JP2003084150A - Optical waveguide device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer optical waveguide device to be used in the field of general optics, micro optics, optical communication or optical information processing and satisfying both of a low price and high performance. SOLUTION: A polymer film obtained by curing a polymerizable mixture containing at least one kind of acrylate compound expressed by general formula (I) and a polymerization initiator which can initiate the polymerization of the acrylate compound by applying heat or light is used for either the core or the clad or the both of them in the optical waveguide device. In formula (I), X represents H or CH3 and n is 0 or any positive number.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device, and more particularly to the field of general optics or micro optics, or the field of optical communication or information processing. The present invention relates to an optical waveguide device that can be used for various optical integrated circuits or optical wiring boards used in the above. 2. Description of the Related Art Optical waveguides used in the field of optical information processing and optical communication have been actively studied in recent years for the purpose of integration, miniaturization, high functionality and low cost. In fact, a silica-based optical waveguide device using a silica-based material has been put to practical use in a part of the optical communication field (Masao Kawauchi, NT
TR & D, Vol. 43, No. 11, p. 101, 1994). [0003] On the other hand, polymer optical waveguides using a material less expensive than quartz and capable of adopting a simple manufacturing method have been actively studied. The following can be cited as an example of studying a method for producing such a polymer optical waveguide. (1) Photolocking or selective photopolymerization method in which a monomer is contained in a polymer material and the monomer is polymerized by light irradiation to produce a difference in refractive index from a non-irradiated portion (Kurokawa et al.
Applied Physics, vol. 17, p. 646, 19
(1980), (2) Application of a method used for semiconductor processing such as lithography or etching (Imamura et al., Electronics Letter, Vol. 27, pp. 1342, 1991)
And (3) a method using a polymerizable polymer or a resist (Treware et al., SPIE, Vol.
79, 1989). [0004] The conventional method of manufacturing a polymer optical waveguide, particularly the method of forming a core ridge using a polymerizable polymer to form a waveguide, is simple and low-priced. Suitable for pricing. However, there are problems such as that the transparency of the polymerizable polymer is insufficient and the absorption loss is large, and there is a problem in the uniformity and reproducibility of the formed core ridge shape and the scattering loss is large. Therefore, at present, a polymer optical waveguide having a waveguide characteristic equivalent to that of a silica-based optical waveguide element has not been prepared. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polymer optical waveguide device that satisfies both low cost and high performance. An optical waveguide device according to the present invention has the following general formula (I): Wherein X is H or CH ₃ , n is 0 or any positive number, and Rf is A polymerizable mixture comprising at least one acrylate compound represented by formula (I) selected from the group consisting of: and a polymerization initiator capable of initiating polymerization of the acrylate compound by application of heat or light. Is characterized in that a polymer film obtained by curing is used for one or both of a core part and a clad part. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention solves the problems of the conventional polymer optical waveguide by a low-loss and high-performance optical waveguide device using an acrylate compound having the structure of the general formula (I). Things. In the present invention, the polymerizable mixture comprises at least one acrylate compound represented by the following general formula (I) and a polymer which can initiate polymerization of the acrylate compound by application of heat or light. And an initiator. Embedded image In the general formula (I), X is H or CH ₃ . n is 0 or any positive number, and is preferably from 0 to 5 in order to realize heat resistance required as an optical waveguide. Rf is selected from the group consisting of the following partial structures. Embedded image Here, 2 in the above partial structure (b)
The two hexafluoro-2-propylidene groups may be in para, meta or ortho positions to one another, and the substructure (b) may be a mixture of these positional isomers. The above acrylate compound can be synthesized by acrylate or methacrylate of the corresponding polyol. The acrylation or methacrylation can be carried out by anionization of the polyol followed by reaction with acrylic acid chloride or methacrylic acid chloride. The polyol can be synthesized by a method known in the art, or a commercially available polyol can be used. The polymerizable mixture is used for one or both of the core and the clad of the optical waveguide. Further, in the polymerizable mixture of the present invention, X, n and / or R
A plurality of acrylate compounds of the general formula (I) having different f may be used, or an acrylate compound having another structure may be mixed and used. Other acrylate compounds that can be used in the present invention include, for example, acrylate compounds represented by the general formula (II). In the general formula (II), X is H or CH ₃ , and n
Is 0 or any positive number. In order to realize the heat resistance required for the optical waveguide, n is preferably from 0 to 5. As R, for example, a divalent group having 2 to 12 carbon atoms can be used. The divalent group can include an aliphatic ring or an aromatic ring, but is preferably a linear or branched alkylene group. As described above, by appropriately mixing a plurality of acrylate compounds to form a polymerizable mixture, it is possible to control physical properties such as the refractive index of the formed core or clad. Embedded image The viscosity can be adjusted by adding a diluent to the polymerizable mixture of the present invention. The diluent may itself be reactive or non-reactive. Reactive diluents that can be added to the polymerizable mixture of the present invention include styrene, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, isobornyl acrylate, isobornyl methacrylate, diallyl phthalate , Diallyl isophthalate, diallyl terephthalate, butylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
Lauryl acrylate, modified dicyclopentynyl acrylate (for example, compound (IV) below), glycidyl methacrylate, tetrahydrofurfuryl acrylate, and 1,3-butanediol dimethacrylate include, but are not limited to, Absent. Non-reactive diluents that can be added to the polymerizable mixture of the present invention include organic solvents such as toluene and 1,2-dimethoxyethane. Embedded image As the polymerization initiator used in the polymerizable mixture of the present invention, a general photopolymerization initiator can be used. Such a photopolymerization initiator is, for example, 2,2-
Diethoxyacetophenone, 2,2-dimethoxy-2-
Phenylacetophenone, benzophenone, methyl o-benzoylbenzoate, benzoin isobutyl ether,
Includes, but is not limited to, 2-chlorothioxanthone, and 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one. In addition, a thermal polymerization initiator can be used as the polymerization initiator in the present invention. Such thermal polymerization initiators include organic peroxides such as 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2-methylpropionitrile), benzoyl peroxide and dicumyl peroxide. But not limited thereto. Next, a method of forming an optical waveguide device using a polymerizable mixture containing at least one kind of the acrylate compound represented by the general formula (I) and a polymerization initiator will be described. The first method is to cure the polymerizable mixture, first form a clad, apply a polymerizable mixture having a higher refractive index when cured from the clad, and irradiate the mask with a mask or directly irradiate light. A pattern-like latent image is formed, and then a pattern is formed by removing the non-irradiated portion with a solvent, and this portion is used as a core portion through which light passes. This is a method in which a lower polymerizable substance is applied and an upper clad is formed by irradiation with ultraviolet rays. As a solvent for removing the unirradiated portion,
A solvent that dissolves each component of the polymerizable mixture and does not dissolve the cured pattern is preferable. Examples of such solvents include acetone, ethanol, methyl ethyl ketone, and the like. As the light for forming a patterned latent image, those generally used for optical image formation, such as ultraviolet light and visible light, can be used. In the present invention, the polymerizable mixture containing the acrylate compound having the general formula (I) has excellent light transmission characteristics in the ultraviolet and visible regions, and is advantageous for pattern formation by the above method. That is, even when a film that is cured by light irradiation is obtained, even when the film becomes thicker, the irradiation light reaches the bottom of the film, so that a uniform polymerization reaction occurs over the entire film. The resulting pattern latent image has sufficient resolution, and by developing the latent image with an appropriate solvent, a pattern having steep and smooth wall surfaces can be formed. Conventional pattern formation methods of this type make it difficult to form a thick film and have poor reproducibility of processing, whereas the method of the present invention is extremely excellent in pattern formation ability and can form a pattern with good reproducibility. It is. Furthermore, since uniform polymerization occurs over the entire pattern, it is possible to realize an optical waveguide with little scattering loss. As a second method of forming an optical waveguide device according to the present invention, first, a lower clad layer and a flat film of a core layer are stacked, and then a patterned photoresist is formed on the core layer by a photoresist process. After that, the core layer which is not covered with the photoresist is removed by reactive ion etching to form a core ridge, and thereafter, an upper clad may be covered to form a waveguide structure. The formation of the core layer by curing of the polymerizable mixture at this time includes the steps of a)
Either using a photopolymerization initiator as a polymerization initiator and irradiating the entire surface of the polymerizable mixture with light, or b) using a thermal polymerization initiator as a polymerization initiator and uniformly heating the polymerizable mixture. Can be performed. When forming a core ridge by reactive ion etching,
It was found that an optical waveguide having a smooth etched surface could be manufactured. In any of the above methods, in the polymerizable mixture of the present invention, the bifunctional acrylate compound is randomly linked and cured, so that the molecular chains do not align in one direction. Therefore, according to the method of the present invention, it is possible to obtain an optical waveguide having a small birefringence and thus a small polarization dependence of loss. The polymerizable mixture containing the acrylate compound having the general formula (I) of the present invention is prepared by mixing several kinds of polymerizable compounds. By adjusting the mixing ratio, the refractive index of the core and / or clad obtained by curing the mixture can be controlled in a wide range. Therefore, using the polymerizable mixture of the present invention, various optical waveguide devices from a multimode waveguide to a single mode waveguide can be manufactured. Further, the acrylate compound having the general formula (I) of the present invention can be used in the near infrared region (wavelength around 1.4 μm).
In the optical waveguide according to the present invention, the loss in the near infrared region can be reduced. The optical functional device that can be formed by the method of the present invention is a linear component, which is a basic component of an optical circuit.
Y-shaped (symmetric and asymmetric) and asymmetric X-branch optical waveguides, directional couplers, star couplers, optical waveguide gratings, ring resonators, M × N branching, various waveguide elements for plastic optical fibers (POF) , And branch (TAP) waveguides. In the method of the present invention, by using a mask or a photoresist having a pattern corresponding to the core portion of the device, the device can be manufactured at low cost and with high quality. EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. Example 1 An 80% by weight acrylate compound having the structural formula (Ia), 18% by weight of an acrylate compound having the structural formula (IIa), and 2% by weight of a photopolymerization initiator (benzyldimethyl ketal) were prepared. 1 polymerizable resin was prepared. This polymerizable resin was applied to the substrate 11 by spin coating, and was cured by irradiating UV light to form a lower clad 10 (FIG. 1A). The refractive index of the lower clad 10 with respect to light having a wavelength of 1.55 μm was 1.47. Embedded image Embedded image Next, a second composition containing 70% by mass of the acrylate compound having the structural formula (Ia), 28% by mass of the acrylate compound having the structural formula (IIa), and 2% by mass of a photopolymerization initiator (benzyl dimethyl ketal). A polymerizable resin is prepared and applied on the lower clad 10 to form a polymerizable resin layer 1.
2 was obtained (FIG. 1 (b)). Then, UV light (300 to 400 nm) 14 was irradiated through a mask 13 having a waveguide pattern disposed on the polymerizable resin layer 12 to cure only the irradiated portion (FIG. 1C). The irradiation amount of the UV light was 2000 mJ / cm ² . Next, this sample was developed using acetone to remove the polymerizable resin layer 12 in a portion not irradiated with UV light, thereby obtaining a ridge pattern core 15 (height 8 μm, width 8 μm) shown in FIG. Was. Core 15
Has a refractive index of 1.476 for light having a wavelength of 1.55 μm.
Met. Next, the lower clad 10 is placed on the core 15.
Was coated with the first polymerizable resin used to prepare the above, and was cured by irradiating UV light to produce an upper clad. By the above operation, the cladding 10 having the refractive index of 1.47
And 16, with a refractive index of 1.476, a height of 8 μm, and a width of 8 μm
A single-mode channel waveguide 18 having a core 15 having m was produced (FIG. 1E). The optical waveguide 18 was cut into a length of 1 cm by a dicing saw, and the insertion loss was measured. As a result, it was 0.5 dB or less at a wavelength of 1.55 μm and 0.2 dB or less at a wavelength of 1.3 μm. Further, the polarization dependence of the insertion loss is about 0.3 at a wavelength of 1.3 μm.
It was 1 dB or less. Example 2 A composition containing 80% by mass of an acrylate compound having the structural formula (Ia), 18% by mass of an acrylate compound having the structural formula (IIa), and 2% by mass of a photopolymerization initiator (benzyldimethyl ketal). 1 polymerizable resin was prepared. The polymerizable resin was applied to a substrate by spin coating, and was cured by irradiating UV light to form a lower clad. 1.3μ wavelength of lower cladding
The refractive index for light of m was 1.45. Next, a second compound containing 70% by mass of the acrylate compound having the structural formula (Ia), 28% by mass of the acrylate compound having the structural formula (IIa), and 2% by mass of a photopolymerization initiator (benzyl dimethyl ketal). A polymerizable resin was prepared and applied on the lower clad 10 to obtain a polymerizable resin layer. Then, UV light (300 to 300) is passed through a mask having a Y-branch waveguide pattern arranged on the polymerizable resin layer.
(400 nm) to cure only the irradiated portion.
The irradiation amount of the UV light was 2000 mJ / cm ² . Next, this sample was developed using acetone to remove the polymerizable resin layer in the portion not irradiated with UV light, thereby obtaining a Y-branch ridge pattern core 20 (40 μm in height and 40 μm in width) shown in FIG. The refractive index of the core 20 for light having a wavelength of 1.3 μm is:
1.478. Next, the first polymerizable resin used to form the lower clad is applied on the core 20 and
It was cured by irradiating V light to produce an upper clad. By the above operation, the clad having the refractive index of 1.45 and the core 2 having the refractive index of 1.478, the height of 40 μm, and the width of 40 μm were obtained.
Thus, a multimode channel waveguide having 0 was produced. The optical waveguide 18 was cut into a length of 5 cm by a dicing saw, and the insertion loss was measured. As a result, 0.5 dB or less at a wavelength of 0.85 μm, 0.5 dB or less at a wavelength of 1.3 μm, and 1.55 μm.
m was 0.25 dB or less. The polarization dependence of the insertion loss is 0.1 dB at a wavelength of 1.3 μm.
It was below. Furthermore, even at a high temperature of 150 ° C., there was no remarkable increase in loss, indicating a sufficient heat resistance. The excess loss for the Y-branch waveguide was a good result of about 0.2 dB. Example 3 A 75% by weight acrylate compound having the structural formula (Ia), 23% by weight of an acrylate compound having the structural formula (IIa), and 2% by weight of a photopolymerization initiator (benzyldimethyl ketal) were prepared. Polymerizable resin No. 3 was prepared. The polymerizable resin was applied to a substrate by spin coating, and was cured by irradiating UV light to form a lower clad. Wavelength of lower cladding 1.55
The refractive index for light of μm was 1.471. Next, a second composition containing 70% by mass of the acrylate compound having the structural formula (Ia), 28% by mass of the acrylate compound having the structural formula (IIa), and 2% by mass of a photopolymerization initiator (benzyldimethyl ketal). A polymerizable resin was prepared and applied on the lower clad to obtain a polymerizable resin layer. Then, the UV light (300 to 4) is passed through a mask having a Y-branch waveguide pattern disposed on the polymerizable resin layer.
00 nm) to cure only the irradiated portions. U
The irradiation amount of the V light was 2000 mJ / cm ² . Next, this sample was developed using acetone, and the polymerizable resin layer in the portion not irradiated with UV light was removed to obtain a Y-branch ridge pattern core 20 (8 μm in height and 8 μm in width) shown in FIG.
The refractive index of the core 20 for light having a wavelength of 1.3 μm is 1.
476. Next, the third polymerizable resin used for forming the lower clad is applied on the core 20 and
It was cured by irradiating V light to produce an upper clad. By the above operation, the clad having the refractive index of 1.471 and the core 20 having the refractive index of 1.476, the height of 8 μm, and the width of 8 μm are obtained.
Thus, a single mode channel waveguide having: This optical waveguide is separated by a dicing saw into 5
cm, and the insertion loss was measured. At a wavelength of 1.3 μm, 0.5 dB or less, and 1.55
It was 1.5 dB or less at μm. The polarization dependence of the insertion loss is 0.1 dB at a wavelength of 1.3 μm.
It was below. Furthermore, even at a high temperature of 150 ° C., there was no remarkable increase in loss, indicating a sufficient heat resistance. The excess loss for the Y-branch waveguide was a good result of about 0.2 dB. Example 4 A linear waveguide having a height of 8 μm and a width of 8 μm was prepared by using the acrylate compounds (Ib) and (Ic) of the structural formula (Ia) in which Rf was changed. The method of 3 was repeated to produce a single mode channel waveguide. 0.63 μm, 0.85
Table 1 below shows the waveguide loss at each of the μm, 1.3 μm, and 1.55 μm wavelengths. [Table 1] Embedded image (Synthesis Example 1) 82.16 g (200 mmol) of the compound (IIIb) was added to a 2 L four-necked flask.
And 14.4 g (600 mmol) of NaH and 1.2
L of toluene was added, and the mixture was heated to 70 ° C. and stirred for anionization. After performing the reaction for 15 hours, the reaction mixture was ice-cooled. Under ice cooling, 39.8
2 g (440 mmol) of acrylic acid chloride was added dropwise. After the exotherm subsided, the reaction mixture was heated again to 70 ° C. and the reaction was allowed to proceed for another 5 hours. After completion of the reaction, the reaction solution was filtered, the filtrate was washed with a saturated aqueous solution of sodium hydrogen carbonate, and the organic layer was concentrated. The resulting residue is dried in vacuo to give the desired compound (Ib) as crystals 72.78.
g (70% yield). Embedded image According to the present invention, a high quality optical waveguide device can be easily realized, and by using the device of the present invention, it can be used in the fields of general optics, micro optics, optical communication or optical information processing. Various optical transmission systems to be used can be introduced at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a general production example of an optical waveguide device of the present invention. FIG. 2 is a diagram showing a Y-branch core of the present invention. DESCRIPTION OF SYMBOLS 10 Lower clad 11 Substrate 12 Polymerizable resin layer 13 Mask 14 UV light 15 Core 16 Upper clad 18 Optical waveguide 20 Y branch core

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Norio Murata             2-1-1 Nishi Shinjuku, Shinjuku-ku, Tokyo             NTT Advanced Technology Corporation             In the formula company (72) Inventor Hiroshi Murakoshi             2-1-1 Nishi Shinjuku, Shinjuku-ku, Tokyo             NTT Advanced Technology Corporation             In the formula company (72) Inventor Saburo Imamura             2-1-1 Nishi Shinjuku, Shinjuku-ku, Tokyo             NTT Advanced Technology Corporation             In the formula company (72) Inventor Akira Tomaru             2-1-1 Nishi Shinjuku, Shinjuku-ku, Tokyo             NTT Advanced Technology Corporation             In the formula company (72) Inventor Makoto Hikita             2-1-1 Nishi Shinjuku, Shinjuku-ku, Tokyo             NTT Advanced Technology Corporation             In the formula company (72) Inventor Kazuhiko Maeda             2805 Imafukunakadai, Kawagoe-shi, Saitama             Le Glass Co., Ltd. (72) Inventor Nao Koga             2805 Imafukunakadai, Kawagoe-shi, Saitama             Le Glass Co., Ltd. (72) Inventor Satoru Miyazawa             2805 Imafukunakadai, Kawagoe-shi, Saitama             Le Glass Co., Ltd. (72) Inventor Kentaro Tsutsumi             2805 Imafukunakadai, Kawagoe-shi, Saitama             Le Glass Co., Ltd. F term (reference) 2H047 KA04 KA05 LA12 QA05                 4J027 AC02 AC06 AC09 BA05 BA07                       BA08 BA09 BA17 BA19 BA21                       BA22 CB08                 4J100 AG69Q AL05Q AL08Q AL09Q                       AL62Q AL66P AL66Q BA02P                       BA03P BB11P BB12P BC07Q                       BC36Q BC43P BC43Q BC53Q                       CA01 CA04 DA62 JA36

Claims (1)

[Claim 1] The following general formula (I): Wherein X is H or CH ₃ , n is 0 or any positive number, and Rf is A polymerizable mixture comprising at least one acrylate compound represented by the formula (I) selected from the group consisting of: and a polymerization initiator capable of initiating polymerization of the acrylate compound by application of heat or light. An optical waveguide element, wherein the polymer film obtained by the above is used for one or both of a core part and a clad part.