JP2001305382A - Optical fiber end face lens processing method - Google Patents

Abstract

(57) [Problem] To improve the light propagation efficiency, the method of forming a lens by processing the tip surface of an optical fiber, which is currently performed, makes the shape of the coupling portion compact. It requires advanced processing technology, requires many man-hours, and it is difficult to form a large number of lenses with uniform characteristics, so that it has not yet been put to practical use. SOLUTION: The present invention provides a step of applying a resist having a uniform thickness on an end face of an optical fiber, a step of transferring a circular pattern on the resist, and a step of forming an optical fiber having a resist cylindrical shape. An optical fiber comprising a step of deforming a cylindrical shape into a hemispherical shape by surface tension by baking at a high temperature, and a process of dry-etching an optical fiber on which a hemispherically deformed resist pattern is formed to form a lens. The present invention solves the conventional problem by realizing a method of processing an end face lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing a lens of an end face of an optical fiber in which a portion near the core of the end face of the optical fiber is processed into a hemisphere to form a lens. The optical fiber which has been subjected to the lens processing method of the end face of the optical fiber of the present invention,
Since a complicated component structure is not required, the coupling efficiency of the optical fiber is improved.

[0002]

2. Description of the Related Art With the rapid development of current communication technology and the expansion of communication networks, communication lines using optical fibers are expanding. In communication lines using optical fibers, optical fibers are used to improve the light transmission efficiency by adjusting the difference in the refractive index between the core and the clat in the coupling between the optical fiber and an optical module such as an optical circuit. There is a method of inserting a micro lens into a joint between a fiber and an optical fiber.
However, this method requires the manufacture of microlenses and the precise adjustment of the positional relationship between the optical fiber and the lens, which is not only time-consuming, but also requires the use of independent microlenses, which makes the connection of the joints difficult. It is not in a situation where it is widely used because of problems such as an increase in size and cost. In order to solve this problem, the tip of the optical fiber is melted with a burner flame, and the tip is made spherical by the surface tension of the melted glass to form a lens. And the like, a method of directly forming a lens, etc., have been attempted. However,
Currently, the method of forming the lens by processing the tip surface of the optical fiber makes the shape of the joint part compact, but requires advanced processing technology and requires many man-hours,
Since it is difficult to form a large number of lenses having uniform characteristics, it has not yet been put to practical use.

[0003]

In spite of such circumstances, the rapid development of the current communication technology and the expansion of the communication network have made it possible to improve the coupling efficiency of the optical fiber. There is a demand for the development of a technique for producing a large number of lenses having uniform characteristics on a surface at low cost.

[0004]

SUMMARY OF THE INVENTION The present invention comprises a step of applying a resist having a uniform thickness on an end face of an optical fiber; a step of transferring a circular pattern to the resist applied on the end face of the optical fiber; Baking an optical fiber having a resist cylindrical shape on the end surface at a high temperature to change the resist into a fluid state and deforming the resist cylindrical shape into a hemispherical shape by surface tension; and The present invention realizes a lens processing method for an end face of an optical fiber, comprising a step of forming a lens by dry-etching an optical fiber on which a pattern is formed. The lens processing method of the end face of the optical fiber of the present invention is such that a lens is formed on the end face of the optical fiber by an etching technique. It has established technology for mass production at low cost.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a view for explaining steps of a method for processing a lens of an optical fiber end face according to the present invention. The optical fiber is as thin as hair (outer diameter 125 μm), and it is difficult to perform additional processing on the end face or side face. In the present invention, a fine pattern is manufactured on the end face of an optical fiber by photolithography, which is the most proven technique for manufacturing a fine pattern. The lens processing method of the optical fiber end face according to the present invention is performed by four steps as shown in FIG. A: a step of applying a resist having a uniform thickness on the end face of the optical fiber; B: a step of transferring a circular pattern onto the resist applied on the end face of the optical fiber; C: a cylindrical shape of the resist is formed on the end face Baking the formed optical fiber at a high temperature for a certain period of time to change the resist into a fluidized state and deform the cylindrical resist into a hemispherical shape by surface tension. D: A hemispherical resist on the end face of the optical fiber Forming the lens by dry-etching the end face of the optical fiber on which the pattern has been formed by etching the optical fiber and the resist together.

Hereinafter, each step shown in FIG. 1 will be described in detail. First, the step A of applying a resist having a uniform thickness on the end face of the optical fiber will be described. FIG. 2 is a view showing an example in which a resist is applied on the end face of the optical fiber. In FIG. 2, 3 is a resist, and 5 is an optical fiber. When photolithography is performed on the end face of an optical fiber, the first problem is the method of forming a resist. Generally, a spin coating method is used as a film forming method on a flat silicon wafer. However, when a film is formed on an object having severe irregularities or a finely-shaped object by the spin coating method, a uniform resist film cannot be obtained due to the surface tension of the resist. When a film is formed on the end face of the optical fiber 5 by the spin coating method, as shown in FIG. 2B, the resist 3 becomes a lump at the tip due to surface tension. For this reason, it is impossible to transfer a pattern to a lump that is rounded at the tip as shown in FIG.

In the present invention, a technique has been developed in which a uniform resist film is formed on the end face of an optical fiber using a method of spraying a resist in the form of a mist, and photolithography is performed.
According to the present invention, in order to form a resist on the end face of the optical fiber, a single-mode optical fiber (outer diameter 125 μm) is cut into a flat face and a small particle diameter is applied to the end face using a two-fluid mixed spray. The resist fine particles having a typical value of 6 μm were deposited several times to form a film. Even on a fine end face as thick as the hair, the outer diameter of the end face of the optical fiber is 1
Since 25 μm is sufficiently larger than the resist particle diameter of 6 μm, a uniform film can be formed. Further, in the present invention, in order to quickly vaporize the solvent of the resist, the optical fiber is sandwiched between aluminum work pieces of 20 × 20 × 8 mm and heated in advance at 145 ° C. During the spraying of the resist, the temperature was set at 120 ° C. on the work fixing table, and spraying was performed while heating. At this time, the set temperature is 120 ° C., but the optical fiber end face is considered to be 60 ° C. or less.

FIG. 2A shows an end face of the optical fiber 5 after film formation. The negative resist 3 is formed uniformly over the entire surface without protruding near the circumference. The film thickness is 1 to 5 μm. FIG. 3 shows the conditions for resist coating in which a resist is uniformly formed on the end face of the optical fiber. Resist is negative "60cp OMR-83"
(Tokyo Oka Kogyo Co., Ltd.)
ORFR-800 (Tokyo Ohka Kogyo Co., Ltd.) "also has a spray pressure of 0.4 MPa and a syringe pressure of 0.1 MPa.
4 Mpa, feed rate 2.0 mm / sec, temperature 120
The coating was performed five times at a temperature of 20 ° C. and a dilution of 20 times.

Next, the step B of transferring a circular pattern onto the resist applied on the end face of the optical fiber will be described. In order to apply photolithography to a concentric pattern on the end face of a thin optical fiber having an outer diameter of 125 μm, alignment between the optical fiber and a mask is important. In the present invention, in order to transfer a circular pattern to the resist applied on the end face of the optical fiber, a mask that can be easily and accurately aligned with the center axis of the end face of the optical fiber was manufactured. The mask was manufactured by electrolytically plating Ni on a SiO ₂ substrate having a pattern to be transferred to an optical fiber.
A thick film was grown and Ni guide holes were created to accommodate the optical fiber. At the bottom of the guide hole, a pattern to be transferred to the optical fiber is formed in advance, and the alignment is automatically performed by inserting the optical fiber into the hole.

FIG. 4 is an explanatory view of a process of manufacturing a pattern transfer mask for transferring a circular pattern onto an end face of an optical fiber coated with a positive resist film. By using this pattern transfer mask, it is possible to easily and accurately align with the central axis of the end face of the optical fiber. In FIG. 4, 1 is a SiO ₂ substrate, 2 is Cr-A
u, 3 is a resist, 4 is Ni, and 5 is an optical fiber.
The manufacturing process of the mask will be described with reference to FIG. Step 1: SiO ₂ for forming a pattern to be transferred to an optical fiber
Cr-Au serving as a plating electrode is sputtered on the substrate. Step 2: Patterning a circle for inserting the optical fiber and a pattern to be drawn on the end face of the optical fiber coated with the positive resist with the resist. Pattern is about 10μm by plating
Since it became narrow, the circle into which the optical fiber was inserted was 136 μm.

Step 3: The Cr-Au film is etched. Step 4: A highly viscous negative resist [450 cp OMR-8] is applied to the SiO ₂ substrate on which the Cr—Au film has been etched.
3 (Tokyo Ohka Kogyo Co., Ltd.)] to the extent that it is swollen by surface tension. The SiO2 substrate on which the positive resist is laid is slightly smoothed at 2000 rpm for 2 to 3 seconds, and baked to form a resist thick film having a thickness of about 20 μm.
Prebaking is performed by placing the wafer on a flat plate at 90 ° C. for 30 minutes so that the resist film does not tilt. The exposure was performed from the reverse side of the surface on which the resist was applied, using a self-alignment technique that exactly matched the pattern initially patterned. The condition is 5 minutes with a 120 mW ultraviolet light source. Step 5: Develop the substrate on which the positive resist thick film is formed. The development is performed for 40 minutes, and the rinsing is performed for 30 minutes. A thick resist pattern having a height of 20 μm can be manufactured. This thick resist pattern prevents lateral Ni growth during Ni plating. After patterning, baking is performed at 90 ° C. for 1 hour.

Step 6: A Ni layer is grown in a Ni sulfamate bath. The plating conditions were a bath temperature of 55 ° C., a current density of about 0.1 mA / mm ² (40 m in 20 mm square).
A). Under these conditions, plating is about 0.08 μm / mi
grow at a rate of n. Step 7: grow Ni layer to about 20 μm. Step 8: The resist is removed with a remover (502A), and the mask is completed. Step 9: Applying a resist to the end face of the optical fiber,
It is inserted into a hole of Ni and exposed to ultraviolet light from the opposite side. Step 10: Develop to obtain a resist pattern accurately aligned with the center of the end face of the optical fiber. FIG. 6 shows the shape of the mask completed by the process shown in FIG. An outer diameter of about 125 μm is applied to a Ni film having a thickness of 20 μm.
A hole of m is manufactured, and a circular pattern of Cr-Au is drawn on the bottom.

FIG. 5 is an explanatory view of a process of manufacturing a pattern transfer mask for transferring a circular pattern onto an end face of an optical fiber coated with a negative resist film. By using this pattern transfer mask, it is possible to easily and accurately align with the central axis of the end face of the optical fiber. In FIG. 5, 1 is a SiO ₂ substrate, 2 is Cr-A
u, 3 is a resist, 4 is Ni, and 5 is an optical fiber.
The manufacturing process of the mask will be described with reference to FIG. Step 1: SiO ₂ for forming a pattern to be transferred to an optical fiber
Cr-Au serving as a plating electrode is sputtered on the substrate. Step 2: The circle for inserting the optical fiber and the pattern to be drawn on the end face of the optical fiber coated with the negative resist are patterned with the resist. Pattern is about 10μm by plating
Since it became narrow, the circle into which the optical fiber was inserted was 136 μm.

Step 3: The Cr-Au film is etched. Step 4: The Cr-Au film on SiO ₂ substrate was etched, viscous negative resist [450cp, OMR-
83 (Tokyo Ohka Kogyo Co., Ltd.)] to the extent of swelling due to surface tension. The SiO ₂ substrate on which the negative resist is laid is somewhat smoothed at 2000 rpm for ₂ to 3 seconds, and baked to form a thick resist film having a thickness of about 20 μm.
Prebaking is performed by placing the wafer on a flat plate at 90 ° C. for 30 minutes so that the resist film does not tilt. The exposure was performed from the reverse side of the surface on which the resist was applied, using a self-alignment technique that exactly matched the pattern initially patterned. The condition is 5 minutes with a 120 mW ultraviolet light source. Step 5: Develop the substrate on which the resist thick film is formed. The development is performed for 40 minutes, and the rinsing is performed for 30 minutes. Height 20μ
m thick resist pattern can be manufactured. This thick resist pattern prevents lateral Ni growth during Ni plating. After patterning, baking is performed at 90 ° C. for 1 hour.

Step 6: A Ni layer is grown in a Ni sulfamate bath. The plating conditions were a bath temperature of 55 ° C., a current density of about 0.1 mA / mm ² (40 m in 20 mm square).
A). Under these conditions, plating is about 0.08 μm / mi
grow at a rate of n. Step 7: grow Ni layer to about 20 μm. Step 8: The resist is removed with a remover (502A), and the mask is completed. Step 9: Applying a resist to the end face of the optical fiber,
It is inserted into a hole of Ni and exposed to ultraviolet light from the opposite side. Step 10: Develop to obtain a resist pattern accurately aligned with the center of the end face of the optical fiber. FIG. 7 shows the shape of the mask completed by the process shown in FIG. An outer diameter of about 125 μm is applied to a Ni film having a thickness of 20 μm.
A hole of m is manufactured, and a hollow circle pattern of Cr-Au is drawn on the bottom.

The masks manufactured by any of the processes shown in FIGS. 4 and 5 also have a circle for inserting an optical fiber and a pattern to be drawn on the end face of the optical fiber at one time when the Cr-Au film is patterned. Since the pattern is transferred by patterning, high precision of alignment with the fiber end face is possible with high precision of the pattern generator for producing this mask. Next, the step C of baking the optical fiber having the resist cylindrical shape formed on the end face at a high temperature to change the resist into a fluid state and deforming the resist cylindrical shape into a hemispherical shape by surface tension will be described. FIG. 8 is a view for explaining a processing method for deforming the cylindrical shape of the resist into a hemispherical shape. In FIG. 8, 3 indicates a resist, and 5 indicates an optical fiber. FIG. 8A shows an optical fiber in which a resist column is formed by using the mask having the connector guide on the end face of the optical fiber by the process described in FIG. 4 or FIG. The thickness of the resist on the end face of the optical fiber was made somewhat thicker by lowering the feed rate, increasing the number of times of coating, and increasing the flow rate of the resist so that a sufficient curvature could be obtained after baking.

FIG. 9 shows resist coating conditions for forming a negative resist to obtain a hemispherical shape on the end face of the optical fiber. The spray pressure is 0.4 MPa, the syringe pressure is 0.2 MPa, the feed rate is 1.5 mm / sec, and the temperature is 12 MPa.
8 to 12 μm by coating 6 times at 0 ° C., 20 times dilution
m can be formed. The resist pattern thus formed is baked at a high temperature of 155 ° C. for one hour, as shown in FIG. 8A. When exposed to high temperatures, the negative resist on the end face of the optical fiber undergoes polymerization, shrinkage, and drooping.
At 50 ° C., the flow at the edge begins. At this time, surface tension acts on the resist, and the cylindrical resist is rounded and deformed. It was confirmed from experiments that the material deformed into a hemispherical shape at around 155 ° C. The resist pattern after baking at 155 ° C. for 1 hour is shown in FIG. Negative cysts are formed hemispherically on the end face. The diameter on the end face is 60 μm and the height of the membrane is 14 μm, but this dimension is adjustable.

Next, a step D of forming a lens by dry-etching the optical fiber having a resist pattern deformed into a hemispherical shape on the end face of the optical fiber by etching.
Will be described. FIG. 10 is an explanatory view of a method of forming a lens by dry-etching an optical fiber end surface in which a hemispherically deformed resist pattern is formed on the optical fiber end surface shown in FIG. 8B. FIG.
As shown in FIG. 0 (a), an optical fiber having a hemispherically deformed resist pattern formed on the end face of the optical fiber shown in FIG. 8 (b) is connected to a FAB (Fast Atom B).
(eam = high-speed atomic beam) By using an etching apparatus, the end face of the optical fiber is processed perpendicularly without the influence of side etching, and the shape of the resist pattern is transferred to the optical fiber.

Etching is performed until the resist on the end face of the optical fiber is completely removed by FAB. The etching of the FAB is anisotropic dry etching, which can vertically etch the resist and the optical fiber (SiO ₂ ). F
In the AB etching, the resist is etched at a rate about 1.4 times that of the optical fiber (SiO ₂ ), and the semi-spherical resist pattern is transferred to the optical fiber while keeping the shape substantially. In this case, the curvature of the processed lens surface is lower than that of the hemispherical negative resist pattern. As shown in FIG. 10B, the etching is completed after all the resist is etched. The lens processing method of the end face of the optical fiber of the present invention is such that a lens is formed on the end face of the optical fiber by a photolithography and etching technique. It becomes possible to produce a large number of lenses at low cost.

[0020]

As is apparent from the above description, the method for processing the lens of the end face of the optical fiber according to the present invention comprises the steps of applying a resist having a uniform thickness on the end face of the optical fiber, Step of transferring a circular pattern onto the resist that has been formed, and baking at a high temperature the optical fiber with the resist cylindrical shape formed on the end surface, changing the resist into a fluid state and surface resist forming the resist cylindrical shape Forming a lens on the end face of the optical fiber by a step of deforming the end face of the optical fiber into a hemispherical form, and a step of dry-etching the end face of the optical fiber on which the resist pattern deformed hemispherically on the end face of the optical fiber is formed. It was made. The lens processing method of the end face of the optical fiber of the present invention is such that a lens is formed on the end face of the optical fiber by a photolithography and etching technique. This makes it possible to produce lenses in large quantities at low cost, which will greatly contribute to the development of optical communication technology in the future.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining steps of a method for processing a lens of an optical fiber end face according to the present invention.

FIG. 2 is a diagram showing an example in which a resist is applied on an end face of an optical fiber.

FIG. 3 is an example showing conditions of resist coating in which a negative registrat is uniformly formed on an end face of an optical fiber using a two-fluid mixed spray.

FIG. 4 is an explanatory diagram of a process of manufacturing a transfer mask for easily and accurately aligning the center axis of an optical fiber end face coated with a positive resist.

FIG. 5 is an explanatory diagram of a process of manufacturing a transfer mask for easily and accurately aligning the center axis of an optical fiber end face coated with a negative resist.

FIG. 6 shows the shape of a mask completed by the process shown in FIG.

7 shows the shape of a mask completed by the process shown in FIG.

FIG. 8 is a view for explaining a processing method for deforming the cylindrical shape of the resist into a hemisphere.

FIG. 9 shows the conditions of a resist cloth for forming a negative resist to obtain a hemispherical shape on the end face of the optical fiber.

FIG. 10 is an explanatory view of a method of dry-etching an optical fiber end face having a hemispherically deformed resist turn formed on the optical fiber end face shown in FIG. 8B to form a lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... SiO2 substrate, 2 ... Cr-Au, 3 ... Resist, 4 ... Ni, 5 ... Optical fiber

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiro Hane 9-21-5 Nakayama, Nakayama, Aoba-ku, Sendai, Miyagi Prefecture (72) Inventor Noriyuki Tanaka 1382-1, Shiono Oto, Oto-gun, Tobu-cho, Nagano Prefecture Mimaki Electronics In Parts Co., Ltd. (72) Inventor Koichi Oda 1382-1, Shino Otsu, Tobu-cho, Oguni-gun, Nagano Prefecture F-term in Mimaki Electronic Components Co., Ltd.

Claims (6)

[Claims] A step of applying a resist having a uniform thickness on the end face of the optical fiber; a step of transferring a circular pattern to the resist applied on the end face of the optical fiber to form a cylindrical shape; Baking the optical fiber with the cylindrical shape at a high temperature to change the resist into a fluid state and deform the resist cylindrical shape into a hemispherical shape by surface tension, and forming a hemispherical resist pattern Forming a lens by dry etching the optical fiber end face and transferring the resist shape to the optical fiber, and a lens processing method for the optical fiber end face. A step of applying a resist film having a uniform thickness by depositing resist fine particles smaller than the diameter of the optical fiber on the end face of the optical fiber in several steps and forming a film; A step of transferring a circular pattern using a pattern transfer mask to the resist applied on the end face to form a cylindrical shape, and baking the optical fiber having the resist cylindrical shape formed on the end face at a high temperature, thereby forming a resist. Changing the resist into a fluid state and deforming the resist cylindrical shape into a hemispherical shape by surface tension, and a process of dry-etching the end face of the optical fiber on which the hemispherically deformed resist pattern is formed to form a lens. Lens processing method of the optical fiber end face. 3. A step of applying a resist film having a uniform thickness by depositing and depositing resist fine particles smaller than the diameter of the optical fiber several times on the end face of the optical fiber, and forming the resist film on the end face of the optical fiber. Using a pattern transfer mask to transfer a circular pattern to the resist applied thereon to form a cylindrical shape, and baking the optical fiber having the resist cylindrical shape formed on the end face at a temperature of 155 ° C. for about 1 hour. By changing the resist to a fluid state, the cylindrical shape of the resist is deformed into a hemisphere by surface tension, and the end face of the optical fiber where the hemispherically deformed resist pattern is formed on the end face of the optical fiber is dry-etched. Forming a lens by performing the method, and a lens processing method for the end face of the optical fiber. 4. A step of applying a resist film having a uniform thickness by depositing and depositing resist fine particles smaller than the diameter of the optical fiber several times on the end face of the optical fiber to form a film. Using a pattern transfer mask to transfer a circular pattern to the resist applied thereon to form a cylindrical shape, and baking the optical fiber having the resist cylindrical shape formed on the end face at a temperature of 155 ° C. for about 1 hour. In this process, the resist is changed to a fluid state and the resist is deformed into a hemispherical shape by surface tension.The optical fiber end face with the hemispherically deformed resist pattern formed on the end face of the optical fiber is subjected to high-speed atomization. Forming a lens by etching with a dry etching apparatus such as a line (FAB) etching apparatus; Engineering method. 5. The method according to claim 2, wherein the pattern for transferring the transfer mask to the optical fiber on the glass substrate and the pattern for the guide hole of the optical fiber are simultaneously transferred by photolithography. Using a transfer mask having a structure having a transfer pattern for an optical fiber at the bottom of the guide hole, which is manufactured by forming a guide hole of the optical fiber by growing a metal film by a plating process on the pattern of the guide hole. A method of transferring a pattern to an end face of an optical fiber, whereby a transfer pattern is accurately aligned with the center of the end face of the optical fiber. 6. The photomask according to claim 2, wherein a pattern for transferring the transfer mask to an optical fiber after sputtering Cr-Au on a glass substrate and a pattern for a guide hole of the optical fiber are formed by photolithography. Simultaneously transfer, C
After forming a resist film on a glass substrate etched with r-Au and performing exposure and development by a self-alignment method,
A Cr-Au is used as an electrode on a guide hole pattern on a glass substrate, and a metal film is grown by a plating process to form an optical fiber guide hole. A pattern transfer method to an optical fiber end face, wherein a transfer pattern having a structure having an Au optical fiber transfer pattern is used to accurately align the transfer pattern with the center of the optical fiber end face.