JPH0566435A - Production of nonlinear optical element - Google Patents

Abstract

PURPOSE:To obtain the method for working a channel waveguide without deteriorating quadratic nonlinear characteristics in the production process for the channel waveguide. CONSTITUTION:The process for producing the channel type optical waveguide consisting of a high-polymer material exhibiting the nonlinear optical characteristics as a core and a high polymer having the refractive index slightly smaller than the refractive index of the core as a clad consists in producing the above-mentioned waveguide by applying a UV curing resin 2 on an arbitrary substrate 1, then applying a high polymer 3 exhibiting the nonlinear optical characteristics thereon, applying a water-soluble high polymer 4 to allow spin coating thereon, applying a UV curing resin 5 or providing a metallic film, further, applying a resist 6, subjecting the resist to exposing and developing to arbitrary patterns by using UV rays, etching the layers down to the nonlinear high-polymer layer by reactive ion etching using the patterned resist as a mask, lifting off the layers upper than the water-soluble high polymer 4 with water and applying a UV curing resin.

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 nonlinear channel waveguide having a polymer having a nonlinearity as a core.

[0002]

2. Description of the Related Art A typical application using an optical nonlinear material is an electro-optical element using a material having a large second-order nonlinear susceptibility, which is expected to be incorporated into an optical integrated circuit as an active element. ing. Inorganic substances such as potassium dihydrogen phosphate (KH ₂ PO ₄ ) and lithium niobate (LiNbO ₃ ) have been known as materials exhibiting the first-order electro-optical effect (Pockels effect) due to the second-order nonlinearity. In recent years, organic crystal materials exhibiting a larger electro-optic constant and faster response than these materials have been found. However, organic crystal materials are generally fragile and inferior in workability, so that it is difficult to manufacture an electro-optical element.

On the other hand, a material has been developed in which a second-order nonlinear material is bonded to the main chain of a polymer material having excellent moldability so that a thin film can be easily formed by a spin coating method or the like. As a typical material, a material in which an azo dye is bonded to the main chain of polymethylmethacrylate (PMMA) is known. When these materials are used as an electro-optical element, various applications can be developed by using the above-mentioned material as a core, and a channel type waveguide with a material having a slightly smaller refractive index than the above-mentioned material as a clad, which is further advantageous. Is.

FIG. 3 shows a conventional manufacturing process of a nonlinear polymer channel waveguide. Here, a conventional technique will be described with reference to FIG. 3 in the case where PMMA, which is known to have excellent light transmittance, is used as a clad. First, PMMA 16 to be a clad is applied onto an arbitrary substrate 15 (step (1)) by spin coating and sufficiently dried. Next, the polymer layer 17 containing the second-order nonlinear material to be the core is spin-coated (step (2)).

At this time, it is necessary to prevent the lower layer PMMA 16 and the non-linear polymer 17 from intermixing. However, the solvent of the nonlinear polymer 17 is PMMA16.
In the case of the good solvent of No. 2, intermixing of the non-linear polymer 17 and PMMA 16 occurred, and the boundary became unclear, which was a problem.

Next, PMMA 18 is formed as an upper clad layer.
Spin coat. Also in this case, the nonlinear polymer 17
If the solvent is a good solvent for PMMA18, the problem of intermixing occurs. Next, the thermosetting resin 19 is spin-coated, baked at about 200 ° C., then the silicon-based photoresist 20 is spin-coated, exposed to ultraviolet rays through a mask, and the resist 20 is developed into an arbitrary pattern ( (3) step). Using this resist pattern as a mask, the polymer layer up to the core layer 17 is etched by reactive reactive ion etching (oxygen ions 21) (step (4)). Next, in order to cover the side wall of the core layer exposed by etching with the cladding material, PMMA is used.
16 is spin-coated (step (5)).

Although it is desirable to remove the resist 20 and the thermosetting resin 19 before the step of finally spin-coating PMMA, the side surface of the channel waveguide formed in the step of removing the resist 20 is a strong alkaline solution or a strong acid solution. You will need to soak it in. At this time, the azo dye is violated by acid or alkali, and the second-order nonlinear characteristic is significantly deteriorated.
Conventionally, the resist 20 could not be peeled off. Therefore,
Conventionally, a channel waveguide has been manufactured without removing the resist 20.

[0008]

It is an object of the present invention to use a method of removing a resist with neutral water only in a step of removing a resist in a channel waveguide manufacturing process without using acid or alkali. It is an object of the present invention to provide a method for processing a channel waveguide without deteriorating the nonlinear characteristic.

[0009]

In order to solve the above problems, a method of manufacturing a nonlinear optical element according to the present invention uses a polymer material exhibiting nonlinear optical characteristics as a core, and a high refractive index slightly smaller than the core. In the step of producing a channel type optical waveguide having a molecule as a clad, an ultraviolet curable resin is applied on an arbitrary substrate, then a polymer showing nonlinear optical characteristics is applied, and then a water-soluble polymer is applied, Next, an ultraviolet curable resin is applied, a resist is further applied, and an arbitrary pattern is exposed and developed by using ultraviolet rays, and the non-linear polymer layer is etched by reactive ion etching using the patterned resist as a mask. After that, the layer above the water-soluble polymer is lifted off with water, and then an ultraviolet curable resin is applied to manufacture.

According to the second method for producing a nonlinear optical element of the present invention, a channel type optical waveguide having a core made of a polymer material exhibiting nonlinear optical characteristics and a cladding made of a polymer having a refractive index slightly smaller than that of the core is used. In the step of producing, a UV curable resin is applied on any substrate, then a polymer exhibiting nonlinear optical characteristics is applied, then a water-soluble polymer is applied, and then a metal such as aluminum is vapor-deposited or Laminated by sputtering or the like, further, a resist is applied, exposed and developed to an arbitrary pattern using ultraviolet rays, the patterned resist is used as a mask to etch the layer of the non-linear polymer by reactive ion etching, and then, It is characterized in that the layer above the water-soluble polymer is lifted off with water and then an ultraviolet curable resin is applied to produce the layer.

The present invention will be described in more detail with reference to the drawings.

FIG. 1 is a process diagram showing the first manufacturing method of the present invention. As is clear from this diagram, the substrate 1
On top of ((1) step), ultraviolet rays (U
V) The cured resin 2 is spin-coated, irradiated with UV to be cured, and then the secondary nonlinear polymer 3 dissolved in an organic solvent is spin-coated and dried (step (2)). Next, for example, polyvinyl alcohol (PVA) 4 dissolved in water is spin-coated, and further UV-curable resin 5 is spin-coated,
After irradiating with UV to cure the resin, the silicone-based positive resist 6 is applied by spin coating, and the desired pattern is exposed and developed (step (3)). At this time, an alkaline solution is used as the developing solution, but since it does not come into direct contact with the nonlinear polymer, it does not affect the nonlinear polymer.

Next, using the resist as a mask, reactive reactive ion etching is performed in an oxygen atmosphere to etch the layer of the nonlinear polymer 3 with oxygen ions 7 (step (4)). By performing reactive reactive ion etching with oxygen gas 7 in a region where the pressure is relatively low, etching can be performed substantially perpendicular to the substrate surface. Next, when the substrate 1 after etching is immersed in distilled water, the PVA 4 dissolves in water, so the upper portion is peeled off from the PVA 4 (step (5)). That is, it is lifted off. When this substrate is dried and the UV resin 2 is spin-coated, the non-linear polymer is covered with a single polymer clad material.

Here, by applying water-soluble PVA before applying the resist, it is possible to remove the resist only with water without using an acid or an alkali when the resist is removed. Although PVA is used in the above example, it is desirable to use a water-soluble polymer that can be easily thinned, that is, an aqueous solution can be spin-coated. As such a water-soluble polymer, there is polymethacrylic acid in addition to PVA, which can be used in the same manner as PVA.

Further, when the resist is directly applied on the water-soluble polymer, the water-soluble polymer is also dissolved at the time of development, so that a layer which is insoluble in water and insoluble in the resist solvent is required. In the first manufacturing method, a UV curable resin dissolved in an organic solvent was used as a polymer satisfying this condition. Instead of the UV curable resin, a metal layer 12 such as aluminum may be laminated by vapor deposition or the like as shown in FIG. In this case, it is necessary to etch aluminum using the resist as a mask, and then to etch the water-soluble polymer and the non-linear polymer. The layers can still be lifted off with water.

Polymers in which dye molecules such as azo dyes are bound to side chains include monochlorobenzene, methyl ethyl ketone,
It is easily soluble in organic solvents such as toluene, and often insoluble in water. Therefore, the water-soluble polymer also has an advantage that it does not intermix with the nonlinear polymer even when applied on the nonlinear polymer. As described above, the use of the step of coating the water-soluble polymer such as PVA directly on the nonlinear polymer is advantageous in producing the channel waveguide of the nonlinear polymer.

Hereinafter, description will be given based on an embodiment.

[0018]

[Embodiment 1] FIG. 1 shows a process chart of a first embodiment of the present invention.

First, on the silicon substrate 1 ((1) step),
Acrylic UV curable resin 2 is applied by spin coating 15
It was applied to a thickness of μm and irradiated with ultraviolet rays for 15 minutes. next,
PMMA (M. AMANO and T. Kaino, J. Appl. Phys., Vo containing 5 × 10 ²⁰ cm ^{−3 of} azo dye as a non-linear polymer 3)
(1. 68, p. 6024 (1990)) was dissolved in monochlorobenzene to give a solution of 5 μm by spin coating ((2) step). Next, a 5% PVA4 aqueous solution was applied by spin coating to a thickness of 0.5 μm, a UV curable resin 5 dissolved in ethyl alcohol was applied to a thickness of 0.5 μm, and UV rays 7 were irradiated for 15 minutes. Next, a silicone photoresist 6 was spin-coated to a thickness of 0.3 μm. This substrate was exposed using an ultraviolet exposure device, developed, and processed into a line having a width of 5 μm (step (3)). Using this resist pattern as a mask, reactive reactive ion etching was performed for 60 minutes with oxygen ions 7 in an oxygen atmosphere in a reactive reactive ion etching apparatus to etch up to the nonlinear polymer layer 3
A pattern almost like the step (4) in FIG. 1 was obtained. next,
It was immersed in distilled water and the portion above PVA4 was lifted off. Next, from above, add 15μ of acrylic curing resin 2
m spin coating was performed to prepare an element having a structure as shown in step (6) of FIG.

The manufactured element was cut into a length of 10 mm, put in a poling device, heated to 140 ° C., and then heated to 2 MV.
/ Cm voltage was applied and the mixture was cooled to room temperature at 1 minute / ° C. Next, using a fiber from a 1.06 μm laser, 1
The output of the second harmonic (SHG) was measured by introducing light of 00 mW, and the conversion efficiency η of the SHG (= SHG intensity / incident power) was determined to be 0.3%, which was a high value. .. This is due to the fact that a channel-type waveguide that does not cause intermixing with the core is produced by using lift-off with water without damaging the nonlinear polymer material and by using UV resin for the cladding.

[0021]

[Embodiment 2] FIG. 2 shows a process chart of a second embodiment of the present invention.

On the silicon substrate 8 (step (1)), the acrylic UV curing resin 9 is spin-coated to 15 μm.
And was irradiated with ultraviolet rays for 15 minutes. Next, a non-linear polymer 10 containing P containing an azo dye of 5 × 10 ²⁰ cm ^{-3 was} added.
A solution of MMA in monochlorobenzene was applied by spin coating to a thickness of 5 μm. Next, a 5% PVA11 aqueous solution was applied by spin coating to a thickness of 0.5 μm. Next, the substrate was placed in a vacuum vapor deposition apparatus and aluminum 12 was laminated to a thickness of 0.1 μm. Next, the silicone photoresist 13 was spin-coated to a thickness of 0.3 μm. This substrate is exposed and developed using an ultraviolet exposure device,
A line having a width of 5 μm was processed ((3) step). Using this resist pattern as a mask, in the reactive reactive ion etching apparatus, reactive reactive ion etching was performed for 3 minutes in carbon tetrachloride and then for 55 minutes in an oxygen atmosphere. Then, when the linear polymer layer 10 was etched, a pattern similar to that in the step (4) in FIG. 2 was obtained. Next, soak in distilled water,
The portion above the PVA 11 was lifted off (step (5)). Next, from above, add 15μ of acrylic curing resin.
m spin coating was performed to fabricate a device having a structure as shown in step (6) of FIG.

The produced element was cut into a length of 10 mm, put in a poling device, heated to 140 ° C., and then heated to 2 MV.
/ Cm voltage was applied and the mixture was cooled to room temperature at 1 minute / ° C. Next, using a fiber from a 1.06 μm laser, 1
When the output of the second harmonic (SHG) was measured by introducing light of 00 mW and the conversion efficiency η (= SHG intensity / incident power) of SHG was obtained, it was 0.25% as in Example 1. , Got a high value. This is due to the fact that a channel-type waveguide that does not cause intermixing with the core is produced by using lift-off with water without damaging the nonlinear polymer material and by using UV resin for the cladding.

[0024]

As described above, when a channel waveguide of a non-linear polymer is produced, a step of laminating a water-soluble polymer such as PVA on the non-linear polymer is inserted to obtain a non-linear polymer layer. A non-linear element can be manufactured without damaging the.

[Brief description of drawings]

FIG. 1 is a first embodiment of the present invention and claim 1 of the present invention.
FIG. 9B is a manufacturing process diagram of a channel waveguide using a nonlinear polymer.

FIG. 2 shows Claim 2 of the present invention and Example 2 of the present invention, and is a step of manufacturing a channel waveguide using a nonlinear polymer.

FIG. 3 is a process drawing of a conventional channel waveguide using a nonlinear polymer.

[Explanation of symbols]

 1 Substrate 2 UV Curing Resin 3 Nonlinear Polymer 4 Water-Soluble Polymer 5 UV Curing Resin 6 Photoresist 7 Oxygen Ion 8 Substrate 9 UV Curing Resin 10 Nonlinear Polymer 11 Water-Soluble Polymer 12 Metal Film 13 Photoresist 14 Carbon Tetrachloride Ions or oxygen ions 15 Substrate 16 Polymethylmethacrylate (PMMA) 17 Non-linear polymer 18 PMMA 19 Thermosetting resin 20 Photoresist 21 Oxygen ion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Akira Tomaru, 1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Michiyuki Amano 1-1-1, Uchisaiwaicho, Chiyoda-ku, Tokyo No. 6 Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A process for producing a channel type optical waveguide having a core made of a polymer material exhibiting non-linear optical characteristics and a clad made of a polymer having a refractive index slightly smaller than that of the core, in which an ultraviolet curable resin is coated on an arbitrary substrate. Coating, then coating a polymer showing non-linear optical characteristics, then coating a spin-coatable water-soluble polymer, then coating a UV curable resin, further coating a resist, using UV light After exposure and development to any pattern, using the patterned resist as a mask,
A non-linear optical element, characterized in that a layer of a non-linear polymer is etched by reactive ion etching, a layer above the water-soluble polymer is lifted off with water, and then an ultraviolet curable resin is applied. Of manufacturing. 2. A process for producing a channel type optical waveguide having a core made of a polymer material exhibiting non-linear optical characteristics and a clad made of a polymer having a refractive index slightly smaller than that of the core. Coating, then polymer with non-linear optical characteristics, then spin-coatable water-soluble polymer, then metal such as aluminum is laminated by vapor deposition or sputtering, and then resist is coated. Then, the layer is exposed to light and developed using UV light, and the non-linear polymer layer is etched by reactive ion etching using the patterned resist as a mask. A method for manufacturing a non-linear optical element, characterized in that it is lifted off by (1), and then an ultraviolet curable resin is applied to manufacture it.