JPH1054917A - Optical waveguide module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a clad mode generated within a laser diode (LD)-optical waveguide coupling part and an optical waveguide element from leakage into optical fibers facing this LD by forming grooves of the direction crossing the optical waveguides on both sides of the optical waveguides and applying light shieldable films on the inside walls of these grooves. SOLUTION: The light of a wavelength (λ2) of 1.3μm emitted from the LD is guided through an LD port 19, a branching part 12b and a filter 13 to a common port 14. At this time, the clad mode is generated in the coupling part of the LD and the optical waveguides 11, the branching part 12a and the branching part 12b of the yshaped waveguides. This clad mode is confined and propagated between a substrate 10 and the air layer in the upper part of the clad layer 21, is reflected and absorbed by the grooves 28 formed with the metallic films 30 and is shut off by a groove side bench 29. The leaking of the clad mode from the LD into the optical fibers 18 of the reflection port 17 is, therefore, suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide module.

[0002]

2. Description of the Related Art In order to spread optical fiber communications, especially optical subscriber systems, it is important to reduce the size and cost of optical waveguide modules. To solve this problem, an optical waveguide type module in which an optical waveguide is formed on a Si substrate and a chip-level LD (laser diode) and PD (photodiode) are surface-mounted has been studied (SiO ₂ / S).
LD chip surface mounting using i-hybrid optical integration platform; see C-287, 1994 IEICE Spring Conference).

FIG. 4 is a schematic view of a platform structure of an optical waveguide module in which an LD is surface-mounted on a substrate, and FIG. 5 is an external perspective view showing a conventional example of the optical waveguide module having the platform structure shown in FIG. It is.

[0004] The platform structure of the optical waveguide module shown in FIG. 4 is a combination of a buried quartz optical waveguide comprising a core 1, a buffer layer 2 and a cladding layer 3 and a Si substrate 4 having a terrace structure. The terrace 5 made of a Si bench supports the semiconductor element (LD) 6 and has a function as a heat sink.

The optical waveguide type module transmits a video signal (wavelength λ1) and a communication signal (wavelength λ2: λ2 ≠ λ1) through light having a wavelength λ2 inserted into the optical waveguide and reflects light having a wavelength λ1. A method of multiplexing / demultiplexing with a filter having the following characteristics is being studied, and a method shown in FIG. 5 is used.

The optical waveguide module shown in FIG.
A single-mode optical waveguide 11 of y-shaped quartz glass is formed on a substrate 10 made of, and light having a wavelength of λ2 is transmitted through a y-shaped branch portion 12a, and light having a wavelength of λ1 (λ1 ≠ λ2) is transmitted. Is provided with a filter 13 that reflects light.

Next, the light propagating through such an optical waveguide module will be described in order.

When light of wavelength λ1 and light of wavelength λ2 enter the common port 14 from the optical fiber 15, the light of wavelength λ2 passes through the core of the optical waveguide 11, passes through the filter 13, and
The PD 12 is branched at a desired distribution ratio at the branch unit 12b, and the PD port 1
6 to PD. The light of wavelength λ1 incident on the common port 14 is reflected by the filter 13 through the core of the optical waveguide 11, guided to the reflection port 17, and incident on the optical fiber 18.

On the other hand, when the light having the wavelength λ2 is emitted from the LD, the light having the wavelength λ2 is transmitted to the common port 14 through the LD port 19, the branch portion 12b and the filter 13.

Reference numeral 20 denotes a buffer layer, 21 denotes a cladding layer, 22 denotes a PD electrode as a metal film for extracting a signal current from the PD, 23 denotes an oblique cut, 24 denotes an airtight lid, and 27 denotes an LD. An LD electrode as a metal film for supplying a current is shown.

Next, the manufacturing process of such an optical waveguide module will be described.

FIG. 6 is a manufacturing process diagram of the optical waveguide module shown in FIG.

First, a substrate 10 made of Si is prepared (FIG. 6A).

By etching the substrate 10, the LD
Then, an element-side bench 25 is formed at a position where the PD is mounted (FIG. 6B).

A buffer layer 20 is formed on the substrate 10 on which the element-side bench 25 is formed so that the element-side bench 25 is exposed, and a core 26 and a cladding layer 21 are formed on the buffer layer 20 and the element-side bench 25. By forming the optical waveguide, a silica glass optical waveguide 11 is formed (FIG. 6).
(C)).

The element side bench 25 is exposed by etching the cladding layer 21 (FIG. 6D).

The PD electrode 2 is placed on the exposed element-side bench 25.
2 and the LD electrode 27 and the cladding layer 21.
Also, a PD electrode 22 and an LD electrode 27 are formed (FIG. 6E).

Thereafter, an optical waveguide type module is formed through a mounting process such as an arrangement process of the filter 13 and an alignment process of the LD and the PD.

[0019]

However, the substrate 1
In the silica-based optical waveguide formed on the substrate 0, the radiation mode of light having a wavelength of λ2 generated in the LD-optical waveguide coupling portion and the optical waveguide device is confined by the air layer on the substrate 10 and the cladding layer 21. As a result, it leaks into the optical fiber 18 connected to the reflection port 17 facing the LD, and in the current communication system, there is a problem that the quality of the optical communication is adversely affected.

Therefore, an object of the present invention is to solve the above-mentioned problem and provide an optical waveguide module in which a clad mode generated in an LD-optical waveguide coupling portion and an optical waveguide element does not leak into an optical fiber facing the LD. To provide.

[0021]

In order to achieve the above object, the present invention provides an optical waveguide in which an optical waveguide for connecting to an optical fiber is formed on a substrate, and a light emitting element and a light receiving element are connected to the optical waveguide. In the mold module, grooves are formed on both sides of the optical waveguide in a direction crossing the optical waveguide, and a light-shielding film is formed on the inner wall of the groove.

In addition to the above-described structure, the present invention provides an element-side bench for mounting a laser diode and a photodiode on a substrate while using Si for a substrate, using a laser diode for a light emitting element, using a photodiode for a light receiving element. It is preferable to form a groove bench at a position where the groove is formed.

In addition to the above structure, the present invention provides a metal film for supplying a current to a laser diode and extracting a signal current from a photodiode on an element-side bench and a cladding layer, and a metal film on a light-shielding film. It is preferable to use

In the present invention, in addition to the above structure, it is preferable that the groove is formed so that its depth reaches the substrate.

In addition to the above configuration, the present invention provides a filter in which an optical waveguide is formed as a y-shaped waveguide, and a light having a wavelength of λ2 is transmitted to a y-shaped branch portion and a light of a wavelength λ1 different from the wavelength λ2 is reflected. And it is preferable to form at least one groove between the end face of the optical waveguide on the emission side of the light reflected by the filter and the branch portion.

According to the above configuration, even if the radiation mode of light of wavelength λ2 generated in the LD-optical waveguide coupling portion and the optical waveguide element is confined by the Si substrate and the air layer above the cladding layer, the mode becomes Since the light is reflected or absorbed by the groove provided with the light-shielding film, the cladding mode is prevented from leaking into the optical fiber facing the LD.

[0027]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an external perspective view showing an embodiment of the optical waveguide module according to the present invention, and FIG.
2A is a sectional view taken along line AA, FIG. 2B is a sectional view taken along line BB in FIG. 1, and FIG. 2C is a sectional view taken along line CC in FIG. Note that the same members as those in the conventional example shown in FIG.

In the optical waveguide type module, a buffer layer 20 is formed on a substrate 10 made of Si single crystal, and a cladding layer 21 and a core 26 described later (FIG. 2) are formed on the buffer layer 20.
By forming (a)), a silica-based optical waveguide 11 is formed. Further, an LD and a PD are arranged on the substrate 10, and the LD and the PD are covered with a hermetic lid 24, and the PD electrode 2 is formed.
2 and the LD electrode 27 are formed, the filter 13 is disposed so as to cross the optical waveguide 11, and the groove 2 in the direction crossing the optical waveguide 11 is formed in the cladding layers 21 on both sides of the optical waveguide 11.
8 (two sets of grooves 28 are formed in the figure, but the present invention is not limited to this).

Since the substrate 10 is exposed in the mount portion of the LD by the glass etching, heat at the time of light emission of the LD is efficiently released. The oblique cut 23 of the end face of the optical waveguide 11 is for reducing the return light from the end face of the optical waveguide 11 to the LD and the return loss from the end face of the optical waveguide 11.

The optical waveguide 11 is formed in a y-shape, and a short wavelength region that transmits light having a wavelength (λ2) of 1.3 μm and reflects light having a wavelength (λ2) of 1.55 μm to the branch portion 12a. A filter 13 having a transmission type dielectric multilayer structure is arranged. The width between the end surface of the optical waveguide 11 on the reflection port 17 side and the branch portion 12a of the y-shaped optical waveguide and the width between the branch portions 12a and 12b of the y-shaped optical waveguide are about 300 μm.
The metal film 30 made of the same material as the electrodes 22 and 27 is deposited on the inner wall of the groove 28.

The manufacturing steps of such an optical waveguide module will be described with reference to FIGS. 3 (a) to 3 (e). 3A to 3E are manufacturing process diagrams of the optical waveguide module shown in FIG.

First, a substrate 10 made of Si is prepared (FIG. 3A).

The LD is formed by etching the substrate 10.
Then, an element-side bench 25 is formed at a position where a PD is to be mounted, and a groove-side bench 29 is formed at a position where a groove 28 is to be formed (FIG. 3B).

The buffer layer 20 is exposed on the substrate 10 on which the benches 25 and 29 are formed so that the benches 25 and 29 are exposed.
Is formed, and a silica glass optical waveguide 11 composed of a core 26 and a cladding layer 21 is formed on the buffer layer 20 and the element-side bench 25 (FIG. 3C).

The benches 25 and 29 are exposed by etching the cladding layer 21 (FIG. 3D).

A PD electrode 22 and an LD electrode 27 are formed on the cladding layer 21 and the exposed element-side bench 25, and a metal film 30 as a light-shielding film is formed on the inner wall of the groove 28 by vapor deposition (FIG. 3 ( e)).

After that, an optical waveguide module is formed through a mounting process such as a process of disposing the filter 13 and an alignment process of the LD and PD.

When such an optical waveguide module is operated, light having a wavelength (λ2) of 1.3 μm emitted from the LD passes through the LD port 19, the branch portion 12b, and the filter 13, and is guided to the common port 14. Waved. At this time, LD
A cladding mode is generated at the junction between the optical waveguide 11 and the branch 12a and the branch 12b of the y-shaped waveguide.
This cladding mode is confined and propagated between the substrate 10 and the air layer above the cladding layer 21, but is reflected or absorbed by the groove 28 provided with the metal film 30 and cut off by the groove side bench 29. You. Therefore, it is possible to suppress the cladding mode from the LD from leaking into the optical fiber 18 of the reflection port 17. In this embodiment, the leakage loss of 1.3 μm wavelength (λ2) light from the LD into the optical fiber on the reflection port side is 55 dB, which is 40 dB less than the leakage loss of the conventional optical waveguide type module having no groove. This is improved by 15 dB.

As described above, according to the present invention, a groove extending in a direction crossing the optical waveguide is formed on both sides of the optical waveguide, and a light-shielding film is formed on the inner wall of the groove, so that the cladding mode propagating through the optical waveguide is blocked. As a result, an optical waveguide module with less light leakage can be obtained, whereby high isolation can be obtained.

In this embodiment, the metal film is formed by vapor deposition. However, the present invention is not limited to this, and a material that absorbs light may be inserted into the groove. When a gray silicone resin was applied to the groove, the wavelength (λ)
2) The leakage loss of 1.3 μm light into the optical fiber on the reflection port side was 55 dB. As described above, the light-shielding film applied to the groove may be either a reflecting material or an absorbing material. further,
In the present embodiment, the light wavelengths are 1.3 μm and 1.55 μm.
Although the case of m has been described, the present invention is not limited to this.

[0042]

In summary, according to the present invention, the following excellent effects are exhibited.

A groove is formed on both sides of the optical waveguide of the optical waveguide module in a direction crossing the optical waveguide, and a light-shielding film is formed on the inner wall of the groove. An optical waveguide module in which the generated clad mode does not leak into the optical fiber facing the LD can be realized.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing one embodiment of an optical waveguide module of the present invention.

2A is a cross-sectional view taken along the line AA of FIG. 1, and FIG.
1 is a sectional view taken along line BB of FIG. 1, and FIG. 2C is a sectional view taken along line CC of FIG.

FIGS. 3A to 3E are manufacturing process diagrams of the optical waveguide module shown in FIG.

FIG. 4 is a schematic diagram of a platform structure of an optical waveguide module in which an LD is surface-mounted on a substrate.

5 is an external perspective view showing a conventional example of the optical waveguide module having the platform structure shown in FIG.

FIG. 6 is a manufacturing process diagram of the optical waveguide module shown in FIG.

[Explanation of symbols]

 Reference Signs List 10 substrate 18 optical fiber 21 cladding layer 30 light-shielding film (metal film) LD laser diode PD photodiode

Continuing on the front page (72) Inventor Masahiro Yanagisawa 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Hiroshi Terui 3-2-1-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Telephone Co., Ltd. (72) Inventor Masahiro Okawa 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Hitachi Cable Co., Ltd. Opto-System Laboratories (72) Inventor Naoto Uezuka 5-chome, Hidaka-cho, Hitachi City, Ibaraki Prefecture No. 1-1 Hitachi Cable Co., Ltd. Optro System Research Laboratories (72) Inventor Tatsunori Kanaya 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi, Ltd. Information and Communication Division (72) Inventor Yasunori Iwato Yokohama-shi, Kanagawa 216 Totsuka-cho, Totsuka-ku, Hitachi, Ltd.

Claims (5)

[Claims] 1. An optical waveguide module in which an optical waveguide for connecting to an optical fiber is formed on a substrate, and a light emitting element and a light receiving element are connected to the optical waveguide, and a direction crossing the optical waveguide on both sides of the optical waveguide. An optical waveguide module comprising: a groove; and a light-shielding film provided on an inner wall of the groove. 2. An element-side bench for mounting a laser diode and a photodiode on the substrate while using Si for the substrate, using a laser diode for the light emitting element, using a photodiode for the light receiving element. The optical waveguide module according to claim 1, wherein a groove bench is formed at a position where the groove is formed. 3. A metal film for supplying a current to the laser diode and extracting a signal current from the photodiode is formed on the element-side bench and the cladding layer, and a metal film is used as the light-shielding film. The optical waveguide module according to claim 1 or 2, wherein 4. The optical waveguide module according to claim 1, wherein said groove is formed so that its depth reaches the substrate. 5. The optical waveguide is formed as a y-shaped waveguide,
The light having the wavelength λ2 is transmitted through the y-shaped branch portion and the wavelength λ
A filter that reflects light of wavelength λ1 different from 2 is arranged,
The optical waveguide module according to any one of claims 1 to 4, wherein at least one groove is formed between an end surface of the optical waveguide on the emission side of the light reflected by the filter and the branch portion.