U.S. patent application number 14/524411 was filed with the patent office on 2016-04-28 for hybrid integrated optical device with high alignment tolerance.
This patent application is currently assigned to LAXENSE INC.. The applicant listed for this patent is LAXENSE INC.. Invention is credited to Ningning Feng, Xiaochen Sun.
Application Number | 20160116687 14/524411 |
Document ID | / |
Family ID | 55754635 |
Filed Date | 2016-04-28 |
United States Patent
Application |
20160116687 |
Kind Code |
A1 |
Sun; Xiaochen ; et
al. |
April 28, 2016 |
HYBRID INTEGRATED OPTICAL DEVICE WITH HIGH ALIGNMENT TOLERANCE
Abstract
An optical device including an optical bench and an optical
chip, the optical bench having multiple optical waveguides formed
on its first side and the optical chip has multiple optical
waveguides formed on its first side. The optical chip is flip-chip
bonded onto the optical bench with its first side facing the first
side of the optical bench. The distance between adjacent waveguides
on the optical bench are designed to be slightly different from the
distance between adjacent waveguides on the optical chip, where the
latter usually is a pre-designed value under certain conventions.
The difference amount is properly designed such that under
reasonable misalignment between the optical chip and the optical
bench in the in-plane direction perpendicular to waveguide
propagation one can always find that one of the multiple waveguides
is aligned sufficiently well with the corresponding waveguide on
the optical chip.
Inventors: |
Sun; Xiaochen; (Chino Hills,
CA) ; Feng; Ningning; (Arcadia, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LAXENSE INC. |
Walnut |
CA |
US |
|
|
Assignee: |
LAXENSE INC.
Walnut
CA
|
Family ID: |
55754635 |
Appl. No.: |
14/524411 |
Filed: |
October 27, 2014 |
Current U.S.
Class: |
385/14 ;
438/25 |
Current CPC
Class: |
G02B 6/4224 20130101;
G02B 6/4233 20130101; G02B 6/4238 20130101; G02B 6/4249 20130101;
G02B 6/42 20130101; G02B 6/4245 20130101 |
International
Class: |
G02B 6/42 20060101
G02B006/42 |
Claims
1. A hybrid integrated optical device comprising: an optical bench
having a first side and a second side generally opposite to the
first side and a plurality of optical waveguides formed at the
first side of the optical bench, the plurality of optical
waveguides having a corresponding plurality of ends located on a
facet of the optical bench; and an optical chip having a first side
and a second side generally opposite to the first side and a
plurality of optical waveguides formed at the first side of the
optical chip, the plurality of optical waveguides having a
corresponding plurality of ends located on a facet of the optical
chip; wherein the optical chip is aligned and flip-chip bonded onto
the optical bench with the first side of the optical chip facing
the first side of the optical bench and the end of each of the
plurality of optical waveguides of the optical chip faces the end
of a corresponding one of the plurality of optical waveguides of
the optical bench; wherein a distance between the ends of adjacent
ones of the plurality of optical waveguides of the optical bench is
different from a distance between the ends of adjacent ones of the
plurality of optical waveguides of the optical chip by a
predetermined amount.
2. The hybrid integrated optical device of claim 1, wherein the
optical bench comprises: an etched trench formed at the first side
of the optical bench to receive the optical chip through flip-chip
bonding process.
3. The hybrid integrated optical device of claim 2, wherein the
etched trench of the optical bench comprises: a plurality of spacer
structures formed on a bottom surface of the etched trench to
define a height of the optical chip perpendicular to the first side
of the optical chip during flip-chip bonding process; and a
plurality of metal traces and a plurality of micro solders disposed
on the bottom surface of the etched trench to electrically connect
to a plurality of metal electrodes at the first side of the optical
chip.
4. The hybrid integrated optical device of claim 1, wherein the
optical chip comprises: a plurality of metal electrodes disposed at
the first side of the optical chip to receive external electrical
power and signal to operate the optical chip.
5. The hybrid integrated optical device of claim 1, wherein the
plurality of optical waveguides of the optical bench form bent
shapes to approach each other at an edge of the optical bench.
6. The hybrid integrated optical device of claim 1, wherein the
plurality of waveguides of the optical bench comprises: a first
facet facing the etched trench coated with thin films with a
predetermined reflectivity; and a second facet, located farther
away from the etched trench at a far end of the optical bench,
coated with thin films with a predetermined reflectivity.
7. A hybrid integrated optical device comprising: an optical bench
having a first side and a second side generally opposite to the
first side; a first optical chip having a first side and a second
side generally opposite to the first side and a plurality of
optical waveguides formed at the first side of the first optical
chip, the plurality of optical waveguides having a corresponding
plurality of ends located on a facet of the first optical chip; and
a second optical chip having a first side and a second side
generally opposite to the first side and a plurality of optical
waveguides formed at the first side of the second optical chip, the
plurality of optical waveguides having a corresponding plurality of
ends located on a facet of the second optical chip; wherein the
first optical chip is aligned and flip-chip bonded onto the optical
bench with the first side of the first optical chip facing the
first side of the optical bench, and the second optical chip is
aligned and flip-chip bonded onto the optical bench with the first
side of the second optical chip facing the first side of the
optical bench, wherein the end of each of the plurality of optical
waveguides of the first optical chip faces the end of a
corresponding one of the plurality of optical waveguides of the
second optical chip; and wherein a distance between the ends of
adjacent ones of the plurality of optical waveguides of the second
optical chip is different from a distance between the ends of
adjacent ones of the plurality of optical waveguides of the first
optical chip by a predetermined amount.
8. The hybrid integrated optical device of claim 7, wherein the
optical bench comprises: a first etched trench formed at the first
side of the optical bench to receive the first optical chip through
flip-chip bonding process; and a second etched trench formed at the
first side of the optical bench to receive the second optical chip
through flip-chip bonding process.
9. The hybrid integrated optical device of claim 8, wherein the
first etched trench of the optical bench comprises: a plurality of
spacer structures formed on a bottom surface of the first etched
trench to define a height of the first optical chip perpendicular
to the first side of the first optical chip during flip-chip
bonding process; and a plurality of metal traces and a plurality of
micro solders disposed on the bottom surface of the first etched
trench to electrically connect to a plurality of metal electrodes
at the first side of the first optical chip.
10. The hybrid integrated optical device of claim 8, wherein the
second etched trench of the optical bench comprises: a plurality of
spacer structures formed on a bottom surface of the second etched
trench to define a height of the second optical chip perpendicular
to the first side of the second optical chip during flip-chip
bonding process; and a plurality of metal traces and a plurality of
micro solders disposed on the bottom surface of the second etched
trench to electrically connect to a plurality of metal electrodes
at the first side of the second optical chip.
11. The hybrid integrated optical device of claim 7, wherein the
first optical chip comprised: a plurality of metal electrodes
disposed at the first side of the first optical chip to receive
external electrical power and signal to operate the first optical
chip.
12. The hybrid integrated optical device of claim 7, wherein the
second optical chip comprises: a plurality of metal electrodes
disposed at the first side of the second optical chip to receive
external electrical power and signal to operate the second optical
chip.
13. A method for making a hybrid integrated optical device,
comprising: providing an optical bench having a first side and a
second side generally opposite to the first side and a plurality of
optical waveguides formed at the first side of the optical bench,
the plurality of optical waveguides having a corresponding
plurality of ends located on a facet of the optical bench;
providing an optical chip having a first side and a second side
generally opposite to the first side and a plurality of optical
waveguides formed at the first side of the optical chip, the
plurality of optical waveguides having a corresponding plurality of
ends located on a facet of the optical chip, wherein a distance
between the ends of adjacent ones of the plurality of optical
waveguides of the optical bench is different from a distance
between the ends of adjacent ones of the plurality of optical
waveguides of the optical chip by a predetermined amount; aligning
and flip-chip bonding the optical chip onto the optical bench with
the first side of the optical chip facing the first side of the
optical bench and the end of each of the plurality of optical
waveguides of the optical chip faces the end of a corresponding one
of the plurality of optical waveguides of the optical bench; and
selecting one of the plurality of optical waveguides of the optical
bench and the corresponding optical waveguide of the optical chip,
which has a better alignment to each other than alignment of all
other ones of the plurality of optical waveguides of the optical
bench to their corresponding optical waveguides of the optical
chip, as a light transmitting channel.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to an optical device with hybrid
integrated optical waveguide chips. In particular, the invention
relates to an optical device using flip-chip method to hybrid
integrate one or more optical chips on an optical bench and both
the chips and the optical bench include multiple optical waveguides
with different distances to compensate for alignment errors.
[0003] 2. Description of the Related Art
[0004] Optical interconnects are adopted in data communications at
unprecedented rate as more bandwidth and longer transmission reach
are required by mega datacenters for applications from social
networks, cloud service, to big data analysis and high performance
computing. Unlike optical transceiver modules or subsystems made of
ultrahigh performance discrete components in telecommunications,
lower cost, more compact and more power efficient optical
transceivers or engines are demanded in data communications.
Integrating multiple optical components or chips such as lasers,
modulators, photodetectors, switches, attenuators and etc. on an
optical bench chip to form a hybrid integrated optical device is
one way to reduce assembling cost and footprint.
[0005] In such hybrid integrated optical devices, passively placing
and bonding the optical chips on optical benches is highly
preferred as it enables automated low cost assembling for massive
volume production required by huge data communications market.
However, unlike the mature integrated circuit (IC) fully automated
packaging processes, assembling these optical chips requires very
precise alignment in the range of micrometers or less because these
chips and optical benches usually include tiny optical waveguides
which must be well aligned with each other to form an optical
transmission path.
[0006] Borrowing from the IC packaging industry, people have been
trying to use the tools called flip-chip bonder to bond the optical
chips upside down onto an optical bench. Because the optical
waveguides are almost always formed on the top side of an optical
chip or an optical bench by some semiconductor or other wafer
processing techniques, the distance between the optical waveguide
and the top surface is well controlled. By placing an optical chip
upside down onto an optical bench and with some pre-defined spacer
structures on the optical bench, the optical waveguide alignment in
the direction perpendicular to the surface (out-of-plane) of the
optical chip and the optical bench can be precisely controlled.
This flip-chip bonding approach has been widely discussed.
[0007] On the other hand, the alignment in the directions parallel
to the surface (in-plane) can only be controlled by the flip-chip
bonder's accuracy and bonding process control. A modern
top-of-the-line flip-chip bonder can achieve a +/-0.5 micrometer
alignment accuracy, however, in practice, the bonding involving
processes such as thin metal solder melting, adhesive curing and
etc. inevitably contributing to final alignment error due to
physical movement of the chip under temperature, stress and/or
phase changes. The final alignment error (3.sigma. confidence
interval) is usually +/-2 micrometers or worse from the statistics
of our experiment. The alignment in in-plane waveguide propagation
direction is relatively tolerant and satisfied with this alignment
error while the in-plane direction perpendicular to waveguide
propagation requires accurate alignment, especially for small
optical waveguides such as those in lasers. To increase the
alignment tolerance in this direction, people tried to include
either a taper structure at the end of the waveguide or a lens
structure in order to expand the optical beam for more tolerant
alignment. However, including a taper structure as part of the
optical waveguide requires design change of the optical chips which
prohibits the use of widely available and proven commercial chips
as well as, in many cases, harms device performance. The lens which
can be used in such condition cannot be made monolithically on the
optical bench and has to be installed separately which introduces
additional alignment error during the assembling. These and similar
methods have been proposed but none of them is being adopted in
mass production due to above-stated issues.
SUMMARY OF THE INVENTION
[0008] Optical devices according to embodiments of the present
invention significantly increase the alignment tolerance in the
in-plane direction perpendicular to waveguide propagation during
flip-chip bonding.
[0009] One embodiment is an optical device. The optical device
comprises an optical bench and an optical chip. The optical bench
comprises multiple optical waveguides formed on its first side. The
optical chip comprises multiple optical waveguides formed on its
first side. The optical chip is flip-chip bonded onto the optical
bench with its first side towards the first side of the optical
bench. The waveguides on the optical chip and the waveguides on the
optical bench are in good alignment in out-of-plane direction
guaranteed by the spacer structure formed on the first side of the
optical bench as stated earlier. The distance between the
waveguides on the optical bench are designed to be slightly
different from the distance between the waveguides on the optical
chip which usually is a pre-designed value under certain
conventions. The distance between the waveguides on the optical
bench is properly designed such that under reasonable misalignment
between the optical chip and the optical bench in the in-plane
direction perpendicular to waveguide propagation one can always
find one of the waveguides is aligned sufficiently well with the
corresponding waveguide on the optical chip.
[0010] Another embodiment is an optical device comprising an
optical bench and two optical chips. The optical bench comprises
multiple optical waveguides formed on its first side. The two
optical chips comprise multiple optical waveguides formed on their
first side, respectively. The two optical chips are flip-chip
bonded to the optical bench with good out-of-plane alignment
guaranteed by the spacer structure formed on the first side of the
optical bench. The distance between the waveguides on the first
optical chip is designed to be slightly different from the distance
between the waveguides on the second optical chip. The distance
between the waveguides on the second optical chip is properly
designed such that under reasonable misalignment between the first
optical chip and the second optical chip in the in-plane direction
perpendicular to waveguide propagation one can always find one of
the waveguides is sufficiently well aligned with the corresponding
waveguide on the optical chip.
[0011] The idea behind the invention is based on a finding in
practice that in many cases, the overall cost of a hybrid
integrated optical device or system is dominated by the yield of
high precision optical assembling over optical chips, especially in
high volume market field where the required optical chips become
commodities. A good production model can be established by
balancing the use of a multi-waveguide (i.e. multi-channel) optical
chip, whose cost is roughly scaled with the number of waveguide
channels, and the significant improvement of assembling yield due
to larger alignment tolerance during flip-chip bonding.
[0012] Additional features and advantages of the invention will be
set forth in the descriptions that follow and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims thereof as well as the
appended drawings.
[0013] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1A is a perspective view illustrating a hybrid
integrated optical device according to an embodiment of the present
invention.
[0015] FIG. 1B is an exploded view illustrating the hybrid
integrated optical device shown in FIG. 1A.
[0016] FIG. 2 is a perspective view illustrating a hybrid
integrated optical device according to an embodiment of the present
invention.
[0017] FIG. 3 is a perspective view illustrating a hybrid
integrated optical device according to an embodiment of the present
invention. The optical device comprises an optical bench with two
etched trenches, etched spacers, metal traces and micro solders and
two flip-chip bonded optical chips both with multiple optical
waveguides, respectively.
[0018] FIG. 4A is a cross-sectional view illustrating the
out-of-plane alignment between a waveguide on the optical device
and a waveguide on the optical bench (or on the other optical
device) of the hybrid integrated optical device shown in FIG. 1 and
FIG. 2 (or in FIG. 3).
[0019] FIG. 4B is a cross-sectional view illustrating the in-plane
alignment between a waveguide on the optical device and a waveguide
on the optical bench (or on the other optical device) of the hybrid
integrated optical device shown in FIG. 1 and FIG. 2 (or in FIG.
3).
[0020] FIG. 5A is a plot illustrating the optical loss versus
in-plane misalignment of an example.
[0021] FIG. 5B is a plot illustrating the optical loss versus
in-plane misalignment of another example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] The invention relates to an optical device with hybrid
integrated optical waveguide chips. In particular, the invention
relates to an optical device using flip-chip method to hybrid
integrate one or more optical chips on an optical bench and both
the chips and the optical bench include multiple optical waveguides
with different distances to compensate alignment errors.
[0023] An embodiment of the present invention is described with
reference to FIGS. 1A-1B. The optical device comprises an optical
bench with multiple optical waveguides, an etched trench, etched
spacers, metal traces and micro solders and a flip-chip bonded
optical chip with multiple optical waveguides. FIG. 1A is a
perspective view illustrating the hybrid integrated optical device
while FIG. 1B is an exploded view. The components are drawn in a
way as if they were transparent for the purpose of easy observation
of structures behind (structures behind other structures are shown
in dashed lines). The hybrid integrated optical device comprises an
optical bench 100 and a flip-chip bonded optical chip 200. The
optical bench 100 can be made by any semiconductor or insulating
materials including, but not limited to, silicon, silica, and
indium phosphide. The optical bench 100 comprises a first side and
a second side generally opposite to the first side. The optical
bench 100 further comprises multiple optical waveguides 101A-101C
on the first side formed by etching or deposition technologies. The
waveguides 101A-101C are made of optical transparent materials
including, but not limited to, silicon, silicon nitride, and indium
gallium arsenide phosphide. The optical bench 100 further comprises
a trench 102 and multiple spacers 103 formed by etching
technologies. The depth of both the trench 102 and spacers 103 are
precisely controlled using semiconductor processing techniques. The
optical bench 100 further comprises metal traces 110 and micro
solders 120 in the trench 102 for the purpose of electrically
connecting to the flip-chip bonded optical chip. Both end facets of
the waveguides 101A-101C, i.e. the facet facing the trench and the
facet located farther away from the trench at the far end of the
optical bench, are coated with anti-reflection coating to reduce
light reflection.
[0024] The optical chip 200 can be made by any semiconductor or
insulating materials including, but not limited to, silicon,
silica, and indium phosphide. The optical chip 200 comprises a
first side and a second side generally opposite to the first side.
The optical chip 200 further comprises multiple optical waveguides
201A-201C on the first side. The optical chip 200 can be an active
device which requires external electrical power to operate. An
active device can include, but not limited to, laser, modulator,
photodetector, amplifier, attenuator, and switch. The optical chip
200 further comprises electrodes 210 to receive external electrical
power.
[0025] The optical chip 200 is bonded on to the optical bench 100
though a flip-chip process in which the optical chip 200 is flipped
thus its first side faces the first side of the optical bench 100.
The optical chip 200 is then aligned to the optical bench 100 by
comparing alignment marks on the first side of the optical chip and
the first side of the optical bench. The alignment marks are not
illustrated in the figures. The optical chip 200 is then push on to
the optical bench 100 while heating up either or both the chip 200
and bench 100. The optical chip is stopped by the spacer 103 from
further descending. The micro solders 120 are melted to form
electrical connection and mechanical bonding between the metal
trace 110 and the electrode 210.
[0026] Another embodiment is described with reference to FIG. 2.
This embodiment is similar to the one shown in FIG. 1A with the
exception of different waveguides configuration on the optical
bench 100. In this embodiment, the waveguides 101A-101C are bent or
curved to approach each other at the end of the optical bench 100.
The closely arranged waveguide ends can facilitate packaging design
as the output light location is approximately the same no matter
which waveguide light comes out.
[0027] Another embodiment is described with reference to FIG. 3.
This embodiment comprises an optical bench 100 and two optical
chips 200 and 300. In this embodiment, the optical waveguides
101A-101C in the two previous two embodiments are replaced with the
optical waveguides 301A-301C on the second optical chip 300. The
two optical chips 200 and 300 are both aligned with and flip-chip
bonded to the optical bench 100, in respective etched trenches.
[0028] In hybrid integration, the goal of the flip-chip bonding is
to accurately align the waveguides between chips (or bench) so
light can transmit from one waveguide to another with minimal
optical loss. The optical alignment is explained in cross-sectional
views in FIG. 4A (parallel to the x-z plane of FIG. 1A) and FIG. 4B
(parallel to the x-y plane of FIG. 1).
[0029] FIG. 4A illustrates the out-of-plane (the direction
perpendicular to the first side of the optical bench or the optical
device) alignment between two waveguides. In some embodiments (e.g.
the ones in FIG. 1 and FIG. 2), one waveguide 201 (which may be any
one of 201A-201C) belongs to the optical device 200 and the other
waveguide 101 (which may the corresponding one of 101A-101C)
belongs to the optical bench 100 while in other embodiments (e.g.
the one in FIG. 3), the waveguide 101 belongs to the second optical
device 300. A waveguide (e.g. 201) is always surrounded by cladding
layers (e.g. 205 and 206) which has lower refractive index to make
light confined in the waveguide core layer 201. The thicknesses of
these cladding layers are usually well defined by semiconductor or
other wafer processing techniques, so the distance between the
optical waveguide (e.g. 201) and the surface of the cladding layer
(e.g. 205) is well controlled. By placing an optical chip 200
upside down onto an optical bench and with the pre-defined spacer
103 on the optical bench, the optical waveguide alignment in the
out-of-plane direction of the optical chip and the optical bench
can be precisely controlled. The optical bench includes precisely
etched trench 102 and spacer 103. The spacer 103 serves as a stop
for the flipped chip when it is pushed onto the optical bench. With
precisely controlled trench 102 depth and spacer 103 height, the
waveguide 101 and waveguide 201 can be aligned accurately in the
out-of-plane direction.
[0030] FIG. 4B illustrates the in-plane (in the plane parallel to
the first side of the optical bench or the optical device)
alignment between two waveguides. In some embodiments (e.g. the
ones in FIG. 1 and FIG. 2), one set of waveguides 201A-201C belong
to the optical device 200 and the other set of waveguides 101A-101C
belong to the optical bench 100 while in other embodiments (e.g.
the one in FIG. 3), the set of waveguides 101A-101C belong to the
second optical device 300. The alignment in in-plane waveguide
propagation direction (indicated by "X" direction in FIG. 4B) has
relatively large tolerance while the in-plane direction
perpendicular to waveguide propagation (indicated by "Y" direction
in FIG. 4B) requires accurate alignment, especially for small
optical waveguides such as those in lasers. The latter one is the
focus in the embodiments of this invention. In the illustrated
example in FIG. 4B, the distance between adjacent ones of the
waveguides 101A-101C (pitch) is slightly smaller (or larger) than
the distance between adjacent ones of the waveguides 201A-201C. In
this case, when there is misalignment in either positive or
negative "Y" direction, one can always find one of the waveguides
101A-101C with the best alignment with the corresponding waveguide
among waveguides 201A-201C. By properly designing the distance
difference, a certain coupling loss within the system alignment
tolerance can be guaranteed.
[0031] FIG. 5A and 5B illustrate the optical loss versus in-plane
misalignment of two exemplary designs. In both cases, all the
waveguides are designed to have a mode size of 1.5 micrometers
which is a typical mode size of lasers emitting 1.55 micrometers
wavelength light. In the case shown in FIG. 5A, the difference
between the pitches of two groups of waveguides (i.e. 101A-101C and
201A-201C) is 0.7 micrometer. The solid curve in FIG. 5A shows the
coupling loss versus misalignment (offset) when there is only one
pair of waveguides to align with each other. It can be seen that
the coupling loss increases quickly with misalignment and if -1 dB
coupling loss is the maximal loss allowed then the misalignment
must be controlled within +/-0.8 micrometer which is very difficult
to repeatedly achieve even with a state-of-art flip-chip bonder and
carefully carried bonding process. The dashed curve in FIG. 5A
shows the coupling loss with two waveguides for each group. The
coupling loss is the better of the two waveguides in varying
misalignment conditions. It can be seen that the misalignment
tolerance range corresponding to -1 dB coupling loss is extended to
+/-1.5 micrometers. And the misalignment tolerance range is further
extended to +/-2.1 micrometers with three waveguides in each group
as shown by the dash-dotted curve in FIG. 5A. As stated in the
background section earlier, our experiment showed +/-2 micrometers
is a reasonable range that can be achieved reliably in practice.
Therefore in this particular example, a three-waveguide design can
be adopted.
[0032] FIG. 5B shows another example where the difference between
the pitches of two groups of waveguides (i.e. 101A-101C and
201A-201C) is 1.0 micrometer. With the maximal allowed coupling
loss of -2 dB a two-waveguide design can satisfy the corresponding
+/-2 micrometers misalignment range. And a three-waveguide design
even extends the misalignment tolerance to +/-3 micrometers. In
theory, one can keep increasing the number of waveguides to further
extend misalignment tolerance, however, this will increase the cost
of the optical chip and/or the optical bench which is usually
scaled with the chip size. In practice, a design with an
appropriate number of waveguides may be chosen by balancing the
coupling benefit and associated cost increase.
[0033] After the optical chips 200, 300 are bonded on to the
optical bench 100 though the flip-chip process, only one of the
multiple (e.g. three) waveguides, i.e. the one that has the best
alignment with the corresponding waveguide, is used for actual
signal transmission. Optical tests may be performed after flip-chip
bonding to determine one waveguide with the best alignment result.
For example, if the optical device is a laser chip with three
waveguides (i.e. a 3-channel laser array), after flip-chip bonding
to an optical bench, the output light from the bench may be
measured out of the three optical bench waveguides and the best
channel will be used.
[0034] In this optical device, some waveguides are not used; this
is a tradeoff by "sacrificing" some waveguides to increase
alignment tolerance. Cost-benefit analyses tend to show that using
multiple waveguides as disclosed in the embodiments here decreases
the overall assembling cost by increasing yield.
[0035] It will be apparent to those skilled in the art that various
modification and variations can be made in the optical system and
related fabrication methods of the present invention without
departing from the spirit or scope of the invention. Thus, it is
intended that the present invention cover modifications and
variations that come within the scope of the appended claims and
their equivalents.
* * * * *