U.S. patent application number 11/671775 was filed with the patent office on 2007-06-07 for optical devices and methods to construct the same.
Invention is credited to Daoqiang Lu, Gilroy Vandentop.
Application Number | 20070127865 11/671775 |
Document ID | / |
Family ID | 32989027 |
Filed Date | 2007-06-07 |
United States Patent
Application |
20070127865 |
Kind Code |
A1 |
Lu; Daoqiang ; et
al. |
June 7, 2007 |
OPTICAL DEVICES AND METHODS TO CONSTRUCT THE SAME
Abstract
Optical devices and methods for constructing the same are
disclosed. An example optical device includes an optical
transmitter, a photodetector and a waveguide optically coupling the
optical transmitter and the photodetector. It also includes a
substrate having a first cavity to receive the optical transmitter
and a second cavity to receive the second transmitter. The first
and second cavities are located and dimensioned to passively align
the optical transmitter, the waveguide and the photodetector when
the transmitter is inserted into the first cavity and the
photodetector is inserted into the second cavity.
Inventors: |
Lu; Daoqiang; (Chandler,
AZ) ; Vandentop; Gilroy; (Tempe, AZ) |
Correspondence
Address: |
HANLEY, FLIGHT & ZIMMERMAN, LLC
150 S. WACKER DRIVE
SUITE 2100
CHICAGO
IL
60606
US
|
Family ID: |
32989027 |
Appl. No.: |
11/671775 |
Filed: |
February 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10397580 |
Mar 26, 2003 |
7195941 |
|
|
11671775 |
Feb 6, 2007 |
|
|
|
Current U.S.
Class: |
385/14 |
Current CPC
Class: |
G02B 6/423 20130101;
G02B 6/4232 20130101 |
Class at
Publication: |
385/014 |
International
Class: |
G02B 6/12 20060101
G02B006/12 |
Claims
1. A substrate for an optical module comprising: a substrate; a
first cavity defined in the substrate, the first cavity being
dimensioned to receive an optical transmitter; and a second cavity
defined in the substrate, the second cavity being dimensioned to
receive a photodetector, the first cavity and second cavity being
located and dimensioned to passively align the optical transmitter
and the photodetector when the optical transmitter is positioned in
the first cavity and the photodetector is located in the second
cavity.
2. A substrate as defined in claim 1 further comprising a waveguide
secured to a surface of the substrate between the first and second
cavities.
3. A substrate as defined in claim 2 wherein the waveguide
comprises a waveguide array.
4. A substrate as defined in claim 3 wherein the waveguide array
comprises a first waveguide channel and a second waveguide
channel.
5. A substrate as defined in claim 4 wherein the first waveguide
channel is vertically displaced from the second waveguide
channel.
6. A substrate as defined in claim 4 wherein the first and second
waveguide channels are in a common plane.
7. A substrate as defined in claim 1 further comprising a waveguide
integrated with the substrate between the first and second
cavities.
8. A substrate as defined in claim 7 wherein the waveguide
comprises a waveguide array.
9. A substrate as defined in claim 8 wherein the waveguide array
comprises a first waveguide channel and a second waveguide
channel.
10. A substrate as defined in claim 9 wherein the first waveguide
channel is vertically displaced from the second waveguide
channel.
11. A substrate as defined in claim 9 wherein the first and second
waveguide channels are in a common plane.
12. An optical device comprising: a first optical element; a first
waveguide; a first substrate having a first cavity to receive the
first optical element, the first cavity being located and
dimensioned to passively align the first optical element and the
first waveguide; a second optical element; a second waveguide; a
second substrate having a second cavity to receive the second
optical element, the second cavity being located and dimensioned to
passively align the second optical element and the second
waveguide; and a flying waveguide optically coupling the first and
second waveguides.
13. An optical device as defined in claim 12 wherein the flying
waveguide is coupled to the first substrate and the second
substrate.
14. An optical device as defined in claim 13 wherein the first
waveguide, the second waveguide and the flying waveguide are
passively aligned.
15. An optical device as defined in claim 14 wherein the flying
waveguide includes a first connector and a second connector, and
further comprising a first aligning pin and a first mating bore
positioned to connect the first connector and the first waveguide,
and a second aligning pin and a second mating bore positioned to
connect the second connector and the second waveguide.
Description
RELATED APPLICATION
[0001] This patent arises from a divisional of U.S. patent
application Ser. No. 10/397,580, which was filed on Mar. 26, 2003
and is hereby incorporated by reference in its entirety.
FIELD OF THE DISCLOSURE
[0002] This disclosure relates generally to optical devices, and,
more particularly, to optical devices and methods to construct the
same.
BACKGROUND
[0003] The coherent light generated by edge emitting laser diodes
is emitted in one or more planes that are substantially parallel to
the boundaries between the semiconductor layers that form the
laser. More recently, vertical cavity surface emitting lasers
(VCSEL) have been developed. Unlike edge emitting laser diodes,
VCSELs are laser diodes that are fabricated to emit light in one or
more planes that are substantially perpendicular to the boundaries
formed between their semiconductor layers. VCSELs appear to be
advantageous over edge emitting laser diodes in several respects.
For example, VCSELs generally require lower power and are less
expensive to manufacture than their edge emitting counterparts.
[0004] An example prior art optical device 10 is shown in FIG. 1.
In the example of FIG. 1, a VCSEL 12 is optically coupled to a
photodetector 14 via a waveguide 16. Because, by definition, the
light generated by a VCSEL is transmitted in a plane that is
generally perpendicular to the surface of the VCSEL, the light from
a VCSEL 12 is typically coupled to a waveguide 16 by an expensive
and complicated end finish of the waveguide 16. For example, an end
of the waveguide 16 may be cut and polished to form a 45 degree
total reflection mirror 18 that re-directs a substantial portion of
the light emitted by the laser 12 approximately 90 degrees from its
initial path into the waveguide 16. Typically, the opposite end of
the waveguide 16 is also formed into a 45 degree mirror 18 to
re-direct the light from the waveguide 16 toward the photodetector
14 as shown in FIG. 1.
[0005] This complicated mechanism for directing the light generated
by the VCSEL 12 to the photodetector 14 is expensive and difficult
to manufacture. For example, to manufacture a device 10 such as
that shown in FIG. 1, the die-substrate standoff height (e.g., the
distance between the VCSEL 12 and a substrate 20 of the optical
device 10 and/or the distance between the photodetector 14 and the
substrate 20 (e.g., a printed circuit board) of the optical device
10) must be carefully controlled. Further, the optically active
area of the VCSEL 12 must be precisely aligned with one of the end
mirrors 18 of the waveguide 16 and the active area of the
photodetector 14 must be precisely aligned with the opposite end
mirror 18 of the waveguide 16.
[0006] The tolerances associated with the die-substrate height
standoff requirements and the VCSEL-to-waveguide and
waveguide-to-photodetector alignment requirements dictate that the
placement/bonding of the VCSEL 12, the photodetector 14, and
sometimes the waveguide 16 be carried out through an active
alignment technique. An active alignment technique is a feedback
technique in which a laser (e.g., the VCSEL) associated with the
component(s) being placed is energized, and the position(s) of the
component(s) being placed are adjusted to maximize an output of the
energized laser at an output of those component(s). When the output
is maximized, the component(s) are aligned and bonded in place.
Unfortunately, active alignment processes such as that described
above are slow and do not lend themselves to mass production.
[0007] Additionally, prior art optical devices 10 such as that
shown in FIG. 1 typically do not permit the use of two dimensional
waveguide arrays. As a result, such prior art devices have limited
bandwidth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic illustration of a prior art optical
device.
[0009] FIG. 2 is a perspective view of an example substrate.
[0010] FIG. 3 is a perspective view of an example VCSEL and/or
photodetector.
[0011] FIG. 4 is a perspective view of the example
VCSEL/photodetector of FIG. 3 and a portion of the example
substrate of FIG. 2.
[0012] FIG. 5 is a view similar to FIG. 4 but showing the example
VCSEL/photodetector positioned within a cavity of the example
substrate of FIG. 2.
[0013] FIG. 6 is a cross-sectional view of an example optical
device incorporating the example substrate of FIG. 2 and the
example VCSEL/photodetector of FIG. 3.
[0014] FIG. 7 is a perspective view of a section of an example
waveguide array from the optical device of FIG. 6.
[0015] FIG. 8 is a partial cross-sectional view of another example
substrate.
[0016] FIG. 9 is a perspective view of the example
VCSEL/photodetector of FIG. 3 and a section of the example
substrate of FIG. 8.
[0017] FIG. 10 is a view similar to FIG. 9 but showing the example
VCSEL/photodetector positioned within a cavity of the example
substrate of FIG. 8.
[0018] FIG. 11 is a view similar to FIG. 8 but showing the example
VCSEL/photodetector positioned within a cavity of the example
substrate.
[0019] FIG. 12 is a partial cross-sectional view of a first
assembly including a first substrate, a first optical element, and
a first waveguide.
[0020] FIG. 13 is a partial cross-sectional view of a second
assembly including a flying waveguide.
[0021] FIG. 14 is a partial cross-sectional view of a third
assembly including a second substrate, a second optical element,
and a second waveguide.
[0022] FIG. 15 is a cross-sectional view showing the assemblies of
FIGS. 12-14 coupled to form an optical device.
[0023] FIG. 16 is a perspective view of an alternative
VCSEL/photodetector.
[0024] FIG. 17 is a view similar to FIG. 16 but showing the optical
element of FIG. 16 being soldered in position within the cavity of
an example substrate.
DETAILED DESCRIPTION
[0025] FIG. 2 is a perspective view of an example substrate 30. The
illustrated substrate 30 is structured to passively align an
optical transmitter, a waveguide 36 and a photodetector. In
particular, the substrate 30 includes a first cavity 32 that is
dimensioned to receive the optical transmitter and a second cavity
34 which is dimensioned to receive the photodetector. A waveguide
36 is located between the first and second cavities 32, 34. The
waveguide 36 may be bonded to the surface of the substrate 30 or
integrated with the substrate 30. In either event, the first and
second cavities 32, 34 are located and positioned to passively
align the optical transmitter, the waveguide 36 and the
photodetector when the optical transmitter is positioned in the
first cavity 32 and the photodetector 34 is positioned in the
second cavity. To this end, the cavities 32, 34 are precision
machined in the substrate 30 to precisely locate a corresponding
one of the transmitter and the photodetector in a predetermined
position relative to the waveguide 36. This high precision
machining of the cavities 32, 34 in the substrate 30 enables an
optical device to be assembled from the substrate 30, the waveguide
36, an optical transmitter and a photodetector without performing
active alignment of the same.
[0026] An example optical element 40 is schematically illustrated
in FIG. 3. The optical element 40 may be implemented by an optical
transmitter such as a VCSEL and/or by a photodetector. Therefore,
the optical element 40 is interchangeably referred to herein as an
optical transmitter/photodetector 40 or an optical element 40.
[0027] The optical element 40 of FIG. 3 includes four optically
active areas 42, although persons of ordinary skill in the art will
readily appreciate that greater or fewer optically active areas 42
could alternatively be employed. If the optical element 40 is a
transmitter such as a VCSEL, the optically active areas 42 are
areas at which coherent light is output by the transmitter 40. If
the optical element 40 is a photodetector, the optically active
areas 42 are areas that convert received light into electrical
current. In either event, the illustrated optically active areas 42
are coupled to contacts 44 via metal traces 46. The contacts 44 of
the illustrated example are formed by solder bumps that are formed
in electrically conductive contact with a corresponding one of the
traces 46. The metal traces 46 may be implemented by any
conventional, electrically conductive material such as copper.
[0028] As illustrated in the example of FIGS. 4 and 5, the optical
element 40 is secured in a corresponding one of the cavities 32, 34
of the substrate 30. As mentioned above, the cavities 32, 34 are
manufactured to very tight tolerances (e.g., less than
approximately five micrometers) to ensure that securing the optical
transmitter/photodetector 40 in the corresponding cavity 32, 34
sufficiently aligns the optically active area(s) 42 of that optical
element 40 with corresponding waveguide(s) as explained in further
detail below. The optical element 40 may be secured in its cavity
32, 34 with any conventional bonding agent such as epoxy.
[0029] In the illustrated example, in addition to or instead of
bonding the optical element 40 in the cavity 32, 34 with a
conventional bonding agent, the optical element 40 is secured in
the corresponding cavity 32, 34 via the solder bumps 44. For
instance, in the illustrated example the substrate 30 includes a
plurality of electrically conductive contacts 48 located either in
or adjacent the top surface of the substrate 30. The contacts 48 of
the substrate 30 are positioned adjacent the cavities 32, 34 in
locations to engage the solder bumps 44 of the optical elements 40
when the optical elements 40 are positioned within their
corresponding cavities 32, 34. Thus, when the optical elements 40
are positioned within the cavities 32, 34, the solder bump(s) of
the optical element 40 are reflowed to form solder joints 50 (see
FIG. 5) between the optical elements 40 and the substrate 30. The
solder joints mechanically and electrically couple the contacts 44
of the optical elements 40 to the contacts 48 of the substrate 30.
As will be appreciated by persons of ordinary skill in the art, the
contacts 48 of the substrate 30 may be electrically coupled to
circuitry either on the substrate 30 or off the substrate 30 to
excite the optically active area(s) 42 of the transmitter 40 and/or
to receive the signal(s) generated by the optically active area(s)
of the photodetector 40.
[0030] As mentioned above, the waveguide 36 carried by the
substrate 30 may be positioned above a top surface of the substrate
30 (see FIG. 6), or integrated in the substrate 30 (see FIGS.
8-11). If the waveguide 36 is positioned above the top surface of
the substrate 30 as shown in FIG. 6, the solder bumps 44 of the
optical elements 40 are located beneath the optically active areas
42 of the optical transmitter/photodetector 40. Thus, when the
optical elements 40 are inserted into their corresponding cavities
32, 34, the contacts 44 of the optical elements 40 are positioned
adjacent to and/or in contact with the contacts 48 of the substrate
30 to facilitate the creation of the solder joints 50 mentioned
above. Also, when the optical elements 40 are inserted into their
corresponding cavities 32, 34, the optically active area(s) 42 are
positioned at the proper height and orientation to create an
optical coupling to the waveguide(s) 36.
[0031] If the waveguide(s) 36 are positioned below the top surface
of the substrate 30 (see FIGS. 8-11), the cavities 32, 34 may be
bored deeper into the substrate 30 (compare FIGS. 6 and 8) such
that the optically active areas 42 of the optical elements 40 are
positioned at the proper height and orientation to optically couple
the optical elements 40 to the waveguide(s) 36 when the optical
elements 40 are positioned within their corresponding cavities 32,
34 (see FIGS. 10-11). In such an example, the solder bumps 44 of
the optical elements 40 may be positioned above the active optical
area(s) of the optical elements (see FIGS. 9 and 10). As a result,
when the optical elements 40 are inserted into their cavities 32,
34, the active optical areas 42 of the optical elements 40 are
positioned below the surface of the substrate 30, but the contacts
44 of the optical element 40 are positioned above the top surface
of the substrate 30 in engagement with or adjacent the contacts 48
of the substrate 30 (see FIG. 10) to form the solder joints 50 as
explained above.
[0032] As shown in FIG. 7, the waveguide 36 may be a waveguide
array comprising a plurality of waveguide channels 54. In the
illustrated example, the waveguide array 36 includes four waveguide
channels 54. Two of the waveguide channels 54 are located in a
first common horizontal plane. The other two of the waveguide
channels are located in a second common plane that is vertically
displaced from the first horizontal plane. Persons of ordinary
skill in the art will appreciate that waveguide arrays having fewer
or more waveguide channels than the illustrated array 36 may
alternatively be employed. Such persons will also appreciate that
waveguide arrays having different geometric arrangements of the
waveguide channels 54 than the illustrated waveguide array 36 could
also be employed. As already mentioned, the waveguide array 36 may
be secured to the substrate 30 or integrally formed with the
substrate. Further, the waveguide array 36 may be located generally
above a top surface of the substrate 30 or beneath the surface of
the substrate 30.
[0033] To construct an optical device such as the devices shown in
FIGS. 3-6 and 8-11, a substrate 30 is precision machined to have a
first cavity 32 dimensioned to receive and precisely position the
optical transmitter 40 (e.g., a VCSEL) and a second cavity 34
dimensioned to receive and precisely position the photodetector 40.
A waveguide 36 or a waveguide array 36 may be integrally formed
with the substrate between the first and second cavities 32, 34.
Alternatively, the waveguide or waveguide array 36 may be bonded to
the substrate 30.
[0034] The optical transmitter 40 is then positioned in the first
cavity 32 such that solder bump(s) 44 formed on a side (e.g., the
active side) of the transmitter are located adjacent and/or in
engagement with contact(s) 48 formed on or in the substrate 30. The
photodetector is positioned within the second cavity 34 such that
solder bump(s) 44 formed on a side (e.g., the active side) of the
photodetector are located adjacent and/or in engagement with
contact(s) 48 formed on or in the substrate 30. The solder bumps 44
are then melted to wet the metal contact pads 48 of the substrate
30 to thereby form solder joints 50 that mechanically and
electrically couple the optical elements 40 to the substrate 30.
The close tolerances of the cavities 32, 34 and the optical
transmitter 40 and the photodetector 40 ensure that placing the
optical elements 40 in their corresponding cavities achieves
passive alignment with the waveguide channel(s) 54 and that active
alignment is not necessary.
[0035] Although the examples described above employed a single
substrate 30 defining two cavities 32, 34 dimensioned to receive
two optical elements 40 such that a single substrate 30 carried at
least two optical elements 40 and a waveguide 36, persons of
ordinary skill in the art will appreciate that other numbers of
substrates, waveguides, and/or optical elements may alternatively
be employed. For example, as shown in FIGS. 12-15, an optical
device may be constructed with two or more separate substrates.
[0036] In the example of FIGS. 12-15, the optical device includes a
first substrate 130A defining a cavity 132 which is dimensioned to
receive a first optical element 140A. As in the examples described
above, the cavity 132 is precision machined to close tolerances to
ensure that positioning the optical element 140A within the cavity
132 achieves passive optical alignment. In the example of FIG. 12,
a waveguide array 136A is mounted to the first substrate 130A.
[0037] As shown in FIG. 14, the optical device also includes a
second substrate 130B defining a cavity 134 which is dimensioned to
receive a second optical element 140B. Like the cavity 132, the
cavity 134 is precision machined to close tolerances to ensure that
positioning the optical element 140B within the cavity 134 achieves
passive optical alignment. In the example of FIG. 14, a waveguide
array 136B is mounted to the second substrate 130B.
[0038] To optically couple the first and second substrates 130A,
130B, the illustrated optical device is further provided with a
flying waveguide 137 as shown in FIG. 13. The example flying
waveguide 137 of FIG. 13 is a waveguide array having a first end
mounted in a bore defined in a first connector 141 and a second end
mounted in a bore defined in a second connector 143. Each of the
connectors 141, 143 includes at least one alignment pin 145. As
shown in FIGS. 12 and 14, each of the substrates 140A, 140B defines
a bore 147A, 147B for receiving a respective one of the alignment
pins 145. The pins 145 and the bores 147A, 147B are positioned and
precision dimensioned such that inserting the pins 145 in their
respective bores 147A, 147B passively aligns the first waveguide
array 136A, the flying waveguide 137 and the second waveguide array
136B as shown in FIG. 15.
[0039] Although only two pins 145 and two bores 147A, 147B are
shown in FIGS. 12-15, persons of ordinary skill in the art will
appreciate that other numbers of alignment pins 145 and bores 147A,
147B may alternatively be employed. If, however, only one pin 145
is employed at each end of the flying waveguide 137, persons of
ordinary skill in the art will appreciate that the oppositely
disposed pins 145 should not be in concentric alignment to provide
enhanced stability and greater resistance to unwanted rotation
between the waveguide arrays 136A, 136B and 137.
[0040] Although in the examples discussed above, the optical
elements 40 include pre-deposited solder bumps 44, persons of
ordinary skill in the art will appreciate that these pre-formed
solder bumps 44 are optional. Alternatively, one or both of the
optical elements 240 may exclude the preformed solder bumps as
shown in the example of FIG. 16. Under such circumstances, after
placing the optical element 240 into its intended cavity, a solder
shooter 151 may be used to shoot molten solder balls 150 onto the
metal contact pads 48 of the substrate 30, 130A, 130B and metal
contact pads at the end of the traces 46 of the optical element
240. The molten solder balls wet the metal pads to form electrical
connections.
[0041] From the foregoing, persons of ordinary skill in the art
will readily appreciate that optical devices and methods of
manufacturing the same have been disclosed. Such persons will
further appreciate that the disclosed optical devices and methods
of manufacture are advantageous in several respects. For example,
because the optical devices illustrated in FIGS. 6 and 11 position
their VCSELs 40 in planes perpendicular to their corresponding
waveguide channels 56, the optical devices couple their VCSEL 40 to
their waveguides 36 without requiring an intervening mirror.
Similarly, because the photodetectors 40 are positioned in planes
perpendicular to the waveguide channels 54, no intervening mirrors
are required to couple the waveguide channels 54 to the
photodetectors.
[0042] Also, because the illustrated optical devices employ
cavities 32, 34 to mechanically pre-align their optical elements 40
with their waveguides 36, the illustrated devices can be assembled
without employing an active alignment process and without requiring
die-substrate standoff height control. As a result, the illustrated
optical devices may be more susceptible to mass production and,
thus, less costly to manufacture than their prior art counterparts.
Furthermore, the illustrated devices may employ stacked waveguide
arrays 36 to thereby increase the number of optical channels and,
thus, the operational bandwidth of the devices.
[0043] Although certain example methods and apparatus have been
described herein, the scope of coverage of this patent is not
limited thereto. On the contrary, this patent covers all methods
and apparatus fairly falling within the scope of the appended
claims either literally or under the doctrine of equivalents.
* * * * *