JPH10332971A - Manufacture of optical circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust and control the refractive index of an optical waveguide by optically induced refractive index variation and to provide the manufacture of the optical circuit which has sufficient temperature stability. SOLUTION: In this manufacture of the optical circuit 201 having an optical waveguide consisting of a core part which is formed principally of a quartz- based raw material on a plane substrate and propagates light and a clad part which is formed around the core part and has a lower refractive index than the core part, the optical circuit 201 is held as 200 to 500 deg.C and part or the whole of the optical waveguide of the optical circuit 201 is irradiated with light in the visible or ultraviolet-ray range to vary the refractive index of the optical waveguide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical circuit, and more particularly to an optical circuit having an optical waveguide disposed on a flat substrate, which is useful in the fields of optical communication, optical information processing, and optical measurement. And effective technology.

[0002]

2. Description of the Related Art Quartz-based optical waveguides have low loss, have excellent physical and chemical characteristics in terms of stability and reliability, and are also compatible with quartz-based fibers which are transmission lines for optical communication. It has characteristics such as good matching with the fiber because it has almost the same refractive index.

In many cases, this silica-based optical waveguide is manufactured on a silicon (Si) substrate by a manufacturing process of lower clad film layer deposition → core film layer deposition and core partial patterning → upper clad layer deposition. I have.

Research and development on various practically promising optical circuits, such as an optical power splitter, a wavelength multiplexer / demultiplexer, a filter, and a switch, using this silica-based optical waveguide have been conducted.

Further, in this quartz optical waveguide, the local refractive index change induced by the irradiation of high intensity laser light of visible, ultraviolet, or various wavelengths causes an optical circuit to have a new function such as a light-induced grating. It has been promising as a means for adding a symbol or finely adjusting / compensating the characteristics of an optical circuit.

For example, a light-induced grating induces a periodic refractive index distribution in an optical waveguide by irradiating light, and can produce a reflection wavelength filter and an optical circuit having a dispersion compensation function. As described in the following document (a), a light-induced grating is first prepared by using a phase mask, an interference exposure optical system, or the like on a light guide that is normally manufactured. Form a periodic light intensity distribution. (A) Toru Inoue, "Fiber Grating", Laser Research Vol. 23, No. 10, pp. 880-889, 199
5. As the change in the refractive index in the optical waveguide, the greater the intensity of the irradiated light, the greater the change in the refractive index is induced. Therefore, the periodic refractive index distribution can be induced by reflecting the periodic light intensity distribution. .

[0007] This light-induced grating forms a refractive index modulation distribution after the optical waveguide manufacturing step, and thus complicates the optical waveguide manufacturing step, as compared with a relief type grating manufactured using reactive ion etching (RIE) or the like. In addition, since it is a refractive index modulation type grating, it can be relatively easily manufactured with high reflectivity.

However, the light-induced grating produced on the optical waveguide does not have sufficient thermal stability as a practical optical component due to the change in the light-induced refractive index. There is a problem that the range of application is limited due to the reduction and the displacement of the center wavelength.

On the other hand, a Mach-Zehnder interferometer (MZ)
In an optical circuit device utilizing interference sensitive to the phase of light, such as I) or an arrayed optical waveguide grating (AWG), since the phase of light depends on the length of the optical path, minute refractive index fluctuations that occur in the fabrication of the optical circuit can be reduced.
Fluctuations in the shape of the optical waveguide and strain (stress) applied to the optical waveguide have a great effect on optical circuit element characteristics such as a transmission / blocking wavelength region and an extinction ratio.

In particular, in the case of an optical circuit on a silicon (Si) substrate, strain (stress) is applied to the optical waveguide due to a difference in thermal expansion coefficient between the glass layers of the cladding and the core and the substrate, resulting in birefringence ( B), that is, a difference (B = n _TM −n _TE ) between the core refractive index (n _TM ) in the _TM polarization direction and the core refractive index (n _TE ) in the TE polarization direction.

In an optical circuit element such as a Mach-Zehnder interferometer (MZI) or an arrayed optical waveguide grating (AWG), the birefringence (B) is such that a transmission band (or a stop band) of a wavelength dependent on the polarization of light. ), And consequently,
It causes polarization dependent loss (PDL). In the optical communication field and the like, it is desired to minimize the polarization dependence of these optical circuits (polarization insensitive).

That is, an optical waveguide which enables adjustment and control of optical element characteristics such as a transmission / blocking area and an extinction ratio of an optical circuit, thereby improving the performance of the optical circuit and improving the production yield. There is a demand for a technique for correcting the optical path length by locally and easily changing the refractive index of the optical waveguide after fabrication.

Heretofore, as a method for locally changing the birefringence (B) of an optical circuit on a silicon (Si) substrate,
For example, as described in the following document (b), a stress applying film such as amorphous silicon (a-Si) is patterned into an appropriate shape near the optical waveguide, or a groove is formed near the optical waveguide. A method of adjusting the strain applied to the optical waveguide by manufacturing or the like is disclosed. (B) M.KAWACHI, ”Silica waveguides on silicon and
their application tointegrated-optic comonents, J.
Opt. Quantum. Electron., 22, pp. 391-416, (1990) However, these methods have a problem that the number of steps for manufacturing an optical circuit increases and the method becomes complicated.

As another method, as described in the following document (c), a method utilizing a photo-induced refractive index change caused by irradiating an optical waveguide with ultraviolet or visible light has been disclosed. I have. (C) M.ABE, et al., “Photoinduced Birefringence Co
ntrol in Arrayed-waveguide Grating Multi / Demultipl
exer. ”, Tech.Dig.MOC / GRIN'93, pp66-68, (1993). This method makes it possible to easily control the birefringence of an optical waveguide without complicating the optical circuit fabrication process. Is a promising way.

[0015]

As described above,
The light-induced refractive index change enables simple adjustment and control of the local refractive index of the optical waveguide, making a light-induced grating in an optical circuit, and changing the optical path length to adjust the characteristics of the optical circuit. However, there is a problem in that the photo-induced refractive index change in a quartz-based optical waveguide on a flat substrate has insufficient thermal stability.

As a means for improving the temperature stability of the photo-induced refractive index change, as described in the following document (d), by performing "pre-heat treatment" after performing light irradiation, an apparent In addition, it has been shown that the temperature stability can be improved. (D) T. Erdogan, V. Mizrahi, et al., “Decay of ultrav
iolet-induced fiber Bragg gratings ”, J. Appl. Phys.,
vol.76, pp73-80 (1994) .However, in this method of performing "preliminary heat treatment", the amount of refractive index change that is relaxed by this "preliminary heat treatment" In order to finely adjust the refractive index and birefringence, there is a problem that the controllability is poor and the number of optical circuit fabrication steps and the fabrication time are increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method of manufacturing an optical circuit in which the refractive index of an optical waveguide is changed by a photoinduced refractive index change. It is an object of the present invention to provide a technology that can easily adjust and control and improve the temperature stability.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0019]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

In the method of manufacturing an optical circuit having an optical waveguide, the optical circuit is maintained at a temperature of 200 ° C. or more and 500 ° C. or less,
The main feature is that a part or all of an optical waveguide of an optical circuit is irradiated with light in a visible or ultraviolet region to induce a change in refractive index having excellent temperature stability.

The refractive index in the TM polarization direction (Δn _TM )
And the difference between the refractive index in the TE polarization direction (Δn _TE ) and
The birefringence of the optical waveguide is adjusted.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, components having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.

[Embodiment 1] As a first embodiment of the present invention, a method of fabricating a light-induced grating in a silica-based optical waveguide will be described.

In producing the photo-induced grating, first, a silica-based optical waveguide was prepared, and then the optical waveguide was irradiated with light.

FIG. 1 shows an embodiment of the present invention.
It is a figure for explaining an example of a manufacturing method of a silica system optical waveguide.

In the present embodiment, first, as shown in FIG. 1A, a lower cladding layer made of a quartz-based glass film is formed on a silicon (Si) substrate 101 by a flame hydrolisis deposition (FHD) method. 102, followed by a core glass layer 10 made of a Ge-doped quartz glass film.
Form 3 Next, as shown in FIG. 1B, the core glass layer 103 is processed into a desired pattern by using photolithography and reactive ion etching (RIE) to form a core layer 104. Thereafter, as shown in FIG. 1 (c), the upper cladding layer 105 made of a silica-based glass film was deposited again by the FHD method to produce a buried rectangular optical waveguide. In this case, the core glass layer 103
About 7 mol% of GeO ₂ is added to the cladding layers (the upper cladding layer 105 and the lower cladding layer 102).
The refractive index is set higher than that.

FIG. 2 is a view for explaining a method of manufacturing a light-induced grating on a silica-based optical waveguide according to an embodiment of the present invention.

An optical circuit 20 having a quartz optical waveguide on a silicon (Si) substrate manufactured by the method shown in FIG.
1 is placed on the heater 203. Further, a phase mask 202 for producing a light-induced grating is arranged on the upper surface of the optical waveguide, and alignment is performed through the phase mask 202 so that the optical waveguide is irradiated with ultraviolet laser light.

Thereafter, the temperature of the optical waveguide substrate is detected by the thermocouple thermometer 205, whereby the control computer 206
Controls the heater power supply 204 to set the optical waveguide substrate temperature to 4
Light irradiation is performed while maintaining the temperature at 00 ° C. In this case, the single mode (SM) optical fiber 207 and the single mode (S
M) The polarization maintaining optical fiber 208 is coupled to the end face of the optical waveguide, and the light from the white light source 210 is made incident on the optical waveguide via the polarizer (polarizer) 209 and the polarization maintaining optical fiber 208 to form an optical waveguide. From the spectrum analyzer 21 via the SM optical fiber 207.
1 and a light-induced grating was produced while monitoring the transmission spectrum of the optical waveguide.

The ultraviolet laser beam is applied to the phase mask 202.
The light is diffracted and interfered with each other, so that a periodic light intensity distribution corresponding to the interference fringes is generated on the optical waveguide. This periodic light intensity distribution induces a refractive index change according to the light intensity,
A periodic refractive index distribution, i.e., a light-induced grating, is created in the optical waveguide.

In the present embodiment, an ArF excimer laser (wavelength: 193 nm) was used as an ultraviolet laser, pulse repetition was 20 pps, energy per pulse was 500 mJ / pulse, and irradiation time was 15 minutes. The length (L) of the produced light-induced grating was 7 mm, and the reflection Bragg wavelength (λ _B ) was 1.55 μm.
m.

FIG. 3 is a graph showing a change in reflectance (R) when a photo-induced grating prepared according to the present embodiment is placed in an electric furnace set at a temperature of 400 ° C. and subjected to a heat treatment.

In FIG. 3, for reference, the room temperature (2
The change in reflectance (R) when heat treatment is performed on the light-induced grating manufactured at 7 ° C.) is also shown.

The reflectance (R) is determined by the depth of the refractive index modulation (Δn).
_mod ), the grating length (L), the reflected Bragg wavelength (λ _B ), and the overlap coefficient η that defines the overlap between the core portion and the optical electric field, are represented by the following equation (1).

[0035]

R = tanh ² (πLηΔn _mod / λ _B ) (1) The stability of this reflectance (R) to the heat treatment is the stability of the induced refractive index change. Will be reflected. As is clear from FIG. 3, the photo-induced grating manufactured at the optical waveguide substrate temperature of 400 ° C. was thermally more stable than the photo-induced grating manufactured at room temperature.

As described above, in the present embodiment, since the light irradiation is performed while the optical waveguide is kept at 400 ° C., the change in the refractive index induced is reduced at the same time. A stable refractive index change can be obtained.

The temperature of the optical waveguide substrate is not necessarily 40
The temperature does not need to be 0 ° C., and if the temperature is 200 ° C. or more, the temperature stability is sufficiently higher than the change in the refractive index caused by light irradiation at room temperature. In this case, the higher the temperature, the longer the light irradiation time for obtaining a desired refractive index change by the relaxation process that proceeds in the same manner. It is possible to obtain the rate change in a sufficiently short time for practical use.

As described above, according to the present embodiment, the amorphous silicon (a-S
i) Compared to a method of patterning a film or a method of forming a groove, a light-induced grating can be easily formed without complicating the forming process. Also,
Compared to the case of performing "preliminary heat treatment", the number of manufacturing steps is small, and a light-induced grating can be easily formed.

[Embodiment 2] In this embodiment, a method of finely adjusting the transmission spectrum characteristics of an arrayed optical waveguide grating (AWG) will be described.

FIG. 4 is a plan view showing an arrayed optical waveguide grating optical wavelength multiplexer / demultiplexer which is an optical circuit according to another embodiment of the present invention.

In the figure, 301 is an input / output optical waveguide,
302 is a slab optical waveguide, 303 is an array optical waveguide, 3
04 is a reference optical waveguide. In FIG. 3, the input and output optical waveguides 301 are expressed as CH1, CH2, CH3,. In the array optical waveguide grating optical wavelength multiplexer / demultiplexer of the present embodiment, light is introduced from n = 8 and the channel interval (an arbitrary input optical waveguide CH (k) (k = 1, 2,..., N)). At this time, the output optical waveguides CH (j) and CH (j + 1) (j =
The center wavelength (λcj) of the transmission wavelength range of 1, 2,..., N-1)
And (λcj + 1) were about 0.8 nm using an arrayed optical waveguide grating (AWG).

The optical circuit shown in FIG. 4 was manufactured by a method similar to the method shown in FIG. After fabrication, the optical waveguide end face is cut out with a dicing saw so that the transmission spectrum of the optical circuit is measured for TE polarization and TM polarization, and the center wavelength (λ _CTE ) of the transmission band is measured.
(Λ _CTM ) and its difference (Δλ _C ) were evaluated for initial characteristics. The difference (Δλ _C ) between the center wavelengths of the transmission regions has a substantially proportional relationship with the birefringence (B) of the optical waveguide constituting the optical circuit of the present embodiment.

FIG. 5 shows an optical circuit according to this embodiment.
It is a graph which shows an example of the measurement result of the initial transmission spectrum of output light emitted from output optical waveguide CH5 when light is input from input optical waveguide CH4.

As can be seen from FIG. 5, since the optical waveguide has birefringence, the transmission wavelength range shifts to a longer wavelength side when measured in the TM polarization direction as compared with that measured in the TE polarization direction. The difference is the polarization dependent loss (PDL)
One of the factors.

FIG. 6 is a diagram for explaining a method of finely adjusting the transmission spectrum characteristics of the arrayed optical waveguide grating (AWG) in the present embodiment.

After the initial transmission spectrum characteristic evaluation, the optical circuit 4
01 is placed on the heater 203 as shown in FIG. The entire portion of the array optical waveguide 303 was exposed, and the other portions were covered with a shielding mask 402 made of a metal plate so as not to be exposed to light. Subsequently, the array optical waveguide 30
Alignment (optical axis alignment) is performed so that the three portions are uniformly irradiated with light.

Thereafter, similarly to the method shown in FIG. 2, the initial birefringence of the optical waveguide (or the difference in the center wavelength of the transmission region (Δλ _C) is maintained using the heater 203 while maintaining the optical circuit at 290 ° _C. )), Ultraviolet light irradiation was performed for a set time for compensating the characteristics such that the difference (Δλ _C ) between the center wavelengths of the transmission regions becomes zero. In the present embodiment, the set time is 60 minutes. As a light source, ArF
Using an excimer laser (wavelength λ = 193 nm), the light intensity was 250 mJ / cm ² / pulse, and the pulse repetition was 50 pps.

FIG. 7 is a graph showing the irradiation time dependence of the change in birefringence (B) when light irradiation is performed.

It is also possible to make adjustments while monitoring the optical characteristics of the optical circuit 401 with the spectrum analyzer 211 until the difference (Δλ _C ) between the center wavelengths of the transmission regions becomes zero.

FIG. 8 shows an optical circuit according to this embodiment.
It is a graph which shows an example of the measurement result of the transmission spectrum after light irradiation of output light emitted from output optical waveguide CH5 when light is incident from input optical waveguide CH4.

As can be seen from FIG. 8, as a result of light irradiation, the center of the transmission wavelength range of each of the TE polarization and the TM polarization coincides. Moreover, before and after light irradiation, the loss is hardly increased.

In order to verify the thermal stability of the transmission spectrum characteristic of the optical circuit 401 of the present embodiment, the optical circuit 401 after light irradiation is placed in an electric furnace set at a furnace temperature of 300 ° C. to perform a heat treatment. Then, the change in the transmitted light spectrum was examined.

FIG. 9 shows the dependence of the birefringence (B) of the optical waveguide on the heat treatment time obtained from the difference (Δλ _C ) between the centers of the transmission wavelength ranges in the TE polarization and the TM polarization in the present embodiment. It is a graph shown.

In FIG. 9, for reference, the room temperature (2
FIG. 6 also shows the heat treatment time dependency of the birefringence (B) of the optical waveguide of the optical circuit that was similarly irradiated with light by the method shown in FIG.

In the optical circuit irradiated with light at room temperature, the birefringence (B) is relaxed by the heat treatment and approaches the initial value, whereas the optical circuit of the present embodiment (light irradiation at 290 ° C.) The birefringence (B) of the obtained optical circuit shows almost no relaxation and shows stable characteristics against heat treatment at 300 ° C.
This result indicates that the thermal stability has been improved.

[Embodiment 3] In another embodiment of the present invention, an arrayed optical waveguide grating optical wavelength multiplexer / demultiplexer similar to that shown in Embodiment 2 is used as an optical circuit.

The optical circuit according to the present embodiment is manufactured as follows, similarly to the optical circuit according to the second embodiment.

After the upper cladding layer is formed, the optical waveguide end face is cut out by a dicing saw so that the transmission spectrum of the optical circuit is measured for each of the TE polarization and the TM polarization, and the center wavelength (λ _{CTE) of the} transmission band is measured. ),
(Λ _CTM ) and its difference (Δλ _C ) were evaluated for initial characteristics.

FIG. 10 is a diagram for explaining a method of finely adjusting the transmission spectrum characteristic of the arrayed optical waveguide grating (AWG) in the present embodiment.

After the initial characteristic evaluation, as shown in FIG.
The optical circuit 502 was placed in a constant temperature bath (electric furnace) 501 capable of irradiating the excimer lamp ultraviolet light, the atmosphere in the constant temperature bath 501 was replaced with He, and the temperature in the furnace was set to 250 ° C. With the furnace temperature kept at 250 ° C., the entire array optical waveguide portion was exposed, and the other portions were covered with a shielding mask 402 so as not to be exposed to light, and irradiation with excimer lamp light was performed. . The excimer lamp used in this embodiment has a wavelength of 172 nm and an irradiation energy density of 10 nm.
It was 0 mW / cm ² . Further, in the present embodiment, the light irradiation time was 24 hours.

After the irradiation with ultraviolet light, in order to verify the thermal stability of the optical circuit 502, the optical circuit 502 is placed in a constant temperature bath (electric furnace) in which the furnace temperature is set to 250 ° C., and heat treatment is performed. The change in the spectrum was evaluated.

FIG. 11 shows the dependence of the birefringence (B) of the optical waveguide on the heat treatment time obtained from the difference (Δλ _C ) between the centers of the transmission wavelength bands in the TE polarization and the TM polarization in this embodiment. It is a graph shown.

In FIG. 11, for reference, the birefringence (B) heat treatment time of the optical waveguide of the optical circuit was similarly irradiated with light by the method shown in FIG. 10 while keeping it at room temperature (27 ° C.). Dependencies are also shown.

In the optical circuit irradiated with light at room temperature, the birefringence (B) was relaxed by the heat treatment and approached the initial value. On the other hand, the optical circuit of the present embodiment (light irradiation at 250 ° C.) The birefringence (B) of the obtained optical circuit has almost no relaxation, and shows stable characteristics against heat treatment at 250 ° C.
This result indicates that the thermal stability has been improved.

As the light source for light irradiation, in addition to the ArF excimer laser light and the excimer lamp described in the above embodiments, a KrF excimer laser light (wavelength: 248 n
m), Nd ³⁺ : YAG laser (1064 nm) and its harmonics such as the second harmonic (wavelength 532 nm), the third harmonic (wavelength 355 nm), the fourth harmonic (wavelength 266 nm), and Ar Ion laser light (mainly at a wavelength of 48
8 nm and 515 nm), various dye laser beams, Ti:
A similar effect can be obtained by using a laser light capable of high-intensity output, such as a sapphire laser light, an alexandrite laser light, or a harmonic light thereof, or a light source such as a lamp that emits visible and ultraviolet light.

Further, by irradiating light in a wedge shape or a triangular shape depending on the shape of the shielding mask, it is possible to more efficiently adjust the optical characteristics of the optical circuit.

As described above, the invention made by the present inventor is:
Although a specific description has been given based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the invention.

[0068]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, it is possible to improve the temperature stability of a photo-induced refractive index change caused by irradiating ultraviolet or visible light to a quartz-based optical waveguide.

(2) According to the present invention, it is possible to provide an optical circuit in which the refractive index of the optical waveguide is easily adjusted and controlled, and which has sufficient temperature stability, and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a method for manufacturing a silica-based optical waveguide according to an embodiment of the present invention.

FIG. 2 is a view for explaining a method for producing a light-induced grating on a silica-based optical waveguide, which is one embodiment of the present invention.

FIG. 3 is a graph showing a change in reflectance (R) when a photo-induced grating prepared according to the first embodiment is placed in an electric furnace set at a temperature of 400 ° C. and subjected to a heat treatment.

FIG. 4 is a plan view showing an arrayed optical waveguide grating optical wavelength multiplexer / demultiplexer which is an optical circuit according to another embodiment of the present invention.

FIG. 5 is a graph showing an example of a measurement result of an initial transmission spectrum of output light emitted from an output optical waveguide CH5 when light is input from an input optical waveguide CH4 in the optical circuit according to the second embodiment.

FIG. 6 is a diagram illustrating a method for finely adjusting the transmission spectrum characteristic of an arrayed optical waveguide grating (AWG) according to the second embodiment.

FIG. 7 is a graph showing irradiation time dependence of a change in birefringence (B) when light irradiation is performed.

FIG. 8 is a graph showing an example of a measurement result of a post-light irradiation transmission spectrum of output light emitted from the output optical waveguide CH5 when light is incident from the input optical waveguide CH4 in the optical circuit according to the second embodiment. is there.

FIG. 9 shows TE polarization and T in the optical circuit of the present embodiment.
It was obtained from the difference (Δλ _C ) of the center of the transmission wavelength range in the M polarization.
6 is a graph showing the heat treatment time dependency of the birefringence (B) of the optical waveguide.

FIG. 10 is a diagram illustrating a method for finely adjusting the transmission spectrum characteristic of an arrayed optical waveguide grating (AWG) according to the third embodiment.

FIG. 11 is a graph showing the heat treatment time dependency of the birefringence (B) of the optical waveguide obtained from the difference (Δλ _C ) between the centers of the transmission wavelength ranges in TE polarization and TM polarization in the third embodiment. It is.

[Explanation of symbols]

101: silicon (Si) substrate, 102: lower clad glass layer, 103: core glass layer, 104: core, 10
5: Upper cladding layer, 201, 401, 502: Optical circuit, 202: Phase mask, 203: Heater, 20
4: Power supply for heater, 205: Thermocouple thermometer, 206:
Heater control computer, 207: single mode optical fiber, 208: single mode polarization maintaining optical fiber, 209: polarizer (polarizer), 210: white light source, 211: spectrum analyzer, 301: input / output optical waveguide, 302 ... Slab optical waveguide, 303 ...
Array optical waveguide, 304... Reference optical waveguide, 40
2,504: shielding mask, 501: constant temperature bath (electric furnace),
503: Excimer lamp.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Kitagawa 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Akira Himeno 3- 192-1 Nishishinjuku, Shinjuku-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (72) Inventor Hiroshi Takahashi 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Nippon Telegraph and Telephone Corporation (72) Takuya Tanaka 3-192 Nishi-Shinjuku, Shinjuku-ku, Tokyo No. Japan Telegraph and Telephone Corporation

Claims (6)

[Claims] 1. A light-transmitting core formed on a flat substrate as a main material using quartz and a clad formed around the core and having a lower refractive index than the core. A method for manufacturing an optical circuit having an optical waveguide, comprising: maintaining the optical circuit at a temperature of 200 ° C. or more and 500 ° C. or less;
A method of manufacturing an optical circuit, comprising irradiating a part or all of an optical waveguide of the optical circuit with light in a visible or ultraviolet region to change a refractive index of the optical waveguide. 2. The method according to claim 1, wherein a dopant sensitive to light in an ultraviolet region is added to the optical waveguide. 3. The method of manufacturing an optical circuit according to claim ₂ , wherein GeO ₂ is used as a dopant sensitive to light in an ultraviolet region. 4. The method of manufacturing an optical circuit according to claim 1, wherein said optical circuit includes an arrayed optical waveguide grating composed of an optical waveguide. 5. The method of manufacturing an optical circuit according to claim 1, wherein the optical circuit includes a light-induced grating composed of an optical waveguide. 6. The birefringence of the optical waveguide is adjusted using a difference between a refractive index of the optical waveguide in a TE polarization direction and a refractive index of the optical waveguide in a TM polarization direction. A method for manufacturing the optical circuit according to claim 5.