JPH06138341A - Optical coupler and its production - Google Patents

Abstract

PURPOSE:To provide the optical coupler which does not require axis alignment and can be easily produced and the process for production of this optical coupler. CONSTITUTION:This optical coupler 3 has a flat plate microlens 4 which is formed with >=1 microlenses 12 on the front end face 11a of a transparent substrate 11 and is adjusted in thickness so as to form the focuses P of the microlenses 4 at the rear end face 11b and a silicon guide plate 5 which is adhered to the rear end face 11b thereof. This silicon guide plate 5 has guide holes 16 formed in such a manner that optical fibers 6 can be inserted and adhered therein. These guide holes 16 are formed in the positions where the focuses of the microlenses 12 are included within the cores of the optical fibers 6 inserted therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupler used for causing divergent light from a light source such as a laser diode (LD) and a light emitting diode (LED) to enter an optical fiber with high efficiency, and a manufacturing method thereof.

[0002]

2. Description of the Related Art The field of application of optical communication is optical LAN, CAT
V, and further spread to transmission systems such as subscriber systems of public communication lines. In constructing such a transmission system, an optical coupler that couples the light source and the optical fiber with high efficiency is essential. Conventionally, as a method for coupling a light source and an optical fiber in this type of optical coupler, there are a coupling method by processing an end face of the optical fiber, a single lens coupling method, a two lens coupling method, and the like.

As the coupling method by processing the end faces of the optical fibers, for example, the tip of the optical fiber is processed into a spherical shape as shown in FIG. 4 (a), and the tip is processed into a tapered shape as shown in FIG. 4 (b). Use the one that you made. In these coupling methods, since the light beam from the light source LD is coupled in a place where it does not spread much from the optical fiber core, the coupling is performed with high efficiency. However, noise is generated due to reflection of light from the fiber, and the position is actually increased. It is difficult to align them, and there are problems such as severe tolerance for misalignment.

As a single lens coupling method, there is a method of using a spherical lens shown in FIG. 5 (a) or a distributed index lens shown in FIG. 5 (b). Compared with the method of processing the end face of the optical fiber, these single-lens coupling methods relax the axial deviation tolerance, but the light that spreads outside the acceptance angle of the lens is lost and the coupling efficiency is low.

As the two-lens coupling method, there are a method of using two spherical lenses shown in FIG. 6A, a method of using a spherical lens and a distributed index rod lens shown in FIG. 6B, and the like. Although these methods allow the axial misalignment tolerance to be relaxed most, they have a large number of parts, are not easy to manufacture, and are not suitable for mass production.

All of the above are related to the method of coupling the light source LD and one optical fiber. In order to simultaneously couple one light source LD and a plurality of optical fiber arrays, the above problems are further magnified. To be done.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide an optical coupler which does not require axis alignment and is easy to manufacture, and a manufacturing method thereof.

[0008]

In the optical coupler of the present invention, one or more microlenses are formed on the front end surface of the transparent substrate, and the thickness is adjusted so that the focal points of the microlenses are formed on the rear end surface. And a silicon guide plate adhered to the rear end surface thereof. The silicon guide plate has a guide hole formed so that an optical fiber can be inserted and adhered, and the guide hole is the minute lens. Is formed at a position included in the core of the inserted optical fiber.

In the method of manufacturing the optical coupler, the thickness of the flat plate microlens having one or more microlenses formed on the front end face of the transparent substrate is adjusted so that the focal point of the microlenses is formed on the rear end face thereof. A step of adjusting, a step of manufacturing a single crystal silicon guide plate having a guide hole to be laminated on the flat plate microlens by anisotropic chemical etching, and a center of the guide hole for the silicon guide plate on the rear end face of the flat plate microlens. And a step of adhering so as to substantially match the focal point of the minute lens.

[0010]

By simply inserting the tip of the optical fiber into the guide hole provided in the silicon guide plate and adhering it, when parallel light is incident from the front of the flat microlens, the light is incident on the core of the optical fiber. The light from the light source can be transmitted to the optical fiber with high efficiency.

If the flat microlens and the silicon guide plate are separately adjusted and manufactured with high precision, and both are aligned and bonded, the integration can be facilitated.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a usage state of the optical coupler of the present invention.

In FIG. 1, 1 is a semiconductor laser as a light source, 2 is a collimating lens for distributing the light emitted from the semiconductor laser 1, 3 is an optical coupler comprising a flat plate microlens 4 and a silicon guide 5, and 6 Is an optical fiber.

One or more flat microlenses 4 are provided on the front end surface 11a of the transparent substrate 11 (4 in the illustrated example, for simplicity).
The number of microlenses 12 is illustrated). The thickness T of the flat plate microlens 4 is such that the focal point P of the microlens 12 is formed on the rear end surface 11b of the transparent substrate 11. Such a flat plate microlens 4 can be manufactured by a planar technique. That is, an ion permeation preventive mask having a pattern opening is adhered to the minute lenses 12 of the transparent substrate 11, and the surface on which the mask is adhered is melted containing ions such as thallium and cesium that greatly contribute to the increase in the refractive index. Immerse it in salt,
By natural or ion exchange, the microlenses 12 are formed so that the refractive index gradually decreases toward the outside toward that of the transparent substrate. A perspective view of the flat plate microlens 4 thus manufactured is shown in FIG. 2, and the hemispherical portion 12a is a boundary between a portion having a different refractive index and the transparent substrate.

In FIG. 2, the silicon guide 5 is a silicon single crystal plate 15 having a guide hole 16 in the shape of a truncated quadrangular pyramid. The length of the side of the quadrangle of the quadrangular pyramid head is approximately equal to the outer diameter of the optical fiber 6 to be inserted. And
The guide holes 16 are arranged so that the central axis A of the minute lens 12 coincides with the central axis of the guide hole 16. Then, as shown in FIG. 1, when the optical fiber 6 is inserted into the guide hole 16 with the rear end surface 11b of the flat plate microlens 4 and the silicon single crystal plate 15 adhered to each other, the focal point P of the microlens 12 is Is the position included in the core of the optical fiber 6. Further, the optical fiber 6 can be fixed by filling the inclined space 16a between the optical fiber 6 and the guide hole 16 with an appropriate adhesive.

Such a silicon guide 5 is manufactured by anisotropic chemical etching, and its process will be described with reference to FIG. In FIG. 3A, 17 is a SiO ₂ thermal oxide film, which is formed by steam oxidation, pressure oxidation, or the like. In the same (b), a photoresist film 18 is applied on the thermal oxide film 17 on one surface of the silicon single crystal plate 15. In the same (c), a predetermined mask window 19 is formed in the photoresist film 18. In the same (d), the mask window 19
The underlying thermal oxide film 17 is etched with buffered hydrofluoric acid.
In (e), the silicon single crystal plate 15 is anisotropically etched in a 90 ° direction with EPW (ethylenediaminepyrocatechol aqueous solution) to form a truncated square pyramid-shaped guide hole. At (f), the thermal oxide film 17 is removed by buffered hydrofluoric acid to obtain the silicon guide 5 having a desired shape.

Then, as shown in FIG. 2, the central axes A are aligned with each other and the flat plate microlenses 4 and the silicon guides 5 are adhered to each other to obtain the optical coupler 3 of FIG. That is, as the manufacturing process, a step of manufacturing the flat plate microlens 4 having a predetermined size by itself, a step of manufacturing the silicon guide 5 having a predetermined size by itself, and the silicon guide plate 5 on the rear end surface 11b of the flat plate microlens 4 are performed. The center of the guide hole 16 is the minute lens 1
The step of adhering so as to almost coincide with the focal point of 2. If the flat microlens 4 is manufactured with high accuracy and the silicon guide plate 5 is manufactured with high accuracy, a plurality of optical fibers can be simultaneously coupled by simply aligning the two.
It is possible to easily integrate a multimode optical fiber array.

Next, the operation of the optical coupler 3 thus manufactured will be described with reference to FIG. The emitted light from the semiconductor laser 1 is distributed to each minute lens 12 by the collimator lens 2. Then, the light is focused on the focal point P by each microlens 12. Since the focal point P is located so as to be included in the core of the optical fiber 6 that has been inserted, the condensed light is incident on the optical fiber 6. Due to the coincidence between the center axis of the optical fiber 6 and the position of the focal point P, the coupling efficiency between the semiconductor laser 1 and the multimode optical fiber array is, for example, 52.3%, which is 5
A value close to 6.4% could be obtained.

[0019]

According to the optical coupler of the present invention, one or more microlenses are formed on the front end face of the transparent substrate, and the thickness is adjusted so that the focal points of the microlenses are formed on the rear end face. A microlens and a silicon guide plate adhered to the rear end surface thereof are provided, and the silicon guide plate has a guide hole formed so that an optical fiber can be inserted thereinto and adhered thereto, and the focus of the microlens is inserted into the guide hole. It is formed at a position included in the core of the fitted optical fiber, and the light from the light source is transmitted to the optical fiber with high efficiency simply by inserting and attaching the tip of the optical fiber into the guide hole. It is possible,
No need for troublesome axis alignment. Therefore, they can be easily integrated and large-capacity parallel optical transmission becomes possible.

In this method of manufacturing the optical coupler, the thickness of the flat plate microlens having one or more microlenses formed on the front end face of the transparent substrate is adjusted so that the focal point of the microlenses is formed on the rear end face. A step of adjusting, a step of manufacturing a single crystal silicon guide plate having a guide hole to be laminated on the flat plate microlens by anisotropic chemical etching, and a center of the guide hole for the silicon guide plate on the rear end face of the flat plate microlens. And a step of adhering so as to substantially match the focal point of the minute lens,
Since the flat microlens and the silicon guide plate are separately adjusted and manufactured with high precision, and both are aligned and bonded, the manufacturing is easy.

[Brief description of drawings]

FIG. 1 is a diagram showing a usage state of an optical coupler of the present invention.

FIG. 2 is an exploded perspective view of a flat plate microlens and a silicon guide plate that form an optical coupler.

FIG. 3 is a perspective view showing a manufacturing process of a silicon guide plate.

FIG. 4 is a diagram showing a usage state of a conventional optical coupler.

FIG. 5 is a diagram showing a usage state of a conventional optical coupler.

FIG. 6 is a diagram showing a usage state of a conventional optical coupler.

[Explanation of symbols]

 3 Optical coupler 4 Flat plate microlens 5 Silicon guide plate 6 Optical fiber 12 Microlens 16 Guide hole

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[Procedure amendment]

[Submission date] April 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

Such a silicon guide 5 is manufactured by anisotropic chemical etching, and its process will be described with reference to FIG. In FIG. 3A, 17 is a SiO ₂ thermal oxide film, which is formed by steam oxidation, pressure oxidation, or the like.
In the same (b), a photoresist film 18 is applied on the thermal oxide film 17 on one surface of the silicon single crystal plate 15. In the same (c), a predetermined mask window 19 is formed in the photoresist film 18. In the same (d), the mask window 19
The underlying thermal oxide film 17 is etched with buffered hydrofluoric acid.
In the same (e), the (100) silicon single crystal plate 15 is made of EPW (ethylenediaminepyrocatechol aqueous solution).
Is Rikoto isotropic etching, truncated pyramidal guide hole is formed. At (f), the thermal oxide film 17 is removed by buffered hydrofluoric acid to obtain the silicon guide 5 having a desired shape.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hidehiro Konishi 2-3-1, Iwata-cho, Higashi-Osaka-shi, Osaka Prefecture Tatsuta Electric Wire Co., Ltd. (72) Atsushi Akiba 3-chome, Dosho-machi, Chuo-ku, Osaka-shi, Osaka 5-11 No. 11 Nippon Sheet Glass Co., Ltd. (72) Kenichi Iga 4259 Nagatsuda-cho, Midori-ku, Yokohama-shi, Kanagawa Prefectural Institute of Precision Engineering, Tokyo Institute of Technology (72) Futao Koyama 4259 Nagatsuda-cho, Midori-ku, Yokohama, Kanagawa Institute of Precision Engineering, Institute of Technology

Claims (2)

[Claims] 1. A flat plate microlens having one or more microlenses formed on a front end surface of a transparent substrate and having a thickness adjusted so that a focal point of the microlenses is formed on a rear end surface thereof.
A silicon guide plate adhered to the rear end surface of the optical fiber, wherein the silicon guide plate has a guide hole formed so that the optical fiber can be inserted and adhered, and the guide hole is an optical fiber into which the focal point of the microlens is inserted. An optical coupler formed at a position included in the core of the optical coupler. 2. A step of adjusting the thickness of a flat plate microlens having one or more microlenses formed on the front end face of a transparent substrate so that the focal point of the microlenses is formed on the rear end face of the flat plate microlens. And a step of manufacturing a single crystal silicon guide plate having a guide hole to be stacked on the back surface of the flat microlens, the center of the guide hole being substantially coincident with the focal point of the microlens. A method of manufacturing an optical coupler, comprising the steps of: