JPH1039178A - Optical transmission module and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide an optical transmission module having stable optical system characteristics for a long period of time and a method of manufacturing the same. SOLUTION: A light emitting element 4 or a light receiving element is fixed on a substrate 1, a flat waveguide 11 or an optical fiber 6 for transmitting an optical signal is provided on the substrate 1, and an atmosphere around the element 4 is isolated from outside air by an airtight cap 7. In the light transmission module, the inner wall 20 of the airtight cap 7 is roughened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical transmission module used for optical communication and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an optical transmission module equipped with a semiconductor light emitting element such as an LD (laser diode) or a semiconductor light receiving element such as a PD (photodiode) is soldered to isolate the ambient atmosphere of the semiconductor element from the outside air. Alternatively, one hermetically sealed by welding or the like is used.

In the hermetic sealing, moisture in the outside air is mixed into the ambient atmosphere of the semiconductor element, and when the temperature changes, the moisture condenses and adheres to the light emitting surface of the LD or the light receiving surface of the PD, thereby deteriorating the optical characteristics. It is done as one of the objectives to prevent doing so. However, to perform hermetic sealing by soldering or welding, special equipment was required, and the cost of the optical transmission module was high.

Therefore, in recent years, a simple hermetic optical transmission module that performs hermetic sealing using a resin has been developed.

FIG. 4 is a sectional view of an optical transmission module of a simple hermetic sealing type.

In FIG. 1, an optical bench 2 and a V groove 3 are formed on a Si substrate 1. On the optical bench 2, an LD (PD) 4 is fixed to an electrode 5 by soldering, and an optical fiber 6 is placed in the V groove 3. Further, an airtight cap 7 made of metal is mounted on the optical components 1 to 6 so as to surround the optical bench 2, and a thermosetting adhesive (or a thermoplastic resin) is provided in a gap between the optical component 2 and the Si substrate 1. (Resin) 8 and hermetically sealed. Incidentally, plastic may be used as the material of the above-described hermetic cap 7, and when the hermetic cap 7 is a transparent body, an ultraviolet curable resin may be used.

FIG. 5 is a sectional view of a waveguide type optical transmission module.

In this method, an optical bench 2 on which an LD (PD) 4 is mounted and a waveguide 11 comprising a core glass 9, a lower clad glass 10a, and an upper clad glass 10b are formed on a Si substrate 1, and the LD (PD) is formed. ) 4 is covered with an airtight cap 7. Also in this optical transmission module, the airtight cap 7 is formed of metal or plastic.

[0009]

By the way, in the conventional optical transmission module shown in FIGS. 4 and 5, even if the inside of the airtight cap 7 is filled with a dry inert gas at the time of manufacturing the module, the module cannot be used for a long time. During this time, moisture in the outside air may diffuse into the resin, and the atmosphere inside the airtight cap 7 may be humid.

If the atmosphere inside the airtight cap is humid, when the operating temperature of the optical transmission module is lowered, the humidity is reduced to the end face of the LD (PD) 4, the LD (PD) 4 and the optical fiber 6 or the waveguide 11. There is a possibility that the optical system characteristics such as dew condensation in the gaps between the optical system and the optical transmission loss increase and the like may deteriorate.

It is an object of the present invention to solve the above-mentioned problems and to provide an optical transmission module having stable optical system characteristics for a long period of time and a method of manufacturing the same.

[0012]

In order to achieve the above object, an optical transmission module according to the present invention has a light emitting element or a light receiving element fixed on a substrate and a flat waveguide or an optical fiber for transmitting an optical signal to the substrate. In an optical transmission module provided with an airtight cap for isolating the surrounding atmosphere of the element from the outside air, the inner wall of the airtight cap is roughened.

In addition to the above configuration, the optical transmission module of the present invention may have a roughened surface with a finely textured or porous material fixed to the inner wall of the airtight cap.

In addition to the above configuration, the optical transmission module of the present invention may have a moisture absorbing material fixed to the inner wall of the airtight cap and roughened.

In addition to the above configuration, in the optical transmission module of the present invention, the hermetic cap may be made of a brittle material, metal, resin, or a composite thereof.

Further, according to the method of manufacturing an optical transmission module of the present invention, a light emitting element or a light receiving element is fixed on a substrate, a flat waveguide or an optical fiber for transmitting an optical signal is provided on the substrate, and the periphery of the element is sealed with an airtight cap. In the method for manufacturing an optical transmission module for isolating the atmosphere from the outside air, the inner wall of the hermetic cap is roughened, and then the hermetic cap is fixed on the substrate.

In addition to the above structure, in the method of manufacturing an optical transmission module according to the present invention, the inner wall of the airtight cap may be roughened by subjecting the inner wall of the airtight cap to a fine unevenness or a porous process.

In addition to the above configuration, in the method for manufacturing an optical transmission module of the present invention, the inner wall of the airtight cap may be roughened by a mechanical tool, a mechanical processing means using ultrasonic waves or sandblasting.

In addition to the above structure, in the method for manufacturing an optical transmission module according to the present invention, the inner wall of the airtight cap may be roughened by chemical etching or electrochemical etching.

In addition to the above configuration, in the method for manufacturing an optical transmission module of the present invention, the inner wall of the airtight cap may be roughened by forming a mold.

In addition to the above configuration, in the method for manufacturing an optical transmission module according to the present invention, the inner wall of the airtight cap may be roughened by optical processing means.

In addition to the above configuration, in the method for manufacturing an optical transmission module of the present invention, the inner wall of the airtight cap may be roughened by powder adhesion or powder sintering.

In addition to the above structure, in the method for manufacturing an optical transmission module according to the present invention, the inner wall of the airtight cap may be roughened by generation of a combustion residue of an organic material containing a metal element.

[0024] With the above structure, moisture that has penetrated into the inside of the hermetic cap through the inside of the hermetic cap is adsorbed on the rough surface of the inner wall of the hermetic cap or a rough surface such as a porous material, so that the atmosphere in the hermetic cap is kept at a low humidity. Dripping. Further, even when moisture is excessively permeated, dew is condensed on the inner wall of the airtight cap, so that dew condensation on the end face of the light emitting element or the light receiving element or on the gap between the element and the flat waveguide or the optical fiber is prevented. When the hygroscopic material is fixed to the inner wall of the hermetic cap, the moisture that has entered the hermetic cap is absorbed, and the inside of the hermetic cap is kept at a low humidity.

[0025]

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

FIG. 1 is a sectional view showing one embodiment of the optical transmission module of the present invention. The case of a waveguide type optical transmission module will be described. Note that the same members as those in the conventional example shown in FIG.

In the figure, a substrate 1 made of a Si single crystal is shown.
A trapezoidal optical bench 2 is formed on the upper part of the optical bench, and the optical bench 2 has a laser diode LD.
(Or photodiode PD) 4 is fixed to electrode 5 by soldering. A lower clad glass 10a having a thickness equal to the height t of the optical bench 2 is formed around the optical bench 2 on the substrate 1, and a core glass 9 is formed on the lower clad glass 10a. The core glass 9 is covered with an upper clad glass 10b.
The waveguide 11 is formed by a and 10b. Needless to say, the optical axis of the waveguide 11 is formed to coincide with the optical axis of the LD (PD) 4.

A hermetic cap 7 for isolating the atmosphere around the LD (PD) 4 from the outside air is fixed around the optical bench 2 of the upper clad glass 10b with a thermoplastic adhesive (or a thermoplastic resin) 8. I have. Minute irregularities are formed on the inner wall 20 of the airtight cap 7 so that the inner wall 20 is roughened.

According to the above configuration, when moisture penetrates through the airtight cap 7 and enters the internal space 21, the water is adsorbed on the minute irregularities formed on the inner wall 20 of the airtight cap 7,
The atmosphere in the airtight cap 7 is kept at a low humidity. Also, even when the inside space 21 is excessively permeable to moisture, the airtight cap 7
Of the LD (PD) 4 or the LD
Dew condensation in the gap between the (PD) 4 and the waveguide 11 is prevented.

Next, a method of manufacturing the optical transmission module shown in FIG. 1 will be described.

First, a trapezoidal optical bench 2 is formed on an Si single crystal substrate 1 by anisotropic etching.
The lower clad glass 10a, the glass layer of the core glass 9, and the glass layer of the upper clad glass 10b are sequentially laminated by using an ion beam method and a photolithography technique.

Next, the glass layer laminated on the optical bench 2 is removed using a reactive ion etching technique, and the optical bench 2 is exposed. A metal film to be an electrode is deposited on the optical bench 2, an electrode 5 is formed by etching, and an LD (PD) 4 is soldered to the electrode 5.

The hermetic cap 7 having a U-shaped cross section is formed using glass, and minute irregularities are formed on the inner wall 20 of the hermetic cap 7 by sandblasting.

An optical transmission module is formed by bonding and fixing the hermetic cap 7 having ultraviolet transmittance using a thermosetting adhesive 8 made of an ultraviolet curing epoxy. The airtight cap 7 is mounted in a dry nitrogen atmosphere, and the internal space of the airtight cap 7 is filled with dry nitrogen and is simultaneously isolated from the outside air.

As the material of the airtight cap 7, any material such as metal and plastic may be used in addition to brittle materials such as glass and ceramics.

For brittle materials such as glass and ceramics, cutting with a diamond tool typified by a diamond drill, ultrasonic processing for cutting by applying ultrasonic vibration to a hard tool, and sandblasting for blowing hard sand particles together with compressed air. An effective inner wall surface can be formed by processing. When the hermetic cap is formed using metal, an effective uneven surface can be formed by chemical etching or electric discharge machining. Further, an effective uneven surface can be formed by forming an uneven surface on the mold of a plastic or a part of metal which can be formed by a mold and transferring the formed uneven surface. Further, with a material that absorbs laser light, an effective uneven surface can be formed by laser light irradiation. In the case of a material having high heat resistance such as ceramics, an effective porous material can be formed by attaching ceramic powder to the inner wall surface and sintering the powder. By applying an organic material containing a metal element such as a silicone resin to the inner wall and sintering the same, an effective porous metal oxide can be attached to the inner wall of the airtight cap as a combustion residue.

Next, the relationship between the inner wall surface processing of the airtight cap and the change in humidity will be described.

Using the experimental sample shown in FIG. 3, the amount of water entering the airtight space was measured.

The experimental sample shown in FIG. 3 has a transparent quartz plate 32 at both ends of a cylindrical body 31 having an inner wall 30 subjected to various processes.
a and 32b are bonded with a resin 33. Cylindrical body 3
1 is made of quartz glass, and transparent quartz plates 32a,
An anhydrous quartz glass plate was used for 2b, and an ultraviolet-curable epoxy resin was used as the bonding resin 33. Also, dry nitrogen was sealed when the experimental sample was manufactured. The infrared light is transmitted through the transparent quartz plate 32a of this experimental sample, and the magnitude of the infrared absorption peak of the OH ion contained in the water in the internal space 34 is relatively evaluated. The experiment was performed at a temperature of 85 ° C.
After being kept in an atmosphere of 85% humidity for a certain period of time, infrared spectroscopy was performed at room temperature.

FIG. 2 is a diagram showing the relationship of humidity changes in processing the inner wall surface of the airtight cap.

In the figure, the horizontal axis is the time axis, and the vertical axis is the OH ion absorption peak (relative value) axis.

Among the characteristic curves (1) and (2), the one obtained by smoothing the inner wall of the cylindrical body (smooth surface), the one obtained by subjecting the inner wall of the cylindrical body to unevenness by sandblasting (uneven surface),
Is a mixture of glass ceramic powder and water adhering to the inner wall of a cylindrical body, which is then dried and then sintered to form a porous body (porous sintered body). Silicone resin Is adhered to the inner wall of a cylindrical body and burned to form a porous body mainly composed of silicon oxide (porous combustion residue). (Silica gel) adhered to each other.

In the airtight cap having a smooth surface, the magnitude of the OH ion absorption peak became saturated in about 2000 hours. This is considered to be the same humidity as the outside air. On the other hand, the experimental sample in which the inner wall surface is processed based on the gist of the present invention has a small absorption peak of OH ions and indicates that the amount of water in the hermetic space is small. Since the high-temperature and high-humidity test was performed in the same manner for all the samples, it is considered that the amount of water entering through the epoxy resin adhesive layer is almost the same.

Therefore, it can be concluded that this difference is due to the fact that the airtight space has been lowered in humidity due to the adsorption of moisture to the wall surface.

In the above-described embodiment, the form in which the inner wall of the airtight cap is finely unevenly processed has been described, but it is apparent that the present invention is not limited to this.

For example, an effect can be obtained even if a porous body is used instead of the unevenness processing. The same effect can be obtained even if the porous body is ceramics, activated carbon, fiber, or a laminate of fibers. The hygroscopic substance such as silica gel may be an inorganic substance that forms a hydrate, for example, copper sulfate, or an organic substance such as a water-absorbing polymer. Further, in the present embodiment, a waveguide is used for the optical transmission module, but it is not limited to this, and it goes without saying that an optical fiber may be used.

[0047]

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

In a light transmission module in which a light emitting element or a light receiving element is fixed on a substrate, a flat waveguide or an optical fiber for transmitting an optical signal is provided on the substrate, and an atmosphere around the element is isolated from outside air by an airtight cap. Since the inner wall is roughened, it is possible to realize an optical transmission module having stable optical system characteristics for a long period of time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an optical transmission module according to the present invention.

FIG. 2 is a diagram illustrating a relationship of a humidity change in processing an inner wall surface of an airtight cap.

FIG. 3 is a cross-sectional view of an experimental sample.

FIG. 4 is a cross-sectional view of a conventional simple airtight sealing type optical transmission module.

FIG. 5 is a sectional view of a conventional waveguide type optical transmission module.

[Explanation of symbols]

 Reference Signs List 1 substrate (Si substrate) 2 optical bench 4 light emitting element (LD, laser diode) 5 electrode 7 hermetic cap 11 flat waveguide (waveguide) 20 inner wall 21 internal space

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeki Ishibashi 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Tatsuo Teraoka 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture 1 Opto-Systems Research Laboratory, Hitachi Cable, Ltd. (72) Inventor Tomoyuki Nishio 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture In-Optro Systems Research Laboratory, Hitachi Cable, Ltd. (72) Inventor, Satoshi Aoki Yokohama, Kanagawa Prefecture 216 Totsuka-cho, Totsuka-ku, Ichitoshi Information and Communications Division, Hitachi, Ltd. (72) Inventor Yasunori Iwato 216, Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture In the Information and Communications Division of Hitachi, Ltd.

Claims (12)

[Claims] 1. An optical transmission module in which a light emitting element or a light receiving element is fixed on a substrate, a flat waveguide or an optical fiber for transmitting an optical signal is provided on the substrate, and an ambient atmosphere of the element is isolated from the outside air by an airtight cap. 3. The optical transmission module according to claim 1, wherein an inner wall of the airtight cap is roughened. 2. The optical transmission module according to claim 1, wherein a finely textured product or a porous material is fixed to an inner wall of the airtight cap and roughened. 3. The optical transmission module according to claim 1, wherein a hygroscopic material is fixed to an inner wall of the airtight cap and is roughened. 4. The optical transmission module according to claim 1, wherein the airtight cap is made of a brittle material, metal, resin, or a composite thereof. 5. An optical transmission module in which a light emitting element or a light receiving element is fixed on a substrate, a flat waveguide or an optical fiber for transmitting an optical signal is provided on the substrate, and an atmosphere around the element is isolated from the outside air by a hermetic cap. The method for manufacturing an optical transmission module according to claim 1, wherein the inner wall of the airtight cap is roughened, and then the airtight cap is fixed on the substrate. 6. A roughened surface by subjecting an inner wall of the hermetic cap to a fine unevenness process or a porous process.
The manufacturing method of the optical transmission module described in the above. 7. The inner wall of the hermetic cap is a machine tool,
6. The method for manufacturing an optical transmission module according to claim 5, wherein the surface is roughened by mechanical processing means using ultrasonic waves or sandblasting. 8. The method according to claim 5, wherein the inner wall of the airtight cap is roughened by chemical etching or electrochemical etching. 9. The method according to claim 5, wherein the inner wall of the airtight cap is roughened by forming a mold. 10. The method for manufacturing an optical transmission module according to claim 5, wherein an inner wall of the airtight cap is roughened by optical processing means. 11. The method according to claim 5, wherein an inner wall of the airtight cap is roughened by powder adhesion or powder sintering. 12. The method for manufacturing an optical transmission module according to claim 5, wherein an inner wall of the airtight cap is roughened by generation of a combustion residue of an organic material containing a metal element.