JP3057621B2 - Manufacturing method of nonlinear optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical nonlinear channel waveguide having a polymer having nonlinearity as a core.

[0002]

2. Description of the Related Art As a typical application using an optical nonlinear material, there is an electro-optical element using a material having a high second-order nonlinear susceptibility, and it 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 a first-order electro-optic effect (Pockels effect) due to 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 brittle and have poor processability, so that it has been difficult to manufacture electro-optical elements.

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 spin coating or the like. As a typical material, a material in which an azo dye is bonded to the main chain of polymethyl methacrylate (PMMA) is known. When these materials are used as an electro-optical element, various applications are developed by using the above materials as a core and using a material having a refractive index slightly smaller than that of the above materials as a clad as a channel type waveguide. It is.

[0004] FIG. 3 shows a conventional manufacturing process of a nonlinear polymer channel waveguide. Here, the prior art 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 serving as a clad is applied on an arbitrary substrate 15 (step (1)) by spin coating and dried sufficiently. Next, the polymer layer 17 containing a secondary nonlinear material serving as a 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, the non-linear polymer 17 and the PMMA 16 were intermixed, and the boundary was not clear, which was a problem.

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

[0007] Finally, it is desirable to remove the resist 20 and the thermosetting resin 19 before the step of spin-coating PMMA. However, in the step of removing the resist 20, the side surface of the formed channel waveguide is subjected to a strong alkali solution or a strong acid solution. It is necessary to soak 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 cannot be removed. Therefore,
Conventionally, a channel waveguide has been manufactured without removing the resist 20.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for removing a resist in a channel waveguide manufacturing process, in which a resist is removed using only neutral water without using an acid or an alkali. An object of the present invention is to provide a method of processing a channel waveguide without deteriorating nonlinear characteristics.

[0009]

Means for Solving the Problems To solve the above problems, a method for manufacturing a nonlinear optical element according to the present invention uses a polymer material having a nonlinear optical characteristic as a core, and has a high refractive index slightly smaller than that of 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, a polymer exhibiting nonlinear optical properties is applied, and then a water-soluble polymer is applied, Next, apply an ultraviolet curable resin, apply a resist, expose and develop an arbitrary pattern using ultraviolet rays, and etch the non-linear polymer layer by reactive ion etching using the patterned resist as a mask. Thereafter, the layer above the water-soluble polymer is lifted off with water, and thereafter, an ultraviolet curable resin is applied to form a layer.

According to the second method of manufacturing a nonlinear optical element of the present invention, a channel type optical waveguide having a polymer material having nonlinear optical characteristics as a core and a polymer having a refractive index slightly smaller than that of the core as a clad. In the process of manufacturing, a UV curable resin is applied on an arbitrary 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 deposited or Laminate by sputtering etc., further apply a resist, expose and develop an arbitrary pattern using ultraviolet rays, and use the patterned resist as a mask, etch by reactive ion etching to the layer of non-linear polymer, It is characterized in that a layer above the water-soluble polymer is lifted off with water, and thereafter, 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 chart showing a first manufacturing method of the present invention. As is apparent from FIG.
On top of the ((1) process), ultraviolet rays (U
V) The cured resin 2 is spin-coated, irradiated with UV and cured, and then the second-order nonlinear polymer 3 dissolved in an organic solvent is spin-coated and dried ((2) step). Next, for example, polyvinyl alcohol (PVA) 4 dissolved in water is spin-coated, and further, a UV curable resin 5 is spin-coated,
After the resin is cured by irradiating UV, a silicone positive resist 6 is applied by spin coating, and an arbitrary pattern is exposed and developed (step (3)). At this time, although an alkaline solution is used as the developing solution, it does not directly contact the nonlinear polymer, and thus does not affect the nonlinear polymer.

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

Here, by applying a water-soluble PVA before applying the resist, the resist can be removed only with water without using an acid or alkali when the resist is removed. Although PVA is used in the above-described example, it is desirable to use a water-soluble polymer that can be easily formed into a thin film, that is, that can be spin-coated with an aqueous solution. As such a water-soluble polymer, there is polymethacrylic acid other than PVA, and it can be used similarly to PVA.

Further, if a resist is applied directly on the water-soluble polymer, the water-soluble polymer is also dissolved at the time of development, so that a layer insoluble in water and insoluble in the resist solvent is required. In the first production 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 of aluminum or the like may be laminated and used by vapor deposition as shown in FIG. In this case, it is necessary to etch aluminum using the resist as a mask, and then to etch with a water-soluble polymer and a non-linear polymer. The layers can still be lifted off with water.

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

Hereinafter, description will be made based on embodiments.

[0018]

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

First, on the silicon substrate 1 (step (1)),
Acrylic UV curable resin 2 is applied by spin coating to 15
It was applied to a thickness of μm and irradiated with ultraviolet rays for 15 minutes. next,
PMMA containing an azo dye at 5 × 10 ²⁰ cm ^-3 as a nonlinear polymer 3 (M. AMANO and T. Kaino, J. Appl. Phys., Vo
l. 68, p. 6024 (1990)) in monochlorobenzene was applied by spin coating to a thickness of 5 μm (step (2)). Next, a 5% PVA4 aqueous solution was applied to a thickness of 0.5 μm by spin coating, a UV curable resin 5 dissolved in ethyl alcohol was applied to a thickness of 0.5 μm, and irradiated with ultraviolet rays 7 for 15 minutes. Next, a silicone-based photoresist 6 was spin-coated to a thickness of 0.3 μm. The 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, and etching was performed up to the 3 nonlinear polymer layer.
A pattern almost as shown in step (4) of FIG. 1 was obtained. next,
It was immersed in distilled water, and the part above PVA4 was lifted off. Next, 15 μm of the acrylic cured resin 2 was applied from above.
By spin coating for m times, an element having a structure as shown in step (6) of FIG. 1 was produced.

The produced device was cut into a length of 10 mm, placed in a poling device, heated to 140 ° C.
/ Cm, and cooled to room temperature at 1 minute / ° C. Next, using a fiber from a 1.06 μm laser,
The output of the second harmonic (SHG) was measured by introducing a light of 00 mW, and the conversion efficiency η (= SHG intensity / incident power) of the SHG was obtained. . This is because a non-linear polymer material is not damaged by lift-off using water, and a channel-type waveguide that does not cause intermixing with the core is produced by using a UV resin for the clad.

[0021]

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

Acrylic UV curable resin 9 is applied on silicon substrate 8 (step (1)) by spin coating to a thickness of 15 μm.
And irradiated with ultraviolet rays for 15 minutes. Next, the non-linear polymer 10 is used to form a P containing an azo dye at 5 × 10 ²⁰ cm ^−3.
A solution in which MMA was dissolved in monochlorobenzene was applied by spin coating to a thickness of 5 μm. Next, a 5% PVA11 aqueous solution was applied to a thickness of 0.5 μm by spin coating. Next, the substrate was placed in a vacuum evaporation apparatus, and aluminum 12 was laminated thereon in a thickness of 0.1 μm. Next, a silicone-based photoresist 13 was spin-coated to a thickness of 0.3 μm. This substrate is exposed and developed using an ultraviolet exposure device,
It was processed into a line having a width of 5 μm (step (3)). Using this resist pattern as a mask, reactive reactive ion etching is performed in carbon tetrachloride for 3 minutes and then in an oxygen atmosphere for 55 minutes in a reactive reactive ion etching apparatus to obtain carbon tetrachloride ions or oxygen ions 14. Then, when the etching was performed up to the linear polymer layer 10, a pattern substantially as shown in the step (4) of FIG. 2 was obtained. Next, immerse in distilled water,
The portion above the PVA 11 was lifted off (step (5)). Next, from above, 15 μl of acrylic cured resin
By spin coating for m times, an element having a structure as shown in step (6) in FIG. 2 was produced.

The produced device was cut into a length of 10 mm, placed in a poling device, heated to 140 ° C.
/ Cm, and cooled to room temperature at 1 minute / ° C. Next, using a fiber from a 1.06 μm laser,
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 the SHG was determined. The result was 0.25% as in the first embodiment. , Got a high value. This is because a non-linear polymer material is not damaged by lift-off using water, and a channel-type waveguide that does not cause intermixing with the core is produced by using a UV resin for the clad.

[0024]

As described above, in fabricating a channel waveguide of a nonlinear polymer, a step of laminating a water-soluble polymer such as PVA on the nonlinear polymer is inserted. A non-linear element can be manufactured without damaging the device.

[Brief description of the drawings]

FIG. 1 shows the first embodiment of the present invention and the first embodiment of the present invention.
FIG. 3 is a view showing a manufacturing process of a channel waveguide using a nonlinear polymer.

FIGS. 2A and 2B are diagrams illustrating a second embodiment of the present invention and a second embodiment of the present invention, in which a manufacturing process of a channel waveguide using a nonlinear polymer is illustrated.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 UV curable resin 3 Nonlinear polymer 4 Water soluble polymer 5 UV curable resin 6 Photoresist 7 Oxygen ion 8 Substrate 9 UV curable resin 10 Nonlinear polymer 11 Water soluble polymer 12 Metal film 13 Photoresist 14 Carbon tetrachloride Ion or oxygen ion 15 substrate 16 polymethyl methacrylate (PMMA) 17 nonlinear polymer 18 PMMA 19 thermosetting resin 20 photoresist 21 oxygen ion

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Tomaru 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Michiyuki Amano 1-16-1 Uchisaiwaicho, Chiyoda-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/00-1/035 G02F 1/29-1/365 G02B 6/12-6/14 WPI / L (QUESTEL)

Claims (2)

(57) [Claims] In a step of manufacturing a channel type optical waveguide having a polymer material having nonlinear optical characteristics as a core and a polymer having a refractive index slightly smaller than the core as a clad, an ultraviolet curable resin is coated on an arbitrary substrate. Apply, then apply a polymer that exhibits nonlinear optical properties, then apply a water-soluble polymer that can be spin-coated, then apply an ultraviolet curable resin, apply a resist, and use ultraviolet light. Exposure and development to any pattern, using the patterned resist as a mask,
Nonlinear optical element characterized by etching by reactive ion etching up to the layer of the non-linear polymer, then lifting off the layer above the water-soluble polymer with water, and then applying an ultraviolet curable resin. Method of manufacturing. 2. A process for producing a channel type optical waveguide comprising a polymer material having a nonlinear optical characteristic as a core and a polymer having a refractive index slightly smaller than that of the core as a clad, wherein an ultraviolet curable resin is coated on an arbitrary substrate. Coating, then apply a polymer that exhibits nonlinear optical properties, then apply a water-soluble polymer that can be spin-coated, then deposit a metal such as aluminum by vapor deposition or sputtering, and then apply a resist Then, exposure and development are performed on an arbitrary pattern using ultraviolet light, and the patterned resist is used as a mask to etch up to the layer of the non-linear polymer by reactive ion etching. And then applying an ultraviolet curable resin to manufacture the nonlinear optical element.