JPH0367204A - Integrated optical device and production thereof - Google Patents

Abstract

PURPOSE:To exactly realize a desired optical circuit function by providing stress-imparting films contg. stripe parts consisting of plural fine lines having a prescribed angle with the eight propagation direction of a core part. CONSTITUTION:Two flat plate-shaped stress imparting films 22A, 22B are loaded on the optical waveguide 1a between directional couplers 2a and 2b and are partly trimmed to a stripe shape. The flat plate-shaped stress imparting films 22A, 22B on the optical waveguides 1a, 1b between the directional couplers 2a and 2b are a-S1. The one a-S1 film 22a is partly trimmed to the stripe shape perpendicularly to the light propagation direction and the other a-S1 film 22b is previously trimmed to the stripe shape 22d parallel with the light propagation direction over the entire surface; thereafter, a part 22e thereof is trimmed perpendicularly to the light propagation direction. The desired optical circuit function is exactly attained in this way.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an integrated optical device in which an optical waveguide is disposed on a substrate. More specifically, the present invention relates to an integrated optical device that accurately realizes a desired optical circuit function by adjusting the stress applied to an optical waveguide, and a method for manufacturing the same. [Prior Art] A single-mode optical waveguide formed on a flat substrate, particularly a silica-based single-mode optical waveguide formed on a silicon substrate,
For example, N, Takato et al.:”5ilic
a-Based Single-Mode Waveg
uides on 5ilicon andTheir
Application to Guided-Wa
ve optical Interferometers
”, J, Li3htwave Tech,, vol, F
i,pp. 1003-1010.1988. In such a quartz spinning wheel-mode optical waveguide, the cross-sectional dimension of the core portion can be set to approximately 5-10 μm to match the normally used quartz-based portion-mode optical fiber. It is expected that this will be a means of realizing a practical integrated optical device with improved compatibility. Figures 12 and 13 show a conventional integrated optical device using such a silica-based single mode optical waveguide. 12 and 13 are enlarged cross-sectional views of a plan view and a cross section taken along line AA', respectively, for explaining the configuration of a waveguide-type Matsuha-Zehnder optical interferometer as an example. , 1 is a silicon substrate. 1a and 1b are silica-based single mode optical waveguides formed of a silica-based glass material on a silicon substrate.The optical waveguides 1a and 1b are located close to each other at two locations and are directional. Coupler 2a and 2b are configured, and their coupling ratios are set to be approximately 50%.Optical waveguide 1a
, lb is the cross-sectional size embedded in the Sin-based glass cladding layer 5 with a film thickness of about 50μω. The directional couplers 2a and 2b are made of a 5iOz-Ti02-based or SiO□-GeO□-based glass core portion with a fE of about 7 μm x 7 μm.
The two optical waveguides 1a and lb are kept at a spacing of several μ, and d
- It is constructed by arranging them in parallel over a distance of about 0.5a+m. Two directional couplers 2a, 2
The waveguide lengths of the portions connecting b are L+Δ14 and the lengths differ by Δ1°, respectively. In the future, when the device changes the optical frequency of the signal 9 light incident from the human power port 1-3b, △f-c/(
It is known that signal light can be taken out alternately from the output boats 4a and 4b with a period of 2n·ΔL) (1) (n is the refractive index of the optical waveguide, C is the speed of light). FIG. 14 is a diagram showing this periodicity, and shows TE polarized light (or 7M polarized light) in the 1.55 μm band from the human-powered boat 3b.
3 shows the optical frequency characteristics of the light output from the output ports 4a and 4b when the signal light of 1 is input. Here, the solid line indicates the output light Pout2 from the output boat 4a, and the broken line indicates the output light Poutl from the output boat 4b. When two signal beams f, , f2 separated by an optical frequency interval △f-106I+□ are simultaneously input from the input boat 3b, when △1, -10 mm, the two signal beams are separated from the output boats 4a and 4b. You can take it out. In other words, a multiplexer/demultiplexer operation can be obtained. In reality, in order to accurately match the operating wavelength, it is necessary to set the optical path length difference (n・△L) with high precision;
10 or less. This is difficult to achieve at the stage of fabricating the waveguide due to limitations in the accuracy of the photomask for fabricating the optical waveguide, slight fluctuations in the refractive index of the optical waveguide glass, and the like. For this reason, a method of adjusting the temperature using the thermo-optical effect of the heater 21 has been conventionally used, but this had the problem of having to be constantly energized. Japanese Patent Application No. 63-283793 proposes a method of finely adjusting the optical path length by loading the optical fiber onto the cladding and trimming the stress-applying film. On the other hand, in the aforementioned Matsuha-Zenda optical interferometer, the glass waveguide section is subjected to strong compressive stress due to the difference in thermal expansion coefficient between the silica glass and the silicon substrate, and this causes the optical waveguide to exhibit stress birefringence. ing. Its stress birefringence value is about Bo=5x 10-' ([1o-nt
v−nTEv where ntE: effective refractive index of TE polarized light, I
'lrM: effective refractive index of 7M polarized light). Figure 15 shows the first
In the optical interferometer circuit shown in FIG. 2, optical frequency characteristics are shown when light with different polarization directions enters from the input boat 3b. Here, the solid line represents the case where 7M mode light is incident, and the broken line represents the case where TE mode light is incident. From this figure, it can be seen that due to the stress birefringence of the optical waveguide, a phase difference occurs in the optical frequency characteristics due to the difference in the polarization direction of the incident light. Therefore, when a polarized light different from the set polarization direction is incident, there is a problem in that the above-mentioned multiplexing/demultiplexing operation is not performed at all. In order to eliminate this polarization dependence, a method was proposed in which the birefringence value was adjusted by loading a strip-shaped stress-applying film on the cladding above the core and trimming the stress-applying film. It is proposed in No. 116938. Patent Application No. 63-283793 and Patent Application No. 116-1983
The two methods of No. 938 use almost the same technology,
Specifically, by loading a stress imparting film, such as an amorphous silicon (a-5+) film, onto the cladding above the core by sputtering or the like, new stress other than the compressive stress received from the substrate is applied to the core. and add the amount to Ar laser or YA laser.
The birefringence value or optical path length is changed by trimming using a G laser or the like. Both of these methods are extremely effective methods for manufacturing integrated optical devices because they are simple and can be adjusted with high precision using an online monitor. [Problems to be Solved by the Invention] However, although both of the above methods use the same technology, the shape of the stress applying film is flat for stress birefringence value adjustment, and light propagation shape for optical path length adjustment. Since it is different from a striped pattern parallel to the direction, it is only possible to adjust one side or the other, so at the time of design, it is necessary to predict in advance which type of triching will be needed and how much it will need to be applied to which part, and then adjust the stress-applying film accordingly. The problem was that it had to be placed. Furthermore, the shape of the stripes of the stress imparting film for adjusting the optical path length is, for example, 7-8 μm thick.
On the other hand, since it is fine and has a high aspect ratio, with a period of about 10 μm and a line width of about 5 to 7 μm in the untrimmed portion, an extremely advanced processing technique is required and the manufacturing process is difficult. SUMMARY OF THE INVENTION An object of the present invention is to provide an integrated optical device that solves the above problems and a method for manufacturing the same. [Means for Solving the Problems 1] The integrated device of the present invention comprises a substrate, a cladding layer disposed on the substrate, a single mode optical waveguide embedded in the cladding layer and having a core portion having a light propagation function, and a cladding layer. It is arranged at a predetermined portion on the layer and can irreversibly change the stress acting on the core portion to simultaneously adjust the optical path length and birefringence value of the single mode optical waveguide. It is characterized by comprising a stress applying film including a striped portion consisting of a plurality of angled thin lines. The method of the present invention includes the steps of creating a single mode optical waveguide having a cladding layer disposed on a substrate and a core portion embedded in the cladding layer and having a light propagation effect, and a stress applying film applied to a predetermined portion on the cladding layer. and a step of repeatedly trimming a predetermined portion of the stress-applying film by irradiating the stress-applying film with an energy beam to form a plurality of thin lines on the stress-applying film to form a striped shape.

[For use]

According to the present invention, a part of the stress-applying film is trimmed in an appropriate direction relative to the light propagation direction and in a striped form, and, for example, by laser beam irradiation, phase change or evaporation is caused in the stress-applying film at the irradiated portion. By this, the birefringence value and the optical path length of the integrated optical device can be adjusted simultaneously C1 and precisely. In addition, since the birefringence value and the amount of change in optical path length can be freely selected depending on the direction of the stripes, there is no need to determine the purpose and amount of trimming from the design stage, and there is no need for fine striped films. Therefore, machining accuracy can be significantly reduced. [Examples] Hereinafter, the present invention will be described in detail based on Examples. Embodiment 1 FIGS. 1 and 2 show a Matsuha-Zehnder optical interferometer circuit operating as a two-wavelength optical multiplexer/demultiplexer or an optical frequency selection switch, respectively, as a first embodiment of the integrated optical device of the present invention. 3 is a plan view showing the circuit configuration and its manufacturing method, and a sectional view showing an enlarged cross section along the ^^' line.
FIG. 7 is a plan view showing another configuration of the Zehnder optical interference circuit and an enlarged cross-sectional view thereof taken along line 8B'. The difference from the conventional example in FIG. 12 is that two flat stress applying films 22A and 22B are loaded on the waveguide la between the directional couplers 2a and 2b, and a part of the film is striped. The point is that it has been cropped. Here, in FIGS. 1 and 3, the trimmed portions are shown as striped lines. Silica-based single mode optical waveguide 1a in FIGS. 1 to 4
, lb were formed on a silicon substrate by flame deposition method and reactive ion etching method, and the 12th
It has the same composition and structure as the conventional example shown in the figure. Specifically, the glass composition is S,0□-7102 series or S,O□
~6002 series, core dimensions are approximately 7μ-X7μm, S, 0
The thickness of the second cladding is about 50 μm. Heater 21
is not required. The difference in length between the waveguides 1a and ib between the directional couplers 2a and 2b is ΔL=10 mm. The plate-shaped stress-applying plates g22^ and 22B on the waveguides 1a and ib are made of a-5H, and are fabricated by magnetron sputtering and reactive ion etching. Its dimensions are, for example, a thickness of 7 μm, a width of 200 μgm, and a length of 5 mm. a-51
Part of the membrane is trimmed in stripes, as shown in Figure 1.
One part of the a-51 film 22a is trimmed in stripes (22c) perpendicular to the light propagation direction, and the other a-3I film 22b is trimmed in stripes (22d) parallel to the light propagation direction over the entire surface. After being trimmed, a portion 22e thereof is trimmed perpendicularly to the light propagation direction. In FIG. 3, a part 22f of one a-5I film 22a is trimmed at a predetermined angle with respect to the light propagation direction. The shape of the trimming stripes is, for example, a pitch of 10μI11. ) - Rimming width 5 μm5 The width of the untrimmed portion is 5 μm. For example, a laser beam is used for this trimming, and the a-5I in the portion irradiated with the laser beam is heated by the laser and crystallized or evaporated, and the stress in that portion is completely eliminated. By focusing this laser beam with a lens, it is possible to narrow it down to about several μm. FIGS. 5 and 6 are plan views showing an experimental method for investigating the effect of striped trimming. The integrated optical device used in this experiment is a Matsuha-Zehnder optical interferometer circuit with no difference in optical path length (ΔL・0 in FIGS. 1, 3, and 12), and includes two directional couplers 6a. , a-
5 I membranes 24a, 24b are loaded. Waveguide 6a
The upper a-51 film 24a is partially 24c in FIG.
is trimmed perpendicular to the light propagation direction and in a striped pattern. On the other hand, in FIG. 6, a
After the -5l films 24a and 24b are trimmed in advance into stripes (24d) parallel to the light propagation direction, only a part 24e of the a-5I film 24a on the waveguide 6a is trimmed perpendicular to the light propagation direction. There is. Waveguide cross-sectional structure, a-5
, the shape of the film, and the shape of the trimming stripes are shown in Figures 1 to 4.
The same as in the case of Fig. 5 and Fig. 6,
The treated areas are shown as striped lines. Figures 5 and 6 show extreme examples of the present invention in which the angle between the light propagation direction and the trimming stripe is Oo and 90°, and in the present invention, this angle takes an intermediate value between 0 and 90@. Needless to say, there are cases. First, let's examine the difference in stress effect between a wide a-5+ film and that film trimmed into stripes. Figure 7 shows the 0
．． It is a diagram showing the stress distribution of a sample in which an a-5Il layer 22 is formed on a 7 mm thick quartz glass plate 25. The stress distribution was derived from measurements using the photoelastic effect and stress analysis using the finite element method. FIG. 7(a) shows the thickness of 2.
The case where a uniform film of 5 μm and width of 100 μm is formed is shown.
FIG. 7(b) shows the case where a uniform film of 5 μm in thickness and 100 μm in width is trimmed perpendicularly to the cross section over 5 μm at a pitch of 10 μm using an argon (^r) laser beam. 26 indicates a region where tensile stress occurs, and 27 indicates a region where compressive stress occurs. It is known that such stress distribution is caused by strong compressive residual stress in a-5+@ formed by magnetron sputtering, and that the depth to which the stress extends is approximately the width of the stress-applying film. Figure 7 (
In a), the stress extends to a depth as deep as the width of the membrane 22, confirming this fact. In FIG. 7(b), the stress is a-S+ film 2
2 and the quartz glass substrate 25, and its depth is approximately 5 μm. This means that the stress in the a-5t portion 23 irradiated with the laser beam in Fig. 7(b) has almost disappeared, and the stressed portion, that is, the untrimmed portion, has become a thin stripe shape of about 5 μm. It shows. From this result, a-5xllI
If you trim 22 and make it into thin stripes like the above,
The stress in the in-plane direction perpendicular to the trimming direction does not reach the core located 20μ below the stress-applying film, but there is sufficient length in the assembling direction, so the stress does not reach the core. It can be concluded that it does not remain near the surface but also extends near the core. Of course, if there is sufficient width and length as shown in FIG. 7(a), stress in the cross-sectional direction perpendicular to the assembly direction and in the assembly direction will act on the core portion. Here, the stress in the assembly direction is shown in Figure 7 (a
). It should be noted that both (b) are the same. Next, the effect that trimming has on propagating light will be explained. When stress is applied to a material or the applied stress is changed, the refractive index changes according to the photoelastic effect. This is actually used for applying stress on the optical waveguide in Figures 5 and 6.
Let us consider the case of trimming a 5L membrane. Stress in the in-plane direction perpendicular to the light propagation direction (principal C
Parallel stress is applied to the substrate from the substrate and stress-applying film)
The birefringence value B (・ntg−ntM) changes due to
As shown in the figure, by trimming the wide A-51 film 24a perpendicular to the light propagation direction, the birefringence value B and the optical path length change simultaneously, and as shown in Fig. 6, the birefringence value B and the optical path length can be changed simultaneously. By trimming the striped a-5L film 24a perpendicular to the light propagation direction, only the optical path length changes. The effect of the above operation is that the symmetry of the Matsuha-Zehnder optical interferometer in FIGS. 5 and 6 is
This is confirmed by the collapse of the I film 24a by trimming it, and this appears as a phase difference Δφ between the light propagating through the waveguides 6a and 6b in the directional coupler 2b when light enters from the input boat 3b. Injection boat 3b
If the power of the light when the light enters from the output port 4a and 4b is output from Pout2 and Poutl, the phase difference △φ is △φ−2CO5−′ (Po.t+/
(+)out+◆POt+t2))-”” (2)
It is expressed as Figure 8 shows two pieces of 7 μm thick and 20 mm wide in Figure 5.
0 μm 1 length I O+u+ for applying stress like -S+
Trimming length and output light p when @Z4a on the waveguide 6a of 1ki24a and 24b is trimmed in a striped pattern perpendicular to the light propagation direction. utl and P. FIG. 6 is a diagram showing the phase difference between the lights propagating in the waveguides 6a and 6b in the directional coupler 2b calculated from ut2, that is, the amount of phase change caused by trimming. The shape of the trimmed stripes is equal to the above value, the pitch is 10μ, the width of the trimmed part is the width of the untreated part! It was set to 5 μ-. In the case of Fig. 5, in addition to the optical path length corresponding to the trimming length changing, the stress in the in-plane direction perpendicular to the light propagation direction in the trimmed part disappears, and the birefringence value changes accordingly.
Mode dependence can be seen in FIG. FIG. 9 shows two pieces of 7 μm thick in FIG. 6. A-5 for applying stress such as width 200μ and length 10m
Trimming length and output light when only a-5 on the waveguide 6a and the film 24a are trimmed perpendicularly to the optical propagation direction after trimming the I films 24a and Z4b in a striped pattern parallel to the optical propagation direction p. utl and Po, , is a diagram showing the phase difference between the lights propagating in the waveguides 6a and 6b in the directional coupler 2b, that is, the amount of phase change caused by trimming. Here, the shape of the trimmed stripes is the same as in the case of FIG. Figure 9 shows the amount of phase change caused by a change in optical path length, and as shown in Figure 8, there is almost no difference due to polarization. Since the stress applied in the direction is almost equal, Fig. 8 includes the amount of phase change in Fig. 9, that is, the amount of phase change caused by the change in stress applied in the direction of light propagation, and the amount subtracted by this amount is the amount of light This is the amount of phase change caused by a change in stress in the in-plane direction perpendicular to the propagation direction.As shown in Figure 3, when trimmed in a striped manner at an angle between Q-9θ° with respect to the light propagation direction, , the phase change with respect to the trimming length has an intermediate slope between FIGS. 8 and 9. Therefore, by appropriately selecting the trimming angle, the desired amount of phase change can be obtained. We have explained the stress-applying film that plays an important role in the present invention and the effect obtained by trimming the stress-applying film into a striped pattern. This laser trimming is performed by inputting monitor light into the input boat 3b, for example, and adjusting the optical path length at the same time as shown in FIG.
Here, the optical characteristics of the Matsuha-Zenda optical interferometer circuit (hereinafter referred to as an optical interferometer circuit) can be monitored while using a so-called online monitoring method, which is unique in that accurate adjustments can be made regardless of manufacturing errors in the optical waveguide or stress-applying film. Polarization dependence of the Matsuha-Zehnder optical interferometer shown in Figures 1 to 4 (shift in optical frequency due to polarization direction of light in Figure 15)
Two methods for solving this will be explained. Figure 1 shows a method in which an area for adjusting the optical path length is created in advance. First, a part of the stress applying a-5 + line 22b is trimmed into a striped shape parallel to the light propagation direction to create an area for adjusting the optical path length. After that, polarization dependence is eliminated by trimming a part 22c of the --like film 22a perpendicular to the light propagation direction, and then the optical path length adjustment region prepared in advance is trimmed perpendicular to the light propagation direction. 22e), waveguide 1
By adjusting the optical path length difference ΔL between a and lb, the optical frequency is adjusted to a desired value. In this case, it is possible to perform optical path length adjustment trimming and polarization dependence elimination trimming by reversing the order, but since polarization dependency elimination trimming also changes the optical path length, polarization dependency elimination trimming should be performed first. The method is extremely practical. In addition, when trimming to eliminate polarization dependence, it is recommended to perform trimming while adjusting the optical path length shift using the thermo-optic effect C of the heater 21 when the wavelength of the light source is not variable or when the variable range is insufficient. It should also be noted that it is effective for FIG. 3 shows a method of simultaneously adjusting the optical path length and birefringence value by triangulating a part of the stress applying A-51 film 22a at a certain angle with respect to the light propagation direction. The ratio between the optical path length and the amount of change in birefringence value can be obtained by adjusting this angle. This method does not require creating an optical path length adjustment region in advance unlike the method shown in FIG. 1, and can be performed by trimming - times, so that the trimming time can be shortened. However, this is based on the amount of birefringence and optical path length that are changed by trimming in advance, the amount of phase change with respect to the amount of trimming of the stress-applying A-51 film (for example, as shown in FIGS. 8 and 9), Alternatively, it is a method that can be applied when the birefringence value and the amount of change in optical path length are accurately known. In cases where the above amount is not accurate but roughly known, or in cases where the same sample has a large amount and the above amount is close to each other although there are individual differences in each sample, Figure 1 and It is effective to combine the methods shown in Figure 3. Specifically, the birefringence value and the optical path length are roughly adjusted simultaneously using the method shown in FIG. 3, and only the final fine adjustment is performed using the method shown in FIG. This allows the triangulation time to be reduced compared to the method of FIG. Embodiment 2 FIGS. 10 and 11 are plan views showing a method of manufacturing a mode splitter as a second embodiment of the present invention, respectively. In this example, the directional couplers 2a and 26 have a coupling rate of 50%.
The lengths of the waveguides 6a and 6b between them are equal (ΔL-0).A-5, a part of the film loaded on the waveguide between the directional couplers 2a and 2b of the Matsuha-Zehnder optical interferometer circuit Figure 3 shows a method for fabricating integrated optical devices by trimming into stripes. Here, the cross-sectional structure of the waveguide, the shape of the a-51 film, and the shape of the trimming stripes are the same as in FIGS. 1 to 4. For example, in FIGS. 10 and 11, the mode splitter is configured so that T
The E mode component is outputted from the output port 4a, the TM mode component is outputted from the output port 4b, or vice versa, the TE mode is outputted from the output port 4b, and the 7M mode is outputted from the output port 4a. It is an optical circuit element with In order to realize this function, the phase difference between the light propagated through the waveguides 6a and 6b in the directional coupler 2b must be an odd multiple of π/2 in the TE mode (or 7M mode), and an odd number multiple of π/2 in the 7M mode (or TE mode). must be an integral multiple of π, and for this purpose it is necessary to adjust the optical path length and control the birefringence value. Figure 1O shows the stress applying a-5, similar to the method shown in Figure 1.
1[24b is trimmed in a striped shape parallel to the light propagation direction to prepare an optical path length adjustment region in advance, and then the output boat 4a of the light Pin input from the input boat 3b is trimmed.
, 4b, while observing the polarization component ratio of the output light P 6+jt2 , Poutl, first apply −-like stress [24a
After controlling the birefringence value by trimming a part 24c perpendicular to the light propagation direction, the optical path length control region is trimmed perpendicularly to the light propagation direction 24e) to obtain the desired optical path length difference. It's a method. The dimension of the triling stripe is the pitch lO
The trimming width is approximately 5 μm. In this step of controlling the birefringence value, there is an optimal optical path length difference (the optical path length difference closest to the desired mode splitter operation in the trimming state) for each state during the birefringence value control, It is necessary to perform control while always realizing the optical path length difference. To achieve this, there are two methods: controlling the optical path length and birefringence value at the same time by trimming, or using the thermo-optic effect of the heater 21 to provide a difference in optical path length, but the latter is more practical in terms of avoiding the complexity of trimming. This seems like a good method. In FIG. 11, as in FIG. 3, the stress applying a-5 and the part 24f of the film 24a are trimmed in a striped manner at a certain angle with respect to the light propagation direction, thereby increasing the optical path length and the birefringence value. This is a method of adjusting both at the same time. A desired ratio of optical path length to birefringence value change can be obtained by adjusting this angle. This method does not require creating an optical path length adjustment region in advance unlike the method shown in FIG. 1O, and can be performed by only -times of trimming, so that the trimming time can be shortened. However, this is the amount of birefringence and optical path length that are changed by trimming in advance, and the amount of phase change (for example, shown in Figures 8 and 9) for the amount of trimming of the stress-applying A-51 film, or the amount of birefringence that is changed by trimming. This method can be applied when the value and amount of change in optical path length are accurately known. In cases where the above amount is not accurate but approximately known, or
In cases where there are a large number of the same samples and the above values (there are individual differences in each sample but have almost similar values), it is effective to combine the methods shown in Figures 10 and 11.Specifically. In this case, the birefringence value and the optical path length are mostly adjusted at the same time using the method shown in Figure 11, and only the final fine adjustment is made using the method shown in Figure 11.
Perform as shown in the figure. This reduces the trimming time to 10th
It is shorter than the method shown in the figure. In the above example, the width of the stripes in the untrimmed portion was made smaller than the core depth to prevent stress in the cross section perpendicular to the stripe direction from reaching the vicinity of the core, but the width of the untrimmed portion By widening and subtly changing the width, it is possible to finely adjust the stress applied to the vicinity of the core in the inward direction of the cross section, making it possible to delicately control the birefringence value ft1lJ. Further, in the above embodiments, the stress imparting film to be trimmed was installed on a straight optical waveguide, but depending on the case, it may be installed on a curved optical waveguide. Even in such a case, the same effect can be obtained by making sure that the angle between the waveguide and the trimming stripe always forms a predetermined angle. Therefore, the trimming stripes may be curved. Furthermore, in the above embodiments, the angle between the trimming stripe and the waveguide was always constant, but the same effect can be obtained even if the angle is changed continuously or discontinuously. can. Further, in the above embodiment, a continuous wave argon (Ar) laser was used as the trick/knob means for the stress applying film, but a Q-switch YAG laser may also be used. In the latter case, a phenomenon was observed in which the a-5I film in the region irradiated with the laser beam did not change to a polycrystalline state but vaporized. If it disappears by vaporization, the stress effect in that region also disappears selectively, so the Q-switched YAG laser can be effectively used as a trimming means. Furthermore, in the above examples, a-5l was used as the material of the stress applying film.
However, the present invention is not limited to this, and other materials such as an amorphous metal film (such as a Co4r film) can also be used. Amorphous films are more suitable than crystalline films because crystal transitions are less likely to occur in amorphous films, and stress remains stable over long periods of time without relaxation. It is. Furthermore, in the above embodiment, a silica-based single mode optical waveguide on a silicon substrate was used as the single mode optical waveguide.
The present invention is not limited to this, but if there is a car-mode optical waveguide whose core portion is buried in the cladding layer,
The present invention can also be applied to optical waveguides made of other materials. ? . In the case of an ion-diffusion optical waveguide in which metal ions are diffused on a multi-component glass substrate, there is a problem in that the core portion is located near the surface of the substrate and cannot be sufficiently distanced from the stress-applying film. In such a case, prior to forming the stress imparting film, for example, 5iOJ with a thickness of about 5 μm is applied to the surface of the substrate on which the core portion is formed.
By vapor-depositing I and forming a stress imparting film thereon, it is possible to equivalently increase the embedding depth of the core portion and set the width of the trimming stripes to be smaller than the embedding depth of the core portion. In the above embodiments, the Matsuha-Zehnder tip interferometer circuit has been explained as an example of an integrated optical device, but the present invention is not limited to this optical interferometer circuit, and can be applied to other integrated optical device circuits, such as Needless to say, the present invention can be applied to a wide range of single-mode integrated optical devices that require optical path length control and polarization control, such as optical ring resonant circuits, Fabry-Perot resonant circuits, and waveguide wave plates. [Effects of the Invention] According to the toothpick 5 described above, the stress imparting film loaded on the cladding layer at the top of the optical waveguide is trimmed in a striped shape and at an appropriate angle to the light propagation direction.
Birefringence value and optical path length can be controlled simultaneously. Since trickling can be performed while observing the output of the monitor light input to the integrated optical device, desired characteristics can be imparted to the device without depending on manufacturing errors in manufacturing the optical waveguide. Accurate setting of birefringence values and optical path lengths is expected to play a major role in realizing coherent light iIlfg, Iff optical devices, optical devices for optical switching systems, and the like.

[Brief explanation of drawings]

FIGS. 1 and 2 are a plan view and a cross-sectional view taken along the ^^" line, respectively, showing the circuit configuration of an optical interferometer and its manufacturing method as a first embodiment of the integrated optical device manufacturing method of the present invention; 3 and 4 are plan views showing other circuit configurations of the optical interferometer and their manufacturing method, respectively, and a sectional view taken along the line BB', and FIGS. 5 and 6 show the trimming used in the present invention. Figures 7(a) and (b) are vertical cross-sectional views of stress distribution showing the effect of trimming used in the present invention; Figure 8 is the experiment of Figure 5. Fig. 9 is a diagram showing the amount of phase change with respect to the trimming length of a-5+II!ii obtained from the experiment in Fig. 6; 1O and 11 are diagrams showing the circuit configuration of a mode splitter and its manufacturing method as a second embodiment of the integrated optical device manufacturing method of the present invention, and FIGS. 12 and 13 are diagrams showing a conventional integrated optical device manufacturing method. FIG. 14 is a plan view and a cross-sectional view along line A of the optical interferometer circuit as a device, FIG. 14 is a diagram explaining the device characteristics of the optical interferometer circuit of FIG. 12, and FIG. , is a diagram illustrating the polarization characteristics of the optical interferometer circuit in Fig. 12. l...Silicon substrate, la, lb, 6a, 6b... Optical waveguide (core part),
2a, 2b...Directional coupling part, 3a, 3b input boat, 4a, 4b...output boat, 5...cladding layer, 21...heater, 22.22a, 22b, 24a, 24b - stress For grant a
-51 film, 23... Stress applying a-5+II@laser trimming portion, 25... Quartz glass substrate, 26... Tensile stress generation area, 27... Compressive stress generation area.

Claims (1)

[Scope of Claims] 1) A single mode optical waveguide having a substrate, a cladding layer disposed on the substrate, a core portion embedded in the cladding layer and having a light propagation function, and a predetermined portion on the cladding layer. The core portion has a predetermined angle with respect to the light propagation direction, and is arranged at a predetermined angle with respect to the light propagation direction, and can irreversibly change the stress acting on the core portion to simultaneously adjust the optical path length and birefringence value of the single mode optical waveguide. 1. An integrated optical device comprising: a stress-applying film including a striped portion made up of a plurality of thin wires. 2) The integrated optical device according to claim 1, wherein the single mode optical waveguide is a quartz optical waveguide mainly composed of SiO_2, and the stress applying film is an amorphous silicon film. . 3) The integrated optical device according to claim 1 or 2, wherein the width of each of the plurality of thin lines of the stress applying film is smaller than the depth of the core portion buried in the cladding layer. 4) A step of creating a single mode optical waveguide having a cladding layer disposed on a substrate and a core portion embedded in the cladding layer and having a light propagation effect, and applying a stress imparting film to a predetermined portion on the cladding layer. and a step of repeatedly trimming a predetermined portion of the stress applying film by irradiating it with an energy beam to form a plurality of thin lines on the stress applying film to form a striped shape. Method of manufacturing integrated optical devices. 5) The method for manufacturing an integrated optical device according to claim 4, characterized in that a plurality of thin lines are formed in the stress applying film so as to intersect at a predetermined angle with respect to the light propagation direction of the core portion.