700 and
components of laser writing system 800. Unless context below
dictates otherwise, the disclosure of components in FIG. 7 and FIG.
8 is applicable to similarly numbered components in FIG. 10A and
will not be repeated in the interests of brevity. Photonic
integrated circuit writing system 1000a includes laser writing
system 800, which, during operation, writes a photonic integrated
circuit in a block of writeable glass 820 in a manner similar to
the operation of laser writing system 800 described above with
reference to FIG. 8. Photonic integrated circuit writing system
1000a can be utilized to manufacture an optical engine using a
process that is similar in at least some respects to method 900 of
FIG. 9, but with photonic integrated circuit writing system 1000a,
act 914 can be performed before act 912, as detailed below.
[0168] Writeable glass 820 is bonded to cap 720 prior to writing a
photonic integrated circuit therein, using any of the bonding
techniques discussed above. The writeable glass 820 may comprise a
contiguous piece of glass or similar transparent material that
undergoes a change in refractive index when exposed to
high-intensity laser light. Bonding the writeable glass to the cap
includes positioning and orienting the writeable glass 820 relative
to each laser diode 710 to place the writeable glass 820 in the
path of the beam of light emitted by each laser diode 710, such
that the beam of light emitted by each laser diode 710 impinges on
the writeable glass.
[0169] Writeable glass 820 can be positioned against optical window
730, such that beams of light from laser diodes 710 pass through
optical window 730 directly into writeable glass 820.
Alternatively, the writeable glass 820 may optionally form optical
window 730.
[0170] The entire base substrate 702 and all components bonded
thereto can be physically coupled to translatable mount 830, such
as with clamps 821, adhesives, and/or any other appropriate
coupling mechanism. Such coupling mechanism is preferably
removable, such that base substrate 702 and all components bonded
thereto can be detached from translatable mount 830 after laser
writing of writeable glass 820 is complete.
[0171] With writeable glass 820 bonded to base substrate 702
indirectly via cap 720, and base substrate 702 physically coupled
to translatable mount 830, at least one waveguide 822 can be laser
written into writeable glass 820 by translating base substrate 702
and all components thereon using translatable mount 830. At least
one input facet 612 (for example at least one grating input
coupler) can also be written into writeable glass 820 by
translating base substrate 702 and all components thereon using
translatable mount 830. Consequently, writeable glass 820 becomes a
photonic integrated circuit.
[0172] To determine where the at least one waveguide 822 should be
written, laser diodes 710 could be activated, thus causing beams of
light therefrom to impinge on writeable glass 820. Writing laser
810 can be aligned to directly write waveguides and input facets
(e.g. grating couplers as shown in FIG. 10A) at the exact location
where the beams of light from laser diodes 710 impinge on the
writeable block 820. In this way, the input facets of the resulting
photonic integrated circuit will be accurately aligned with the
laser diodes, ensuring efficient incoupling of the beams of light
into the photonic integrated circuit.
[0173] Alternatively, the writeable glass 820 could be illuminated,
such as by being backlit if base substrate 702 is at least
partially transparent. Writing laser 810 can then be aligned to
directly write waveguides based on locations of shadows caused by
laser diodes 710, CoS's 712 and optical redirector element 718. In
this way, the input facets of the resulting photonic integrated
circuit will be accurately aligned with the laser diodes, ensuring
efficient incoupling of the beams of light into the photonic
integrated circuit.
[0174] Aligning the input facets of the photonic integrated circuit
to the beams of light during the writing stage will be more
accurate than trying to mechanically align a pre-fabricated
photonic integrated circuit, due to deviations that can arise in
the bonding processes of not only the pre-fabricated photonic
integrate circuit, but also the laser diodes. As one example, if
each of four laser diodes is randomly misaligned, it would be
difficult to align a prefabricated photonic integrated circuit to
match the beam of light from each diode, since not only could the
photonic integrated circuit be misaligned during the bonding
processes, but also the spacing between each laser diode may not
match the spacing between each waveguide in the photonic integrated
circuit due to the random misalignment of each of the laser diodes.
Direct laser writing the photonic integrated circuit after all of
the components have been mechanically bonded obviates these issues,
by allowing the position and spacing of each laser diode relative
to the writeable glass to be accounted for after bonding is
complete.
[0175] FIG. 10B is a left side sectional view of photonic
integrated circuit writing system 1000b. Photonic integrated
circuit writing system 1000b includes components that may be
substantively similar to components of photonic integrated circuit
writing system 1000a as discussed with regards to FIG. 10A. Unless
context below dictates otherwise, the disclosure related to
components in FIG. 10A is applicable to similarly numbered
components in FIG. 10B and will not be repeated in the interests of
brevity.
[0176] In FIG. 10B, instead of writing the input facets of the
photonic integrated circuit 600 as grating input couplers, a
reflective surface is instead written to redirect input beams of
light 610 into at least one waveguide 822 of photonic integrated
circuit 600. For example, the at least one reflective surface could
be a planar region with lower index of refraction than the material
from which writeable glass 820 is formed. Consequently, laser light
610 can be redirected by the planar region with lower index of
refraction due to total internal reflection.
[0177] Additionally, FIG. 10B illustrates an implementation in
which at least one laser diode 710 is a vertical-cavity
surface-emitting laser (VCSEL), such that laser light emitted by
the laser diode is directed towards optical window 730 without the
need for an optical redirecting element. Such a laser diode setup
could be implemented in any of the implementations discussed
herein. The implementation of FIG. 10B does not require the use of
a VCSEL, but could instead use a side emitting laser with an
optical redirecting element such as shown in FIGS. 1A and 1B.
[0178] In some implementations, a photonic integrated circuit could
be manufactured using a combination of the techniques described
with reference to FIGS. 8, 9, 10A, and 10B, as discussed below.
[0179] In one example, a large portion of a photonic integrated
circuit could be first written, except for a small portion of the
photonic integrated circuit at the input of writeable glass.
Subsequently, the photonic integrated circuit could be bonded to
the cap such as in FIG. 10, and the remaining small portion of the
photonic integrated circuit at the input of the writeable glass
could be written to couple the output of each laser diode to the
portion of the photonic integrated circuit which is already
written.
[0180] In another example, a first photonic integrated circuit
could be written as in FIG. 8. Subsequently, the first photonic
integrated circuit could be bonded to the cap similar to as in FIG.
7, with the first photonic integrated circuit being offset from the
output of each laser diode such that the output from each laser
diode does not impinge on the first photonic integrated circuit. In
the area in the output path of each laser diode, a block of
writeable glass could be bonded to the cap. Subsequently, a second
photonic integrated circuit could be written in the writeable glass
similar to in FIGS. 10A and 10B to couple the output of each laser
diode to an input edge of the previously written first photonic
integrated circuit. In this example, the block of writeable glass
could be formed as the optical window, and/or could be formed to
cover a portion of the first photonic integrate circuit.
[0181] FIGS. 11A and 11B are isometric views showing
implementations of optical engines having differing positions for a
laser diode driver circuit. The implementations shown in FIGS. 11A
and 11B are similar in at least some respects to the implementation
of FIGS. 1A and 1B, and one skilled in the art will appreciate that
the description regarding FIGS. 1A and 1B is applicable to the
implementations of FIGS. 11A and 11B unless context clearly
dictates otherwise.
[0182] FIG. 11A shows an optical engine 1100a which includes a base
substrate 1102. The base substrate 1102 may be formed from a
material that is radio frequency (RF) compatible and is suitable
for hermetic sealing. For example, the base substrate 1102 may be
formed from low temperature co-fired ceramic (LTCC), aluminum
nitride (AlN), alumina, Kovar.RTM., etc.
[0183] The optical engine 1100a also includes a plurality of laser
diodes aligned in a row across a width of the optical engine 1100a,
including an infrared laser diode 1110a, a red laser diode 1110b, a
green laser diode 1110c, and a blue laser diode 1110d. In
operation, the infrared laser diode 1110a provides infrared laser
light, the red laser diode 1110b provides red laser light, the
green laser diode 1110c provides green laser light, and the blue
laser diode 1110d provides blue laser light. Each of the laser
diodes may comprise one of an edge emitter laser or a
vertical-cavity surface-emitting laser (VCSEL), for example. In
FIG. 11A, laser diodes 1110a, 1110b, 1110c, and 1110d are shown as
being bonded (e.g., attached) directly to base substrate 1102, as
described above with regards to act 504 in FIG. 5, but one skilled
in the art will appreciate that laser diodes 1110a, 1110b, 1110c,
and 1110d could each be mounted on a respective submount, similar
to as in FIGS. 1A and 1B.
[0184] The optical engine 1100a also includes a laser diode driver
circuit 1114 which can be bonded to the same surface of base
substrate 1102 as the laser diodes 1110a, 1110b, 1110c, 1110d. In
alternative implementations, laser diode driver circuit 1114 can be
bonded to a separate base substrate, such as in FIG. 11B discussed
later. The laser diode driver circuit 1114 is operatively coupled
to the plurality of laser diodes 1110a, 1110b, 1110c, and 1110d via
respective electrical connections 1116a, 1116b, 1116c, 1116d to
selectively drive current to the plurality of laser diodes. In at
least some implementations, the laser diode driver circuit 1114 may
be positioned relative to the laser diodes 1110a, 1110b, 1110c, and
1110d to minimize the distance between the laser diode driver
circuit 1114 and the laser diodes. Although not shown in FIG. 11A,
the laser diode driver circuit 1114 may be operatively coupleable
to a controller (e.g., microcontroller, microprocessor, ASIC) which
controls the operation of the laser diode driver circuit 1114 to
selectively modulate laser light emitted by the laser diodes 1110a,
1110b, 1110c, and 1110d. In at least some implementations, the
laser diode driver circuit 1114 may be bonded to another portion of
the base substrate 1102, such as the bottom surface of the base
substrate 1102. In at least some implementations, the laser diode
driver circuitry 1114 may be remotely located and operatively
coupled to the laser diodes 1110a, 1110b, 1110c, and 1110d. In
order to not require the use of impedance matched transmission
lines, the size scale may be small compared to a wavelength (e.g.,
lumped element regime), where the electrical characteristics are
described by (lumped) elements like resistance, inductance, and
capacitance.
[0185] Proximate the laser diodes 1110a, 1110b, 1110c, and 1110d
there is positioned an optical director element 1118. Like the
laser diodes 1110a, 1110b, 1110c, and 1110d, the optical director
element 1118 is bonded to the top surface of the base substrate
1102. The optical director element 1118 may be bonded proximate to
or adjacent each of the laser diodes 1110a, 1110b, 1110c, and
1110d. In the illustrated example, the optical director element
1118 has a triangular prism shape that includes a plurality of
planar faces, similar to optical director element 118 in FIGS. 1A
and 1B. The optical director element 1118 may comprise a mirror or
a prism, for example.
[0186] The optical engine 1100a also includes a cap 1120 similar to
cap 120 in FIGS. 1A and 1B. For clarity, cap 1120 is shown as being
transparent in FIG. 11A, though this is not necessarily the case,
and cap 1120 can be at least partially formed of an opaque
material. Cap 1120 includes a horizontal optical window 1130 that
forms the "top" of the cap 1120. Although optical window 1130 in
FIG. 11A is shown as comprising the entire top of cap 1120, in
alternative implementations optical window could comprise only a
portion of the top of cap 1120. Cap 1120 including optical window
1130 defines an interior volume sized and dimensioned to receive
the plurality of laser diodes 1110a, 1110b, 1110c, 1110d, and the
optical director element 1118. Cap 1120 is bonded to the base
substrate 1102 to provide a hermetic or partially hermetic seal
between the interior volume of the cap 1120 and a volume exterior
to the cap 1120.
[0187] The optical director element 1118 is positioned and oriented
to direct (e.g., reflect) laser light received from each of the
plurality of laser diodes 1110a, 1110b, 1110c, and 1110d upward
toward the optical window 1130 of the cap 1120, wherein the laser
light exits the interior volume, similar to FIGS. 1A and 1B.
[0188] The cap 1120 may have a round shape, rectangular shape, or
other shape, similarly to as described regarding FIGS. 1A and 1B
above. The optical window 1130 may comprise an entire top of the
cap 1120, or may comprise only a portion thereof. In at least some
implementations, the optical window 1130 may be located on a
sidewall of cap 1120 rather than positioned as a top of the cap
1120, and the laser diodes 1110a, 1110b, 1110c, 1110d and/or the
optical director element 1118 may be positioned and oriented to
direct the laser light from the laser diodes toward the optical
window on the sidewall. In at least some implementations, the laser
diodes 1110a, 1110b, 1110c, and 1110d may be positioned and
oriented to direct the laser light from the laser diode toward the
optical window on the sidewall without optical director element
1118. In at least some implementations, the cap 1120 may include a
plurality of optical windows instead of a single optical
window.
[0189] The optical engine 1100a can also include four
collimation/pointing lenses similarly to as discussed regarding
FIGS. 1A and 1B above and FIGS. 12A and 12B below. Each of the
collimation lenses can be operative to receive laser light from a
respective one of the laser diodes 1110a, 1110b, 1110c, or 1110d,
and to generate a single color beam.
[0190] The optical engine 1100a may also include, or may be
positioned proximate to, a beam combiner that is positioned and
oriented to combine the light beams received from each of the
collimation lenses or laser diodes 1110a, 1110b, 1110c, or 1110d
into a single aggregate beam. As an example, the beam combiner may
include one or more diffractive optical elements (DOE) and/or one
or more refractive/reflective optical elements that combine the
different color beams in order to achieve coaxial superposition.
Exemplary beam combiners are shown and discussed with reference to
FIGS. 3, 12A, 12B, and 12C.
[0191] In at least some implementations, the laser diodes 1110a,
1110b, 1110c, 1110d, the optical director element 1118, and/or the
collimation lenses may be positioned differently. As noted above,
laser diode driver circuit 1114 may be mounted on a top surface or
a bottom surface of the base substrate 1102, depending on the RF
design and other constraints (e.g., package size). In at least some
implementations, the optical engine 1100a may not include the
optical director element 1118, and the laser light may be directed
from the laser diodes 1110a, 1110b, 1110c, and 1110d toward
collimation lenses without requiring an intermediate optical
director element, such as illustrated in FIGS. 12A and 12B.
Additionally, in at least some implementations, one or more of the
laser diodes may be mounted indirectly on the base substrate 1102
with a submount.
[0192] Optical engine 1100a in FIG. 11A also includes an
electrically insulating cover 1140. In FIG. 11A, laser diodes
1110a, 1110b, 1110c, and 1110d are each connected to laser diode
driver circuitry 1114 by a respective electrical connection 1116a,
1116b, 1116c, or 1116d positioned as described above with regards
to act 508 in FIG. 5. Electrical connections 1116a, 1116b, 1116c,
and 1116d run across a surface of the base substrate 1102. As
described above with regards to act 510 in FIG. 5, electrically
insulating cover 1140 is placed, adhered, formed, or otherwise
positioned over electrical connections 1116a, 1116b, 1116c, and
1116d, such that each of the electrical connections 1116a, 1116b,
1116c, and 1116d run through electrically insulating cover 1140.
Also as described above with regards to act 510 in FIG. 5, cap 1120
is placed, adhered, formed, or otherwise positioned over
electrically insulating cover 1140, such that cap 1120 does not
contact any of the electrical connections 1116a, 1116b, 1116c, or
1116d. For clarity, cap 1120 is shown as being transparent in FIG.
11A, though this is not necessarily the case, and cap 1120 can be
at least partially formed of an opaque material. Electrically
insulating cover 1140 can be formed of a material with low
electrical permittivity such as a ceramic, such that electrical
signals which run through electrical connections 1116a, 1116b,
1116c, and 1116d do not run into or through electrically insulating
cover 1140. In this way, electrical signals which run through
electrical connections 1116a, 1116b, 1116c, and 1116d can be
prevented from running into or through cap 1120, which can be
formed of an electrically conductive material. Although FIG. 11A
shows electrically insulating cover 1140 as extending along only
part of a side of cap 1120, one skilled in the art will appreciate
that electrically insulating cover 1140 can extend along an entire
side length of cap 1120.
[0193] One skilled in the art will appreciate that the positions of
laser diode driver circuitry 1114, electrical connections 1116a,
1116b, 1116c, 1116d, and electrically insulating cover 1140 as
shown in FIG. 11A could also be applied in other implementations of
the subject systems, devices and methods. For example, in the
implementations of FIGS. 1A and 1B, laser diode driver circuitry
114 could be positioned on top surface 104 of base substrate 102,
and electrical connections 116 could run across top surface 104
under an electrically insulating cover, such that electrical
connections 116 do not contact any conductive portion of cap
120.
[0194] FIG. 11B is an isometric view an optical engine 1100b
similar in at least some respects to optical engine 1100a of FIG.
11A. One skilled in the art will appreciate that the description of
optical engine 1100a in FIG. 11A is applicable to optical engine
1100b in FIG. 11B, unless context clearly dictates otherwise. The
optical engine 1100b includes a base substrate 1103a. Similar to
base substrate 1102 in FIG. 11A, base substrate 1103a may be formed
from a material that is radio frequency (RF) compatible and is
suitable for hermetic sealing. For example, the base substrate
1103a may be formed from low temperature co-fired ceramic (LTCC),
alumina, Kovar.RTM., etc.
[0195] One difference between optical engine 1100b in FIG. 11B and
optical engine 1100a in FIG. 11A relates to what components are
bonded (e.g. attached) to base substrate 1103a. In optical engine
1100b, each of: laser diodes 1110a, 1110b, 1110c, 1110d; cap 1120;
electrical connections 1116a, 1116b, 1116c, 1116d; and electrically
insulating cover 1140 are bonded (e.g., attached) to base substrate
1103a. However, laser diode driver circuit 1114 is not necessarily
bonded directly to base substrate 1103a. Instead, laser diode
driver circuit 1114 could be bonded to a separate base substrate
1103b. Similar to base substrate 1102 in FIG. 11A and base
substrate 1103a in FIG. 11B, base substrate 1103b may be formed
from a material that is radio frequency (RF) compatible and is
suitable for hermetic sealing. For example, the base substrate
1103b may be formed from low temperature co-fired ceramic (LTCC),
alumina, Kovar.RTM., etc. In an alternative implementation, laser
diode drive circuit 1114 may not need to be bonded to a substrate
at all, and could simply be mounted directly within a frame of a
WHUD.
[0196] For implementations where laser diode drive circuit 1114 is
not bonded to base substrate 1103a, electrical contacts 1117a,
1117b, 1117c, and 1117d could be bonded to base substrate 1103a,
each at an end of a respective electrical connection 1116a, 1116b,
1116c, or 1116d as described above with regards to act 508 in FIG.
5. In this way, electrical contacts 1117a, 1117b, 1117c, and 1117d
could be used to electrically couple laser diode drive circuit 1114
to electrical connections 1116a, 1116b, 1116c, and 1116d and
consequently laser diodes 1110a, 1110b, 1110c, and 1110d.
[0197] In some implementations, an optical engine similar to
optical engine 700 may include a beam combiner 316 as described
with regards to FIG. 3 in place of photonic integrated circuit 600.
FIG. 12A illustrates an exemplary optical engine 1200a in this
regard.
[0198] FIG. 12A is a side sectional view of optical engine 1200a.
The optical engine 1200 includes several components that may be
similar or identical to the components of the optical engine 100 of
FIGS. 1A and 1B and/or the optical engine 700 of FIG. 7. Thus, some
or all of the discussion above may be applicable to the optical
engine 1200a.
[0199] The optical engine 1200a includes a base substrate 1202. The
base substrate 1202 may be formed from a material that is radio
frequency (RF) compatible and is suitable for hermetic sealing. For
example, the base substrate 1202 may be formed from low temperature
co-fired ceramic (LTCC), aluminum nitride (AlN), alumina,
Kovar.RTM., etc.
[0200] The optical engine 1200a also includes a plurality of laser
diodes 1210a, 1210b, 1210c, 1210d bonded thereto. The plurality of
laser diodes could include an infrared laser diode 1210d which
provides infrared laser light 1238d, a red laser diode 1210a which
provides red laser light 1238a, a green laser diode 1210b which
provides green laser light 1238b, and a blue laser diode 1210c
which provides blue laser light 1238c. Each of the laser diodes
1210a, 1210b, 1210c, and 1210d may comprise one of an edge emitter
laser or a vertical-cavity surface-emitting laser (VCSEL), for
example. For ease of illustration, each of the laser diodes in FIG.
12A is shown as a VCSEL, but it is within the scope of the present
systems, devices, and methods to use an edge emitting laser and an
optical redirector element such as shown in FIGS. 1A and 1B
instead. For clarity, each of the laser diodes is shown as being
bonded directly to base substrate 1202, but in some implementations
each laser diode could be bonded to a respective submount that is
bonded to the base substrate 1202. The plurality of laser diodes
1210a, 1210b, 1210c, and 1210d are aligned in a row across a width
of the optical engine 1200a between the left and right sides
thereof.
[0201] Although not explicitly shown in FIG. 12A, the optical
engine 1200a can include a laser diode driver circuit which
selectively drives each of the laser diodes. Such a laser diode
driver circuit can be bonded to a top surface of base substrate
1202 similar to as in FIG. 11A, bonded to another portion of the
base substrate 1202 such as a bottom surface of the base substrate
1202 similar to in FIGS. 1A, 1B and 7, or separate from the base
substrate 1202 similar to in FIG. 11B. Such a laser diode driver
circuit may be operatively coupleable to a controller (e.g.,
microcontroller, microprocessor, ASIC) that controls the operation
of the laser diode driver circuit to selectively modulate laser
light emitted by the laser diodes 1210a, 1210b, 1210c, and 1210d.
In at least some implementations, the laser diode driver circuitry
may be remotely located and operatively coupled to the laser diodes
1210a, 1210b, 1210c, and 1210d. In order to not require the use of
impedance matched transmission lines, the size scale may be small
compared to a wavelength (e.g., lumped element regime), where the
electrical characteristics are described by (lumped) elements like
resistance, inductance, and capacitance.
[0202] The optical engine 1200a also includes a cap 1220, which can
be similar to cap 720 as discussed regarding FIG. 7. Within a
portion of the cap 1220 there is an optical window 1230 positioned
proximate the laser diodes 1210a, 1210b, 1210c, and 1210d to pass
light therefrom out of the cap 1220. The cap 1220 and optical
window 1230 define an interior volume 1232 sized and dimensioned to
receive the plurality of laser diodes 1210a, 1210b, 1210c, and
1210d. Cap 1220 is bonded to the base substrate 1202 to provide a
hermetic seal or a partial hermetic seal between the interior
volume 1232 of the cap and a volume exterior to the cap.
[0203] The cap 1220 may have a round shape, rectangular shape, or
other shape. The optical window 1230 may comprise an entire side of
the cap 1220, or may comprise only a portion thereof. In at least
some implementations, the cap 1220 may include a plurality of
optical windows instead of a single optical window 1230.
[0204] The optical engine 1200a can include four
collimation/pointing lenses 1236a, 1236b, 1236c, and 1236d, one for
each respective laser diode 1210a, 1210b, 1210c, and 1210d. Each of
the plurality of collimation lenses 1236a, 1236b, 1236c, and 1236d
can be positioned and oriented to receive light from a
corresponding one of the laser diodes 1210a, 1210b, 1210c, and
1210d through the optical window 1230. In some implementations,
each of the collimation lenses can be bonded to optical window
1230. In other implementations, the optical window 1230 can be
formed to include each of the collimation lenses.
[0205] The collimation lenses 1236a, 1236b, 1236c, and 1236d couple
the respective beams of light 1238a, 1238b, 1238c, and 1238d into
respective optical elements 328, 330, 332, and 334 of a beam
combiner 316. Beam combiner 316 in FIG. 12A could be similar to
beam combiner 316 illustrated in FIG. 3, such that the description
regarding FIG. 3 can be applicable to the beam combiner 316 in FIG.
12A. The beam combiner 316 may be bonded to the collimation lenses
1236a, 1236b, 1236c, and 1236d. As discussed above regarding FIG.
3, in operation, beam combiner 316 receives a plurality of beams of
light 1238a, 1238b, 1238c, and 1238d and combines the plurality of
beams to provide a coaxially superimposed aggregate beam of light
336.
[0206] In at least some implementations, at least some of the
components may be positioned differently. As noted above, the laser
diode driver circuit 1214 may be mounted on a top surface or a
bottom surface of the base substrate 1202, or may be positioned
remotely therefrom, depending on the RF design and other
constraints (e.g., package size). In at least some implementations,
the optical engine 1200a may include an optical director element
(e.g., optical director element 118 of FIG. 1), and the laser light
may be directed from the laser diodes 1210a, 1210b, 1210c, and
1210d toward the collimation lenses 1236a, 1236b, 1236c, 1236d via
an intermediate optical director element.
[0207] Even though FIG. 12A shows a gap between the collimation
lenses and the optical window 1230, it is within the scope of the
present systems, devices, and methods to bond the collimation
lenses directly to the optical window 1230, or to form the
collimation lenses as part of the optical window 1230. Further,
even though FIG. 12A shows a gap between the collimation lenses and
the beam combiner 316, it is within the scope of the present
systems, devices, and methods to bond the collimation lenses
directly to beam combiner 316, or to form beam combiner 316 and the
collimation lenses together as a single element.
[0208] For the sake of a controlled atmosphere inside the interior
volume 1232, it may be desirable to have no organic compounds
inside the interior volume 1232. In at least some implementations,
the components of the optical engine 1200a may be bonded together
using no adhesives. In other implementations, a low amount of
adhesives may be used to bond at least one of the components, which
may reduce cost while providing a relatively low risk of organic
contamination for a determined lifetime (e.g., 2 or more years) of
the optical engine 1200a. Similarly to as detailed above regarding
FIGS. 1A and 1B, partial hermeticity, a particulate dust cover, or
even no protective cover may be acceptable for certain
applications. Various bonding processes (e.g., attaching processes)
for the optical engine 1200a are discussed above with reference to
FIG. 5.
[0209] Due to the divergent beam from each of the laser diodes
1210a, 1210b, 1210c, and 1210d and the lateral distances between
the laser diodes, the collimation lenses 1236a, 1236b, 1236c, and
1236d, and the beam combiner 316, it may be advantageous to
minimize a distance between the respective output facets of the
laser diodes 1210a, 1210b, 1210c, and 1210d and the optical window
1230. For the same reason, it may be advantageous to minimize the
thickness of the optical window 1230 so that the collimation lenses
1236a, 1236b, 1236c, and 1236d can be positioned relatively close
to the output facets of the laser diodes 1210a, 1210b, 1210c, and
1210d.
[0210] In at least some implementations, the collimation lenses
1236a, 1236b, 1236c, and 1236d may be actively aligned. In at least
some implementations, the laser diodes 1210a, 1210b, 1210c, and
1201d, the cap 1220 (including optical window 1230), and/or the
beam combiner 316 may be passively aligned.
[0211] FIGS. 12B and 12C illustrate alternative implementations of
the optical engine 1200a shown in FIG. 12A. One skilled in the art
will appreciate that, unless context clearly dictates otherwise,
the description of FIG. 12A is applicable to the implementations of
FIGS. 12B and 12C.
[0212] FIG. 12B is a side sectional view of an optical engine 1200b
similar to optical engine 1200a of FIG. 12A. Optical engine 1200b
includes a beam combiner 317 which is similar to beam combiner 316
as shown in FIG. 12A, but bigger in size relative to the other
components of FIG. 12B. Beam combiner 317 functions to produce an
aggregate beam 337 in a similar manner to how beam combiner 316
produces aggregate beam 336 as disclosed regarding FIGS. 3A and 3B,
such that the descriptions throughout this application pertaining
to beam combiner 316 are applicable to beam combiner 317. Further,
the descriptions pertaining to optical elements 328, 330, 332, and
334 of beam combiner 316 are applicable to optical elements 329,
331, 333, and 335 of beam combiner 317.
[0213] In optical engine 1200b of FIG. 12B, beam combiner 317 is
large in size relative to the other components of the FIG. 12B,
such that each light beam 1238a, 1238b, 1238c, and 1238d does not
line up directly with a respective optical element 329, 331, 333,
and 335. To address this issue, at least one of collimation lens
1236a, 1236b, 1236c, and 1236d can be aligned to redirect a
respective light beam 1238a, 1238b, 1238c, or 1238d towards a
respective optical element 329, 331, 333, or 335. As an example, at
least one collimation lens 1236a, 1236b, 1236c, or 1236d could be
rotated with respect to a respective beam of light 1238a, 1238b,
1238c, or 1238d. As another example, at least one collimation lens
1236a, 1236b, 1236c, and 1236d could be formed in a skewed shape
which redirects a respective beam of light 1238a, 1238b, 1238c, or
1238d appropriately. As another example, at least one collimation
lens 1236a, 1236b, 1236c, or 1236d could include a waveguide, or be
formed as a waveguide, to redirect a respective beam of light
1238a, 1238b, 1238c, or 1238d. Even though FIG. 12B shows a gap
between the collimation lenses and the optical window 1230, it is
within the scope of the present systems, devices, and methods to
bond the collimation lenses directly to the optical window 1230, or
to form the collimation lenses as part of the optical window 1230.
Further, even though FIG. 12B shows a gap between the collimation
lenses and the beam combiner 317, it is within the scope of the
present systems, devices, and methods to bond the collimation
lenses directly to beam combiner 317, or to form beam combiner 317
and the collimation lenses together as a single element.
[0214] FIG. 12C is a side sectional view of an optical engine 1200c
similar to optical engine 1200a of FIG. 12A and optical engine
1200b of FIG. 12B. Optical engine 1200c includes a collimation lens
1237 positioned near an output side of beam combiner 316. In one
implementation, collimation lens 1237 could replace collimation
lenses 1236a, 1236b, 1236c, and 1236d, such that uncollimated beams
of light 1238a, 1238b, 1238c, and 1238d enter beam combiner 316,
and collimation lens 1237 collimates aggregate beam 336 output from
beam combiner 316. In another implementation, collimation lens 1237
could be in addition to collimation lenses 1236a, 1236b, 1236c, and
1236d, such that roughly collimated or partially collimated beams
of light 1238a, 1238b, 1238c, and 1238d enter beam combiner 316,
and collimation lens 1237 fully collimates and/or corrects
aggregate beam 336 output from beam combiner 316.
[0215] Throughout this application, collimation lenses have been
represented in the Figures by a simple curved lens shape. However,
the subject systems, devices, and methods can utilize more advanced
collimation schemes, as appropriate for a given application.
[0216] FIG. 13 shows an exemplary situation where using an advanced
collimation scheme would be helpful. FIG. 13 is an isometric view
of a laser diode 1300. The laser diode 1300 may be similar or
identical to the various laser diodes discussed herein. The laser
diode 1300 outputs a laser light beam 1302 via an output facet 1304
of the laser diode. FIG. 13 shows the divergence of the light 1302
emitting from the laser diode 1300. As shown, the light beam 1302
may diverge by a substantial amount along a fast axis 1306 (or
perpendicular axis) and by a lesser amount in the slow axis 1308
(parallel axis). As a non-limiting example, in at least some
implementations, the light beam 1302 may diverge with full width
half maximum (FWHM) angles of up to 40 degrees in the fast axis
direction 1306 and up to 10 degrees in the slow axis direction
1308. This divergence results in a rapidly expanding elliptical
cone.
[0217] FIGS. 14A and 14B show an exemplary collimation scheme that
can be used to circularize and collimate an elliptical beam such as
that shown in FIG. 13. FIG. 14A illustrates an orthogonal view of
the fast axis 1306 of light beam 1302 emitted from laser diode
1300. FIG. 14B illustrates an orthogonal view of the slow axis 1308
of light beam 1302 emitted from laser diode 1300. As shown in FIG.
14A, a first lens 1400 collimates light beam 1302 along fast axis
1306. As shown in FIG. 14B, first lens 1400 is shaped so as to not
substantially influence light beam 1302 along slow axis 1308.
Subsequently, as shown in FIG. 14B, light beam 1302 is collimated
along slow axis 1308 by a second lens 1402. As shown in FIG. 14A,
second lens 1402 is shaped so as to not substantially influence
light beam 1302 along fast axis 1306. In essence, light beam 1302
is collimated along fast axis 1306 separately from slow axis 1308.
By collimating light beam 1302 along fast axis 1306 separately from
slow axis 1308, the collimation power applied to each axis can be
independently controlled by controlling the power of lens 1400 and
lens 1402 separately. Further, spacing between each of laser diode
1300, lens 1400, and lens 1402 can be controlled to collimate light
beam 1302 to a certain width in each axis separately. If light beam
1302 is collimated along fast axis 1306 to the same width as slow
axis 1308, light beam 1302 can be circularized. Because light beam
1302 will typically diverge faster in the fast axis 1306, it is
generally preferable to collimate light beam 1302 along fast axis
1306 first, then collimate light beam 1302 along slow axis 1308
after. However, it is possible in certain applications to collimate
light beam 1302 along slow axis 1308 first, and subsequently
collimate light beam 1302 along fast axis 1306 after. This can be
achieved by reversing the order of first lens 1400 with second lens
1402, with respect to the path of travel of light beam 1302.
[0218] FIGS. 14C and 14D are isometric views which illustrate
exemplary shapes for lenses 1400 and 1402. Each of lens 1400 and
1402 can be for example a half-cylinder as in FIG. 14C, a full
cylinder as in FIG. 14D, a quarter cylinder, a three-quarter
cylinder, any other partial cylinder, or any other appropriate
shape. Lenses 1400 and 1402 can be similarly shaped, or can have
different shapes.
[0219] FIGS. 15A and 15B illustrate an alternative collimation
scheme. FIG. 15A illustrates an orthogonal view of the fast axis
1306 of light beam 1302 emitted from laser diode 1300. FIG. 15B
illustrates an orthogonal view of the slow axis 1308 of light beam
1302 emitted from laser diode 1300. As shown in FIG. 15A, a first
lens 1500 redirects light beam 1302 along fast axis 1306, to reduce
divergence of light beam 1302 along fast axis 1306. As shown in
FIG. 15B, first lens 1500 is shaped so as to not substantially
influence light beam 1302 along slow axis 1308. Preferably, first
lens 1500 will reduce divergence of light beam 1302 along fast axis
1306 to match divergence of light beam 1302 along slow axis 1308.
That is, first lens 1500 preferably circularizes light beam 1302.
Subsequently, as shown in FIGS. 15A and 15B, light beam 1302 is
collimated along both fast axis 1306 and slow axis 1308 by a second
lens 1502. As shown in FIGS. 15A and 15B, second lens 1502 is
shaped similarly with respect to both the fast axis 1306 and the
slow axis 1308, to evenly collimate light beam 1302. In essence,
first lens 1500 circularizes light beam 1302, and subsequently
second lens 1502 collimates light beam 1302 along both axes. First
lens 1500 can for example be shaped similarly to lens 1400 or lens
1402 discussed above, and shown in FIGS. 14C and 14D. Second lens
1502 can for example be shaped as a double convex lens as
illustrated in FIG. 15C, or a single convex lens (convex on either
side) as illustrated in FIG. 15D, or any other appropriate shape of
collimating lens.
[0220] The collimation schemes illustrated in FIGS. 14A-14D and
15A-15D, and discussed above could be used in place of any of the
collimation lenses described herein, including at least collimation
lenses 136a, 136b, 136c, 136d.
[0221] A person of skill in the art will appreciate that the
teachings of the present systems, methods, and devices may be
modified and/or applied in additional applications beyond the
specific WHUD implementations described herein. In some
implementations, one or more optical fiber(s) may be used to guide
light signals along some of the paths illustrated herein.
[0222] The WHUDs described herein may include one or more sensor(s)
(e.g., microphone, camera, thermometer, compass, altimeter, and/or
others) for collecting data from the user's environment. For
example, one or more camera(s) may be used to provide feedback to
the processor of the WHUD and influence where on the display(s) any
given image should be displayed.
[0223] The WHUDs described herein may include one or more on-board
power sources (e.g., one or more battery(ies)), a wireless
transceiver for sending/receiving wireless communications, and/or a
tethered connector port for coupling to a computer and/or charging
the one or more on-board power source(s).
[0224] The above description of illustrated embodiments, including
what is described in the Abstract, is not intended to be exhaustive
or to limit the embodiments to the precise forms disclosed.
Although specific embodiments of and examples are described herein
for illustrative purposes, various equivalent modifications can be
made without departing from the spirit and scope of the disclosure,
as will be recognized by those skilled in the relevant art. The
teachings provided herein of the various embodiments can be applied
to other portable and/or wearable electronic devices, not
necessarily the exemplary wearable electronic devices generally
described above.
[0225] For instance, the foregoing detailed description has set
forth various embodiments of the devices and/or processes via the
use of block diagrams, schematics, and examples. Insofar as such
block diagrams, schematics, and examples contain one or more
functions and/or operations, it will be understood by those skilled
in the art that each function and/or operation within such block
diagrams, flowcharts, or examples can be implemented, individually
and/or collectively, by a wide range of hardware, software,
firmware, or virtually any combination thereof. In one embodiment,
the present subject matter may be implemented via Application
Specific Integrated Circuits (ASICs). However, those skilled in the
art will recognize that the embodiments disclosed herein, in whole
or in part, can be equivalently implemented in standard integrated
circuits, as one or more computer programs executed by one or more
computers (e.g., as one or more programs running on one or more
computer systems), as one or more programs executed by on one or
more controllers (e.g., microcontrollers) as one or more programs
executed by one or more processors (e.g., microprocessors, central
processing units, graphical processing units), as firmware, or as
virtually any combination thereof, and that designing the circuitry
and/or writing the code for the software and or firmware would be
well within the skill of one of ordinary skill in the art in light
of the teachings of this disclosure. When logic is implemented as
software and stored in memory, logic or information can be stored
on any processor-readable medium for use by or in connection with
any processor-related system or method. In the context of this
disclosure, a memory is a processor-readable medium that is an
electronic, magnetic, optical, or other physical device or means
that contains or stores a computer and/or processor program. Logic
and/or the information can be embodied in any processor-readable
medium for use by or in connection with an instruction execution
system, apparatus, or device, such as a computer-based system,
processor-containing system, or other system that can fetch the
instructions from the instruction execution system, apparatus, or
device and execute the instructions associated with logic and/or
information.
[0226] In the context of this specification, a "non-transitory
processor-readable medium" can be any element that can store the
program associated with logic and/or information for use by or in
connection with the instruction execution system, apparatus, and/or
device. The processor-readable medium can be, for example, but is
not limited to, an electronic, magnetic, optical, electromagnetic,
infrared, or semiconductor system, apparatus or device. More
specific examples (a non-exhaustive list) of the computer readable
medium would include the following: a portable computer diskette
(magnetic, compact flash card, secure digital, or the like), a
random access memory (RAM), a read-only memory (ROM), an erasable
programmable read-only memory (EPROM, EEPROM, or Flash memory), a
portable compact disc read-only memory (CDROM), digital tape, and
other non-transitory media.
[0227] The various embodiments described above can be combined to
provide further embodiments. To the extent that they are not
inconsistent with the specific teachings and definitions herein, at
least the following are incorporated herein by reference in their
entirety: U.S. Provisional Patent Application Ser. No. 62/438,725,
U.S. Non-Provisional patent application Ser. No. 15/848,265 (U.S.
Publication Number 2018/0180885), U.S. Non-Provisional patent
application Ser. No. 15/848,388 (U.S. Publication Number
2018/0180886), U.S. Provisional Patent Application Ser. No.
62/450,218, U.S. Non-Provisional patent application Ser. No.
15/852,188 (U.S. Publication Number 2018/0210215), U.S.
Non-Provisional patent application Ser. No. 15/852,282, (U.S.
Publication Number 2018/0210213), U.S. Non-Provisional patent
application Ser. No. 15/852,205 (U.S. Publication Number
2018/0210216), U.S. Provisional Patent Application Ser. No.
62/575,677, U.S. Provisional Patent Application Ser. No.
62/591,550, U.S. Provisional Patent Application Ser. No.
62/597,294, U.S. Provisional Patent Application Ser. No.
62/608,749, U.S. Provisional Patent Application Ser. No.
62/609,870, U.S. Provisional Patent Application Ser. No.
62/591,030, U.S. Provisional Patent Application Ser. No.
62/620,600, U.S. Provisional Patent Application Ser. No.
62/576,962, U.S. Provisional Patent Application Ser. No.
62/760,835, U.S. Non-Provisional patent application Ser. No.
16/201,664, U.S. Non-Provisional patent application Ser. No.
16/168,690, U.S. Non-Provisional patent application Ser. No.
16/171,206, U.S. Non-Provisional patent application Ser. No.
16/203,221, and/or PCT Patent Application PCT/CA2018051344. Aspects
of the embodiments can be modified, if necessary, to employ
systems, circuits and concepts of the various patents, applications
and publications to provide yet further embodiments.
[0228] These and other changes can be made to the embodiments in
light of the above-detailed description. In general, in the
following claims, the terms used should not be construed to limit
the claims to the specific embodiments disclosed in the
specification and the claims, but should be construed to include
all possible embodiments along with the full scope of equivalents
to which such claims are entitled. Accordingly, the claims are not
limited by the disclosure.
* * * * *