U.S. patent application number 11/237900 was filed with the patent office on 2006-04-13 for waveguide type optical device and manufacturing method thereof.
This patent application is currently assigned to NEC Corporation. Invention is credited to Shigeru Yoneda.
Application Number | 20060078245 11/237900 |
Document ID | / |
Family ID | 19131240 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060078245 |
Kind Code |
A1 |
Yoneda; Shigeru |
April 13, 2006 |
Waveguide type optical device and manufacturing method thereof
Abstract
An array waveguide diffraction grating 201 as waveguide type
optical device comprises a planer lightwave circuit 203 with an
optical waveguide layer 211 formed on a silicon substrate 212 and
having a predetermined thickness h.sub.0, a first compensation
substrate 204 bonded to the side of the optical waveguide layer 211
and having a thickness h.sub.1 and a second compensation substrate
205 formed on the silicon substrate 212 and having a thickness
h.sub.4. The linear expansion coefficients .alpha..sub.1 and
.alpha..sub.4 of the two compensation substrates 204 and 205 are
set to be greater than that of the optical waveguide element 203,
and highly rigid adhesives are used as a first and a second
adhesive 214 and 215. It is thus possible to have the contraction
of the optical waveguide element 203 due to a temperature change
increased with the first and second substrates, thus permitting the
center frequency setting to a desired value in a predetermined
temperature range. Similar effects are obtainable by merely
providing a support substrate on the substrate side of the optical
waveguide element 203.
Inventors: |
Yoneda; Shigeru; (Tokyo,
JP) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY;LAW GROUP, PLLC
Suite 200
8321 Old Courthouse Road
Vienna
VA
22182-3817
US
|
Assignee: |
NEC Corporation
Tokyo
JP
|
Family ID: |
19131240 |
Appl. No.: |
11/237900 |
Filed: |
September 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10266631 |
Oct 9, 2002 |
6993232 |
|
|
11237900 |
Sep 29, 2005 |
|
|
|
Current U.S.
Class: |
385/14 ;
385/49 |
Current CPC
Class: |
G02B 6/1203
20130101 |
Class at
Publication: |
385/014 ;
385/049 |
International
Class: |
G02B 6/12 20060101
G02B006/12 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 10, 2001 |
JP |
312611/2001 |
Claims
1-9. (canceled)
10. A method of manufacturing a waveguide type optical device
comprising: an element preparation step of preparing an optical
waveguide element; a checking step for checking whether the center
wavelength of the prepared optical waveguide element can be set to
a predetermined value under temperature control in a predetermined
temperature range; and a bonding step of bonding, to the substrate
side of an optical waveguide element having judged in the checking
step to be incapable of setting the desired value, a support
substrate having a predetermined linear expansion coefficient
greater than that of the substrate itself of the optical waveguide
element.
11. A method of manufacturing a waveguide type optical device
comprising: an element preparation step of preparing an optical
waveguide element; and a bonding step for bonding, to the substrate
side of optical waveguide element prepared in the element
preparation step, a support substrate having a predetermined linear
expansion coefficient greater than that of the substrate itself of
the optical waveguide element.
12. The waveguide type optical device according to claim 10,
wherein the adhesive used for bonding in the bonding step is highly
rigid when hardened.
13. A method of manufacturing a waveguide type optical device
comprising: an element preparation step of preparing an optical
waveguide element; a checking step for checking whether the center
wavelength of the prepared optical waveguide element can be set to
a desired value under temperature control in a predetermined
temperature range; a first substrate bonding step of bonding, to
the waveguide side of an optical waveguide element judged in the
checking step to be incapable of setting the desired value, a first
substrate having a linear expansion coefficient greater than that
of the substrate itself of the optical waveguide element; and a
second step of bonding, to the substrate side of the optical
waveguide element judged in the checking step to be incapable of
setting the desired value, a second substrate having a linear
expansion coefficient greater than that of the substrate itself of
the optical waveguide element.
14. A method of manufacturing a waveguide type optical device
comprising: an element preparation step of preparing an optical
waveguide element; a first substrate bonding step of bonding, to
the waveguide side of the optical waveguide element prepared in the
element preparation step a first substrate having a linear
expansion coefficient greater than that of the substrate itself of
the optical waveguide element; and a second step of bonding, to the
substrate side of the optical waveguide element prepared in the
element preparation step a second substrate having a linear
expansion coefficient greater than that of the substrate itself of
the optical waveguide element.
15. The waveguide type optical device according to claim 13,
wherein the first and second substrates are substantially equal in
thickness and linear expansion coefficient.
16. A method of manufacturing a waveguide type optical device
comprising: an element preparation step of preparing an optical
waveguide element; a temperature measuring step of measuring a
temperature, at which the center wavelength of the prepared optical
waveguide element is set to a desired value; a support substrate
linear expansion coefficient selecting step of selecting the
extent, by which the linear expansion coefficient of the support
substrate to be bonded to the substrate side of the optical
waveguide element is greater than that of the substrate in the
optical waveguide element, on the basis of the temperature measured
in the ideal temperature measuring step; and a bonding step of
bonding, to the substrate side of the optical waveguide element, a
support substrate having the linear expansion coefficient selected
in the support substrate linear expansion coefficient selecting
step.
17. A method of manufacturing a waveguide type optical device
comprising: an element preparation step of preparing an optical
waveguide element; a temperature measuring step of measuring a
temperature, at which the center wavelength of the prepared optical
waveguide element is set to a desired value; a first/second
substrate linear expansion coefficient selecting step of selecting
the extent, by which the linear expansion coefficient of the first
substrate to be bonded to the waveguide side of the optical
waveguide element and the liner expansion coefficient of the second
substrate to be bonded to the substrate side of the optical
waveguide element are greater than that of the substrate of the
optical waveguide element, on the basis of the temperature measured
in the ideal temperature measuring step; and bonding step of
bonding the first and second substrates with the linear expansion
coefficient selected in the first/second substrate linear expansion
coefficient selecting step to corresponding parts of the optical
waveguide element.
18. The waveguide type optical device according to claim 11,
wherein the adhesive used for bonding in the bonding step is highly
rigid when hardened.
19. The waveguide type optical device according to claim 14,
wherein the first and second substrates are substantially equal in
thickness and linear expansion coefficient.
Description
[0001] The present Application is a Divisional Application of U.S.
patent application Ser. No. 10/266,631 filed on Oct. 9, 2002.
[0002] This application claims benefit of Japanese Patent
Application No. 2001-312611 filed on Oct. 10, 2001, the contents of
which are incorporated by the reference.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to waveguide type optical
device used as filter device in such fields as optical
communication and data processing using light and also to method of
manufacturing the same. More specifically, the present invention
relates to a waveguide type optical device permitting improvement
of the yield in manufacture and also to method for manufacturing
the same.
[0004] With spread of optical communication techniques and
development of data processing techniques using light, optical
waveguide elements have become in wide spread use as optical
waveguide filters. Such optical waveguide elements permitting
various functions by utilizing interference of light generally vary
in refractive index and optical path length in dependence on the
ambient temperature. Therefore, the pass bandwidth and center
wavelength fluctuate with individual manufactured optical waveguide
elements.
[0005] Accordingly, the center wavelength of optical waveguide
elements including AWG (arrayed waveguides) is adjusted by using a
Velch element or heater as a temperature controller such as to
satisfy grid specifications prescribed in ITU (International
Telecommunication Unison). For example, in a quartz system optical
waveguide element, the center wavelength has a temperature
dependency of about 0.1 nm/.degree. C., and adjustment to a desired
center wavelength is made by adjusting the preset temperature of a
waveguide type optical device using such an optical waveguide
element.
[0006] However, the center wavelength of manufactured optical
waveguide elements or waveguide type devices incorporating such
elements may not always be preset to a desired value in a
temperature range adjusted by the above temperature controller. The
optical waveguide elements and waveguide type optical devices,
which are incapable of being temperature adjusted with the
temperature controller, have heretofore become rejected products,
and this has been a significant cause of the fact that the yield of
manufactured elements or devices can not be improved.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide a waveguide
type optical device capable of improving the yield when
manufacturing waveguide type optical devices, with which a desired
center wavelength is obtainable, irrespective of the difference of
the temperature characteristics of individual optical waveguide
elements.
[0008] According to a first aspect of the present invention, there
is provided a waveguide type optical device comprising: a planar
lightwave circuit; a support substrate disposed on the substrate
side of the optical waveguide element and having a predetermined
linear expansion coefficient greater than that of the substrate;
and a temperature controller assembled in the support substrate and
serving to control the temperature of the optical waveguide
element.
[0009] In this aspect of the present invention, on the substrate
side of the planar lightwave circuit a support substrate having a
greater linear expansion coefficient than that of the substrate is
disposed, and the temperature of the support substrate and the
optical waveguide element is controlled with the temperature
controller assembled in the support substrate. In the temperature
control, the support substrate causes expansion and contraction of
the optical waveguide element such as to substantially increase the
linear expansion coefficient of the optical waveguide element. It
is thus possible to control the center wavelength in a broader
range, and this control is possible since a predetermined linear
expansion coefficient is provided even when a desired center
wavelength could not have been obtained in the case of using no
support substrate having a great linear expansion coefficient.
Thus, it is possible to improve the yield.
[0010] In a second aspect of the present invention, in the
waveguide type optical device of the first, the substrate in the
optical waveguide element and the support substrate are bonded to
each other by highly rigid adhesive.
[0011] According to this aspect of the present invention, the
optical waveguide element substrate and the support substrate are
bonded together by using a highly rigid adhesive to let expansion
and contraction of the support substrate to be efficiently
transmitted to the optical waveguide element side.
[0012] According to this aspect of the present invention, with the
planar lightwave circuit sandwiched between the first and second
substrates having a linear expansion coefficient greater than its
linear expansion coefficient, these linear expansion coefficients
are set adequately to preclude warping with temperature changes
that would take place in the case of bonding only one substrate to
the optical waveguide element.
[0013] According to this aspect of the present invention, the first
and second substrates having a linear expansion coefficient greater
than that of the planer lightwave circuit are disposed to sandwich
the optical waveguide element to substantially increase the linear
expansion coefficient of the optical waveguide element. It is thus
possible to control the center wavelength of the optical waveguide
element in a broader range and obtain a desired center wavelength.
Thus, it is possible to obtain the desired center wavelength and
hence improve the yield.
[0014] In a fourth aspect of the present invention, in the
waveguide type optical device of the third aspect, a first adhesive
used for bonding together the waveguide in the optical waveguide
element and the first substrate and a second adhesive used for
bonding together the substrate in the optical waveguide element and
the second substrate are highly rigid.
[0015] According to this aspect of the present invention, the
optical waveguide element substrate and the support substrate are
bonded together by using a highly rigid adhesive to let expansion
and contraction of the support substrate to be efficiently
transmitted to the optical waveguide element side.
[0016] In a fifth aspect of the present invention, in the waveguide
type optical device of the fourth aspect, the linear expansion
coefficient of the first substrate is selected to a value such as
to reduce the warping of the whole structure, obtained by disposing
the second substrate to the substrate side of the optical waveguide
element, with temperature changes.
[0017] According to this aspect of the present invention, with the
planer lightwave circuit sandwiched between the first and second
substrates having a liner expansion coefficient greater than its
linear expansion coefficient, these linear expansion coefficients
are set adequately to preclude warping with temperature changes
that would take place in the case of bonding only one substrate to
the optical waveguide element.
[0018] In a sixth aspect of the present invention, the waveguide
type optical device of the third aspect further comprises: a fiber
array optically coupled to the optical waveguide element; and
reinforcement glass 209 disposed on the waveguide side of the
optical waveguide element as shown in FIG. 1 and serving to
reinforce the bonding strength of the fiber array; the first
substrate having a thickness equal to or less than the thickness of
the reinforcement glass 209.
[0019] According to the sixth aspect, with the first substrate
disposed on the waveguide side of the optical waveguide element in
the waveguide type optical device total thickness of the device may
be increased. On the contrary, in this aspect, because of the
presence, on the waveguide side, of the reinforcement glass 209 for
reinforcing the bonding strength of the fiber array, the increase
of the overall thickness is prevented by setting the thickness of
the first substrate to be equal to or less than the thickness of
the reinforcement glass 209.
[0020] In a seventh aspect of the present invention, in the
waveguide type optical device of the first aspect the support
substrate and the temperature controller are substantially equal in
thickness.
[0021] According to this aspect, with the support substrate and the
temperature controller made substantially equal in thickness, it is
made possible to manufacture the waveguide type optical device
having a thickness substantially equal to the thickness in the case
of the waveguide type optical device, in which the temperature
controller essential on the substrate side of the optical waveguide
element is used.
[0022] In an eighth aspect of the present invention, in the
waveguide type optical device of the third aspect the second
substrate and the temperature controller are substantially equal in
thickness.
[0023] According to this aspect, like the waveguide type optical
device as set forth in claim 1, the waveguide type optical device
can be manufactured with a thickness which is substantially equal
to the overall thickness of the waveguide type optical device, the
essential temperature controller is used on the substrate side of
the optical waveguide element.
[0024] In a ninth aspect of the present invention, in the waveguide
type optical device of the third aspect the first and second
substrates are substantially equal in thickness and linear
expansion coefficient.
[0025] According to this aspect, the simplest selection standards
of the first and second substrates bonded to the opposite side of
the optical waveguide element are specified. By using, as the first
and second substrates, those which are entirely the same in
specifications and have a linear expansion coefficient than that of
the optical waveguide element, warping is hardly generated so long
as warping of the optical waveguide element is hardly generated. It
is thus possible to increase only the expansion/contraction factor
of the optical waveguide element. Besides, since it is possible to
provide common specifications to the first and second substrates,
it is possible to realize cost reduction and readier parts
management.
[0026] According to a tenth aspect of the present invention, there
is provided a method of manufacturing a waveguide type optical
device comprising: an element preparation step of preparing an
optical waveguide element; a checking step for checking whether the
center wavelength of the prepared optical waveguide element can be
set to a predetermined value under temperature control in a
predetermined temperature range; and a bonding step of bonding, to
the substrate side of an optical waveguide element having judged in
the checking step to be incapable of setting the desired value, a
support substrate having a predetermined linear expansion
coefficient greater than that of the substrate itself of the
optical waveguide element.
[0027] According to this aspect, a method of manufacturing the
waveguide type optical device according to the present invention as
set forth in claim 1 is shown. First, in the element preparation
step the optical waveguide element is prepared. Then, in the
checking step a check is made as to whether the center wavelength
of individual optical waveguide elements can be set to the desired
value under temperature control in the predetermined temperature
range. In the prior art, it was inevitable to discard those which
are found in the checking step to be incapable of setting the
center wavelength to the desired value, as rejected parts.
According to this aspect of the present invention, in the bonding
step to the optical waveguide element, judged in the checking step
to be incapable of setting the center wavelength to the desired
value is bonded a support substrate having a predetermined linear
expansion coefficient greater than that of the substrate itself of
the optical waveguide element, thus permitting the use of the
resultant element as waveguide type optical device.
[0028] According to an eleventh aspect of the present invention,
there is provided a method of manufacturing a waveguide type
optical device comprising: an element preparation step of preparing
an optical waveguide element; and a bonding step for bonding, to
the substrate side of optical waveguide element prepared in the
element preparation step, a support substrate having a
predetermined linear expansion coefficient greater than that of the
substrate itself of the optical waveguide element.
[0029] In this aspect, a different method of manufacturing the
waveguide type optical device according to the present invention as
set forth in claim 1 is shown. First, in the element preparation
step the optical waveguide element is prepared. In the bonding
step, to the substrate side of the prepared optical waveguide
element is bonded a support substrate having a predetermined linear
expansion coefficient greater than that of the substrate itself to
the optical waveguide element, thus permitting the use of the
resultant element as waveguide type optical device. This aspect of
the present invention is different from the aspect of the present
invention as set forth in claim 10 in that to the substrate side of
the optical waveguide element is non-conditionally bonded the
support substrate having the predetermined linear expansion
coefficient greater than that of the substrate itself of the
optical waveguide element.
[0030] In a twelfth aspect of the present invention, in the method
of manufacturing the waveguide type optical device of the tenth or
eleventh aspect, the adhesive used for bonding in the bonding step
is highly rigid when hardened.
[0031] According to the aspect, a highly rigid adhesive is used in
the bonding step to permit the expansion and contraction of the
support substrate to be efficiently transferred to the optical
waveguide element side.
[0032] According to a thirteenth aspect of the present invention,
there is provided a method of manufacturing a waveguide type
optical device comprising: an element preparation step of preparing
an optical waveguide element; a checking step for checking whether
the center wavelength of the prepared optical waveguide element can
be set to a desired value under temperature control in a
predetermined temperature range; a first substrate bonding step of
bonding, to the waveguide side of an optical waveguide element
judged in the checking step to be incapable of setting the desired
value, a first substrate having a linear expansion coefficient
greater than that of the substrate itself of the optical waveguide
element; and a second step of bonding, to the substrate side of the
optical waveguide element judged in the checking step to be
incapable of setting the desired value, a second substrate having a
linear expansion coefficient greater than that of the substrate
itself of the optical waveguide element.
[0033] According to this aspect, a method of manufacturing the
waveguide type optical device according to the present invention as
set forth in claim 3. First, in the element preparation step the
optical waveguide element is prepared. Then in the checking step,
the prepared optical waveguide element is checked as to whether the
center wavelength of the optical waveguide element can be set to
the desired value under temperature control in the predetermined
temperature range. In the prior art, it is inevitable to discard as
rejected parts those optical waveguide elements which are judged in
the checking step to be incapable of setting the center wavelength
to the desired value.
[0034] According to this aspect, in the first substrate bonding
step to the waveguide side of the optical waveguide element judged
in the checking step to be capable of setting the center wavelength
to the desired value is bonded the first substrate having the
linear expansion coefficient greater than that of the substrate
itself of the optical waveguide element. Also, in the second
substrate bonding step to the substrate side of the optical
waveguide element judged in the checking step to be incapable of
setting the center wavelength to the desired value is bonded the
second substrate having the greater linear expansion coefficient
than that of the substrate itself of the optical waveguide element.
Thus, the waveguide type optical device with the bonded first and
second substrates can be used like other waveguide type optical
devices.
[0035] According to a fourteenth aspect of the present invention,
there is provided a method of manufacturing a waveguide type
optical device comprising: an element preparation step of preparing
an optical waveguide element; a first substrate bonding step of
bonding, to the waveguide side of the optical waveguide element
prepared in the element preparation step a first substrate having a
linear expansion coefficient greater than that of the substrate
itself of the optical waveguide element; and a second step of
bonding, to the substrate side of the optical waveguide element
prepared in the element preparation step a second substrate having
a linear expansion coefficient greater than that of the substrate
itself of the optical waveguide element.
[0036] According to this aspect, a method of manufacturing the
waveguide type optical device according to the present invention as
set forth in claim 3 is shown. First, in the element preparation
step the optical waveguide element is prepared. Then in the first
substrate bonding step to the waveguide side of the prepared
optical waveguide element is bonded the first substrate having the
greater linear expansion coefficient than that of the substrate
itself of the optical waveguide element. Also, in the second
substrate bonding step to the substrate side of the optical
waveguide element prepared in the element preparation step is
bonded the second substrate having the greater linear expansion
coefficient than that of the substrate itself of the optical
waveguide element. Thus, the waveguide type optical device with the
bonded first and second substrates can be used like other waveguide
type optical devices. The first or the second substrate bonding
step may be executed first, or both the steps may be executed at a
time.
[0037] In a fifteenth aspect of the present invention, in the
method of manufacturing the waveguide type optical device of the
thirteenth or fourteenth aspect, the first and second substrates
are substantially equal in thickness and linear expansion
coefficient.
[0038] According to this aspect, the simplest method of selecting
the first and second substrates to be bonded to the opposite sides
of the optical waveguide element is shown. By using as the first
and second substrates those of the same specifications and having
linear expansion coefficient greater than that of the optical
waveguide element, no warping is generated so long as warping of
the optical waveguide element is hardly generated, thus permitting
increase of the sole expansion/contraction factor of the optical
waveguide element. Besides, since it is possible to provide common
specifications to the first and second substrates, it is possible
to realize cost-down and easier parts management.
[0039] According to a sixteenth aspect of the present invention,
there is provided a method of manufacturing a waveguide type
optical device comprising: an element preparation step of preparing
an optical waveguide element; a temperature measuring step of
measuring a temperature, at which the center wavelength of the
prepared optical waveguide element is set to a desired value; a
support substrate linear expansion coefficient selecting step of
selecting the extent, by which the linear expansion coefficient of
the support substrate to be bonded to the substrate side of the
optical waveguide element is greater than that of the substrate in
the optical waveguide element, on the basis of the temperature
measured in the ideal temperature measuring step; and a bonding
step of bonding, to the substrate side of the optical waveguide
element, a support substrate having the linear expansion
coefficient selected in the support substrate linear expansion
coefficient selecting step.
[0040] According to this aspect, after preparation of the optical
waveguide element in the element preparation step, the temperature,
at which the center wavelength of the prepared optical waveguide
element is set to the desired value, is measured. Then in the
support substrate linear expansion coefficient selecting step,
according to the measured temperature it is selected the extent, by
which the linear expansion coefficient of the support substrate to
be bonded to the substrate side of the optical waveguide element is
greater than that of the optical waveguide element. It is thus
possible to prepare a plurality of support substrates having
different linear expansion coefficients and select the most
adequate support substrate.
[0041] According to a seventeenth aspect of the present invention,
there is provided a method of manufacturing a waveguide type
optical device comprising: an element preparation step of preparing
an optical waveguide element; a temperature measuring step of
measuring a temperature, at which the center wavelength of the
prepared optical waveguide element is set to a desired value; a
first/second substrate linear expansion coefficient selecting step
of selecting the extent, by which the linear expansion coefficient
of the first substrate to be bonded to the waveguide side of the
optical waveguide element and the liner expansion coefficient of
the second substrate to be bonded to the substrate side of the
optical waveguide element are greater than that of the substrate of
the optical waveguide element, on the basis of the temperature
measured in the ideal temperature measuring step; and bonding step
of bonding the first and second substrates with the linear
expansion coefficient selected in the first/second substrate linear
expansion coefficient selecting step to corresponding parts of the
optical waveguide element.
[0042] According to this aspect, first in the element preparation
step the optical waveguide element is prepared. Then, in the ideal
temperature measurement step the temperature, at which the center
wavelength of the prepared optical waveguide element is set to the
desired value, is measured. On the basis of the measured
temperature, the extent is selected, by which the linear expansion
coefficient of the first substrate to be bonded to the waveguide
side of the wavelength element and the linear expansion coefficient
of the second substrate to be bonded to the substrate side of the
optical waveguide element are greater than that of the substrate of
the optical waveguide element. Then the first and second substrates
having the linear expansion coefficients selected in the
first/second substrate linear expansion coefficient selecting means
are bonded to corresponding parts of the optical waveguide element.
Thus, it is possible to prepare first and second substrates having
different linear expansion coefficients and select the most
adequate support substrate.
[0043] Other objects and features will be clarified from the
following description with reference to attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 shows an array waveguide diffraction grating as a
waveguide type optical device, to which the present invention is
applied;
[0045] FIG. 2 shows the sectional structure of the array waveguide
diffraction grating, to which the present invention is applied;
[0046] FIGS. 3(a) and 3(b) show the optical waveguide element
before the elongation and the optical waveguide element after the
elongation;
[0047] FIGS. 4(a) and 4(b) show displacements of wavelengths of TE
and TM polarizations due to such warping generation;
[0048] FIG. 5 shows the summary of the process of manufacturing the
array waveguide diffraction element in the embodiment;
[0049] FIG. 6 shows a first modification of the process of
preparing the array waveguide diffraction grating;
[0050] FIG. 7 shows a second modification of the process of
preparing the array waveguide diffraction grating;
[0051] FIG. 8 shows a third modification of the process of
preparing the array waveguide diffraction grating; and
[0052] FIG. 9 shows a fourth modification of the process of
preparing the array waveguide diffraction grating.
PREFERRED EMBODIMENTS OF THE INVENTION
[0053] Preferred embodiments of the present invention will now be
described with reference to the drawings.
[0054] The principal construction according to the present
invention will now be described.
[0055] FIG. 1 shows an array waveguide diffraction grating as a
waveguide type optical device, to which the present invention is
applied. The array waveguide diffraction grating 201 comprises a
optical waveguide element 203 with an optical waveguide pattern 202
formed therein and a first and a second compensation substrate 204
and 205 sandwiching the optical waveguide element 203 from the
opposite sides thereof.
[0056] Usually, the temperature dependency of the center wavelength
of the optical waveguide can be represented by the following
formula (1). d .lamda. 0 d T = .lamda. 0 n eq ( 1 L .times. d S d T
) ( 1 ) ##EQU1##
[0057] In this formula (1), .lamda..sub.0 is the center wavelength,
no is the equivalent refractive index of the optical waveguide, and
1/Lds/dT is the optical length temperature coefficient. The optical
length temperature coefficient can be given by the following
formula (2). 1 L .times. d S d T = d n eq d T + n eq .times.
.alpha. ( 2 ) ##EQU2##
[0058] In this formula (2), .alpha. is the linear expansion
coefficient of the optical waveguide. The linear expansion
coefficient .alpha. can be usually approximated by the linear
expansion coefficient of the substrate material. From the formulas
(1) and (2), it is seen that the temperature dependency of the
center wavelength of the waveguide type optical device can be
varied by adjusting the linear expansion coefficient of the
substrate.
[0059] FIG. 2 shows the sectional structure of the array waveguide
diffraction grating, to which the present invention is applied. The
array waveguide diffraction grating 201 includes a planar lightwave
circuit 203, which is constituted by a silicon substrate 212 and an
optical waveguide layer 211 formed thereon and has a predetermined
thickness h0, a first compensation substrate 204 bonded to the
optical waveguide 211 and having a thickness h1, and a second
compensation substrate 205 bonded to the silicon substrate 212 and
having a thickness h4. The optical waveguide element 203 is
constituted by an optical waveguide layer 211 having a thickness h2
and a silicon substrate 212 having a thickness h3. The optical
waveguide layer 211 and the first compensation substrate 204 are
bonded to each other by first adhesive 214. The silicon substrate
212 and the second compensation substrate 205 are bonded to each
other by a second adhesive 215.
[0060] The first and second adhesives 214 and 215, unlike the prior
art adhesive used for bonding the silicon substrate 212 and the
other substrate to each other, are highly rigid adhesives. In the
prior art, a material having low rigidity and capable of undergoing
expansion and contraction to a certain extent was used as adhesive
from the consideration that the difference expansion and
contraction of two substrates having different linear expansion
coefficients should have as little effect as possible on opposite
side substrates. According to the present invention, adhesives are
used from quite opposite standpoint such that the expansion and
contraction of one of the two substrates efficiently have effects
on the other.
[0061] The linear expansion coefficients and Young's modulus of the
individual layers of the array waveguide circuit diffraction
grating 201 are defined as follows. The linear expansion
coefficient and the Young's modulus of the uppermost first
compensation substrate 204 in the Figure are denoted by
.alpha..sub.1 and E.sub.1, respectively. The linear expansion
coefficient and the Young's modulus of the waveguide substrate 211
in the optical waveguide element are denoted by .alpha..sub.2 and
E.sub.2, respectively. The linear expansion coefficient and the
Young's modulus of the waveguide substrate 212 in the optical
waveguide element are denoted by .alpha..sub.3 and E.sub.3,
respectively. The linear expansion coefficient and the Young's
modulus of the second compensation substrate 205 are denoted by
.alpha..sub.4 and E.sub.4, respectively. Generally, the optical
waveguide layer 211 of the optical waveguide element are very thin
compared to the other parts, i.e., the first compensation substrate
204, the silicon substrate 212 and the second compensation
substrate 205. That is, the thicknesses h1 to h4 are related as
h.sub.2<<h.sub.1, h.sub.3, h.sub.4
[0062] The linear expansion coefficient .alpha. of a substance
represents the extent of thermal expansion and contraction of the
substance itself, and it is a preamble that the substance is open
at the two ends. The stress can be numerically represented by the
Young's modulus multiplied by the strain. The higher the Young's
modulus, the tensile pressure due to expansion or contraction is
the higher. Also, the greater the thicknesses h.sub.1 to h.sub.4 of
the individual substrates or layer, the force, with which the other
substrate or the like is pulled or compressed at the time of the
expansion or contraction, is the higher.
[0063] Before analyzing the structure shown in FIG. 2, with the
optical waveguide element 203 sandwiched between the first and
second compensation substrates 204 and 205, a structure constituted
by the sole optical waveguide element 203, i.e., without presence
of the first and second compensation substrates 204 and 205, will
be considered. The optical waveguide element 203, as described
before, is prepared by forming the optical waveguide layer 211 on
the silicon substrate 212. In this specification, the laminate
structure obtained by bonding together two layers is referred to as
"two-layer laminate".
[0064] FIGS. 3(a) and 3(b) show the optical waveguide element
before and after an elongation change in the waveguide direction
with a temperature rise. FIG. 3(a) shows the optical waveguide
element before the elongation, and FIGS. 3(b) shows the optical
waveguide element after the elongation. In the Figure, reference
numeral 231 shows the waveguide position. The waveguide is disposed
such as to extend in the optical waveguide layer 211 in the
direction of arrow 232. Since the linear expansion coefficients
.alpha..sub.1 and .alpha..sub.2 of the optical waveguide layer 211
and the silicon substrate 212 are different, a temperature change
causes the optical waveguide element 203 as a whole to warp as
shown in FIG. 3(b).
[0065] FIGS. 4(a) and 4(b) show displacements of wavelengths of TE
and TM polarizations due to such warping generation. In FIG. 4(a),
the characteristics 241 and 242 of the TE and TM polarizations are
substantially identical. As a result of the warping generation the
characteristics 241 and 242 become different from each other as
shown in FIG. 4(b). For evading or alleviating such temperature
dependency, it is usually necessary to prevent warping generation
with temperature rise.
[0066] In consideration of the structural relation in the optical
waveguide element 203 that the optical waveguide layer 211 is
formed on the silicon substrate 212, the "two-layer laminate" can
assume either one of two converse states, i.e., concave and convex
states, as a result of warping at the temperature rise time. Of
course in the case of warping in the concave state at the
temperature rise time, convex warping results at the temperature
fall time, while in the case of warping in the convex state at the
temperature fall time concave warping results at the temperature
fill time. Now, various cases of warping of the "two-layer
laminate" will be considered.
[0067] (1) Case of warping of the "two-layer laminate" in the
concave state at the temperature rise time:
[0068] This case arises when the linear expansion coefficient
.alpha..sub.3 is greater than the linear expansion coefficient
.alpha..sub.2 in FIG. 2, and is represented by the following
formula (3-1-1). .alpha..sub.2<.alpha..sub.3 (with
.alpha..sub.2>0) (3-1-1)
[0069] (2) Case of warping of the "two-layer laminate" in the
convex state at the temperature rise time:
[0070] This case arises when the linear expansion coefficient
.alpha..sub.2 is greater than the linear expansion coefficient
.alpha..sub.3 in FIG. 2, and is represented by the following
formula (3-2-1). .alpha..sub.2>.alpha..sub.3 (with
.alpha..sub.3>0) (3-2-1)
[0071] (3) Case of non-warping of the "two-layer laminate" at the
temperature rise time:
[0072] This case arises when the linear expansion coefficients
.alpha..sub.3 and .alpha..sub.2 are equal, and is represented by
the following formula (3-3-1). .alpha..sub.2=.alpha..sub.3
(3-3-1)
[0073] Now, the structure described above, in which the "two-layer
laminate" is sandwiched between the first and second compensation
substrates 204 and 205 as shown in FIG. 2, will be considered. Here
a case when the temperature dependency of the waveguide type
optical device is expanded, will be considered. Like the above
case, various cases of warping will be considered.
[0074] (4) Case of warping of the "two-layer laminate" in the
concave state at the temperature rise time (warping in the convex
state at the temperature fall time):
[0075] The "two-layer laminate" undergoes warping in the concave
state at the temperature rise time under the condition of the
following formula (3-4-1). .alpha..sub.2<.alpha..sub.3 (with
.alpha..sub.2>0) (3-4-1)
[0076] In the case of disposing the first and second compensation
substrates 204 and 205 as shown in FIG. 2 for reducing the
elongation and warping of the optical waveguide element 203, it
suffices that the linear expansion coefficient of the first
compensation substrate 204 is greater than the linear compensation
coefficient of the second compensation substrate 205 (formula
(3-4-3)). In other words, the linear expansion coefficients of the
first and second compensation substrates are set such that the
warping thereof is converse to the warping of the optical waveguide
element 203. For increasing the linear expansion coefficient of the
optical waveguide element, .alpha..sub.1 and .alpha..sub.2 should
have greater values than 3 (formula (3-4-4)).
.alpha..sub.1>.alpha..sub.4 (3-4-3) .alpha..sub.1,
.alpha..sub.4>.alpha..sub.3 (3-4-4)
[0077] Now, other material characteristics of the compensation
substrates will be considered. As shown in the following formulas,
the greater the Young's modulus E, the rigidity is the greater, and
the strain is the less the greater the strain corresponding to the
stress and the substrate thickness h. This means that even when the
formulas (3-4-4) and (3-4-4) fail to be held, it is possible to
reduce the warping of the optical waveguide element 203 at the
temperature rise time if the following formulas (3-4-5) and (3-4-6)
are held. When the formulas (3-4-3-), (3-4-4), (3-4-5) and (3-4-6)
are all held, the maximum effect can be obtained. However,
increasing the differences of the individual inequalities, it is
possible to obtain a sufficient effect for reducing the warping
even with a less number of formulas to be held. .epsilon.=.sigma./E
[0078] .epsilon.: strain .sigma.: bending stress [0079] E: Young's
modulus .sigma.=M/Z [0080] M: bending moment [0081] Z: section
coefficient Z=1/6bh.sup.2 [0082] b substrate section length [0083]
h: substrate section thickness E.sub.4<E.sub.1 (E.sub.2,
E.sub.3<E.sub.1) (3-4-5) h.sub.4<h.sub.1(h.sub.2,
h.sub.3<h.sub.1) (3-4-6)
[0084] (5) Case of warping of the "two-layer laminate" undergoes
convex warping at the temperature rise time under the condition of
the following formula (3-5-1). .alpha..sub.2>.alpha..sub.3 (with
.alpha..sub.2>0) (3-5-1)
[0085] In the case when the first and second compensation
substrates 204 and 205 are disposed as shown in FIG. 2 for reducing
the elongation and warping of the optical waveguide element 203, it
suffices that the linear expansion coefficient of the first
compensation substrate 204 is greater than that of the second
compensation coefficient 205 (formula (3-5-1)). In other words, the
linear expansion coefficients of the first and second compensation
substrates are set such that the warping thereof is converse to the
warping of the optical waveguide element 203. Also, for increasing
the linear expansion coefficient of the optical waveguide element
as a whole, it is necessary that .alpha..sub.1 and .alpha..sub.1
both have values greater than .alpha..sub.3. (formula 3-5-4)
.alpha..sub.1>.alpha..sub.4 (3-5-3) .alpha..sub.1,
.alpha..sub.4>.alpha..sub.3 (3-5-4)
[0086] As for the other compensation substrate materials, it is
possible to apply the same concept as in the case (4).
[0087] (6) Case when the "two-layer laminate" itself does not
undergo warping with a temperature change.
[0088] Even when the "two-layer laminate" does not undergo warping
with a temperature change, by securing the second compensation
substrate 205 as shown in FIG. 2 to the side of the waveguide
substrate 212 for supporting the "two-layer laminate", the overall
structure experiences a force tending to cause its warping in the
convex or concave state even without warping of the optical
waveguide element 203 constituting the "two-layer laminate" unless
the linear expansion coefficient .alpha..sub.4 of the second
compensation substrate 205 is equal to the linear expansion
coefficients .alpha..sub.2 and .alpha..sub.3. To prevent this, it
is necessary to bond the first compensation substrate 204, which
has the same linear expansion coefficient .alpha..sub.1 as the
linear expansion coefficient .alpha..sub.4 of the second
compensation substrate 205, to the side of the optical waveguide
layer 211.
[0089] Now, specific values will be computed with an example of the
waveguide type optical device according to the present
invention.
[0090] The array waveguide diffraction grating 201 shown in FIG. 2
is used as an optical waveguide as a preamble of computation. In
this array waveguide diffraction grating 201, the thickness h.sub.0
and the linear expansion coefficient of the optical waveguide
element 203 are denoted by t.sub.1 and .alpha..sub.0, respectively.
The thicknesses h.sub.1 and h.sub.4 and linear expansion
coefficients of the first and second compensation substrates 204
and 205 are set to equal values of t.sub.2 and .alpha..sub.1,
respectively. Also, for the brevity of description the Young's
modulus of the individual layers are assumed to be equal. In this
case, the linear expansion coefficient of the array waveguide
diffraction grating 201 as a whole can be represented by the
following formula (4). .alpha. all = t 1 .times. .alpha. 0 + 2
.times. t 2 .times. .alpha. 1 t 1 + 2 .times. t 2 ( 4 )
##EQU3##
[0091] Then, the center wavelength .lamda..sub.0 preliminarily
preset in the formula (1) may be converted to the linear expansion
coefficient .alpha. by substituting it into the formula (2), and
the linear expansion coefficients .alpha..sub.0 and .alpha..sub.1
and the thicknesses t.sub.1 and t.sub.2 of the substrates 203 and
204 (205) may be determined from the converted linear expansion
coefficient .alpha. and the formula (4). The values will be
computed in connection with an example, in which the array
waveguide diffraction grating 201 is a quartz optical waveguide
element formed on an Si substrate.
[0092] The thickness and the linear expansion coefficient of the Si
substrate as the optical waveguide element 203 are assumed to be
0.8 mm and 26.3.times.10.sup.-7/.degree. C., respectively. Also,
dn.sub.eq/dT in the formula (2) is assumed to be
6.0.times.10.sup.-6, and the equivalent diffractive index n.sub.eq
are assumed to be 1.46. Furthermore, the center wavelength
.lamda..sub.0 is assumed to be 1.55 .mu.m. In this case, 0.02
nm/.degree. C., i.e., double the value in the case of the prior art
quartz optical waveguide element, is assumed to be set. From the
formula (1), the following formula (5) is held. 1 L .times. d S d T
= 2.072 .times. 10 - 5 ( 5 ) ##EQU4##
[0093] By substituting this into the formula (2), the following
formula (6) is obtained. .alpha.=93.7.times.10.sup.-7 (6)
[0094] The thickness t.sub.2 of the first and second compensation
substrates 204 and 205 bonded one atop the other is assumed to be
1.5 mm. .alpha..sub.1111.7.times.10.sup.-7 (7)
[0095] Thus, it is concluded that a material having such linear
expansion coefficient .alpha..sub.1 may be used as the first and
second compensation substrate 204 and 205.
[0096] Now, the manufacture of optical waveguide as an embodiment
and waveguide type optical device and waveguide type optical device
will be described. First, as an example of the optical waveguide,
an array waveguide diffraction grating as shown in FIG. 1 was
produced. As preamble, like those shown in FIG. 2, the thickness
and the linear expansion coefficient of the optical waveguide
element 203 in the array waveguide diffraction grating 201 were set
to h0 and .alpha..sub.0, respectively. Also, the thicknesses
h.sub.1 and h.sub.4 and the linear expansion coefficients of the
first and second compensation substrates 204 and 205 were set to
equal values of t.sub.1 and .alpha..sub.1, respectively. As the
first and second compensation substrates 204 and 205
temperature-dependent characteristic AEWGs (array waveguide
diffraction gratings) are produced by using glass ceramics. The
linear expansion coefficient .alpha..sub.1 and the thickness
t.sub.2 of the first and sebond compensation substrates 204 and 205
were 130.times.10.sup.-7.sup.7/.degree. C. and 1 mm, respectively.
The linear expansion coefficient .alpha..sub.0 and the thickness t1
of the optical waveguide element 203 were 26.3.times.10-7/.degree.
C. and 0.8 mm, respectively.
[0097] Using the formula (4), the linear expansion coefficient
.alpha..sub.all of the array waveguide diffraction grating 201 as a
whole is 100.37.times.10.sup.-7/.degree. C. The center wavelength
temperature dependency can be obtained by substituting this value
into the formulas (1) and (2).
[0098] In the array waveguide diffraction grating 201 in this
embodiment, the temperature dependency is increased compared to the
case free from the substrates 204 and 205 due to the effects of the
first and second substrates 204 and 205. It is thus possible to set
the center wavelength of the array waveguide diffraction grating
201 to be in a desired range by temperature adjustment with the
temperature controller added to the first or second compensation
substrate 204 or 205. Beside, in this embodiment by using the first
and second compensation substrates 204 and 205 it is possible to
reduce the effects of warping of the array waveguide diffraction
grating 201 as a whole.
[0099] FIG. 5 shows the summary of the process of manufacturing the
array waveguide diffraction element in the embodiment. The optical
waveguide element 203 shown in FIG. 1 is manufactured by using a
wafer (not shown) (step S501). Then, a measurement is made as to
whether it is possible to set the center wavelength to be in a
predetermined desired range in the working temperature range of a
temperature controller (not shown), in which the optical waveguide
element 203 is mounted on the substrate side thereof (step S502).
The temperature range of the temperature controller can be set in a
range of, for instance, 75 to 85.degree. C. With a optical
waveguide element 203 which has been capable of setting the center
wavelength in such temperature range ("Y" in step S503), like the
prior art, a normal substrate is bonded to the substrate side (step
S504), thus obtaining the array waveguide diffraction circuit.
[0100] With a optical waveguide element 203 which has been
incapable of setting the center wavelength in such temperature
range ("N" in step S503), heretofore the wavelength element 203
itself was discarded. In this embodiment, a predetermined first
compensation substrate 204 having a greater linear expansion
coefficient than the normal substrate is bonded with highly rigid
adhesive to the waveguide side of the optical waveguide element 203
(step S505). Then, a predetermined second compensation substrate 20
having a greater linear expansion coefficient than the normal
substrate is bonded with the same highly rigid adhesive to the
substrate side of the optical waveguide element 203 (step S506).
The array waveguide diffraction grating 201 manufactured in this
way, permits center wavelength setting to a desired value in the
working temperature range of the temperature controller, and thus
it can be shipped as a product likewise.
[0101] In this manufacturing process, the steps S505 and S506 may
be conversed in order, or it is also possible to make simultaneous
bonding.
First Modification of the Embodiment
[0102] FIG. 6 shows a first modification of the process of
preparing the array waveguide diffraction grating. In this
modification, steps like those in FIG. 5 are designated by like
reference numerals, and their description is adequately
omitted.
[0103] In this first modification, a predetermined compensation
substrate having a greater linear expansion coefficient than the
normal substrate is bonded to only the substrate side of the
optical waveguide elements 203, which have failed in the center
wavelength setting in a predetermined desired range in the step
S503 (step S511). In this way as well, it is possible to set the
center wavelength to a desired value in the working temperature
range of a temperature controller (not shown).
Second Modification of the Embodiment
[0104] FIG. 7 shows a second modification of the process of
preparing the array waveguide diffraction grating. In this
modification, steps like those in FIG. 5 are designated by like
reference numerals, and their description is adequately
omitted.
[0105] In this modification, right after preparation of the optical
waveguide element 203 shown in FIG. 1 by using a wafer (not shown)
(step S501), a step S505 is executed, in which a predetermined
first compensation substrate 204 having a greater linear expansion
coefficient than the normal substrate is bonded with highly rigid
adhesive to the waveguide side of the optical waveguide element
203. Then, a predetermined second compensation substrate 205 having
greater linear expansion coefficient than the normal substrate is
bonded with the same highly rigid adhesive to the substrate side of
the optical waveguide element 203 (step S506). Like the previous
embodiment, the steps S505 and S506 may be conversed in order, or
may be executed as a single step.
[0106] As shown, in this second embodiment the first and second
compensation substrates 204 and 205 are selected such as to cover
the maximum characteristic range of the individual optical
waveguide elements 203 prepared. It is thus adapted that the center
wavelength is set to a desired value without preparation of the
temperature controller. In this case, the first and second
compensation substrates 204 and 205 are disposed on all optical
waveguide elements 203. However, the preparation process is
uniformalized, and the compensation substrates 204 and 205 are
disposed on both sides of the optical waveguide element 203, and it
is thus possible to obtain an advantage that the array waveguide
diffraction grating 201 is less broken and can be more readily
handled.
Third Modification of the Embodiment
[0107] FIG. 8 shows a third modification of the process of
preparing the array waveguide diffraction grating. Again in this
modification, steps like those in FIG. 5 are designated by like
reference numerals.
[0108] In this third modification, after preparation of the optical
waveguide element 203 by using a wafer (not shown) (step S501), the
temperature of the optical waveguide element 203 thus prepared, at
which the center wavelength is set to a desired value, is measured
(step S521). On the basis of this temperature, a compensation
substrate having a desired linear expansion coefficient is selected
among preliminarily prepared compensation substrates having various
linear expansion coefficients (step S522). This compensation
substrate is bonded with highly rigid adhesive to the substrate
side of the optical waveguide element 203 (step S523).
Fourth Modification of the Embodiment
[0109] FIG. 9 shows a fourth modification of the process of
preparing the array waveguide diffraction grating. Again in this
modification, steps like those in FIG. 8 are designated by like
reference numerals, and their description is adequately
omitted.
[0110] In this fourth modification, after the temperature
measurement in the step S521, paired first and second compensation
substrates 204 and 205 having linear expansion coefficients
corresponding to the measured temperature are selected (step S531).
Then, the selected first compensation substrate 204 is bonded with
highly rigid adhesive to the waveguide side of the optical
waveguide element 203 (step S532), and then the selected second
compensation substrate 205 is bonded with highly rigid adhesive to
the substrate side of the optical waveguide element 203 (step
S533). The steps S532 and S533 may be conversed in order, or the
may of course be executed as a single step.
[0111] While the above embodiment and modifications have been
described in connection with the array waveguide diffraction
gratings 201 and 401, the present invention is of course applicable
to other optical waveguide elements such as Machzender
interferometer.
[0112] As has been described in the foregoing, according to the
first and second aspects of the present invention, on the substrate
side of the planar lightwave circuit the support substrate having
the greater linear expansion coefficient than that of the substrate
in the optical waveguide element is disposed, and the temperature
of the support substrate and the optical waveguide element is
controlled with the temperature controller assembled in the support
substrate. The support substrate thus causes expansion and
elongation on the optical waveguide element such as to
substantially increase the linear expansion coefficient of the
optical waveguide element. It is thus possible to increase the
ratio of waveguide type optical devices capable of obtaining the
desired center wavelength by merely considering the linear
expansion coefficient of the support substrate, thus improving the
yield.
[0113] According to the third to ninth aspects of the present
invention, the first and second substrates having linear expansion
coefficients greater than that of the planar lightwave circuit are
disposed to sandwich the optical waveguide element. It is thus
possible to substantially increase the linear expansion coefficient
of the optical waveguide element and improve the yield of product.
Furthermore, since the optical waveguide element is sandwiched
between the first and second substrates, the mechanical shock
resistance is increased. Furthermore, by adequately setting the
linear expansion coefficients of the first and second substrates,
it is possible to prevent or reduce warping due to changes in the
temperature of the waveguide optical device itself, and no adverse
effects are given on characteristics other than the temperature
characteristic of the center wavelength.
[0114] According to the sixth aspect of the present invention, the
thickness of the first substrate is made to be equal or less than
the reinforcement glass 209, thus permitting the thickness increase
of the overall structure.
[0115] According to the seventh aspect of the present invention,
the support substrate and the temperature controller are
substantially equal in thickness, and it is thus possible to
increase the thickness of the waveguide type optical device
itself.
[0116] According to the eighth aspect of the present invention, the
second substrate and the temperature controller are substantially
equal in thickness, and it is possible to prevent increase the
thickness of the waveguide type optical device.
[0117] According to the ninth aspect of the present invention, in
the waveguide type optical device according to the third aspect,
the first and second substrates are equal in thickness and linear
expansion coefficient. Thus, it is possible to provide common
specifications for these parts and realize cost-down and readier
parts management.
[0118] According to the tenth or twelfth aspect of the present
invention, the optical waveguide element is prepared in the usual
manner, and as for the optical waveguide element judged in the
checking step to be our of standards, a support substrate having a
predetermined linear expansion coefficient greater than that of the
substrate of the optical waveguide element is bonded in the normal
substrate bonding step. It is thus possible to reduce adverse
effects on the process of manufacture and preclude the generation
of rejected parts as much as possible.
[0119] According to the tenth or twelfth aspect of the present
invention, the optical waveguide element is prepared in the usual
manner, and then without execution of any checking step a support
substrate having a predetermined linear expansion coefficient
greater than that of the substrate of the optical waveguide element
is bonded to the substrate side of the optical waveguide element.
Thus, it is possible to reduce the number of steps of manufacture.
Also, as for optical waveguide elements which were heretofore
rejected due to substantial linear expansion coefficient increase,
it is possible to set a desired center wavelength in less
temperature range.
[0120] According to the thirteenth aspect of the present invention,
the optical waveguide element is prepared in the usual way, and as
for optical waveguide elements judged in the checking step to be
our of standards, a first and second substrate having a
predetermined linear expansion coefficient greater than that of the
substrate of the optical waveguide element are bonded in the normal
substrate bonding step. Thus, it is possible to reduce adverse
effects on process of manufacture and reduce generation of rejected
parts as much as possible.
[0121] According to the fourteenth aspect of the present invention,
the optical waveguide element in prepared in the usual manner, and
subsequently a first and second substrates having a greater linear
expansion coefficient are bonded to the prepared optical waveguide
element. Thus, it is possible to reduce adverse effect on the
process of manufacture and preclude the generation of rejected
parts as much as possible. Furthermore, since the first and second
substrates are bonded such as to sandwich the optical waveguide
element, it is possible to increase the mechanical shock
resistance.
[0122] According to the fifteenth aspect of the present invention,
in the method of manufacturing the waveguide type optical device in
the thirteenth or fourteenth aspect, the first and second
substrates are set such that they are equal in thickness and linear
expansion coefficient. Thus, it is possible to provide common
specifications for the first and second substrates and realize
cost-down and readier parts management.
[0123] According the sixteenth aspect of the present invention,
after preparation of the optical waveguide element in the element
preparation step, the temperature, at which the center wavelength
of the prepared optical waveguide element is set to a desired
value, is measured in a temperature measuring step, and on the
basis of the measured temperature the extent, by which the linear
expansion coefficient of the support substrate bonded to the
substrate side of the optical waveguide element is greater than the
linear expansion coefficient, is selected in the support substrate
linear expansion coefficient selecting step. It is thus possible to
select the most adequate support substrate form various standpoints
such as saving of consumed power.
[0124] According to the seventeenth aspect of the present
invention, after preparation of the optical waveguide element in
the element preparation step, the temperature, at which the center
wavelength of the prepared optical waveguide element is set to a
desired value is measured in a temperature measuring step, and on
the basis of the measured temperature the extent, by which the
linear expansion coefficient of both the first and second
substrates to be bonded to the waveguide side and the substrate
side, respectively, of the optical waveguide element is made to be
greater than that of the substrate of the optical waveguide
element, is selected in the first/second substrate linear expansion
coefficient selecting step for bonding the first and second
substrates having the selected linear expansion coefficient to
corresponding parts of the optical waveguide element. It is thus
possible to prepare a plurality of first and second substrates
having different linear expansion coefficients and select the most
adequate support substrate from various standpoints such as saving
of consumed power.
[0125] Changes in construction will occur to those skilled in the
art and various apparently different modifications and embodiments
may be made without departing from the scope of the present
invention. The matter set forth in the foregoing description and
accompanying drawings is offered by way of illustration only. It is
therefore intended that the foregoing description be regarded as
illustrative rather than limiting.
* * * * *