U.S. patent application number 09/733049 was filed with the patent office on 2002-06-13 for micro-alignment of optical components.
Invention is credited to Musk, Robert W..
Application Number | 20020071638 09/733049 |
Document ID | / |
Family ID | 24946015 |
Filed Date | 2002-06-13 |
United States Patent
Application |
20020071638 |
Kind Code |
A1 |
Musk, Robert W. |
June 13, 2002 |
Micro-alignment of optical components
Abstract
An assembly for aligning at least one optical component with
respect to a light path is described. This assembly includes a
substrate having at least one integrally formed, flexural member
defined by one portion of the substrate and a primary substrate
portion defined by another portion of the substrate. The flexural
member includes a component mounting area such that the optical
component is mountable thereon and, when the optical component is
so mounted, the optical component is movably alignable in the light
path by displacement of the component mounting area of the flexural
member relative to the primary substrate portion.
Inventors: |
Musk, Robert W.; (Kingston,
GB) |
Correspondence
Address: |
LACASSE & ASSOCIATES, LLC
1725 DUKE STREET
SUITE 650
ALEXANDRIA
VA
22314
US
|
Family ID: |
24946015 |
Appl. No.: |
09/733049 |
Filed: |
December 11, 2000 |
Current U.S.
Class: |
385/52 ; 385/49;
385/90 |
Current CPC
Class: |
G02B 6/4237 20130101;
G02B 6/4226 20130101 |
Class at
Publication: |
385/52 ; 385/49;
385/90 |
International
Class: |
G02B 006/42 |
Claims
What we claim is:
1. A device for aligning a first optical component on a substrate
with a second optical component comprising: arm means pivotally
connected to said substrate, said arm means being pivotable in
every direction; holding means for connecting the first optical
component to said arm means; and actuator interface means on said
arm means enabling manipulation of said arm means by an
actuator.
2. The device according to claim 1, wherein said arm means includes
spring means connecting said arms means to the substrate.
3. The device according to claim 2, wherein said arm means extends
into a cavity in the substrate, forming a groove around most of
said arm means.
4. The device according to claim 3, wherein said spring means is a
baffle spring extending from and contiguous with a side wall of the
cavity.
5. The device according to claim 2, wherein said spring means is a
flat spiral spring, surrounding said holding means.
6. The device according to claim 2, further comprising laser
glazing means for applying a laser glaze across a portion of said
spring means and the substrate to prevent relative movement
thereof.
7. The device according to claim 3, wherein said arm means is
formed in the substrate by an etching process.
8. The device according to claim 1, further comprising fixing means
for securing said arm means to the substrate after the first
component has been aligned with the second component.
9. The device according to claim 8, further comprising first
metallic pads on the substrate, and second metallic pads on said
arm means adjacent said first metallic pads; wherein said fixing
means includes welding means for welding said first metallic pads
to said second metallic pads.
10. The device according to claim 8, wherein said fixing means
comprises welding means for welding said arm means to the
substrate.
11. The device according to claim 8, wherein said fixing means
includes adhesive applicator means for injecting adhesive between
said arm means and the substrate.
12. The device according to claim 8, wherein recessed areas in
edges of said arm means and recessed areas in the substrate, which
are adjacent to the recessed areas in said arm means, form
depressions; and wherein said fixing means includes melting means
for melting glass pre-forms in the depressions to bond said arm
means to the substrate.
13. The device according to claim 1, further comprising an actuator
for engaging said actuator interface means to adjust the position
of said arm means.
14. The device according to claim 13, wherein the actuator includes
opposing bases on the substrate and on said arm means, whereby a
force is applied from the base on said substrate to the base on
said arm means, and wherein the force is of the kind selected from
the group consisting of electromechanical, electrostatic, magnetic,
and thermally induced.
15. A method for aligning a first optical component on a substrate
with a second optical component comprising the steps of: providing
arms means pivotally connected to the substrate, said arm means
having holding means for connecting the optical component thereto,
and actuator interface means enabling manipulation of said arm
means by an actuator; aligning the first optical component with the
second optical component using the actuator to manipulate the
position of said arm means; and fixing said arm means to the
substrate when the first optical component is aligned with the
second optical component.
16. The method according to claim 15, wherein in said aligning step
the actuator applies a force to said arm means, and wherein said
force is of the type selected from the group consisting of
magnetic, electrostatic, electromechanical, and thermally
induced.
17. The method according to claim 15, wherein said fixing step
includes a fixing technique selected from the group consisting of
laser welding the substrate directly to said arm means, welding a
metallic pad secured to the substrate to a metallic pad secured to
said arm means, and adhering said arm means to the substrate using
a suitable adhesive.
18. The method according to claim 15, wherein the providing step
includes etching said arm means from the substrate; and wherein
said arm means includes spring means, integrally connecting said
arm means to the substrate.
19. The method according to claim 18, wherein said spring means is
a baffle spring or a spiral spring.
20. The method according to claim 18, further comprising separating
said spring means from the rest of said arm means after said fixing
step.
Description
BACKGROUND OF THE INVENTION
[0001] Recent developments in optical communication systems have
given rise to miniaturized optical devices that include very small
optical components, most of which must be aligned to micron-scale
tolerances. For example, in an optical transmitter for optical
communications, the output from a light source, such as a laser
diode chip, is focused through a lens and coupled into an optical
fiber. If a single mode fiber is used in this exemplary optical
transmitter, a displacement of the optical fiber by one micron from
the ideal aligned position with respect to the laser diode and lens
may result in a 50% or more reduction in the optical intensity
coupled into the optical fiber. Therefore, the precise alignment of
optical components within the miniaturized optical devices is
crucial. Furthermore, once the optical components are aligned with
respect to each other, it must be possible to secure the optical
components in their aligned positions.
[0002] Currently, several techniques are available in the alignment
and affixation of optical components in miniaturized optical
devices. For instance, the optical components may be manually moved
into position then fixed onto a mounting pad by using an adhesive
or by laser welding, in the case of metalized optical components
or, for example, an optical fiber held in a metal sleeve or jacket.
The alignment of optical components is generally performed in one
of two ways: passive alignment or active alignment.
[0003] In the passive alignment technique, a number of device pits
and/or grooves are formed in a mounting block on which the optical
components are to be supported. The size and position of the device
pits and grooves are predetermined according to the specific
optical components and the desired alignment configuration such
that the optical components, when mounted and fixed in the
appropriate device pits and grooves, will automatically be in their
aligned positions. Some examples of such passive alignment
techniques are commercially available microbench assemblies and
v-groove sub-assemblies.
[0004] The passive alignment technique presents a number of
challenges. High precision fabrication of the optical components as
well as the mounting slots and grooves are required to ensure the
exact positioning of the optical components relative to each other.
If there are slight misalignments, fine adjustments are usually not
possible in the passive alignment scheme because the optical
components are fixed in their respective slots and grooves.
Furthermore, existing passive alignment schemes generally use a wet
etch technology to fabricate the mounting slots and grooves. Since
the shape of features formed by wet etching depends on the
crystallographic plane of the substrate, the use of wet etch
technology imposes limitations on the size, shape and formation
precision of the mounting slots and grooves, thus potentially
leading to inaccuracies in the optical component alignment.
[0005] The active alignment technique is more flexible than the
passive alignment schemes in that the exact position of the
individual optical component can normally be adjusted to fine tune
the alignment of that optical component with respect to other
components on the substrate. An example of an active alignment
system is the Cronos 3D fiber aligner based on a thermal arched
beam micro-electromechanical valve (see U.S. Pat. No. 6,114,794
issued to Dhuler et al). The Cronos system uses
micro-electromechanical systems (MEMS) technology to provide
positioning adjustments in three directions to align, for example,
an optical fiber with respect to a laser diode. The optical
component is mounted on a movable base which is connected to
directional actuators that adjust the position of the movable base,
and thus the optical component, by thermally-induced movement with
respect to a mounting base.
[0006] MEMS devices, such as the Cronos system, are based on fast
micro-machining using plasma etching methods. Plasma etching is a
dry etch technology which exhibits no crystallographic plane
dependency in the shape and depth of etching. Deep etch features
with clean edges and excellent verticality are possible with plasma
etching technology, thus enabling the manufacture of miniature but
complex active alignment systems.
[0007] The currently available, active alignment technologies have
certain drawbacks. Typically, these systems are bulky and complex
in comparison to the passive alignment systems due to the use of
separate actuators. Furthermore, most of these systems do not
provide a mechanism to fix the actuators, and thereby the optical
component, in an aligned position. Accoridingly, constant
adjustment of the actuators is required to correct for potential
drifts in the optical component position. Although the continual
adjustment may be automatically performed by a feedback
arrangement, such additional features add to the cost and
complexity of the alignment system.
[0008] In another aspect of the prior art, certain optical
arrangements (not shown) includes a light source and a
photodetector, which is intended to detect light emitted by the
light source. The photodetector and the light source are normally
fabricated on two separate substrates. The light source emits light
in a direction generally parallel to the light source substrate,
and the photodetector is usually designed to detect light incident
on the photodetector along a normal to the photodetector substrate.
Therefore, in order to use the photodetector to detect light
emitted by this light source, the photodetector substrate must be
oriented at a right angle with respect to the light source
substrate. The orientation of the light source with respect to the
photodetector must be adjustable to provide the optimum coupling of
light from the light source into the photodetector. This prior art
arrangement thus requires the handling and processing of two
separate components with their respective substrates and electrical
connections.
[0009] The present invention provides an optical assembly which
serves to resolve the problems described above with regard to prior
art optical assemblies for alignment of optical components in a
heretofore unseen and highly advantageous way and which provides
still further advantages.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention relates to a device for
aligning a first optical component on a substrate with a second
optical component comprising: arm means pivotally connected to said
substrate, said arm means being pivotable in every direction;
holding means for connecting the first optical component to said
arm means; and actuator interface means on said arm means enabling
manipulation of said arm means by an actuator.
[0011] Another aspect of the present invention relates to a method
for aligning a first optical component on a substrate with a second
optical component comprising the steps of:
[0012] providing arms means pivotally connected to the substrate,
said arm means having holding means for connecting the optical
component thereto, and actuator interface means enabling
manipulation of said arm means by an actuator;
[0013] aligning the first optical component with the second optical
component using the actuator to manipulate the position of said arm
means; and
[0014] fixing said arm means to the substrate when the first
optical component is aligned with the second optical component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention may be understood by reference to the
following detailed description taken in conjunction with the
drawings briefly described below.
[0016] FIG. 1 is a diagrammatic plan view of one embodiment of an
optical component micro-alignment assembly manufactured in
accordance with the present invention shown here to illustrate a
possible arrangement of a substrate including a compliant
lever.
[0017] FIGS. 2A-2C are diagrammatic plan views of the
micro-alignment assembly embodiment of FIG. 1 shown here to
illustrate different methods for affixing the compliant lever to
the remainder of the substrate.
[0018] FIG. 3 is a diagrammatic plan view of a fiber-pigtailed
optical transmitter including the micro-alignment assembly of the
present invention.
[0019] FIG. 4 is a diagrammatic plan view of an optical isolator
including the micro-alignment assembly of the present
invention.
[0020] FIG. 5 is a diagrammatic plan view of an external grating
device including the micro-alignment assembly of the present
invention.
[0021] FIG. 6 is a diagrammatic plan view of a wavelength-locker
including the micro-alignment assembly of the present
invention.
[0022] FIGS. 7A and 7B are diagrammatic partial cut away
elevational views of planar photodetector arrangements including
the micro-alignment assembly of the present invention.
[0023] FIG. 8 is a diagrammatic plan view of the micro-alignment
assembly embodiment of FIG. 1 shown here to illustrate a laser
glazing method for rigidifying the compliant lever.
[0024] FIG. 9 is a diagrammatic plan view of another embodiment of
a micro-alignment assembly manufactured in accordance with the
present invention shown here to illustrate the use of a wedge
structure to induce rotational motion of the compliant lever.
[0025] FIGS. 10A and 10B are diagrammatic plan views of alternative
implementations of the compliant lever in an micro-alignment
assembly manufactured in accordance with the present invention.
[0026] FIG. 11 is a diagrammatic plan view of still another
embodiment of a micro-alignment assembly manufactured in accordance
with the present invention shown here to illustrate an alternative,
contact-free mechanism to provide motion of the compliant
lever.
DETAILED DESCRIPTION
[0027] The following description is presented to enable one of
ordinary skill in the art to make and use the invention and is
provided in the context of a patent application and its
requirements. Various modifications to the described embodiments
will be readily apparent to those skilled in the art and the
generic principles herein may be applied to other embodiments.
Thus, the present invention is not intended to be limited to the
embodiment shown but is to be accorded the widest scope consistent
with the principles and features described herein.
[0028] Turning now to the drawings, wherein like components are
indicated by like reference numbers throughout the various figures,
attention is immediately directed to FIG. 1, which illustrates one
embodiment of a micro-alignment assembly, generally indicated by
the reference number 10, for the alignment of optical components.
Micro-alignment assembly 10 includes a substrate 20. Substrate 20,
in this example embodiment, is fabricated from a semiconductor
material such as, for example, silicon.
[0029] A compliant lever arm 21 is integrally formed from substrate
20 such that substrate 20 is divided into the compliant lever arm
21 and a primary substrate portion 24, which is defined in the
remainder of the substrate. Compliant lever arm 21 includes a
component mounting area 22 and a resilient section 26. Component
mounting area 22 is configured such that an optical component, for
example an end of an optical fiber, fiber grating, microlens, or
laser chip, is mountable on component mounting area 22. In the
embodiment illustrated in FIG. 1, an optical fiber 30 with a lensed
tip 31 is attached to component mounting area 22 by clips 32.
Component mounting area 22 includes a V-groove 34 which is designed
to accommodate and generally position optical fiber 30 in a
predetermined location on component mounting area 22.
[0030] Continuing to refer to FIG. 1, a laser chip 40 and a
photodiode 50 are mounted on mounting pads 60 on primary substrate
portion 24 and electronically connected to the substrate by
connectors 42 and 52, respectively. Light output from laser chip 40
establishes a light path, indicated by an arrow 55. Primary
substrate portion 24 also includes another V-groove 36 for
providing additional support and positional stability for optical
fiber 30.
[0031] Resilient section 26, shown in FIG. 1 as having the form of
a flat, baffle spring, imparts a compliancy to compliant lever 21
such that the compliant lever is movable with respect to primary
substrate portion 24. The optical fiber on component mounting area
22 is thereby movable with respect to the primary substrate portion
by movement of compliant lever 21 such that the position of the
lensed tip of optical fiber 30 is alignable in light path 55. A
groove 27 generally surrounds compliant lever arm 21 and separates
compliant lever arm 21 from primary substrate portion 24 except at
an attachment member 28 such that compliant lever arm 21 is movable
with respect to and independently of primary substrate portion 24.
A circular opening 29, formed in compliant lever arm 21, is
designed to allow compliant lever arm 21 to be mechanically
gripped, such that compliant lever 21 is movable in the
aforedescribed manner. There are several different mechanical
devices that can be inserted into the opening 29 for use by an
actuator in adjusting the position of the compliant lever arm 21,
including a split pin, a cone or a nail head. Alternatively, the
single opening 29 can be replaced by two holes, whereby a gripping
tool can be used.
[0032] With optical fiber 30 fixed on component mounting area 22,
micro-alignment assembly 10 readily allows fine adjustment of the
aligned position of tensed tip 31 of optical fiber 30 with respect
to light path 55 by manipulation of compliant lever 21. For
instance, the free end of compliant lever 21 may be moved in a
plane generally transverse to the light path to bring lensed tip 31
into alignment with the light path. Micro-alignment assembly 10
provides an advantageous way of fiber-pigtailing a laser because
the entire assembly is coplanar. Since the compliant lever can be
moved to compensate for displacements associated with the
difference in optical axes between the laser and the optical fiber,
there is advantageously no need to create additional features in
the substrate (such as a device pit) to counter these mechanical
differences.
[0033] Although micro-alignment assembly 10 of FIG. 1 has been
described as having a specific combination of components, it should
be understood that the micro-alignment assembly may be configured
in a variety of ways without deviating from the spirit of the
present invention. For example, compliant lever 21 may be designed
to accommodate a different optical component, such as a lens,
filter, mirror or a powered component such as a light source or
detector, on the component mounting area in place of optical fiber
30 as shown in FIG. 1. Also, compliant lever 21 may be configured
in a variety of ways provided that it functions as a flexural
member which is integrally formed from the substrate and
independently movable with respect to the primary substrate portion
and on which at least one optical component is mountable.
Furthermore, the specific selection of optical components mounted
on the primary substrate area may also be varied. Still further,
the shapes of substrate 20, compliant lever 21 and primary
substrate portion 24 may be altered in a variety of ways while
still providing adjustable movement of one or more optical
component mounted on the compliant lever with respect to an
associated light path. For example, component mounting area 22 can
be configured to allow an optical component to be adjustably
mounted thereon such that the exact position of that optical
component on the component mounting area can be altered over a
predetermined range. Holding clips 32 shown in FIG. 1 may be
designed to firmly hold optical fiber 30 in V-groove 34 but to also
allow optical fiber 30 to be slidably movable along the axial
direction of the optical fiber such that the intensity of light
coupled from laser chip 40 into optical fiber 30 can be controlled.
Moreover, compliant lever 21 can be configured or biased such that
the optical fiber is located at a predetermined, displaced location
with respect to the laser chip light path. In this way, an initial
bias direction of the compliant lever is advantageously known in
order to bring the tensed tip of optical fiber 30 into alignment
with light path 55. Biasing in this way is submitted to save
processing time during manufacturing.
[0034] Turning now to FIGS. 2A-2C, once lensed tip 31 is brought
into optimal alignment with respect to light path 55, compliant
lever 21 is fixed in the aligned position with respect to primary
substrate area 24 using methods such as those illustrated in FIGS.
2A-2C, for example. FIG. 2A illustrates a micro-alignment assembly
100A, which is essentially identical to micro-alignment assembly 10
of FIG. 1 but includes additional features that allow the securing
of the compliant lever with respect to the primary substrate area.
Micro-alignment assembly 100A includes a substrate 20A, which in
turn includes a compliant lever 21A surrounded by a primary
substrate area 24A. Compliant lever 21A and primary substrate area
24A are slightly modified in comparison to compliant lever 21 and
primary substrate area 24, respectively, of FIG. 1 in that opposing
metal pads 102 are additionally formed on compliant lever 21A and
primary substrate area 24A. Metal pads 102 are configured such that
a weld 104 is formable across each pair of metal pads 102 for
securing compliant lever 21A with respect to primary substrate area
24A. Weld 104 may formed, for example, by conventional laser
welding methods.
[0035] Alternatively, the compliant lever can be fixed to the
primary substrate area by direct laser welding, as shown in FIG.
2B. Micro-alignment assembly 100B includes substrate 20 shown in
FIG. 1, here indicated by the reference number 20B. Micro-alignment
assembly 100B additionally includes silicon-to-silicon laser welds
106 for securing compliant lever 21 with respect to primary
substrate area 24.
[0036] Yet another alternative method for fixing the compliant
lever with respect to the primary substrate portion is shown in
FIG. 2C. Again, micro-alignment assembly 100C includes substrate 20
as shown in FIG. 1, here indicated by reference number 20C. In
micro-alignment assembly 100C, however, space 27 is filled with an
adhesive 108. For instance, adhesive 108 may be an epoxy which is
injected into space 27 such that, when the epoxy is cured, adhesive
108 serves to secure compliant lever 21 with respect to primary
substrate area 24 and lensed tip 31 is fixed in an aligned position
in light path 55. As another example, a low viscosity epoxy can be
used as adhesive 108 such that the epoxy is drawn into space 27 by
capillary action.
[0037] FIG. 2D illustrates a fourth method for fixing the primary
substrate portion 24 to the compliant lever arm 22, in which glass
pre-forms 71 are melted, forming a bond. The glass can be any
suitable glass known in the industry, including specialty solder
glass. It is preferable that the glass have a lower melting point
than the substrate, and that the glass wets to the substrate to
form a bond. Initially, (step 1) a plurality of beveled sections 72
or recessed areas 73 are formed in the edges of the primary
substrate portion 24 and the lever arm 22. The beveled sections 72
(or recessed area 73) of the lever arm 22 are formed adjacent to
the beveled sections 72 (or recessed area 73) of the primary
substrate portion 24, whereby adjacent sections (or areas) form
v-shaped (or square) depressions 74. The glass pre-forms 71 are
placed within the depressions 73 (step 2) and the components are
aligned according to the aforementioned invention. Subsequently,
the glass pre-forms 71 are subjected to a focussed beam of light 75
(step 3), which melts the pre-forms (step 4), forming a bond
between the primary substrate 24 and the lever arm 22. If
necessary, the bottom of the depression 74 is coated with a
metalized layer 76 to facilitate the glass bonding to the
depression. Any suitable material can be used for the layer 76,
e.g. gold (Au) or gold and Tin (AuSn). However, if the primary
substrate portion 24 and the lever arm 22 are silicon, the
metalized layer 76 is normally unnecessary, since the glass wets to
the silicon. The glass preforms can have any applicable form, such
as balls, rods or powder.
[0038] Having described four specific examples of methods for
fixing the compliant lever with respect to the primary substrate
portions, it should be apparent that a variety of specific
configurations are possible while remaining within the scope of the
present invention. Any compatible means for securing the position
of the compliant lever such that at least one optical component
mounted thereon becomes fixed in an aligned position with respect
to the light path is appropriate for use with the micro-alignment
assembly of the present invention. As an additional step, the
resilient section of any of the forgoing can be cut, for example,
by a laser following the fixing process in order to reduce
potential stress effects in the substrate, which may result in
drifting of the alignment with time or due to changes in
environmental conditions.
[0039] Turning to FIGS. 3-6, a few of the many possible
configurations for optical device arrangements based on the optical
component micro-alignment assembly of the present invention will be
described. FIG. 3 illustrates an optical transmitter 200 which
includes a substrate 220. Substrate 220 is essentially identical to
substrate 20 shown in FIG. 1, including compliant lever 21 with
optical fiber 30 mounted thereon, but with a slight modification in
primary substrate area 224. Specifically, primary substrate area
224 includes extra spacing between mounting pads 60 and a nearest
edge of compliant lever 21, in which extra spacing a ball lens 212
is mounted. In the embodiment illustrated in FIG. 3, ball lens 212
is passively aligned and mounted in front of laser chip 40 and is
configured to improve the optical coupling efficiency between laser
chip 40 and optical fiber 30. However, care is required in aligning
tensed tip 31 of optical fiber 30 with respect to ball lens 212 to
avoid lowering the efficiency in the coupling of light into the
optical fiber. In this regard, optical fiber 30 is mounted on
component mounting area 22 such that lensed tip 31 is movable with
respect to ball lens 212 by manipulating compliant lever 21 to vary
the position of lensed tip 31 with respect to ball lens 212 thereby
facilitating adjustment to achieve optimum coupling efficiency of
light into the optical fiber. After the optical fiber has been
brought into an aligned position, compliant lever 21 may be fixed
with respect to primary substrate area 224 by any suitable method,
for example, but not limited to, methods illustrated in FIGS.
2A-2C.
[0040] FIG. 4 illustrates an optical isolator based on the optical
component micro-alignment assembly of the present invention
generally indicated by the reference number 300. Optical isolator
300 includes a substrate 320, which is generally identical to
substrate 220 of FIG. 3, but modified such that primary substrate
area 324 is slightly expanded to accommodate ball lens 212 as well
as a filter 321 between the laser chip and the compliant lever.
Filter 321 is configured to pass light from laser chip 40 toward
optical fiber 30 while substantially blocking any stray light
reflected from optical fiber 30 toward the laser chip. Moreover,
filter 321 transmits only light of the specific optical wavelength
emitted by laser chip 40. The position of lensed tip 31 of optical
fiber 30 is again adjustable by moving compliant lever 21. Once
optimum coupling efficiency is attained, compliant lever 21 may be
secured to primary substrate area 324 by one of the aforedescribed
methods.
[0041] Attention is now directed to FIG. 5, which illustrates a
fiber-pigtailed, external cavity laser assembly based on the
optical component micro-alignment assembly of the present
invention, generally indicated by reference numeral 400.
Fiber-pigtailed, external cavity laser assembly 400 includes a
substrate 420 with first and second compliant levers integrally
formed therein, indicated by the reference numbers 421A and 421B,
respectively. While photodiode 50 and its associated connector 52
are mounted at an outermost edge of primary substrate area 424, as
in previously illustrated embodiments, a modified laser chip 440 is
mounted between the two compliant levers of substrate 420. Laser
chip 440 is configured to cooperate with a fiber grating 421, which
is mounted on a first one of the two compliant levers, such that an
external cavity laser results. Each compliant lever is configured
to accommodate and secure one end of an optical fiber in its
respective component mounting area. An optical fiber 30 is mounted
on a second one of the compliant levers, in an analogous manner to
previously described embodiments, and couples light away from the
external cavity laser set up by the combination of laser chip 440
and fiber grating 421. Primary substrate area 424 is equipped with
additional V-grooves 36 to support optical fiber 30 as well as
fiber grating 421.
[0042] Continuing to refer to FIG. 5, the position of fiber grating
421 in relation to laser chip 440 is adjustable by moving the first
compliant lever. Thus, the alignment of fiber grating 421 with
respect to laser chip 440 is optimizable. Additionally, the
position of the second compliant lever, and thereby optical fiber
30 mounted thereon, is adjustable to improve the coupling of light
from the external cavity laser arrangement into optical fiber 30.
When compliant levers 421A and 421B have been brought into their
respective aligned positions, the compliant levers may be fixed in
place with respect to primary substrate area 424 by one of the
aforedescribed methods.
[0043] Referring now to FIG. 6 in conjunction with FIG. 5, a
wavelength locker based on the optical component micro-alignment
assembly of the present invention is generally indicated by the
reference number 500. Wavelength locker 500 includes a substrate
520. Like substrate 420 of FIG. 5, substrate 520 includes first and
second compliant levers, each of which has an optical component
mounted thereon. Substrate 520 includes compliant lever 521A, on
which optical fiber 30 is mounted, and a modified, compliant lever
521B, which is configured to accommodate ball lens 212 thereon. The
remaining area of substrate 520, outside of the two compliant
levers, defines a primary substrate area 524. Like the
fiberpigtailed, external cavity laser assembly of FIG. 5, a laser
chip 540 is mounted on mounting pads 60 on primary substrate area
524 between the two compliant levers.
[0044] An interference filter 523 and two photodiodes 50 are also
mounted on primary substrate area 524. Laser chip 540 is configured
such that a portion of laser light (indicated by arrow 556)
generated within laser chip 540 is emitted toward ball lens 212.
Ball lens 212, interference filter 523 and photodiodes 50 are
arranged such that this portion of laser light is directed through
ball lens 212 and interference filter 523. Interference filter 523
is oriented to transmit light of a desired laser wavelength to one
of photodiodes 50 while transmitting light of another undesired
wavelength, both of which are potentially present in the test
portion of laser light, to the other of photodiodes 50. Changes in
the ratio of the amount of light of the desired laser wavelength at
the first mentioned photodiode 50 to the amount light of the
undesired wavelength detected at the other photodiode are converted
into an electronic error signal. This electronic error signal is
then used to correct the operating parameters of laser chip 540 to
achieve stable wavelength laser operation.
[0045] Transmission of the test portion of laser light through ball
lens 212 and into interference filter 523 is adjustable by
manipulation of compliant lever 521B, on which ball lens 212 is
mounted. In performing this adjustment, the coupling of the test
portion of laser light into photodiodes 50 is optimized.
Furthermore, as in previously described embodiments, the position
of optical fiber 30 with respect to light path 55 defined by the
light output from laser chip 540 is adjustable by movement of
compliant lever 521A, on which optical fiber 30 is mounted. After
the two compliant levers have been adjusted such that ball lens 212
and optical fiber 30 are in their aligned positions, compliant
levers 521A and 521B are fixed in place with respect to primary
substrate portion 524 by one of the aforedescribed methods.
[0046] Considering the aforedescribed problem relating to
photodetector arrangements, attention is now directed to the
partial cut away elevational views of FIGS. 7A and 7B.
Photodetector arrangements 600A and 600B are shown in cross section
in FIGS. 7A and 7B, respectively, for purposes of eliminating the
problem of having the light source and the photodetector on
separate substrates. To that end, the light sources and the
photodetectors are arranged on common substrates. The photodetector
arrangements shown in FIGS. 7A and 7B are generally called planar
arrangements because the light source and the photodetector are
fabricated essentially on the same substrate plane.
[0047] Referring specifically to FIG. 7A, photodetector arrangement
600A includes a substrate 620A (only partially shown) which is
divided into compliant lever 621A and primary substrate portion
624A. Compliant lever 621A is integrally formed from substrate 620A
in accordance with the teachings above and is designed to
accommodate optical fiber 630 thereon. Optical fiber 630 is
oriented such that a remote end (not shown) is connected to a light
source to provide light output 655A at another end illustrate
mounted on compliant lever 621A. Light output 655A is directed
toward a sloped facet 612 of primary substrate portion 624A. Sloped
facet 612 includes a suitable reflective coating, such as a gold
coating, to redirect light output 655A in a direction perpendicular
to substrate 620A. A rear-entry type photodetector 613A is mounted
on an upper surface of primary substrate portion 624A using a
transmissive mount 614A such that redirected light output 655A is
transmitted through transmissive mount 614A and is detected at a
detector head 616. The intensity of detected light is converted
into an electronic signal by circuitry 618. In order to control the
amount of light output 655A that is received at detector head 616,
the position of the light emitting end of optical fiber 630 is
adjustable by moving compliant lever 621A. Thus, optimum coupling
of light from optical fiber 630 into photodetector 613A is
achieved. Compliant lever 621A is secured relative to primary
substrate portion 624A following alignment such that optical fiber
630 is fixed in its optimum aligned position with respect to
photodetector 613A.
[0048] Turning to FIG. 7B, photodetector arrangement 600B includes
a substrate 620B, which is divided into an integrally formed,
compliant lever 621B and a primary substrate portion 624B.
Compliant lever 621B is configured to accommodate a laser chip 640
thereon. Laser chip 640 emits light output 655B at one of its
edges. An edge detector type photodetector 613B is mounted on
primary substrate portion 624B and opposite laser chip 640.
Photodetector 613B includes a shaped, transparent mount 614B with a
detector head 616 connected to circuitry 618. Transparent mount
614B includes a sloped facet 619 which is configured to receive and
redirect light output 655B toward detector head 616. Light coupling
from laser chip 640 into detector head 616 is adjustable by moving
compliant lever 621B, thus optimizing the position of laser chip
640 with respect to photodetector 613B. Laser chip 640 is then
fixed in an aligned position by securing compliant lever 621 onto
primary substrate portion 624B.
[0049] Referring now to FIG. 8, an additional option for the
optical component micro-alignment assembly of the present invention
is described. A micro-alignment assembly is generally indicated by
reference number 700 and includes substrate 20, which has all of
the features and components as described with reference to FIG. 1.
As discussed in conjunction with FIGS. 2A - 2C, compliant lever 21
is fixable relative to primary substrate area 24 in order to secure
the optical component, which is mounted on compliant lever 21, in
an aligned position. In order to further secure the position of
compliant lever 21, resilient section 26 is independently fixed
such the resilient section 26 is rigidified and no longer provides
compliancy.
[0050] Such a rigidifying effect is obtained in one highly
advantageous way by covering the resilient section with a laser
glaze 702, as shown in FIG. 8. Laser glaze 702 is formed in a
heretofore unseen manner in a silicon-to-silicon laser welding
procedure to be described in further detail. Specifically, laser
glaze 702 is essentially a thin weld formed over most of resilient
section 26 such that the resilient section is no longer flexible.
In other words, the flat baffle spring (see FIG. 1) essentially
formed of spaced apart, resilient strips defining spaces between
adjacent ones of the resilient strips; the spaces between these
adjacent resilient strips of the flat baffle spring are bridged by
laser glazing so that compliant lever 21 becomes rigidified and
cannot be readily moved. Alternatively, space 27 around compliant
lever 21 may be bridged surrounding the component mounting area
using this laser glazing technique. The laser glazing technique may
be used in conjunction with the aforedescribed methods for securing
the compliant lever to the primary substrate portion in order to
further lock the optical component, which is mounted on the
compliant lever, in an aligned position.
[0051] FIG. 9 is an illustration of another variation of a
micro-alignment assembly of the present invention, generally
indicated by reference number 800. Micro-alignment assembly 800
includes a substrate 820. A compliant lever 821 is integrally
formed from substrate 820 and includes a component mounting area
822 and a resilient attachment member 826. In micro-alignment
assembly 800, a beam steering filter 828 is mounted on component
mounting area 822. A movable wedge 860 and an attachment arm 862
are also integrally formed from substrate 820. Substrate 820 also
includes substrate 20 shown in FIG. 1, indicated by the reference
number 824. Primary substrate portion 824 is defined by the main
portion of substrate 820, excluding the compliant lever and movable
wedge components. Optical fibers 830A-830C, each in a sleeve 832,
are mounted on primary substrate portion 824 such that optical
fiber 830A is positioned on one side of compliant lever 821 while
optical fibers 830B and 830C are generally parallel to each other
and are located on an opposing side of compliant lever 821, as
shown in FIG. 9. A remote end of optical fiber 830A is connected to
a light source (not shown) such that light, indicated by arrow 855,
is emitted at an opposing, illustrated end of optical fiber 830A to
define a light path.
[0052] Compliant lever 821 and primary substrate portion 824 are
configured such that one edge of compliant lever 821 and an
opposing edge of primary substrate portion 824 together form a
V-shaped opening 825 which accommodates movable wedge 860. When
movable wedge 860 is biased into or out of opening 825, compliant
lever 821 pivots by compliance of attachment member 826 generally
in the plane of substrate 820, thereby rotating beam steering
filter 82i in a plane parallel to substrate 820. In the
micro-alignment assembly shown in FIG. 9, this accurate movement of
the beam steering filter results in the redirection of light 855
from traveling toward optical fiber 830B to traveling toward
optical fiber 830C, and vice versa. Thus, micro-alignment assembly
800 functions as a spatial switch to switch the light input between
optical fibers 830B and 830C by manipulation of movable wedge 860.
Micro-alignment assembly 800 also has the advantage of excellent
mechanical stability once movable wedge 860, and thereby compliant
lever 821, have been biased into aligned positions and fixed to
primary substrate portion 824 because the movable wedge, compliant
lever, and primary substrate portion are in biasing contact.
[0053] FIGS. 10A and 10B illustrate still further modifications
with respect to the optical component micro-alignment assembly of
the present invention. Specifically, FIGS. 10A and 10B show
alternate configurations for the compliant lever of the present
invention. Substrates 920A and 920B in FIGS. 10A and 10B,
respectively, illustrate embodiments of compliant levers in which
the component mounting area is surrounded by the resilient section.
The configurations shown in FIGS. 10A and 10B have an advantage
over the aforedescribed embodiments in that balanced degrees of
freedom are available in the motion of an optical component mounted
thereon.
[0054] In FIG. 10A, a compliant member 921A is integrally formed
from substrate 920A in a spiral spring configuration. The remaining
area of substrate 920A, excluding compliant member 921A, defines a
primary substrate portion 924A. Compliant member 921A includes a
component mounting area 922A, which is surrounded by resilient
section 926A. Like the compliant levers of aforedescribed
embodiments, compliant member 921A is movable with respect to
primary substrate area 924A such that an optical component (now
shown), which is mounted on component mounting area 922A, is
thereby movable with respect to a light path (not shown). Compliant
member 921A can be moved both in and out of the plane of substrate
920A , be rotated along a rotational axis that is perpendicular to
the plane of substrate 920A by coiling and uncoiling of the spiral
spring, and displaced laterally in the plane of the figure.
[0055] Referring to FIG. 10B, a compliant member 921B is integrally
formed from substrate 920B in the shape of a flat, rectangular
spring, in which a component mounting area 922B is surrounded by
resilient section 926B. Compliant member 921B is movable both in
and out of the plane of substrate 920B and provides a limited
rotational movement along a rotational axis perpendicular to the
plane of substrate 920A by coiling and uncoiling of the spring.
[0056] The embodiments illustrated in FIGS. 10A and 10B, like that
of FIG. 9, are useful in applications in which rotational motion is
desired. Many other shapes of the compliant lever are contemplated
in order to provide different degrees of freedom of motion with
regards to the translation and rotational directions.
[0057] Attention is now directed to FIG. 11, in which an
alternative method for producing motion of a compliant lever is
illustrated in a micro-alignment assembly generally indicated by
reference number 1000. Micro-alignment assembly 1000 includes a
substrate 1020, which is similar to substrate 20 of FIG. 1 with a
few modifications. Whereas substrate 20 includes a circular opening
29 formed in compliant lever 21 for mechanically gripping the
compliant lever, substrate 1020 instead includes an actuator
assembly 1003. Actuator assembly 1003 includes bases 1005, one of
which bases is formed on compliant lever 21 and another of which
bases is formed on primary substrate area 24. Bases 1005 are
connected by a bridge section 1007. As an example, actuator
assembly 1003 can be based on a thermal mechanism in which one or
both of bases 1005 is heated by, for instance, resistive heating
such that bridge section 1007 expands or contracts according to the
amount of applied heat, thereby inducing motion of compliant lever
21. As another example, one or both of bases 1005 can be a PZT
block such that actuator assembly 1003 expands or contracts by
application of a voltage due to electromechanical forces, thus
moving compliant lever 21 by a desired amount. In still another
example, bridge section 1007 can be removed, and bases 1005 can be
configured such that a magnetic force or an electro-static force is
established between bases 1005, thus causing compliant lever 21 to
move in accordance with the applied force. The actuator assembly of
FIG. 11 is advantageous in that the movement of compliant lever 21,
and thereby the optical mounted thereon, is controlled without
having to physically contact any part of micro-alignment assembly
1000. Therefore, barring potential hysteresis effects, the induced
movement of the compliant lever is controlled precisely. As
described with regard to previous embodiments, the compliant lever
may be secured with respect to the primary substrate portion once
the optical component has been brought into a desired aligned
position.
[0058] Although each of the aforedescribed embodiments have been
illustrated with various components having particular respective
orientations, it should be understood that the present invention
may take on a variety of specific configurations with the various
components being located in a wide variety of positions and mutual
orientations and still remain within the spirit and scope of the
present invention. Furthermore, suitable equivalents may be used in
place of or in addition to the various components, the function and
use of such substitute or additional components being held to be
familiar to those skilled in the art and are therefore regarded as
falling within the scope of the present invention. For example, a
U-groove may be used in place of the V-grooves shown in the
aforedescribed figures for accommodating the optical fibers or
fiber grating. Other suitable materials, such as
indium-gallium-arsenide (InGaAs), lithium niobate, metals or
insulators, may be used as the substrate material or incorporated
as a part of the substrate. Still further, more than two
micro-alignment assemblies may be formed in a single substrate, and
two or more optical components may be mounted on a single compliant
lever. For instance, Applicant anticipates the fabrication of an
entire optical system using multiple optical components mounted on
a substrate with several micro-alignment assemblies such that the
single substrate may contain a complex optical system that is
readily optimizable by adjustment of the various compliant levers.
Therefore, the present examples are to be considered as
illustrative and not restrictive, and the invention is not to be
limited to the details given herein but may be modified within the
scope of the appended claims.
* * * * *