JP2003227957A - Optical waveguide, optical waveguide device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide which has low propagation loss and high efficiency and can be miniaturized, and to provide a compact and highly efficient optical waveguide device. <P>SOLUTION: The optical waveguide includes a core part 2 in which light propagates and a clad part 3 which has a low refractive index and is so formed to enclose the core part 2, and the clad part 3 is a gas or a liquid. The difference in the refractive indices of the core part and the clad part is made larger by using a gas or a liquid as the clad part 3. As the gas, air, a rare gas, nitrogen, oxygen or carbon dioxide is employed and as the liquid, alcohol, water or paraffin is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide, an optical waveguide device and a method for manufacturing the same, and in particular, it is used for an optical switch, an optical modulator, an optical demultiplexer and the like in the optical communication field and has a high transmission efficiency. The present invention relates to an optical waveguide having a new structure.

[0002]

2. Description of the Related Art An ordinary optical waveguide used in the field of optical communication is composed of a core portion having a high refractive index for propagating light and a clad portion having a low refractive index disposed around the core portion. The introduced light is propagated by being totally reflected at the interface between the core part and the clad part.

FIG. 14A shows a planar optical waveguide, in which a lower clad layer 101, a core layer 102, and an upper clad layer 103 are sequentially formed on the surface of a substrate 100. is there. On the other hand, FIG. 14B shows a linear optical waveguide, in which the clad layer 105 formed on the surface of the substrate 100 is formed so as to cover the linear core layer 104. Is.

In the optical waveguide, the larger the refractive index difference between the core portion and the clad portion, the greater the light confinement effect. If the refractive index difference between the core and the clad is large, the propagation loss (radiation loss) of light becomes small. Therefore, particularly when the traveling direction of light is changed by the optical waveguide, the radius of curvature of bending can be reduced by using the optical waveguide having a large difference in refractive index. Therefore, the occupied area of the optical waveguide can be reduced, and as a result, the optical communication device using the optical waveguide can be downsized.

[0005]

However, the core portion and the clad portion in the optical waveguide are generally made of a solid material such as quartz glass or a polymer material. For example, in a material transparent in the visible light region, The range of the refractive index is mostly concentrated in the range of 1.3 to 1.6, and the difference in the refractive index is limited within this range, and there is a limit in reducing the propagation loss.

Further, there is a limit to the processing of the solid material in the bent portion, that is, the portion where the light transmission direction is changed, and it is difficult to further reduce the size.

The present invention has been made in view of the above circumstances, and is characterized by providing an optical waveguide having a small propagation loss, a high efficiency, and a small size.

Another object of the present invention is to provide a compact and highly efficient optical waveguide device.

[0009]

Therefore, the optical waveguide of the present invention includes a core portion through which light propagates and a low refractive index clad portion formed so as to surround the core portion, and the clad portion is a gas. Alternatively, it is a liquid.

According to this structure, the gas or liquid is
It has a lower density and a lower refractive index than solids. Further, the shape can be freely changed, miniaturization is possible, and the device can be easily processed.

For example, it is desirable that the clad portion is an air layer.

Further, the clad layer may be made of a rare gas such as helium or argon, or an inert gas such as nitrogen. As a result, deterioration of the core portion can be prevented and the life can be extended.

Furthermore, it is also possible to use oxygen or carbon dioxide.

Although the refractive index of air is 1, it is about 1 for other gases, so that the difference in refractive index from the core can be increased.

The clad portion may be made of alcohol or water.

Alcohol has a lower density than solid,
It is possible to obtain a low refractive index even in a liquid, and it is possible to improve the storage stability of the clad material since the reactivity is low.

The refractive index of water is 1.33, the refractive index of ethanol is 1.36, the refractive index of glycerin is 1.47, the refractive index of paraffin oil is 1.48, and the refractive index of methanol is 1.
33. The material forming the clad may be selected according to the refractive index of the material forming the core.

Further, the core portion may be formed to have a plate-like planar structure.

The core portion may be a linear body.

The core portion may be formed to have a bent portion.

The core part may be an organic-inorganic composite containing an organic polymer and a metal compound.

Preferably, the metal compound is
It is a compound formed by the sol-gel method.

In the sol-gel method, after the precursor solution is applied, it can be formed by heating at about 120 to 200 ° C. and drying, so that it can be formed without going through a high temperature step, and the production is It's easy.

In the optical waveguide device of the present invention, the optical waveguide and the core portion of the optical waveguide are connected to the core portion so that the core portion of the optical waveguide is positioned in the clad portion and supported by the end portion thereof. An optical device is included.

According to this structure, since the optical device is formed so as to be directly connected to the optical waveguide, the transmission loss from or to the optical device is suppressed, and an optical waveguide device with low loss can be obtained. it can.

In the method of the present invention, a step of preparing a mold that can be divided into a plurality of parts is performed, and a precursor solution containing a metal alkoxide and an organic polymer is injected into the mold, and the precursor solution is heated. Then, the mold is divided and removed, and an optical waveguide including a core part made of an organometallic compound and a clad part made of a vapor phase or a liquid phase is formed.

According to this method, a precursor solution containing a metal alkoxide and an organic polymer is poured into a mold, heated and cured, and then the mold is simply removed to improve workability and to improve the metal property. It is possible to form an optical waveguide including a core portion made of an organic hybrid compound and a cladding portion made of a gas phase such as an air layer. Also, by enclosing this air layer portion with a container and filling a liquid such as alcohol between the outer wall of the container and the core portion, it is possible to easily form an optical waveguide using the liquid as a clad.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

First, prior to the description of each embodiment, the operation principle and structure thereof will be described.

As shown in the conceptual diagram of FIG. 1, this optical waveguide has a pedestal 1 made of a quartz substrate or the like and a core portion 2 made of a high refractive index material formed through a support portion 1S. The clad portion 3 made of an air layer is located between the core portion 2 and the pedestal 1, and the incident light 4 passes through the core portion 2 and is emitted as the emitted light 5. There is. In this structure, a part of the back surface of the core portion 2 is supported by the support portion provided on the pedestal.

Further, as shown in another structural conceptual view in FIG. 2, the cylindrical core portion 12 is supported by supporting flat plates 11a and 11b made of a low refractive index material, and the other portions are separated from the air layer. The incident light 14 passes through the cylindrical core 12 and is emitted as the emitted light 15. In this structure, the core portion 12
Has a structure in which only two linear contact portions are supported by two parallel supporting flat plates 11a and 11b. If this contact portion is formed of a material having a refractive index as low as possible, It is possible to reduce the propagation loss.

The core portion size in the optical waveguide can be set to be equal to or smaller than the core width or core diameter of a general optical waveguide, and in the planar optical waveguide, the wave has a thickness of 5 μm to 1 mm. It is desirable that the diameter be 5 μm in a linear optical waveguide.
It is desirable that it is ˜1 mm.

The material forming the optical waveguide is not particularly limited, and a quartz material or an organic polymer material can be used.

In recent years, in particular, a so-called nanocomposite material (organic-inorganic hybrid material) in which an organic material region and an inorganic material region in an organic-inorganic composite material are composited at a nanometer level or a molecular level has been actively developed. Can be dispersed at the nanometer level or the molecular level. Therefore, since the organic region and the inorganic region in the material can be designed to be smaller than the wavelength of light, light absorption and scattering are small, and optical transparency required for materials such as optical waveguides can be added. Becomes

Further, the organic polymer constituting the organic-inorganic composite may be any organic material applicable as a composite of organic-inorganic name or an organic-inorganic hybrid material. For example, polymethylmethacrylate, polyamide, polyimide, polystyrene, polypropylene, polycarbonate, polyvinylpyrrolidone, epoxy resin, phenol resin, acrylic resin, urea resin, melamine resin or precursors thereof can be used. It may also be composed of a plurality of organic polymers.

Furthermore, there is no particular limitation on the metal-based compound as an inorganic component constituting the organic-inorganic composite,
The method for producing the same is not limited, but it is desirable to use an oxide compound formed by the sol-gel method, and it is more desirable to use at least one element of silicon, titanium, zirconium, aluminum, tin, and zinc as the metal element. It is desirable to use an oxide-based compound that contains.

The use of these oxide compounds has the effect of reducing the absorption of light at the optical communication wavelength (0.4 to 1.6 μm).

Furthermore, the ratio of the metal-based compound contained in the organic-inorganic composite material used in the present invention may be in a range such that the organic polymer and the metal-based compound can be composited on the order of nanometers. When the metal of the system compound is silicon, the amount of elemental silicon in the organic-inorganic composite material is preferably 0.1 to 46% by weight. More preferably, it is 5 to 37% by weight.

Here, as a method for evaluating this composition,
Secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XP
S), electron microanalyzer (EPMA), transmission electron microscope (TEM), etc. can be used for observation.

Furthermore, the starting material used for producing the metal compound in the sol-gel method may be a metal alkoxide containing a metal element having at least two hydrolyzable groups. For example, examples of silicon-containing metal alkoxides include tetraethoxysilane, tetramethoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, and phenyltriethoxysilane. A metal alkoxide in which a silicon atom forming the metal alkoxide is substituted with titanium, zirconium, aluminum, tin, zinc atom or the like is also applicable. It is also possible to use two or more metal alkoxides in combination.

The mold used in the sol-gel method is one that can be easily peeled off from the organic-inorganic composite and does not deform or deteriorate at the process temperature or chemicals used in the organic-inorganic composite preparation process. If it is washed with, there is no limitation on metals, organic substances, etc., and it may be selected based on the constituent material of the organic-inorganic composite. It is particularly preferable to use an organic polymer material having high flexibility, and it is preferable to use a fluorine resin such as polypropylene or polytetrafluoroethylene, polyethylene terephthalate, or an organic polymer material containing them as a main component. (Embodiment 1) This optical waveguide is, as shown in FIG.
A flat plate-shaped core portion 32 made of an organic-inorganic composite is supported by a pedestal 31 made of quartz via a spacer 30S. An air layer is provided between the core portion 32 and the pedestal 31. The clad part 33 is located, and the incident light 3
4 passes through the core portion 32 and is emitted as the emitted light 35. In this structure, the spacer 30S in which the end portion of the back surface of the core portion 32 is spotted on the pedestal 31
Is spatially supported by.

In manufacturing this optical waveguide, first, a precursor solution for forming the core portion is prepared by the sol-gel method.

First, tetraethoxysilane 39.6 wt.
%, 0.05 N hydrochloric acid (hydrogen chloride aqueous solution) 6.8 wt
%, Isopropyl alcohol 53.6 wt% mixed solution at a temperature of 26 ℃ for about 24 hours Beaker B
The solution A 38 g formed by advancing the hydrolysis and polycondensation reaction of tetraethoxysilane is mixed with 12 g of the mixed solution B at a ratio of 17.5 wt% polyvinylpyrrolidone and 82.5 wt% isopropyl alcohol. To obtain a solution having an appropriate viscosity.

Next, as shown in FIG. 4, a mold composed of a plate-like body composed of five sheets of polytetrafluoroethylene, that is, a bottom portion 41 and first to fourth side surface portions 42, 43, 44 and 45. A frame is prepared, and the precursor solution 20 formed as described above is poured into the frame (FIG. 4 (b)).

Then, after drying in the atmosphere, the bottom portion 41 of the formwork is
Are removed, and then the first to fourth side surfaces 42, 43, 4
4 and 45 are removed and the width is 10 m as shown in FIG.
A flat optical waveguide (core portion 32) having a length of m, a length of 30 mm (direction of propagation of light) and a thickness of 0.5 mm is formed.

At this time, 50 samples were prepared and the state of cracking was confirmed. As a result, in this sample, cracking occurred in 4 out of 50 samples. On the other hand, when the formwork is not formed into a divided structure as in the first embodiment but integrally formed, 50 samples are prepared and the cracks are confirmed. As a result, 43 out of 50 samples are obtained in this sample. Occurred in the sample. From these comparisons, it is understood that the split structure of the mold reduces the occurrence of cracks and greatly improves the manufacturing yield.

An optical waveguide was formed by fixing the thus formed core portion 32 to the pedestal 31 via the spacer 30S.

Then, as shown in FIG. 5, this optical waveguide is mounted on the optical path of a He-Ne laser device having a wavelength of 632.8 nm so that this laser light can be introduced as incident light 34 to form an optical waveguide device. The emitted light 35 formed and emitted from the end face on the opposite side was enlarged by the optical system 36 and then projected on the screen 37. As a result, a sharp spot is observed, and it can be seen that light propagates satisfactorily without absorption or dispersion.

(Embodiment 2) This optical waveguide is shown in FIG.
As shown in (a) and (b), a cylindrical core portion 52
Are supporting flat plates 61a, 61b made of a low refractive index material.
The clad portion 63 composed of an air layer is provided in the other portion, and the incident light 64 passes through the cylindrical core portion 52 and is emitted as the emitted light 65. In this structure, the core portion 52 is supported only at two contact portions by a spacer 60S made of a low refractive index material supported by two parallel supporting flat plates 61a and 61b. Propagation loss can be further reduced by using a material having a refractive index as low as possible.

In forming this optical waveguide, as shown in FIG.
As shown in (a), the precursor solution formed in the same manner as in the first embodiment is drawn through a die 51 having an opening of a desired diameter formed on the bottom surface of the liquid reservoir 50,
By drying and cutting into a predetermined length, a linear core portion 52 having a diameter of 0.5 mm is formed as shown in FIG. 7B.

The core portion 52 thus formed is provided with two supporting flat plates 61a parallel to each other with a spacer 60S interposed therebetween.
The optical waveguide of the second embodiment of the present invention is formed by supporting it with 61b.

Then, as shown in FIG. 8, this optical waveguide is mounted on the optical path of the He-Ne laser light (beam cross section: circular) having a wavelength of 632.8 nm so that this laser light can be introduced as incident light 84. An optical waveguide device was formed by using the optical waveguide device, and the outgoing light 85 led out from the opposite end face was enlarged by the optical system 86 and then projected on the screen 87. As a result, a sharp spot is observed, and it can be seen that light propagates satisfactorily without absorption or dispersion.

In the first and second embodiments, the tetraexisilane / polyvinylpyrrolidone-based organic-inorganic composite precursor solution is used, but phenyltriethoxysilane or acryl-based solution may be used.

In this case, it is formed as follows.

First, phenyltriethoxysilane 39.
6wt%, 0.05N hydrochloric acid (hydrogen chloride aqueous solution) 6.8
wt% and N-methyl-2-pyrrolidone 53.6 wt% mixed solution was stirred at a beaker for about 24 hours while maintaining it at 26 ° C. to promote hydrolysis and polycondensation reaction of phenylethoxysilane. 38 g of the formed solution A,
Polymethylmethacrylate 17.5 wt%, N-methyl-2
-Pyrrolidone 82.5 wt% mixed solution B
A solution having an appropriate viscosity is obtained by mixing 12 g.

The same core portion can be formed by using the organic-inorganic composite precursor solution thus prepared.

(Third Embodiment) As shown in the sectional view of FIG. 9 and the perspective view of FIG. 10, this optical waveguide has a hollow container 99 attached to a pedestal 91 made of a silicon substrate.
The core portion 9 made of a high refractive index material via the support portion 91S.
2, a clad portion 93 formed of an air layer is present between the core portion 92 and the pedestal 91, and the light emitted from the laser device 94 attached to the support portion 91S is the core. The light passes through the portion 92 and is emitted as outgoing light through the optical connector 95 attached to the other end. In this structure, the functions of the supporting portions for supporting the pedestals at both ends of the core portion 92 are performed by the optical connector 95 and the laser device 94.
In addition, since light directly enters and exits, propagation loss can be reduced.

Next, the manufacturing process of this optical waveguide will be described.

First, as shown in FIG. 11A, the laser 94 is fixed to one end of the groove 1102S formed in the mold 1101 made of silicon rubber.

In this state, as shown in FIG. 11B, the same precursor solution as that prepared in the first and second embodiments is poured into the groove 1102S including the laser device 94 and dried. Then, it is cured to form a core portion 1102 made of an organic-inorganic composite.

Then, as shown in FIG. 11C, the mold 1101 is removed, and the core portion 1102 on which the laser device 94 is mounted is formed on the end face.

As shown in FIGS. 9 and 10, a laser device 94 is fixed to the core 1102 via a support portion 91S attached to a container 99, and an optical connector 95 connected to an optical fiber 97 is attached to the other end. Is fixed to the support portion, and the other end of the core portion 1102 is connected to the optical connector 95, so that the core portion 1102 is supported by the frame body. Therefore, there is no leakage or attenuation at the optical connection portion, and highly efficient propagation is possible.

According to this structure, since the core portion is made of the organic-inorganic composite material, it has flexibility, can be bent even after being removed from the mold, and can be shaped.

When forming the core portion, it is possible to form a curved core by forming the groove itself into a curved shape.

In the third embodiment of the present invention, the optical connector and the photo diode are formed so as to form a straight line, but the optical waveguide can be freely bent.
The degree of freedom in layout is obtained, and the design is free.

The substrate is not limited to the silicon substrate, and a sapphire substrate or the like can be used, and a photoelectric conversion element, a light emitting element such as a semiconductor laser can be integrated on the same substrate. Therefore, it is possible to provide an optical integrated circuit device that is small and can operate at higher speed. (Fourth Embodiment) Further, according to the third embodiment, since the core portion is made of the organic-inorganic composite material, it has flexibility and can be bent even after being removed from the mold. The shape can be freely processed.

Therefore, in this example, as shown in FIG. 12A, the cylindrical core portion formed in the second embodiment is drawn by using a die while supplying the precursor solution,
After forming the cylindrical core portion 1202, as shown in FIG. 12B, a waveguide is formed by bending the core portion 1202 at the bent portion R by approximately 90 degrees.

With the above structure, it is possible to easily form the waveguide having the bent portion R.

The thus formed core portion is held in a container (not shown), and the container is filled with gas or liquid so that the wall surface of the core portion is covered with gas or liquid so as not to contact the container. do it.

Further, a structure is also effective in which the core portion is kept at the center of the flow path while always flowing the fluid to prevent the core portion from contacting the wall surface. (Fifth Embodiment) It is also possible to form a curved core by forming the core portion into a curved shape when forming the core portion.

In this example, as shown in FIG.
The groove portion 130 is formed in the same manner as the throat formed in the third embodiment.
The molds 1301 and 1303 having 2S are used, the same precursor solution is supplied to the groove 1302S, and the molds 1301 and 1303 are removed after drying and curing, and the core 130 is formed.
2 is formed.

In this example, since the groove 1302S has the bent portion R, as shown in FIG.
A cylindrical core portion having is formed.

As described above, also by this method, it is possible to easily form the waveguide having the core portion bent at the bent portion R by approximately 90 degrees.

[0074]

As described above, according to the present invention, since gas or liquid is used as the clad,
The refractive index difference between the core portion and the clad portion can be increased, the optical confinement effect is improved, and an optical waveguide with small propagation loss can be obtained.

Further, since the clad is a gas or a liquid, the shape can be freely changed and the workability is good.

Further, since the refractive index of the clad can be made small, any material can be used for the core portion, and it is possible to obtain an optical waveguide device of free design and low cost.

The precursor solution may be poured into the mold, the core may be formed by the sol-gel method, the mold may be removed, and then the mold may be fixed in a gas or a liquid, resulting in a high manufacturing yield.
It is possible to provide a manufacturing method of an optical waveguide which is easy to manufacture.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an operating principle of an optical waveguide device of the present invention.

FIG. 2 is an explanatory diagram showing the operating principle of the optical waveguide device of the present invention.

FIG. 3 is a diagram showing an optical waveguide according to the first embodiment of the present invention. FIG. 3B is a sectional view taken along the line AA of FIG.

FIGS. 4A to 4C are views showing manufacturing steps of the optical waveguide according to the first embodiment of the present invention.

FIG. 5 is a diagram showing an optical waveguide device according to a first embodiment of the present invention.

FIG. 6 is a diagram showing an optical waveguide according to a second embodiment of the present invention. FIG. 6B is a sectional view taken along the line AA of FIG.

7 (a) and 7 (b) are views showing a manufacturing process of the optical waveguide according to the second embodiment of the present invention.

FIG. 8 is a diagram showing an optical waveguide device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing an optical waveguide device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing an optical waveguide device according to a third embodiment of the present invention.

11 (a) to 11 (c) show a third embodiment of the present invention.
FIG. 7 is a diagram showing a manufacturing process of the optical waveguide according to the embodiment of the present invention.

FIG. 12 is a diagram showing a manufacturing process of a core portion used in a manufacturing process of an optical waveguide according to a fourth embodiment of the present invention.

FIGS. 13A and 13B are views showing a manufacturing process of a core portion used in a manufacturing process of the optical waveguide according to the fifth embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a conventional optical waveguide.

[Explanation of symbols]

1 foundation 1S support 2 core parts 3 Clad part 4 incident light 5 emitted light 11a, 11b Supporting flat plate 12 Core part 13 Clad part 14 incident light 15 Outgoing light

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Yamano             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Yo Denki Co., Ltd. (72) Inventor Hitoshi Hirano             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Yo Denki Co., Ltd. F-term (reference) 2H050 AC62 AC67

Claims (10)

[Claims] 1. An optical waveguide comprising a core part through which light propagates and a clad part having a low refractive index formed so as to surround the core part, wherein the clad part is gas or liquid. 2. The clad portion is formed of air, rare gas, nitrogen,
The optical waveguide according to claim 1, wherein the optical waveguide is composed of oxygen or carbon dioxide. 3. The optical waveguide according to claim 1, wherein the clad portion is made of alcohol, water, glycerin or paraffin oil. 4. The optical waveguide according to claim 1, wherein the core portion is formed to have a plate-shaped planar structure. 5. The optical waveguide according to claim 1, wherein the core portion is a linear body. 6. The optical waveguide according to claim 1, wherein the core portion has a bent portion. 7. The optical waveguide according to claim 1, wherein the core portion is an organic-inorganic composite containing an organic polymer and a metal compound. 8. The optical waveguide according to claim 7, wherein the metal-based compound is a compound formed by a sol-gel method. 9. The optical waveguide according to any one of claims 1 to 8 and an optical waveguide connected to the core portion so that the core portion is positioned in the clad portion and supported by the end portion thereof. An optical waveguide device comprising a device. 10. A step of preparing a mold which can be divided into a plurality of steps, and a step of injecting a precursor solution containing a metal alkoxide and an organic polymer into the mold and heating the precursor solution to cure the precursor solution. And dividing and removing the mold, a core portion made of an organometallic compound, and a gas or liquid is arranged around the core portion,
A method of manufacturing an optical waveguide, characterized in that an optical waveguide having a cladding portion formed of a gas phase or a liquid phase is formed.