JPS6370204A - Manufacturing method of planar optical waveguide - Google Patents

Abstract

PURPOSE:To obtain a low-loss optical waveguide by inserting a core made of a heat resistant material into a hollow glass tube, bringing the tube and core into tight contact with each other, molding the same and cutting out the tube, thereby obtaining the plane optical waveguide. CONSTITUTION:SiCl4 which is a raw material for forming glass and CCl2F4 which is an additive for adjusting refractive index in the form of gas are introduced into hot plasma, and the fine glass particles are deposited on the outside periphery of a glass rod 1A. The deposited layer is converted to transparent glass, by which a clad layer 3 is obtd. The SiCl4 is then supplied into the hot plasma and the core layer 2 consisting of pure quartz glass is formed on the outside periphery. The SiCl4 and CCl2F4 are again supplied to the hot plasma and the clad 3 is formed. The center of the rod 1A which is a product 4 in progress obtd. in the above-mentioned manner is axially ultrasonically bored with a hole and the carbon core 5 is inserted into such hole. The glass tube is shrunk by heating 6 from the outside to obtain the molding conforming to the shape of the core 5. The molding is cut out and the plane optical waveguide is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing optical components useful in optical communication systems, optical information processing systems, etc., particularly planar optical waveguides, which is simple and excellent in mass production. .

Conventional technology In order to configure optical communication systems, optical information processing machines, etc.,
Similar to electronic circuit components that perform various functions found in conventional electronic circuits, such as light emitting/light receiving elements, optical transmission lines (optical fine noise, etc.), optical modulators, optical switches, optical branching/coupling circuits, optical filters, etc. Therefore, optical circuit components that realize the various functions in the light wave domain are required. Regarding this, as systems become more sophisticated and diversified, the types of necessary parts also become more diverse, and more specialized parts are also required. Moreover, mass productivity is also required for the manufacturing method.

Among them, optical waveguides, unlike optical fibers, are used for short-distance light guidance, and are used as optical waveguide means for various optical circuit elements such as modulation, polarization, switches, phase shifts, branching, coupling, multiplexing, and photoelectric conversion. Furthermore, they are widely used as optical waveguide means for optical integrated circuits incorporating these optical circuit elements.

There are two types of optical waveguides: two-dimensional optical waveguides, that is, planar waveguides, which confine light only in the direction perpendicular to the substrate, and three-dimensional waveguides, which guide light in the form of a narrow beam with a constant cross-sectional distribution. A common basic structure is a planar waveguide.

In order to be confined within such an optical waveguide, the light propagation path is made of a material that is as transparent as possible to the wavelength of the propagating light, and yet has a higher refractive index than the surrounding environment. Various methods have been proposed in the past to realize such a configuration, such as forming a transparent layer of optical waveguide material with a high refractive index on the top of the substrate, or forming a substrate using treatments such as ion diffusion and ion implantation. A method of partially changing the refractive index is known.

Next, a typical example of a conventional optical waveguide manufacturing method will be explained with reference to the drawings.

First, there is a method of forming a plastic optical waveguide by selective photopolymerization, the process diagram of which is shown in FIGS. 3(a) to 3(d).

According to this method, a film 10 made of, for example, a photosensitive monomer is formed (FIG. 3(a)), a mask 11 having an optical waveguide pattern is provided on the surface of the film 100, and then UV exposure is performed (FIG. 3(a)). (b)). At this time,
Monomers irradiated with ultraviolet light crosslink and polymerize. Thereafter, the mask 11 is removed, and the unreacted monomer in the portions not irradiated with ultraviolet rays by the mask 11 is removed (FIG. 3(C)). Further, the removed portion is filled with transparent plastic, a cladding layer 12 is applied on both sides of the film 10 (FIG. 3(d)), and the filled plastic portion is used as an optical waveguide 13.

Further, a flame deposition method, the outline of which is shown in FIG. 4, is known. In this method, for example, as shown in FIG. 4, a plurality of flat substrates 15 are arranged on a rotary table 14, and while heating the vicinity of the substrates 15 with a heater such as a burner,
Glass-forming raw material gas 17 and combustion gas 17A are introduced from one end of torch 16 to cause a flame hydrolysis reaction to form glass particles, which are deposited on substrate 15. Exhaust gas is discharged through the exhaust pipe 18. Note that by rotating the rotary table 14, glass particles can be continuously deposited on a plurality of substrates 15. Further, the substrate having the glass fine particle deposited layer is sintered to make the deposited layer transparent.

Problems to be Solved by the Invention Incidentally, the selective photopolymerization method shown in FIG. There is a problem that the loss of light during propagation is greater than that of glass or the like.

Further, in the flame deposition method shown in FIG. 4, unless the glass particles are deposited at a temperature below which they become transparent, the substrate 15 and the rotary table 14 will fuse together.
It becomes impossible to separate the substrate 15 from the rotary table 14. Therefore, after the glass particles are deposited, a step of increasing the temperature and sintering the glass to make it transparent is required, which complicates the manufacturing process. Also, in order to perform high temperature heat treatment at this time,
There is a problem in that the substrate 15, which is usually made of glass, often bends. Furthermore, since the accurate temperature distribution of the substrate 15 cannot be measured, there is also the problem that it is extremely difficult to control the refractive index and film thickness.

In this way, conventional plastic optical waveguides not only require a large number of manufacturing steps, but also have a fundamental problem of large propagation loss.On the other hand, glass optical waveguides do not have the same basic characteristics of optical waveguides, such as refractive index distribution and film thickness. Mass productivity was low because it was difficult to control the thickness.

Thus, an object of the present invention is to achieve low loss, high yield, and
Moreover, it is an object of the present invention to provide a method for manufacturing a planar guided waveguide that can be mass-produced.

Means for Solving the Problems In view of the above-mentioned current state of the manufacturing method of planar waveguides, the present inventor conducted various studies in order to develop a manufacturing method that is simple and has excellent mass productivity. It is extremely effective to achieve the above objective by depositing multiple layers with different refractive indexes on the outer periphery of the glass rod, making a hollow glass tube by perforating the glass rod, and shaping it near its softening point. They discovered something and completed the present invention.

That is, the method for manufacturing a planar waveguide of the present invention includes forming a core layer made of glass and at least one cladding layer made of glass on the outer periphery of a glass rod mainly composed of SiC2.
The core layer becomes an intermediate layer, and the refractive index of the core layer is higher than the refractive index of the layer in contact with the core layer, the glass rod is perforated to form a hollow glass tube, and then the inside of the hollow glass tube is The method is characterized in that a core made of a heat-resistant material is inserted, the cores are molded in close contact with each other, and the core is cut out to obtain a planar waveguide.

In the above method, the glass rod may be perforated to form a hollow glass tube, then further stretched or expanded in diameter, and a core may be inserted into the hollow glass tube.

In the method of the present invention, the glass deposited layer that becomes the core layer or cladding layer is formed by an OVD method (external deposition method) in which a porous glass layer is formed and then sintered to form a transparent glass layer.
Alternatively, it is of course possible to use POD (plasma external deposition method) which directly forms a transparent glass layer.

Examples of the glass rod used as the substrate include quartz glass containing 5102 as a main component, Vycor glass, and Pyrex glass.

In addition, the core layer is made of 5iC1□ as a glass forming raw material gas.
Alternatively, silane gas such as Si HCl3 or Alcorade is mainly used, and in some cases, additives to increase the refractive index such as P 0C12, GeCl4,
It can be obtained by using it in combination with TiCl3, Ta(:1□, 5bC12 or their hydrides, alcoholades, etc.) These additives can also be used as a mixture of two or more types, and furthermore, in addition to the above-mentioned alcoholades. , LiOC2H5, Nb(O
Organic solutions such as C2H5)S and aqueous solutions of water-soluble metal halides (ZnC12, etc.) are atomized using an atomizer or ultrasonic waves, and these are introduced into an oxyhydrogen burner or plasma forming torch to generate glass particles. By depositing this on a glass rod to form a glass layer, a high refractive index glass layer that becomes a core layer can be obtained. It goes without saying that these additives can also be used as glass forming raw materials themselves.

The core layer may be a single layer, but similarly to a graded index optical fiber, a plurality of layers may be formed so that the refractive index changes sequentially.

Furthermore, in relation to the core layer, the cladding layer contains additives (such as SF6, CF, etc.) that have a lower refractive index than the core layer in the glass forming raw material (in addition to the additive raw materials mentioned above). At least one layer is formed by appropriately selecting and using a fluoride gas, a boron halide such as BCl2, BBr2, hydride, alcoholade, etc.).

Furthermore, since the glass rod portion may ultimately function as a cladding layer, the cladding layer obtained from the deposited film may have the same composition as the glass rod.

For example, in the POD method, the glass-forming raw material or mixture with additives is introduced into a plasma torch together with Ar as a plasma-forming gas and 02 as a reactive gas, and is applied by a high-frequency coil set outside the plasma torch. It is excited by high frequency waves, decomposes, and reacts to form glass particles, which are deposited on the outer wall of the glass rod, and at the same time are sintered by a plasma flame to form a transparent glass layer.

The mixing ratio of these raw material gases for glass formation is appropriately selected as required.

In this way, after forming a core layer having a predetermined refractive index on the outer periphery of the glass rod, and at least one layer of deposited layers, a hole is formed in the center of the glass rod in the axial direction to form a hollow glass. Use it as a tube. In this case, the holes are drilled using an ultrasonic drill or by melt drilling using a CO2 laser. The hole diameter is determined in consideration of the outer diameter of the glass rod and the thicknesses of the core layer and crat layer formed on the outer periphery. In other words, if the hole is drilled as large as possible without damaging the core layer and cladding layer formed on the outer periphery,
This is advantageous in the subsequent drawing, diameter expanding and flattening steps. for example,
When a glass layer is formed in the order of cladding layer, core layer, and cladding layer with a thickness of 2 mm on the outer periphery of a glass rod having an outer diameter of 15φ, the hole diameter is preferably about 12φ to 14φ. The core layer and cladding layer are stretched and diameter-expanded to the final required thickness, and then a core made of a heat-resistant material having a flat part is placed inside the glass tube, and the hollow glass tube is By heating the glass tube from its periphery using an appropriate means, the glass tube contracts toward the center and comes into close contact with the core. A planar waveguide having a predetermined size and shape can be obtained by cutting it using a suitable means such as a lathe or a diamond cutter.

Various methods can be used as heating means at this time, but
Resistance heating furnaces and high frequency induction heating furnaces are preferred because more uniform heating can be expected.

The planar waveguide obtained by the method of the present invention is, for example, as shown in FIGS. 2(a) and 2(a).

Here, the optical waveguide is composed of a glass layer 1 as a substrate, a core layer 2 of light propagation glass with a high refractive index, and a cladding layer 3 of glass with a lower refractive index than the core layer 2.

Examples of the core material include carbon, poron nitride, alumina, beryllia, and silicon carbide.

Further, the shape of the core may be various, such as a triangular prism, a quadrangular prism, or another polygonal prism.

As described above, according to the method of the present invention, the necessary core layer and glass layer for cladding are first formed on the outer periphery of the glass rod in a series of continuous steps, and the type of additive or the amount supplied is changed. It is possible to change the refractive index by simply changing the refractive index, and it is possible to form the core layer and cladding layer in an almost continuous operation).Then, the center of the glass rod is bored to form a hollow glass tube, which can be used later as needed. By adjusting the thickness of the core layer and cladding layer by stretching or expanding the diameter accordingly, then molding using a core, and simply cutting the molded product obtained as a result of close contact with the core, It becomes possible to easily form a planar leading waveguide.

Furthermore, not only can the core layer and the cladding layer be formed through the continuous process as described above, but when forming these layers, the substrate 15 and the rotary table 14 can be formed as in the conventional example shown in FIG.
The transparent core layer and cladding layer can also be directly formed on the glass rod since there is no problem of deformation of the substrate during the fusion with the glass rod or during the long glass forming process.

In addition, since the glass tube is tightly attached to the lump-like core,
By keeping each face of the core flat, a flat glass layer is obtained. Therefore, a planar leading waveguide with excellent flatness can be cut out.

Therefore, there is no need for an independent deposition operation as seen in the conventional method, the process is simplified, mass production can be easily carried out, and it is extremely effective in reducing the manufacturing cost of the product.

Thus, according to the method of the present invention, an optical communication system,
The method of the present invention can be said to be an extremely useful technique in the field of optical applications, since it is possible to advantageously manufacture planar waveguides of various shapes useful in various optical application devices such as optical information processing systems.

EXAMPLES Hereinafter, the method for manufacturing a planar guided waveguide of the present invention will be specifically explained using examples. However, the scope of the present invention is not limited in any way by the following examples.

A planar optical waveguide was fabricated using the POD method described above. 1st
Figures (a) to (C) are process diagrams of a method for manufacturing a planar guided waveguide according to an embodiment of the present invention. 5iCIa as a glass forming raw material gas and CCl2F2 as an additive gas for adjusting the refractive index are introduced into the thermal plasma to generate glass fine particles, which are deposited on the outer periphery of the glass rod IA and made transparent, thereby forming the cladding layer 3. was formed. The glass rod IA is fixed to a lathe chuck (not shown) that can rotate and move in parallel at a constant speed, and by appropriately rotating and moving it forms a uniform glass layer over its entire length in the axial and circumferential directions. be able to.

After forming the cladding layer 3, by supplying 5IC14 as a glass forming raw material gas into the thermal plasma,
A core layer 2 made of pure silica glass was formed on the outer periphery.

Next, the cladding 3 was formed by again supplying 5iC1 as a glass forming raw material gas and CCl2F2 as an additive gas for adjusting the refractive index. 5IC14 above
The flow rate of CCl2F2 gas is 350 for both 5ICI4, CC1, and F2 when forming the cladding layer 3.
CC/min, and in forming the core layer 2, only 5ICI4 was 100 cc/min.

The outer diameter of the glass rod IA is 20+++m1. The thickness of the core layer 2 and the cladding layer 3 was 0.2 mI [l].

The relative refractive index difference between the cladding layer and the core layer was 11%. In this way, an intermediate product 4 as shown in FIG.
After obtaining the glass rod IA, the center of the glass rod IA was perforated in the axial direction using an ultrasonic perforator to obtain a hollow glass tube having an inner diameter of 15 n+n+. The outer diameter was further increased to 22.4m by stretching and expanding the diameter.
A hollow glass tube IB with an inner diameter of 21.0 mm and an inner diameter of 21.0 mm was used, and a core 5 made of a heat-resistant material (carbon) was inserted therein as shown in FIG.

By heating the hollow glass tube IB from its outer periphery to 1,500 degrees using the heating means 6, the hollow glass tube contracted (FIG. 1C), and a molded body corresponding to the shape of the core 5 was obtained. By cutting out this, a planar optical waveguide having the configuration shown in Fig. 2 etc. can be easily obtained. According to this method, the PO
There is no variation in the thickness of the core layer and cladding layer formed by the D method, and there is no variation in the diameter of the glass rod that will ultimately become the substrate, making it possible to efficiently (manufacture) a planar guided waveguide with extremely good film quality. The thickness of the core layer and cladding layer of the final product was about 50 μm each.

As described in detail, according to the method for manufacturing a planar guided waveguide of the present invention, the core layer and cladding layer are first formed using the vapor deposition method, so that an optical waveguide with extremely low loss can be obtained. be able to. Furthermore, since a glass rod is used as the substrate material, there is no deformation of the substrate even during long-term high-temperature processes, and a uniform waveguide layer can be obtained.

Furthermore, the use of a core simplifies operation and allows for miniaturization with planar guided waveguides.

Thus, according to the manufacturing method of the present invention, it is possible to extremely efficiently provide a planar optical waveguide having a shape and performance that can sufficiently respond to advances in optical communication systems and the like.

[Brief explanation of the drawing]

1rgJ(a) to (C) are process diagrams of the method for manufacturing a planar guided waveguide of the present invention, FIG. 2 is a perspective view of a planar optical waveguide manufactured by the present invention, and FIG. a) to (d) are explanatory views showing a manufacturing method using a conventional selective photopolymerization method, and FIG. 4 is an explanatory view showing a manufacturing method using a conventional flame deposition method. (Main reference numbers) 1... Glass eyebrow IA... Glass rod IB... Glass tube, 2... Core layer, 3... Clad layer, 4...
・Intermediate product, 5. Core, 6. Heating means, 1
0... Film, 11... Mask, 12... Clad layer, 13... Optical waveguide, 14... Rotary table, 15... Substrate, 16... Torch, 17... Raw material gas for glass formation, 18... Exhaust pipe

Claims (12)

[Claims] (1) On the outer periphery of the glass rod whose main component is SiO_2,
A core layer made of glass and at least one cladding layer made of glass are formed such that the core layer serves as an intermediate layer and the refractive index of the core layer is higher than the refractive index of the layer in contact with the core layer, and A glass rod is perforated to form a hollow glass tube, a core made of a heat-resistant material is then inserted into the hollow glass tube, the cores are brought into close contact with each other, and the core is molded, and this is cut out to obtain a planar optical waveguide. A method for manufacturing a characteristic planar optical waveguide. (2) After the glass rod is perforated to form a hollow glass tube, the core is inserted into the hollow glass tube after being further stretched or expanded in diameter.
The method described in section. (3) The hollow glass tube and the core are brought into close contact with each other by heating the hollow glass tube from the outside to shrink it. Method. (4) The method according to any one of claims 1 to 3, characterized in that the glass rod is perforated by ultrasonic vibration. (5) The method according to any one of claims 1 to 3, characterized in that the glass rod is melted and perforated using a CO_2 laser. (6) The formation of the core layer and the cladding layer is characterized by forming the core layer on the outer periphery of the glass rod, and then forming the cladding layer on the core layer. A method according to any one of claims 1 to 5. (7) Formation of the core layer and the cladding layer consists of forming the cladding layer, the core layer, and the cladding layer in that order around the outer periphery of the glass rod. The method according to any one of the ranges 1 to 5. (8) Claim 1, wherein the core layer is composed of a single layer made of glass having the same refractive index.
The method described in any one of paragraphs to paragraphs 7 to 7. (9) Any one of claims 1 to 7, characterized in that the core layer is composed of a plurality of glass layers whose refractive index decreases as it approaches the cladding layer.
The method described in section. (10) According to any one of claims 1 to 9, the core is made of carbon, boron nitride, alumina, beryllia, or silicon carbide. the method of. (11) The method according to any one of claims 1 to 10, wherein the core layer and cladding layer are formed by a chemical vapor deposition method. (12) The core layer is formed by a chemical vapor phase reaction of a glass forming raw material gas, and the cladding layer is formed by a chemical vapor phase reaction of a mixed gas of a glass forming raw material gas and a refractive index adjusting additive. Claim 1 characterized in that
The method described in Section 1.