JPH10111426A - Optical fiber coupler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable optical axis alignment of high accuracy and to simplify connection work by forming an optical fiber introducing hole tapered so that the front end of an optical fiber to be inserted is retained to a substrate. SOLUTION: The optical fiber introducing hole 2 tapered so that the front end of the optical fiber to be inserted is retained to the front end is formed by dry etching at the silicon substrate 1 or silicon laminated substrate from its one surface or both surfaces. This coupler is thus constituted in such a manner that the optical axis alignment may be executed simply by inserting the optical fiber into this introducing hole 2. According to this coupler, the front end of the optical fiber is detained by the tapered part and the optical axis alignment with high accuracy is automatically executed when the optical fiber is inserted into the introducing hole 2. In such a case, the introducing hole 2 is formed by manufacturing a mask at the time of dry, etc., with a resist and is formed by a dry etching device capable of controlling a side wall angle 3. The mask is thereafter removed and the substrate is subjected to dicing, thereby, connector parts having one piece each of the introducing hole 2 are completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coupler for connecting optical fibers, and more particularly, to an improvement in optical axis alignment accuracy in optical fiber connection and simplification of connection.

[0002]

2. Description of the Related Art Conventionally, in connecting optical fibers, an optical axis alignment method using a V-shaped groove (V groove) as shown in FIG. 6 has been frequently used. 6A is a side view, and FIG. 6B is a cross-sectional view. Reference numeral 10 denotes a support member having a V-shaped groove, and reference numerals 11 and 12 denote optical fibers. The optical fibers 12 and 13 have the same outer diameter, and if they are placed in the V-groove, the optical axes of both naturally coincide.

[0003]

However, in such a system, in order to improve the optical axis alignment accuracy, it is necessary to improve the manufacturing accuracy of the V-groove and maintain the optimal optical axis alignment when fixing the fiber. However, there is a limit to the reduction of the optical axis shift when the manufacturing accuracy is fixed. For example, in a single mode optical fiber, since the core diameter is about 10 μm, a severe optical axis shift amount of 1 μm or less is required, and there is a problem in manufacturing the V-groove with an accuracy of 1 μm or less.

In order to align the optical axes, the length (length in the longitudinal direction) of the V-groove holding the optical fiber is, for example, 1
About 0 mm is necessary, but this causes a problem that the size of the connector becomes large.

[0005] In the direct fusion splicing of optical fibers by arc discharge or the like as shown in FIG. 7, since the positioning of the fibers is performed by a magnifying glass or a microscope, it is difficult to improve the accuracy, and scattering of the connection portion is difficult. There are problems such as loss of light due to light and variations in loss due to differences in the skills of connection workers.

In view of the foregoing, an object of the present invention is to form a hole for introducing an optical fiber from one or both surfaces of a substrate such as silicon (Si) and insert an optical fiber into this hole to achieve high precision. An object of the present invention is to realize an optical fiber coupler which achieves easy optical axis alignment and connection work.

[0007]

According to the present invention, in order to achieve the above object, one side or both sides of a silicon substrate or a silicon-based laminated substrate is dry-etched.
At least at the end, an optical fiber introduction hole tapered so that the tip of the optical fiber to be inserted is locked is formed, and the optical axis can be aligned simply by inserting the optical fiber into this introduction hole. It is characterized by the following.

[0008]

A tapered optical fiber introduction hole is formed in a silicon substrate or a silicon-based laminated substrate. When the optical fiber is inserted into the introduction hole, the tip of the optical fiber is locked at the tapered portion, and the optical axis can be automatically aligned with high accuracy regardless of the skill of the operator.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the optical fiber coupler according to the present invention.

In FIG. 1, reference numeral 1 denotes a silicon substrate, and 2 denotes an introduction hole. The introduction hole 2 is formed by dry etching with a controlled side wall angle. The side wall angle (θ) 3 is deformed in the figure, but is actually several degrees or less. Also, FIG. 2B shows a case where processing is performed from one side, and FIG. 3C shows a case where processing is performed from both sides. The introduction hole processed from one side assumes the connection between the optical fiber and the light emitting element or light receiving element,
The introduction holes processed from both sides are assumed to connect optical fibers.

FIG. 2 shows an example of a process for producing an introduction hole from one side. In a photolithography process generally used in a semiconductor process, as shown in FIG. 2A, a mask for dry etching is made of a resist, and an introduction hole is formed by a dry etching apparatus capable of controlling a side wall angle (FIG. 2B). , (C)). Thereafter, the mask is removed as shown in FIG. 2 (c), and then dicing is performed as shown in FIG. 2 (e) to complete a connector part having one introduction hole at a time.

When a silicon substrate having a diameter of 4 inches is used, assuming a square connector part of 4 mm square, 1
Approximately 300 wafers can be manufactured from a single wafer, and processing accuracy on the order of sub-μm can be obtained because a semiconductor process is used.

[0013] As a method of forming the introduction holes, the silicon substrate is cooled to a low temperature to enhance the anisotropy of the processing and a deep hole having a high aspect ratio is formed by low-temperature RIE or induction plasma (helicon plasma). It is possible to use dry etching such as a device for improving the anisotropy. Wet etching involves over-etching under the mask, and there is no flexibility in controlling the anisotropy of the processing, and it is difficult to form a deep hole with a high aspect ratio.

The processing of the introduction hole 2 of the optical fiber is performed by a method of forming a taper uniformly from the upper part to the lower part as shown in FIG. 3 (a), and as shown in FIGS. 3 (b) and 3 (c). There is a method of forming a taper for optical axis alignment only at the tip without a taper for holding the optical fiber.

The outer diameter of a general optical fiber is 125 μm, and an introduction hole mask is designed at 125 μm + α (α is a significant size) to form a hole of 125 μm + α or 12 μm + α.
A hole of 125 μm + α is formed by overexposure in a photolithography process using a 5 μm mask. The shape of the taper at the tip forms a hole with no curvature (FIG. 3B) or with a curvature (FIG. 3C) depending on the control of the substrate temperature and the plasma intensity.

The optical axis error of the optical fiber is theoretically zero if the introduction hole and the center of the core of the optical fiber coincide with each other, and the angular error is also zero. However, in connection between optical fibers, a loss due to the gap of the optical fiber occurs,
The air gap needs to be set small (μm order). This can be realized by shortening the tapered portion of the introduction hole.

It is to be noted that the above description of the present invention has been presented by way of illustration and example only, and of particular preferred embodiments. Thus, it will be apparent to one skilled in the art that the present invention may be modified or modified in many ways without departing from its essentials.

For example, the shape in which a through hole is formed in a silicon substrate by dry etching has already been described. However, in order to improve the production yield due to the tapered shape of the hole and the stopper layer at the end of etching, as shown in FIG. It is preferable to use a bonded wafer substrate of Si, SiO ₂ and Si.

As shown in FIG. 5, when the refractive index is increased by slightly doping the center of SiO ₂ of the stopper layer 4 with Ge or the like, the function of a simple microlens is achieved, so that the loss due to the gap is reduced. Can be reduced. There is also a method of combining a light emitting element and a light receiving element with a similar structure.

[0020]

As described above, according to the present invention, the following effects can be obtained. (1) Since the processing accuracy can be improved as compared with the conventional V-groove method, connection loss due to optical axis shift can be reduced.
In connection, the center of the optical fiber and the center of the introduction hole are easily matched by inserting the optical fiber into the introduction hole, minimizing optical axis deviation and angle deviation, and ensuring simplicity during connection. In addition, the variation in connection loss caused by the operator can be reduced. (2) Since it can be processed by a conventional semiconductor processing apparatus using a Si-based material, it can be manufactured in a manner compatible with the manufacturing process of the light-emitting element and the light-receiving element, and can be incorporated into each element.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an optical fiber coupler according to the present invention.

FIG. 2 is a diagram showing a manufacturing process.

FIG. 3 is a detailed view of an introduction hole.

FIG. 4 is a configuration diagram of another embodiment of the present invention.

FIG. 5 is a configuration diagram of still another embodiment of the present invention.

FIG. 6 is a diagram showing an example of a conventional coupler having a V-groove structure.

FIG. 7 is a view for explaining an optical fiber connection by a conventional fusion splicing method.

[Explanation of symbols]

 Reference Signs List 1 Si substrate 2 Through hole 3 Side wall angle 4 Stopper layer

Claims (1)

[Claims] An optical fiber introduction hole tapered so that the tip of an optical fiber is locked is formed by dry etching from one or both surfaces of a silicon substrate or a silicon-based laminated substrate, and the optical fiber is inserted into the introduction hole. An optical fiber coupler configured to allow optical axis alignment when inserted.