JP2855092B2 - Manufacturing method of optical waveguide - 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 manufacturing an optical waveguide, and more particularly to a method for manufacturing an optical waveguide in which the manufacturing steps are shortened.

[0002]

2. Description of the Related Art Conventionally, the manufacturing process of an optical waveguide requires many film forming steps and complicated etching steps. Hereinafter, steps performed when a conventional optical waveguide is manufactured will be described with reference to the drawings. FIG. 3 is a diagram illustrating an example of a conventional optical waveguide manufacturing process. (A) First, a Si wafer corresponding to the substrate of the optical waveguide is prepared. (B) On the Si wafer prepared in the step (a), SiO ₂ corresponding to the cladding layer of the optical waveguide is deposited to a thickness of about several μm. (C) S on the SiO ₂ deposited on the Si substrate in step (b)
A material having a higher refractive index than iO ₂ , for example, Ge—SiO ₂
It is deposited to a film thickness of the order. This Ge—SiO ₂ corresponds to the core of the optical waveguide. (D) A photoresist is applied on the Ge—SiO ₂ film deposited in the step (c) to a thickness of about several μm. (E) On the photoresist applied in the step (d), a photomask separately formed so as to have a desired waveguide circuit shape is arranged, and is exposed to ultraviolet rays. (F) The photoresist exposed in the step (e) is subjected to a development process, and only the photoresist corresponding to the circuit shape remains. (G) Ge—SiO ₂ is etched from the photoresist that has been exposed and developed in steps (e) and (f). In the Ge—SiO ₂ thus etched, only a portion corresponding to the circuit shape remains. (H) The photoresist remaining in step (g) is removed. (I) SiO ₂ film corresponding to the clad layer of the optical waveguide, and Ge corresponds to the core - SiO ₂ corresponding to the cladding layer of the optical waveguide on the SiO ₂ film is coated with a thickness of about several [mu] m.

Conventionally, in coating each layer in the above process, each layer is coated by so-called deposition such as flame deposition (FHD), physical vapor deposition (PVD), chemical vapor deposition (CVD), or by a sol-gel method. ing. In these steps, a vacuum apparatus is used, and a lot of manufacturing time and cost are required.

[0004]

In today's information society, it is required that a large amount of information be communicated with each other at high speed, and for that purpose, optical communication is indispensable. Also, Fi
Optical networks are being extended to homes, as typified by ber To The Home (FTTH).

[0005] However, an optical waveguide indispensable for optical communication is an extremely high-precision part, which has stability in the shape of the core, surface roughness of the interface between the core and the clad, and the near infrared region ( (1.3 to 1.5 μm) is required. In addition, the manufacturing process of such an optical waveguide requires many manufacturing processes, and there is a problem that the manufacturing cost is high. This is a major obstacle to the development of optical communication networks.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing an optical waveguide which can reduce the manufacturing time and the manufacturing cost. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention has been made based on the above problems, and has a core corresponding to a desired shape on one surface of a first glass material corresponding to a cladding layer of an optical waveguide. A first step of forming a recess by etching a portion to be formed, and a second glass material having a different refractive index from the first glass material in the recess formed in the first step. A second step of filling until filled, and a second step of removing at least a second glass material overflowing from the concave portion while leaving the second glass material filled in the concave portion in the second step. 3 steps,
On the front surface of the first glass material to remove a second glass material which is overflowing from the at least recess in said third step,
A fourth step of forming a clad layer by joining the first glass material and a glass material having at least approximately the same refractive index;
At least the second step includes a pair of upper and lower molds.
Heated by heating device with glass material placed between
And press-forming with a pair of upper and lower molds
The present invention provides a method for manufacturing an optical waveguide.

Further, according to the present invention, the press molding
Is one of infrared lamp heating and high frequency induction heating
One heating device and an electric motor or a hydraulic mechanism as a drive source
Press temperature, press shaft position, press force and press
Control device for controlling the speed;
A method for manufacturing an optical waveguide is provided.

Further, according to the present invention, at least
The second step is performed on the lower mold or between a pair of upper and lower molds.
Place the glass material and heat it with a heating device.
Weight, the weight of the mold placed on the glass material, and this mold
At least one of the weights of the weights placed on the
A method for manufacturing an optical waveguide performed by being pressed by weight is provided.

Still further, according to the present invention, the heating
Equipment is continuously arranged from heating zone to cooling zone
A continuous furnace with a lower or upper and lower glass material
Both are configured to move from the heating zone to the cooling zone.
An optical waveguide manufacturing method is provided.

Further, according to the present invention, the third
Process is at least one of grinding, polishing and etching
Also provided is a method of manufacturing an optical waveguide performed by one of the methods.

[0012]

[0013]

In the optical waveguide manufactured by the above-described manufacturing process, if the concave shape is formed directly in the first glass material by etching, the first waveguide is easily formed in the concave portion corresponding to the core shape. A second glass material having a different refractive index and softening point from the glass material can be filled. In addition, conventionally, in order to manufacture one optical waveguide, many film forming steps and etching steps using a vacuum device were required. However, these steps can be reduced, and the manufacturing cost can be significantly reduced. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view schematically showing an example of an optical element molding apparatus according to the present invention. That is,
A fixed shaft 2 extends downward from an upper portion of the frame 1, and an upper die assembly 4 is attached to a lower end of the fixed shaft 2 with a bolt or the like (not shown) via a heat insulating cylinder 3 made of ceramic. The upper mold assembly 4 includes a metal die plate 5, an upper mold 6 made of ceramic or cemented carbide, or the like.
And a fixed die 7 for attaching the upper die 6 to the die plate 5 and forming a part of the die.

On the other hand, a drive unit 8 such as a screw jack for converting the rotational motion of an electric motor, for example, a servomotor 8a into a linear motion thrust is provided below the frame 1. A moving shaft 9 is attached to the driving device 8 via a load detector 8b. The moving shaft 9 attached to the driving device 8 as described above extends upward facing the fixed shaft 2 and is movable in the vertical direction. The moving axis can control the moving speed, the position, and the torque by a program input to the control device 28. In this embodiment, the driving device 8 using an electric motor such as the servo motor 8a is controlled by the control device. However, a hydraulic mechanism using a hydraulic pump may be used as a driving source of the moving shaft 9. .

At the upper end of the moving shaft 9, a heat insulating cylinder 10 similar to the heat insulating cylinder 3 is attached. The lower shaft assembly 11 is attached to the moving shaft 9 via the heat insulating cylinder 10. The lower die assembly 11 includes a die plate 12, a lower die 13, and a moving die 14, similarly to the upper die assembly 4.
Consists of

FIG. 5 is a view showing the structure of the upper and lower molds 6, 13 used in this embodiment. FIG. 5 (a) is a plan view of the molds 6, 13 and FIG. () Shows sectional views of the molds 6 and 13 shown in (a), respectively.

A bracket 15 which is moved up and down by a driving device (not shown) is movably engaged with the fixed shaft 2. A transparent quartz tube 16 surrounding the upper and lower mold assemblies 4 and 11 forming a pair is attached to the bracket 15. The lower end of the transparent quartz tube 16 is hermetically contacted with the intermediate plate 1a through which the moving shaft 9 passes, and a molding chamber 17 is formed to shield the mold assemblies 4 and 11 from the atmosphere. The bracket 15 has an outer cylinder 1
A lamp unit 19 is mounted on the inner surface of the outer cylinder 18 as a heating mechanism. The lamp unit 19 attached to the inner surface of the outer cylinder 18
Is an infrared lamp 20, a reflection mirror 2 disposed behind the infrared lamp 20 and reflecting infrared light toward the quartz tube.
1 and a water cooling pipe 22 arranged on the outer surface of the reflection mirror 21 for cooling the reflection mirror 21. In this lamp unit 19, the mold assemblies 4 and 11 are heated at the press temperature set in the control device 28. This temperature is detected by a temperature detecting thermocouple 27 provided at the lower end of the lower die assembly 11.

In this embodiment, infrared lamp heating is used as a heating mechanism, but other means such as high-frequency induction heating may be used. The fixed shaft 2, the moving shaft 9 and the bracket 15 are provided with gas supply paths 23, 24 and 25 for making the inside of the molding chamber 17 an inert gas atmosphere and for cooling the mold assemblies 4 and 11, and are not shown. An inert gas can be supplied to the molding chamber 17 at a predetermined flow rate via the flow rate control meter. The inert gas supplied to the molding chamber 17 is exhausted from the exhaust port 26.

Next, a method for manufacturing an optical waveguide according to the present invention will be described. FIG. 2 is a diagram showing an example of the optical waveguide manufactured in this embodiment. FIG. 2A is a plan view showing an example of a desired optical waveguide, for example, a four-branch optical waveguide,
FIG. 2B is a cross-sectional view of the optical waveguide shown in FIG.

FIG. 4 is a view showing a process of manufacturing an optical waveguide according to the present invention. (11) First, a disk-shaped glass material flat on both sides, for example, B
K7 (manufactured by SCHOTT, refractive index: 1.51680, glass transition point;
557 ° C). The shape of the glass material is not limited to a disk shape. (12) On the BK7 prepared in the step (11), a photoresist film of a photosensitive polymer for wet etching is applied to a thickness of several μm by whirl coating.
It is formed with a film thickness of about. The film forming method used in this step is not limited to the spin coating method, and may be, for example, a dipping method (dip method).
coating), flow coating method, spray method (s
It is also possible to form a film by a method such as pray coating) or a roller method. (13) On the photoresist formed in the step (12), a photomask formed in a shape of a target optical waveguide is arranged, and the photoresist is irradiated with ultraviolet rays through the photomask, and the photoresist is removed. Exposed.
Generally, photomasks are classified into a positive type and a negative type. In this embodiment, a positive type, that is, a photomask in which a circuit shape portion transmits ultraviolet light is used. In this step, ultraviolet light is used as a light source for exposing, but by appropriately selecting photoresists having different photosensitive characteristics, the light source can be, for example, a far-infrared ray, an excimer laser, an X-ray, an electron beam, or the like. It is also possible to change and use it. (14) The photoresist exposed in the step (13) is developed, and the photosensitive portion, that is, the photoresist in the circuit shape portion is dissolved in the developing solution. By removing the dissolved portion, a desired circuit pattern of the photoresist is obtained. This step can be performed by another method. For example, after the photoresist is exposed using a negative photomask in step (13), the exposed portions become insoluble in the developing solution, and the unexposed portions, that is, the portions corresponding to the circuit shapes, are exposed to the developing solution. Dissolved and removed. By such a method, a desired circuit pattern by the photoresist can be obtained. (15) After the photoresist is developed in step (14), the glass material (BK7) is wet-etched with an etchant (eg, an etchant). In this step, a portion having no photoresist, that is, an exposed portion corresponding to a desired circuit shape is chemically eluted and removed, and a recess having a desired circuit shape is formed on BK7. Note that, in this step, a method using wet etching to form the concave portion forming the core in the glass material has been described, but dry etching may be used. (16) The photoresist remaining on the BK7 etched in the step (15) is removed. (17) A glass material having a different refractive index and softening point from BK7, for example, VC which is a glass material having a higher refractive index and a lower softening point than BK7, is formed in the concave portion of BK7 formed by the wet etching shown in step (15). -78 (manufactured by Sumita Optical Glass Co., Ltd., refractive index: 1.66910, glass transition point: 530 ° C.) is filled by press molding using the optical element molding apparatus shown in FIG. At this time, VC-78 is placed on the etched surface of BK7, and both are placed between upper and lower molds 6 and 13 of the optical element molding apparatus. Pressing with a pressing force of In this embodiment, press forming is performed at a press forming temperature of 600 ° C. and a pressing force of 200 kgf. The upper and lower dies 6, 13 used in the press forming are flat dies as shown in FIG. (18) Glass material V pressed in step (17)
C-78 and BK7 are processed by machining such as grinding and polishing until they have the desired core shape. In this process, not only machining such as grinding and polishing, but also
A method of processing a glass material by chemical treatment such as etching may be used. (19) Shows the molded product after being polished in step (18). (20) a glass material having the same or almost the same characteristics as the cladding layer on the surface ground and polished in the step (18);
For example, BK7 is placed, and both are heated and pressed by using the optical element molding apparatus shown in FIG. At this time, as in the step (17), both are arranged between the upper and lower molds shown in FIG. 5, and both are heated to a predetermined temperature and press-joined with a predetermined pressing force. As bonding conditions at this time, the heating temperature is near the transition point of BK7, a temperature at which BK7 forming the clad layer is not deformed as much as possible, and a temperature at which VC-78 forming the core is deformed. . The pressing force at this time is desirably formed with a small pressing force that does not damage the glass material. Moreover, at this time, it is important that the clad and the core are sufficiently bonded. In the present embodiment, press bonding is performed at a press forming temperature of 700 ° C. and a pressing force of 50 kgf. (21) Through the manufacturing steps (11) to (20),
2 shows a manufactured optical waveguide.

By these manufacturing steps, the role of the cladding layer on the wet-etched glass material BK7,
The optical waveguide in which the glass material VC-78 filled in the concave portion formed in the glass material has a role of a core and the glass material BK7 finally coated has a role of a cladding layer is completed.

Next, the filling property of VC-78 filled in BK7 by the press working in the step (17) was evaluated. FIG. 6 shows an enlarged photograph of the filling portion of BK7 and VC-78. In the step (17), there is a problem whether the concave portion of the BK7 formed by the wet etching is sufficiently filled with the VC-78 by pressing, but as shown in the enlarged photograph of FIG. The filling properties were good. Therefore, it is judged that sufficient pressurization can be obtained by the press working in the step (17).

Next, the bondability between BK7 and BK7 joined by the press joining in the step (20) was evaluated. FIG.
Shows an enlarged photograph of BK7 and the joint of BK7. FIG.
As shown in the enlarged photograph, the bonding state between BK7 and BK7 was good, and there was no boundary between the two bonding surfaces. Therefore, it is determined that sufficient bondability can be obtained by the press bonding in the step (20).

Next, the transmission loss of the optical waveguide manufactured in this example was measured. The transmission loss of the manufactured optical waveguide depends on the refractive index of the glass material, the amount of absorption in the near-infrared region, the surface accuracy of the portion corresponding to the outer peripheral portion of the core, and the like. It was 1.5 db / km or less. This value sufficiently serves as an optical waveguide.

The optical waveguides manufactured in such a manufacturing process can be manufactured individually one by one, but it is also possible to manufacture a plurality of optical waveguides simultaneously by a method as shown in FIG. FIG. 8A is a plan view illustrating an outline of the processing method, and FIG. 8B is a cross-sectional view of the processing method. In this processing method, a plurality of optical waveguides formed in one large glass material are processed by a diamond slicer or the like. That is, a plurality of optical waveguides having a desired size are manufactured by cutting the glass material with broken lines shown in the drawing. Such a processing method has an advantage that a plurality of optical waveguides can be efficiently manufactured in a short time in a small number of manufacturing steps.

In this embodiment, the type of glass material is described as BK7 and VC-78. However, if the refractive index can be used as an optical waveguide, the material is not limited to this embodiment. Absent. Further, in this embodiment, the manufacturing process of the embedded type optical waveguide has been described.
The present invention is also applicable as a manufacturing process of other types of optical waveguides, for example, optical waveguides of a strip type, a lens type, and the like.

In the above-described method for manufacturing an optical waveguide,
A step (17) of filling the concave portion with glass, and a step (2).
Although the example of both the press-molding and the joining and fixing of the clad layer of 0) is shown, it is needless to say that the present invention is not limited to this. For example, a core material and a cladding layer may be formed by depositing a glass material by a method such as a flame deposition method (FHD), a physical vapor deposition method (PVD), and a chemical vapor deposition method (CVD). Further, instead of the press molding, the glass is heated by a heating device, and the glass itself, a mold placed on the glass, and a weight placed on the mold, or any one of these, Filling and joining may be performed by the combined gravity.

The heating device is not limited to a device in which a glass material and a mold are fixedly arranged in a heating unit such as an infrared lamp or a high-frequency induction heating, but is continuously arranged from a heating zone to a cooling zone. It may be a continuous furnace in which the glass material moves from the heating zone to the cooling zone together with the mold.

[0030]

As described above, according to the method for manufacturing an optical waveguide of the present invention, it is possible to reduce the film forming process and the etching process using a vacuum apparatus which have been conventionally performed,
The manufacturing time is shortened and the manufacturing process is simplified, resulting in significant cost reduction. In addition, if a concave portion having a complicated shape is formed by etching, a fine core portion can be easily and accurately manufactured, and a large amount of optical waveguides can be stably manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing an optical element molding apparatus according to the present invention.

FIG. 2 is a diagram schematically showing an example of an optical waveguide manufactured in an embodiment of the present invention.

FIG. 3 is a diagram showing a manufacturing process of a conventional optical waveguide.

FIG. 4 is a diagram showing a manufacturing process of the optical waveguide of the present invention.

FIG. 5 is a view showing the structure of upper and lower molds used for press molding in the manufacturing process of the present invention.

FIG. 6 is an enlarged micrograph of a cross section of a thin film of a glass material filled by press molding in a manufacturing process of the present invention.

FIG. 7 is a micrograph showing an enlarged cross section of a thin film of a glass material joined by press joining in the manufacturing process of the present invention.

FIG. 8 is a diagram showing an outer periphery processing of the optical waveguide by the manufacturing method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Frame 2 ... Fixed base 4 ... Upper die assembly 5 ... Die plate 6 ... Upper die 7 ... Fixed die 8 ... Drive device 8a ... Servo motor 8b ... Load detector 9 ... Moving shaft 11 ... Lower die assembly 12 ... Die plate DESCRIPTION OF SYMBOLS 13 ... Lower mold 14 ... Moving die 15 ... Bracket 16 ... Transparent quartz tube 17 ... Molding chamber 19 ... Lamp unit 20 ... Infrared lamp 23, 24, 25 ... Gas supply path 27 ... Temperature detection thermocouple 28 ... Control device part

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Matsuzuki 2068-3 Ooka, Numazu-shi, Shizuoka Prefecture Numazu office of Toshiba Machine Co., Ltd. (56) References JP-A-88914 (JP, A) JP-A-3-215805 (JP, A) JP-A-7-287141 (JP, A) JP-A-64-26805 (JP, A) (58) Fields investigated (Int. . ⁶ , DB name) G02B 6/13

Claims (5)

(57) [Claims] A first waveguide corresponding to a cladding layer of the optical waveguide;
On one side of the lath material, corresponds to the core of the desired shape
The first step of forming a concave portion by etching a portion
A first glass material in the recess formed in the first step;
A second glass material having a different refractive index is at least
A second step of filling until the portion is filled, and a second glass filled in the recess in the second step
The material remaining and at least the
A third step of removing the second glass material; and
Remove 2 glass materialOf the first glass materialOn the surface,
Glass with a refractive index at least approximately equal to the first glass material
A fourth step of forming a clad layer by joining the raw materials;
With At least the second step is a process in which glass is placed between a pair of upper and lower molds.
With the material placed, heat it with a heating device.
It is performed by press molding with a mold Specially
A method of manufacturing an optical waveguide. 2. The press molding includes infrared lamp heating and
One of the high-frequency induction heating devices and the electric motor
Press or hydraulic mechanism as the drive source,
A control device for controlling the position, the pressing force and the pressing speed,
The method for manufacturing an optical waveguide according to claim 1 , wherein the method is performed by an optical element molding apparatus having : 3. The method according to claim 1, wherein at least the second step is performed on a lower mold.
Alternatively, a glass material is placed between a pair of upper and lower
Heating, place the glass material on its own weight, placed on the glass material
Of the weight of the mold placed and the weight of the weight placed on this mold.
Of which at least one is pressurized by its own weight
The method according to claim 1 , wherein the method is performed. 4. The heating device is provided with a cooling zone from a heating zone.
Is a continuous furnace with glass material
From the heating zone to the cooling zone
The method for manufacturing an optical waveguide according to claim 1 , wherein the optical waveguide is configured to move between the optical waveguides. 5. The method according to claim 1, wherein the third step includes grinding, polishing, and etching.
The method according to any one of claims 1 to 4, wherein the method is performed by at least one of the following .