JPH1124015A - Optical integrated element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical integrated element which has a mode filter function and an optical modulating function. SOLUTION: A waveguide layer 24 formed of a material which develops refractive index anisotropy and optical nonlinearlity or a material having the material dispersed in matrix is laminated. Part of the waveguide layer 24 constitutes a mode filter A which transmits light of TE mode or TM mode selectively and the rest of the waveguide layer 24 constitutes an optical modulator B which executes optical modulation by varying the refractive index to the light as an electric field is applied. The mode filter A is formed by light irradiation with ultraviolet rays, etc., and the optical modulator B is formed by a polling process to which an electric field is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical integrated device.

[0002]

2. Description of the Related Art Conventionally, a technique called photobleach using light irradiation has been proposed as one of the techniques for manufacturing a channel-type waveguide (Electronics).
Lett. , 26, 1990, p379). This technique irradiates light to a portion constituting a waveguide layer laminated on a substrate, lowers the refractive index of the irradiated portion, thereby forming a waveguide layer having a core that confines and transmits light. Technology.

[0003] This technique is directed to a waveguide layer formed of an optically isotropic medium, and an analysis on an optically anisotropic medium has not been performed. FIG. 4 of JP-A-62-29913 shows a waveguide type element functioning as a mode filter, in which a metal is disposed on a core of a glass waveguide layer that transmits light, On the other hand, there is disclosed a technique of disposing an optically anisotropic crystal (calcite, Nb ₂ O ₅ film, or the like) having a different refractive index on a core.

[0004]

DISCLOSURE OF THE INVENTION The present invention is a further technical advance from the above-mentioned publication, and is directed to a waveguide layer formed by using a material exhibiting refractive index anisotropy and optical nonlinearity. Is to provide an optical integrated device having both functions of a mode filter and an optical modulator.

[0005]

An optical integrated device according to the present invention is formed of a polymer material exhibiting refractive index anisotropy and optical nonlinearity or a material in which a polymer material is dispersed in a matrix. A waveguide layer and a substrate holding the waveguide layer, and a part of the waveguide layer includes a TE mode and a T mode.
A mode filter that selectively transmits one of the M-mode lights is formed, and the other part of the waveguide layer modulates the refractive index of the light transmitted through the waveguide layer by changing the refractive index with the application of an electric field. A light modulator for performing the above.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described. A material exhibiting refractive index anisotropy and optical nonlinearity As a material exhibiting refractive index anisotropy, a light anisotropic refractive index variable material can be employed. As an anisotropic refractive index variable material, it shows an anisotropic refractive index before light irradiation, and further, the refractive index changes with light irradiation, and both refractive index change due to light irradiation increases and decreases. Refers to a material having As such a material, a material that changes its molecular structure by light irradiation can be adopted. As a compound that causes a change in the molecular structure due to light irradiation, specifically, a compound having a carbon-carbon double bond or an azo group capable of being trans-cis photoisomerizable is exemplified.

In order to cause a desired refractive index change, it is important to use a molecule having a large anisotropic refractive index change.
Azobenzene derivatives and stilbene derivatives are preferred. Alkyl groups, carboxyl groups, nitro groups,
By bonding a functional group such as a cyano group, an amino group, or a methoxy group, the anisotropic change can be further increased. Further, electron-withdrawing groups such as nitro group and cyano group,
By introducing electron donating groups such as an amino group and a methoxy group at both ends of the molecule, it is possible to further increase the change in the refractive index anisotropy.

In the above-mentioned materials, reduction, oxidation, cleavage and the like of a carbon-carbon double bond or an azo group may be caused by continuing light irradiation, but any material which causes a desired change in anisotropy can be obtained. It doesn't matter. Rather, it is preferable to the case where cis-trans photoisomerization occurs thermally and the refractive index returns to the original value. Light irradiation is performed at a wavelength that causes photoisomerization. Generally, light having a wavelength in the ultraviolet to visible range is applied. A high-pressure mercury lamp is generally used as a light source for light irradiation, but an excimer laser or the like can also be used.

The desired optically anisotropic refractive index can be obtained by binding these anisotropic compounds to a polymer or by dispersing or binding to an appropriate matrix (for example, resin or glass). Variable material can be provided. The resin serving as the matrix is not particularly limited. For example, a thermoplastic resin such as a urethane resin, a polyester resin, and an acrylic resin, and a thermosetting resin such as a phenol resin can be used.

In order to exhibit an anisotropic refractive index before light irradiation, a polymer material containing the above-mentioned material is molecularly oriented in the plane of the waveguide layer by spin coating or melt extrusion. Can be realized by: The degree of anisotropy can be controlled by the viscosity, the number of rotations in the spin coating method, the stretching ratio during molding, and the like. Examples of those exhibiting optical nonlinearity include a π-electron conjugated system having a mobile electron, such as a benzene ring, a naphthalene ring, an azobenzene ring, and a functional group such as an electron-withdrawing nitro group and a cyano group. A molecule in which electron donating functional groups such as an amino group and an alkoxy group are simultaneously introduced can be employed. These can exhibit relatively large optical nonlinearity.

In order to actually impart optical nonlinearity, it is necessary to orient these molecules in order to break the central symmetry in the molecular arrangement. In order to perform this molecular orientation,
A poling process for orienting molecules by applying an electric field can be employed. In this case, it is preferable to heat the waveguide layer in order to smooth the molecular orientation. By the way, as a material constituting the waveguide layer of the present invention, it is necessary to introduce molecules capable of exhibiting both the above-described function of the refractive index anisotropy and the function of the optical nonlinearity. Such two functions can also be achieved by having two types of molecules having separate functions, or by introducing a molecule having both functions into one molecule. is there.

When two types of molecules are used, there is an advantage that a very wide variety of materials can be provided by combining the molecules. When a molecule having both functions is used, there is an advantage that a large amount of optically nonlinear molecules can be introduced. In addition, it is preferable that the material and the matrix having the above-described properties have low waveguide loss. Generally, the wavelength region used as an optical integrated device is a region from visible to near infrared, and therefore, it is preferable that the loss in the wavelength region where the optical integrated device is used is low. That is, it is sufficient that the loss is low in the region when the wavelength is used in the visible wavelength range and in the near-infrared wavelength range.

Mode Filter In the optical integrated device according to the present invention, a part of the waveguide layer forms a mode filter that selectively transmits one of the TE mode light and the TM mode light. The mode filter can be composed of a core for confining and transmitting light and a clad coated on the core. Here, when the ordinary light refractive index is defined as no and the extraordinary light refractive index is defined as ne, the mode filter according to the present invention is set to one of the following relationships.

Core no> cladding no and core ne ≦ cladding ne core ne> cladding ne and core no ≦ cladding no With reference to FIG. FIG. 1 shows a mode filter satisfying the above-mentioned relationship. That is, no of core 2A
= 1.706, no of the cladding 3A = 1.702, ne of the core 2A = 1.676, and ne of the cladding 3A = 1.680.

According to the relationship described above, the no of core 2A
> The TE mode light can be confined and transmitted through the core 2A due to the relationship of clad no, and ne of the core 2A ≦ ne of the clad.
, The light in TM mode cannot be confined,
Will radiate. As a result, the mode filter shown in FIG. 1 can function as a filter capable of selectively extracting only light in the TE mode.

In manufacturing the mode filter shown in FIG. 1, the following can be performed. That is, as shown in FIG. 2, the waveguide layer 24 is laminated on the substrate 20 via the under clad 22, the mask 40 is covered on the portion corresponding to the core 2A, and the portion corresponding to the clad 3A is exposed. In that state, ultraviolet rays are irradiated through the mask 40. In the portion corresponding to the clad 3A thus irradiated, n
As o decreases, ne increases. As a result, a mode filter having the above relationship is formed.

Conversely, the mode filter shown in FIG. 3 satisfies the above relationship. , T
E-mode light can be radiated, TM mode light can be confined in the core 2A and transmitted, and it can function as a filter that can selectively extract only TM mode light. Manufacturing of the mode filter shown in FIG. 3 can be performed as follows.
That is, as shown in FIG. 4, the waveguide layer 24 is laminated on the substrate 20 with the under clad 22 interposed therebetween, the mask 40 is covered on the part corresponding to the clad 3A, and the part corresponding to the core 2A is exposed. In that state, ultraviolet rays are irradiated through the mask 40. As a result, in the portion corresponding to the core 2A irradiated, no decreases and ne increases. As a result, a mode filter having the above relationship is formed.

Light Modulator In the optical integrated device of the present invention, as described above, the other part of the waveguide layer modulates the light modulation by changing the refractive index of the light transmitted through the waveguide layer with the application of an electric field. The optical modulator to be performed.
The waveguide layer has a material exhibiting optical nonlinearity. Therefore, the refractive index can be controlled by applying an electric field to the waveguide layer. Generally, an electrode is mounted on a region of the waveguide layer that constitutes the optical modulator.

FIG. 5 shows an essential part of an example of the embodiment. In this example, an under clad 22 is laminated on a substrate 20 as a base,
The waveguide layer 24 is laminated thereon. One side of the waveguide layer 24 forms a mode filter A, and the other side of the waveguide layer 24 forms an optical modulator B. In the mode filter A,
The waveguide layer 24 includes a core 2A for confining and transmitting either the TE mode light or the TM mode light, and a core 2A.
And claddings 3A disposed on both sides of the cladding 3A. The relationship between the refractive index of the core 2A and the refractive index of the clad 3A is set as described above or any one of the above.

In the optical modulator B, the waveguide layer 24 is made of TE
A core 2B for confining and transmitting one of the light in the mode and the TM mode, and claddings 3B arranged on both sides of the core 2B. A pair of light modulation electrodes 4 formed in a thin film shape by vapor deposition or the like is mounted on the upper surface of the clad 3B facing each other. When forming the optical modulator B, the material forming the core 2B of the waveguide layer 24 includes:
If a portion having the above-mentioned optical nonlinearity is introduced and a DC voltage is supplied to the electrode 4 to perform an electric field application process called a poling process, a molecular orientation is induced in a material constituting the core 2B. Thereby, the core 2B whose refractive index can be controlled by the electro-optic effect can be manufactured. Alternatively, electrodes may be provided after molecular orientation is performed by a corona poling technique.

When performing light modulation, an AC voltage is supplied to the electrode 4 mounted on the waveguide layer 24, and an external electric field is applied to the core 2B.
, Light modulation by the external electric field is possible based on the change of the external electric field. The light modulation here is the core 2B
Refers to an operation in which a change in retardation resulting from a phase change due to the application of an electric field of light passing through is replaced by a change in intensity through a polarizer. Therefore, the electrode 4 according to the present embodiment serves both as an electric field application in the poling process and an electric field application in the light modulation. The light modulation in the present invention is not limited to the intensity modulation, but includes phase modulation.

FIGS. 6 and 7 show a main part of another example of the embodiment.
(A) and (B) show. Also in this embodiment, an under clad 22 and a waveguide layer 24 are sequentially laminated on a substrate 20 as a base. Also in this embodiment, one side of the waveguide layer 24 forms the mode filter A, and the other side of the waveguide layer 4 forms the optical modulator B. FIG. 7A shows a mode filter A.
7B shows a cross section of the optical modulator B.
In the mode filter A, one side of the waveguide layer 24 includes a core 2A and clads 3A arranged on both sides of the core 2A. The relationship between the refractive indices of the core 2A and the cladding 3A is set to one of the above or one of the above. In the optical modulator B, the other side of the waveguide layer 24 includes a core 2B and clads 3B arranged on both sides of the core 2B. A lower electrode 4 (4d) formed by vapor deposition or the like is disposed between the substrate 22 and the under clad 22. The upper electrode 4 (4u) formed by vapor deposition or the like is mounted on the core 2B. When the light modulation is performed, an AC voltage is supplied to the electrodes 4 (4d, 4u) and an external electric field is applied to the core 2B, so that the light modulation by the external electric field can be performed based on a change in the external electric field. . Due to the manufacturing process, the mode filter substrate 20 and the under clad 22
A lower electrode may be formed between them, but there is no problem in principle.

In the optical integrated device according to the embodiment shown in FIG. 5, the mode filter A may be set to the incident side and the optical modulator B may be set to the output side, and conversely, the optical modulator B may be set to the input side. , And the mode filter A may be the emission side. The same applies to the optical integrated device of the embodiment shown in FIG. In the embodiment shown in FIG. 5 and the embodiment shown in FIG. 6, the mode filter A and the optical modulator B are respectively provided in one place in series, but if necessary, the mode filter A and the optical modulator B may be provided. It is also possible to increase the number of A and the number of optical modulators B.

Cores 2A, 2B in an optical integrated device
May be of a channel type in which they are buried, as shown in FIGS. 1 to 4, or may be of a ridge type. In some cases, like a fiber, a cylindrical core and a clad may be used. As shown in FIG. 7, the over-cladding 5 may be present above the waveguide layer 24. In this case, the material of the over-cladding 5 may be the same as the refractive index of the claddings 3A and 3B in the lateral direction, or may be a material having another refractive index as long as the performance of the mode filter is not impaired.

Manufacturing Method In manufacturing the optical integrated device described above, a light irradiation process for manufacturing a mode filter and a poling process for performing molecular orientation for light modulation can be employed. (1) Light Irradiation Treatment Light irradiation for causing a change in the refractive index in the waveguide layer is performed at a wavelength that causes photoisomerization. Generally,
Light having a wavelength from the ultraviolet region to the visible region is emitted. A high-pressure mercury lamp is generally used as a light source for light irradiation, but an excimer laser or the like can also be used. Irradiation light intensity and irradiation time necessary to cause a desired refractive index change amount are appropriately selected. Further, if the irradiation is performed at a high sample temperature in order to shorten the process time, the efficiency of the change in the refractive index increases.

In the light irradiation, the irradiation light intensity and irradiation time necessary to cause a desired amount of change in the refractive index in the refractive index anisotropic variable material are appropriately selected. In addition, when the temperature of the variable refractive index anisotropic material is increased to reduce the manufacturing time, the efficiency of the refractive index change of the variable refractive index anisotropic material generally tends to be high. The irradiation light intensity, irradiation time, material temperature at the time of irradiation, and the like can be appropriately selected according to the type of the refractive index anisotropic variable material, the film thickness, and the type of the waveguide device. As an example, when irradiating an ultraviolet ray having a central wavelength of 365 nm, the sample temperature is from room temperature to 160 ° C. and the irradiation time is from 30 minutes to 30 minutes under the condition of an irradiation light intensity of 80 mW / cm ^2.
In one hour, a mode filter having a core and a clad having a desired refractive index can be obtained. If the irradiation light intensity is increased, the processing time can be shortened.

The relationship between the light irradiation time and the change in the refractive index is shown in FIG. 11 as described later. As can be understood from the test results in FIG. 11, in the refractive index anisotropy variable material described above, the normal light refractive index no is reduced by light irradiation as indicated by ◆ or ◆, and abnormal as indicated by ◆ or ●. The light refractive index ne tends to increase. (2) Poling In order to develop optical nonlinearity, a molecular orientation operation is performed by applying a DC electric field to the material constituting the waveguide layer. In this case, corona poling using a needle electrode may be used,
The poling using a parallel plate electrode is also good. Generally, as the degree of molecular orientation increases, the optical non-linearity increases. Therefore, in order to more easily orient the molecules, usually, the material for forming the waveguide layer is heated. Although depending on the material, the heating temperature is generally preferably equal to or higher than the glass transition point.

FIGS. 8 to 10 show conceptual diagrams of the polling process. FIG. 8 illustrates the concept of corona polling. In this case, an electrode arranged below the waveguide layer M and a needle electrode arranged above the waveguide layer M are used, and both electrodes are connected to a DC high-voltage power supply. An electric field is applied to. FIG. 9 shows the concept of poling using parallel plate electrodes. In this case, the electrode disposed below the waveguide layer M and the waveguide layer M
, And both electrodes are similarly connected to a DC high-voltage power supply to apply an electric field to the waveguide layer M.

FIG. 10 shows the concept of poling using parallel plate electrodes. In this case, two electrodes arranged above the waveguide layer M are used, and both electrodes are similarly connected to a DC high-voltage power supply to apply an electric field to the waveguide layer M. When such a poling process is performed on the waveguide layer M, molecules inside the waveguide layer M are oriented, optical non-linearity is given, and an electro-optical effect is obtained. The molecular orientation direction in this case is a direction orthogonal to the examples of FIGS. Further, as the poling method, a method of applying an electric field while irradiating light, and a method of irradiating polarized light are also possible.

(3) Operation Procedure As an operation procedure, a method of first performing a light irradiation process, and then performing a polling process, and the reverse method can be adopted. In the former method, first, the light irradiation treatment
Forming a waveguide structure having a filtered function,
The polling process is performed only on the waveguide portion constituting the optical modulator in the waveguide structure. In this case, it is preferable to perform the poling process so that the electric field of the poling process is not applied to the waveguide portion functioning as the mode filter.

In the latter method, the polling process is performed only on the waveguide portion constituting the optical modulator in the waveguide structure. In this case, it is preferable to perform a polling process on the waveguide portion functioning as a mode filter so that an electric field by the polling process is not applied. afterwards,
When light irradiation is performed using a mask, a waveguide portion functioning as a mode filter is formed.

[0032]

Embodiments of the present invention will be described below. First, a method of synthesizing the variable refractive index anisotropy material constituting the waveguide layer used in the examples will be described, and then a method of manufacturing the optical integrated device will be described for each item. In this example, the molecular structure was confirmed by an infrared absorption spectrum and an H nuclear magnetic resonance spectrum. The measurement of the melting point and the glass transition temperature was performed by a differential scanning calorimeter. The refractive index was determined from the mode angle when light was incident on the waveguide layer using a coupling prism to excite the waveguide mode.

(Method of synthesizing variable refractive index anisotropy material)
7.61 g of methyl-4-nitroaniline was added to 100 ml of water.
And a 36% aqueous hydrochloric acid solution (45 ml), and cooled to 3 ° C. 3.80 g of sodium nitrite dissolved in 18 ml of water was added to the solution. Keep the solution at 3 ° C for 1
Stirred for hours. Further, a solution obtained by dissolving 9.76 g of m-tolyldiethanolamine in a mixed solution of 125 ml of water and 7.5 ml of a 36% hydrochloric acid aqueous solution was added to this solution over 30 minutes, followed by stirring at 3 ° C. for 20 minutes, and further at 20 ° C. At 6
The reaction was stirred for 0 minutes. A solution obtained by dissolving 35.4 g of potassium hydroxide in 200 ml of water was added to the reaction mixture for neutralization, and the precipitated crude product was separated by filtration, washed with water, and dried.
The product was recrystallized twice from ethanol to give 4-N, N-bis (2-
(Hydroxyethyl) amino-2,2′-dimethyl-4 ′
-Nitroazobenzene was obtained (yield; 80%, melting point; 1).
69 ° C).

[0034]

Embedded image

0.686 g of the compound of the structural formula (Chemical Formula 1) and 0.500 g of tolylene-2,4-diisocyanate are combined with N
-Methyl-2-pyrrolidone dissolved in 10 ml
Stirred at C for 1 hour. After cooling this solution to 20 ° C,
0.109 g of trans-2,5-dimethylpiperazine was added and reacted by stirring at 20 ° C. for 7 hours. The reaction mixture was poured into 400 ml of a 1: 1 mixture of ethanol and hexane, and the precipitated polymer precipitated was separated by filtration and dried under reduced pressure.

The resulting polymer was confirmed to have the following structural formula (Formula 2) (yield: 89%, glass transition temperature: 142 ° C., intrinsic viscosity in N-methyl-2-pyrrolidone: 0.1). 28 dl / g, absorption maximum wavelength; 474n
m).

[0037]

Embedded image

Next, 1.50 g of the compound of the structural formula (Chemical Formula 1) synthesized as described above and 1.571 g of 4,4'-diphenylmethane diisocyanate were dissolved in 90 ml of N-methyl-2-pyrrolidone. And stirred at 100 ° C. for 90 minutes. After cooling the solution to 20 ° C., N-methyl-2 was added.
Trans-2,5- dissolved in 10 ml of pyrrolidone
0.239 g of dimethylpiperazine was added and reacted by stirring at 20 ° C. for 5 hours. The reaction mixture is ethanol 300
The solution was poured into 0 ml, and the precipitated precipitated polymer was separated by filtration and dried under reduced pressure.

The resulting polymer was confirmed to have the following structural formula (Formula 3) (yield: 96%, glass transition temperature: 114 ° C., intrinsic viscosity in N-methyl-2-pyrrolidone: 0.1). 80 dl / g, absorption maximum wavelength; 475 n
m).

[0040]

Embedded image

(Manufacturing Method of Optical Integrated Device) The manufacturing method of this embodiment is an example in which an optical integrated device shown in FIGS. 6 and 7 is formed. As a substrate functioning as a substrate, a crystal axis <10
0>, a single-sided mirror-finished 4-inch silicon wafer (manufactured by Mitsubishi Materials; n-type) having a thickness of about 500 μm
The divided one was used.

HF: pure water = 1: 50
For about 1 minute to wash the surface. Next, the substrate was washed with running pure water for about 5 minutes, dried with a spin drier, and provided for the next electrode deposition step. In the electrode deposition step, 100 Å of Cr was deposited on the silicon wafer using an EB deposition apparatus (manufactured by Anelva; EVD-500B).
Subsequently, Al was vapor-deposited at 2,000 Å to form a lower electrode 4d. At this time, a mask was placed on a silicon wafer in a portion intended to be used as a mode filter so that the lower electrode was not deposited.

Next, as the under cladding 22, polyimide (PlX2400, manufactured by Hitachi Chemical Co., Ltd.) was used. That is, polyimide is directly applied to the lower electrode 4d obtained as described above, and heat-treated (1 hour at 150 ° C., 300 ° C.).
For 1.5 h) to obtain an under clad. The thickness of a thin film formed on glass under the same conditions is measured using a stylus type surface roughness needle (manufactured by SloanTechnology Corp; D
EKTAKII) and used as the sample thickness. The film thickness was similarly determined in the following steps. The thickness of the polyimide layer serving as the under cladding was about 7 μm.

In forming a polymer thin film portion corresponding to the waveguide layer 24, the refractive index anisotropy variable material manufactured as described above is mixed with pyridine as a solvent, and a relatively low concentration (1% by weight) is mixed. A) pyridine solution was formed. The pyridine solution was filtered through a 0.2 μm Teflon filter (Advantech Toyo; DISMIC13P), and then concentrated by an evaporator to obtain a high-concentration solution (about 6% by weight). Thereafter, this high concentration solution was laminated on the under clad 22 by spin coating using a photoresist spinner.

After spin coating, vacuum drying was performed at room temperature for about 6 hours. The thickness of the obtained waveguide layer 24 is 1.3 μm.
Met. Next, light irradiation treatment called photobleaching was performed. That is, an ultra-high pressure mercury lamp (made by Ushio;
USH-250BY) is used as a light source, and a light source unit for an exposure apparatus (manufactured by Ushio; Multilight ML-251A / B) capable of irradiating parallel light is used to irradiate the waveguide layer 24 on the substrate with ultraviolet (UV) light. went. Irradiation power is 80m
W / cm ² . In the case of light irradiation, width 2 to 10 μm
A photomask (manufactured by Toppan Printing Co., Ltd.) in which a linear waveguide having the following size was drawn on quartz glass with low reflection chrome was used. This photomask is brought into contact with the sample surface, and the sample is heated to 110 ° C.
And irradiated for 1 hour through the mask from above the sample.

The core 2A and the clad 3A constituting the mode filter A are formed by the irradiation of the ultraviolet rays.
The relationship between the refractive index and the refractive index of the cladding 3A was one of the relationships described above. Thereafter, a fluoropolymer solution for spin coating (CYTOP-805A, manufactured by Asahi Glass Co., Ltd.) was applied to a photoresist spinner (K-33359, manufactured by Kyowa Riken).
It was spin-coated on the waveguiding layer by using SD-1) at a rotation speed of 1000 rpm, and a protective film was laminated. Subsequently, it was dried at 80 ° C. for 1 hour by vacuum drying. The thickness of the protective layer is 0.65 μm
m.

Next, a polymethyl methacrylate (PMM) is used as the over cladding 5 covering the upper part of the waveguide layer 24.
A) obtained by purifying A) with an acetone-methanol system was used. That is, a 5% by weight PMMA chloroform solution was prepared, and a photoresist spinner (K-335 manufactured by Kyowa Riken; K-335) was prepared.
Using 9SD-1), spin coating was performed on the sample on which the protective film had been applied at a rotation speed of 1000 rpm. Subsequently, it was dried at room temperature for 2 hours in a vacuum dryer. The film thickness of the over clad 5 was 1.5 μm.

Next, the sample was immersed in liquid nitrogen to cool the sample. The sample was cleaved including the waveguide layer 24 in the <010> and <001> directions in the crystal plane which had been damaged in advance, exposing the end face. A high-speed vacuum deposition apparatus (Vacuum Kiko; V
About 2000 Å of Al was deposited using PC-410) to form an upper electrode 4u. The sample thus manufactured was masked with a cover glass, and electrodes were deposited only at desired positions. After the lower electrode 4d was exposed, a lead wire was bonded to each of the upper electrode 4u and the lower electrode 4d with a silver paste.

Next, while heating the sample (target temperature: 17
(0 ° C.), an electric field was applied through the upper electrode 4 u and the lower electrode 4 d to impart optical nonlinearity to the portion of the waveguide layer 24 that constitutes the optical modulator. In the optical integrated device according to this embodiment, the refractive index anisotropy of the waveguide layer 24 can be controlled. Therefore, the degree of freedom in design can be secured as compared with the case where anisotropic crystals are used. This material is also less expensive than when anisotropic crystals are used. Further, it has the advantages that the structure is simple, the number of processing steps is small, and the cost is low.

(Light Modulation Experiment) A light modulation experiment was performed using the sample manufactured as described above. In this case, the wavelength 8
A 30 nm semiconductor laser was used as a light source. Basically, a semiconductor laser, a lens, a Ramipole fiber polarizer (manufactured by Sumitomo Osaka Cement), which is an optical fiber, and an optical integrated device are arranged in this order. The optical filter was coupled to a fiber polarizer, and a mode filter A of the optical integrated device was disposed at the emission section.

In the light modulation experiment, the TE mode and the TM mode were used.
Mode was excited at an intensity of 1: 1 and incident. The light intensity from the output end of the Ramipole fiber polarizer (manufactured by Sumitomo Osaka Cement) is adjusted to be equal in the vertical direction (corresponding to TM mode) and in the horizontal direction (corresponding to TE mode), This was coupled to the incident part of the waveguide of the optical integrated device as a sample.

A high frequency was generated by a high frequency oscillator, amplified by an amplifier, and an AC voltage was applied between the lower electrode and the upper electrode of the sample. AC voltage frequency 1KHz
Thus, the modulation of the light intensity could be confirmed by the change of the retardation of the optical modulator portion of the sample and the selection of the waveguide mode by the mode filter portion.

(Irradiation Test) The relationship between the irradiation time of the light irradiation treatment and the degree of change in the refractive index was examined in the case where the refractive index anisotropic variable material according to the above example was employed. Further, the relationship between the temperature of the sample and the degree of change in the refractive index during the irradiation treatment was examined. In the measurement of the refractive index, a prism coupler (manufactured by Metricon; PC2010) was used, and a wavelength of 633 nm and a wavelength of 830 nm were used as guided light.

The test results are shown in FIGS. FIG.
Is the relationship between irradiation time and refractive index (irradiation temperature is 110 ° C
). FIG. 12 shows the relationship between the irradiation temperature and the refractive index (when the irradiation time is one hour). 11 and 12, ■ indicates no at a wavelength of 633 nm, and ● indicates ne at a wavelength of 633 nm. ▲ indicates no at a wavelength of 830 nm, and ◆ indicates ne at a wavelength of 830 nm.

It can be understood from the test results indicated by Δ and ▲ in FIG.
As shown in FIG. _OThe refractive index of
And it is understood from the test results indicated by △ and ● in FIG.
Confirmed that the refractive index of ne has increased so that it can
Was done. Further, as can be understood from FIG.
For a variable refractive index anisotropic material, the refractive index is the temperature of the sample.
Was confirmed to be affected. In particular, the higher the temperature,
It was confirmed that the rate of change in the refractive index was large.

(Supplementary Note) The following technical idea can be understood from the above description. ○ A waveguide layer made of a material whose refractive index anisotropy is variable by light irradiation and which can impart optical nonlinearity or a material in which the material is dispersed in a matrix is used. An operation of forming a mode filter for selectively transmitting one of the light in the TE mode and the light in the TM mode by irradiating, and applying an electric field to the other part of the waveguide layer to orient the molecules to thereby form an optical filter. To give a non-linear
Forming an optical modulator for performing optical modulation.

[0057]

According to the present invention, a part of the waveguide layer is made of TE.
Modulator that constitutes a mode filter that selectively transmits any one of the mode and TM modes, and modulates the light by changing the refractive index of the other part of the waveguide layer with respect to the light that passes through the waveguide layer. Therefore, the mode filter and the waveguide layer forming the optical modulator can be formed as an integrated element using the same material. Therefore, an integrated element having a simple configuration and a simple manufacturing process can be obtained.

Further, since the waveguide structure in the mode filter and the waveguide structure in the optical modulator are continuously connected by the same material, the coupling loss in the connection portion between the mode filter and the optical modulator connection portion can be reduced. According to the present invention,
In the waveguide layer of the mode filter, if the ne and no of the waveguide layer are adjusted by using light irradiation, the refractive index relationship between the core and the clad constituting the mode filter may be any of the above-mentioned relationships or the relationship thereof. And a mode filter capable of selecting and transmitting only one of the light in the TE mode and the TE mode.

In general optical systems, control and measurement using TE mode or TE mode polarized light are frequently performed, and a mode filter for separating polarized light in the system is becoming indispensable. Further, in order to use the optical system more generally, a small optical system using a waveguide integrated device has been constructed in recent years. In this system, similarly to the above system, it becomes necessary to separate the polarization of either the TE mode or the TE mode. The mode filter in the optical integrated device according to the present invention is a device useful for separating the polarization mode in such a waveguide structure, and can be an important component in a small optical system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the concept of the configuration of a mode filter portion of a waveguide layer.

FIG. 2 is a configuration diagram conceptually showing a manufacturing process when a mode filter having the form shown in FIG. 1 is formed.

FIG. 3 is a configuration diagram illustrating a concept of a configuration of a mode filter portion of a waveguide layer according to another embodiment.

FIG. 4 is a configuration diagram conceptually showing a manufacturing process when a mode filter having the form shown in FIG. 3 is formed.

FIG. 5 is a perspective view showing the general concept of an optical integrated device having a mode filter and an optical modulator.

FIG. 6 is a perspective view showing the general concept of an optical integrated device according to another embodiment including a mode filter and an optical modulator.

7A is a cross-sectional view of a mode filter part of the optical integrated device shown in FIG. 6, and FIG. 7B is a cross-sectional view of an optical modulator part of the optical integrated device shown in FIG. .

FIG. 8 is a configuration diagram illustrating a concept of a corona poling process using a needle electrode.

FIG. 9 is a configuration diagram illustrating a concept of a poling process using parallel plate electrodes.

FIG. 10 is a configuration diagram illustrating a concept of a poling process using another parallel plate electrode.

FIG. 11 is a graph showing a relationship between irradiation time and refractive index in light irradiation.

FIG. 12 is a graph showing the relationship between sample temperature and refractive index during light irradiation.

[Explanation of symbols]

In the figure, 20 is a substrate (base), 24 is a waveguide layer, 2A, 2B
Indicates a core, 3A and 3B indicate claddings.

Claims (1)

[Claims] 1. A waveguide layer formed of a material exhibiting refractive index anisotropy and optical nonlinearity or a material in which the material is dispersed in a matrix, and a base holding the waveguide layer. A part of the waveguide layer constitutes a mode filter that selectively transmits one of light in a TE mode and a TM mode, and the other part of the waveguide layer, with application of an electric field, An optical integrated device, comprising: an optical modulator that performs optical modulation by changing a refractive index of light transmitted through the waveguide layer.