JPH07191236A - Optical circuit and its production - Google Patents

Abstract

PURPOSE:To obtain an optical circuit with which optical coupling between an optical waveguide and various respective optical parts with high efficiency and a reduction of the cost of the optical circuit are possible and which has reliability to a temp. fluctuation, vibration impact, etc., CONSTITUTION:The optical waveguide 2 consisting of a quartz member and a reflection mirror 7 which is formed by using the same material as the material of the optical waveguide 2 on the Si substrate l between the optical waveguide 2 and a semiconductor light source and is solid-state element on the Si substrate 1 are formed on the Si substrate 1. And the reflection surface 71 is formed. The reflection mirror consisting of the Si member is otherwise formed on the Si substrate l and the reflection surface is formed by anisotropic etching of Si. The reflection mirror and the Si substrate are respectively provided with recessed and projecting structures which are respectively fittable to each other by anisotropic etching of the Si, by which the mirror and the substrate are fitted and fixed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical circuit and a method for manufacturing the same, and more particularly to an optical network system, which uses a light guide formed on a substrate such as a Si (silicon) substrate. In the optical device, the present invention relates to an optical circuit for performing optical axis conversion of light emitted from an optical waveguide, an optical circuit for optically coupling with a light receiving element, and a manufacturing method thereof.

[0002]

2. Description of the Related Art While the capacity of optical communication systems is increasing and the demand for multifunctional advanced systems, there is a strong demand for cost reduction of optical fiber networks. Among them, downsizing, high integration, and cost reduction of optical devices such as optical transmitters and optical receivers are essential. At present, optical transmitters and optical receivers that are practically used have a structure in which a lens is installed between a semiconductor light source and a semiconductor photodetector and an optical fiber to spatially secure optical connection. . The structure that spatially secures the optical connection using this lens is called micro optics. In the micro-optics structure, it is difficult to reduce the size because the shape of the lens and the shape of the package of the semiconductor light source and the semiconductor photodetector are limited. Further, in order to efficiently couple the light propagating in the space to the optical fiber or the photodetector, it is necessary to adjust the optical axis with high accuracy, and a large number of man-hours are required for the work, which does not reduce the cost. Is the current situation. Also,
It goes without saying that it is completely unsuitable for high integration of the same function or different functions.

Recently, there is an increasing need for a two-way communication system, and it is desired to introduce this system into homes. An optical transmitter and a receiver are required as an optical device that enables bidirectional communication, but if they are individually configured, the optical transmitter / receiver becomes large, which hinders the spread of the system. Therefore, an optical device (optical transceiver) that integrates two functions is desired, but it is difficult to use the micro-optics structure for the above-mentioned reasons. From such a background, a structure using an optical waveguide is being studied as a structure aiming at downsizing, high integration, and cost reduction. FIG. 4 shows a plan view of the optical circuit of this example.

In the optical circuit of FIG. 4, an optical waveguide 10 including an optical power branching or optical wavelength demultiplexing function optical circuit 15 on a substrate 9.
The optical waveguide 10, the optical fiber 11, the semiconductor light source 12, and the semiconductor photodetector 13a for signal detection are optically coupled directly on the same substrate 9.
In FIG. 4, the semiconductor photodetector 13b for monitoring the optical output of the semiconductor light source 12 is also integrated on the same substrate 1, and the optical waveguide 1
Although it is optically connected to 0, even if there is no semiconductor photodetector 13b for monitoring the optical output of the semiconductor light source 12,
It does not affect the function of the transceiver for bidirectional optical communication. Further, whether or not the receiving circuit electronic devices of the semiconductor photodetectors 13a and 13b are provided on the same substrate 9 does not affect the securing of the function of the transceiver for bidirectional optical communication. If an optical transmitter / receiver is configured using the optical waveguide 10 shown in FIG. 4, miniaturization is of course facilitated, and the optical axis propagates through the optical waveguide whose optical axis can be determined by the lithography process and is constant. Since the coupling with the wave light may be performed, the optical axis adjustment is also simplified, and further, the optical waveguide itself is mass-produced in a lump by using the lithography process, so that the cost can be reduced.

[0005]

In this conventional optical circuit, in order to extract the light emitted from the optical waveguide to the upper part and optically couple it to an optical component such as a back surface or front surface incident type semiconductor detector, etc., in an efficient manner. , A mirror that reflects the light emitted from the optical waveguide is required.

FIG. 5 is a cross-sectional view showing the structure of a conventional optical circuit, in which a reflecting mirror 18 having an inclination angle of 45 degrees facing the emitting end face 171 of the optical waveguide 17 is positioned on the optical axis using a manipulator or the like. After being adjusted, it is fixed to the substrate 16 with an adhesive or the like, and the reflection surface 181 provides the reflected light 20. The reflected light 20 extracted to the upper side by the reflection mirror 18 is coupled to an optical component such as a semiconductor detector (not shown) via an optical fiber 19. However, with this processing method, it is difficult to adjust the position of the optical axis, which hinders cost reduction, and it is difficult to easily secure reliability against temperature fluctuations, vibration shocks, and the like. In addition, since it is necessary to use the reflection mirror 18 as an individual component, this also hinders cost reduction.

The object of the present invention is to solve the above-mentioned problems,
Light emitted from the optical waveguide is extracted to the top by a reflection mirror and optically coupled to optical components such as backside or front-illuminated type semiconductor detectors with high efficiency and low cost, and against temperature fluctuations and vibration shocks. Even so, it is to provide an optical circuit having extremely high reliability and a manufacturing method thereof.

[0008]

The optical circuit of the present invention is made of Si.
In an optical circuit in which an optical waveguide is formed on a substrate and the emitted light from the optical waveguide is converted into an optical axis, a reflection mirror for reflecting the emitted light from the optical waveguide is provided on a reflection surface formed by Si anisotropic etching. Si coated with a reflective film
It is composed of a member and is S
A concave portion is formed on one of the reflection mirror formed of the i member and the Si substrate, and a convex portion that fits with the concave portion is formed on the other side, and the reflection mirror and the Si substrate are formed into the concave portion and the concave portion. It has a configuration in which it is fitted and fixed via a convex portion.

Another optical circuit according to the present invention is an optical circuit in which a silica-based optical waveguide is formed on a substrate and the output light from the silica-based optical waveguide is converted into an optical axis. A reflecting mirror that reflects light has a reflecting surface formed in an oblique shape with a substantially trapezoidal cross section, and is used when the reflecting surface is coated with a reflecting film to form the quartz optical waveguide on the substrate. It has a structure formed into a solid element by using the quartz member.

The optical circuit manufacturing method of the present invention is a method for manufacturing an optical circuit in which a silica-based optical waveguide is formed on a substrate and the light emitted from the silica-based optical waveguide is converted into an optical axis. The reflection mirror that reflects the light emitted from has a reflection surface that is formed in an oblique shape with a cross section of a substantially trapezoidal shape,
The reflective surface is coated with a reflective film to form a solid element by using the quartz member used when forming the quartz optical waveguide on the substrate, and the reflective surface is reflowed by heating. And a step of forming.

[0011]

A highly efficient optical circuit for extracting light emitted from an optical waveguide according to the present invention to an upper portion by a reflection mirror and optically coupling it efficiently to an optical component such as a backside or front incidence type semiconductor detector, and a method for manufacturing the same. Then, in one invention,
By using Si material as the base material of the reflection mirror, the inclination angle of the reflecting surface is formed with high accuracy by Si anisotropic etching, and the flatness of the inclined surface is also excellent. One of the reflecting mirror and the Si substrate is formed with a concave shape and the other is formed with a convex shape so that they can be fitted into each other. The reflecting mirror is fitted on the Si substrate through the concavo-convex shape. There is. Therefore, it is not necessary to adjust the position of the optical axis, and the reflection mirror made of Si material can be mass-produced by using the lithography process, so that the cost can be reduced. In another invention, a quartz optical waveguide member formed on a substrate is used as a base material of a reflection mirror, and a position is set and a reflection mirror shape is molded by a lithography process.

Therefore, it is not necessary to adjust the position of the optical axis, and the cost can be significantly reduced. As mentioned above,
It is possible to realize a highly efficient optical circuit that extracts the light emitted from the optical waveguide to the upper part using a reflection mirror and optically couples it to the optical components such as the back-side or front-illuminated type semiconductor detector at low cost, and at the same time, temperature fluctuation. An optical circuit with extremely high reliability against vibration and shock can be realized. Further, according to another invention, in which a silica-based member deposited on a substrate is used as a reflection mirror to be inserted between a silica-based optical waveguide and an optical component, the reflection surface of the reflection mirror is heated. Molded using the reflow of the quartz-based material by S, by this process S similar to the electronic device
A reflection mirror can be formed on the i substrate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a side view showing the structure of an optical circuit according to the first embodiment of the present invention. In the first embodiment, a Si substrate 1 using a Si member and an optical waveguide 2 using a quartz member are used.
And a reflection mirror 3. The optical waveguide 2 has a layered structure of a lower clad 21, a core 22 and an upper clad 23. The same Si member as the Si substrate 1 is used as the base material of the reflection mirror 3. Si can form the tilt angle of the tilted surface to be the reflecting surface 31 with high accuracy by anisotropic etching of the (111) plane, to about 54.8 degrees in this embodiment,
In addition, it is known that the flatness of the sloped surface that becomes the reflection surface 31 composed of the exposed (111) surface is also excellent. Reflective surface 3
1 is coated with Au, Al or the like as a reflecting member for reflecting the light wave from the optical waveguide 2. Further, similar to the formation of the reflection surface 31, the convex portion 4 is formed on the joint surface of the reflection mirror 3 with the Si substrate 1 by using anisotropic etching of the Si member, and the reflection mirror 3 is desired on the Si substrate 1. The concave portion 5 is formed to be installed at the position. The reflection mirror 3 is S
When it is mounted on the i substrate 1, it is carried out by fitting the concavities and convexities formed on the joint surface of both the convex shape portion 4 and the concave shape portion 5 which are formed so as to be fitted to each other. Therefore, it is not necessary to adjust the position of the optical axis when the reflection mirror 3 is mounted, so that the cost can be reduced and the highly accurate position setting can be easily realized. Further, since the reflection mirror 3 made of a Si member and the concave and convex portions 4 and 5 formed on the reflection mirror 3 and the Si substrate 1 can be mass-produced easily by using a lithography process, the cost can be reduced. Further, since the reflection mirror 3 and the Si substrate 1 are fixed in a fitted state by the convex portions 4 and the concave portions 5 having high inclination angles formed respectively, the reflection mirror 3 and the Si substrate 1 are protected against temperature fluctuations, vibration shocks, and the like. On the other hand, a position change does not occur at all, and a highly reliable optical circuit can be obtained.

The concave portion 4 and the convex portion 5 are formed as follows.
Contrary to what is shown in FIG. 1, a concave portion is formed on the bonding surface of the reflection mirror 3 with the Si substrate 1, and a convex portion is formed on the Si substrate 1 at a position where the reflection mirror 3 can be installed at a desired position. You may.

FIG. 2 is a side view showing the structure of the optical circuit of the second embodiment of the present invention. The second embodiment includes a Si substrate 1, an optical waveguide 2 formed on the Si substrate 1 by a silica-based member, and a reflection mirror 7. The optical waveguide 2 has a layered structure of a lower clad 21, a core 22 and a clad 23. A CVD method, a sputtering method, a flame deposition method, or the like is used for depositing the quartz-based member on the Si substrate for forming the optical waveguide 2. The base material of the reflection mirror 7 also uses the quartz-based member deposited on the substrate 1 when forming the optical waveguide 2. The reflecting surface 71 of the reflecting mirror 7 is coated with Au, Al or the like as a material that reflects light waves. To form the reflecting surface 71 having a desired inclination angle, a reactive ion beam etching (RIBE) method or an ion beam etching method having directivity in etching characteristics is used to etch the Si substrate 1. The reflecting surface 71 is formed by inclining to the directivity.

In this way, since it is not necessary to adjust the position of the optical axis of the reflecting mirror 7, cost reduction can be obtained and highly accurate position setting can be easily realized. Further, since the reflection mirror 7 made of a quartz-based member can be mass-produced easily by using a lithography process, cost reduction can be obtained. Further, since the reflection mirror 7 is formed as a solid-state element on the Si substrate 1, there is no positional change with respect to temperature fluctuations, vibration shocks, etc., as compared with the first embodiment shown in FIG. An extremely high optical circuit can be obtained.

FIG. 3 is a process chart showing an embodiment of the method for manufacturing an optical circuit of the present invention. In FIG. 3, the optical waveguide 2 formed on the Si substrate 1 is made of a quartz-based member as in FIG. 2, and includes a lower clad 21-core 22-upper clad 2.
It has a three-layer structure. A CVD method, a sputtering method, a flame deposition method, or the like is used to deposit the quartz-based member on the Si substrate. A quartz member deposited on the Si substrate 1 when forming the optical waveguide 2 is used as the reflection mirror forming member 7a as the base material of the reflection mirror 7 (step a). The reflecting surface 71 is made of a material that reflects light waves, such as Au or Al.
Etc. are coated (step c). The difference from the second embodiment of FIG. 2 is that the reflow of a quartz-based member is used to form the reflecting surface 71 having a desired inclination angle (step b). At this time, the shape before reflow, the reflow temperature,
In addition, the tilt angle is controlled depending on the time. However, FIG.
It is difficult to obtain a linear shape on all the reflecting surfaces, as shown in, and some sag occurs near the upper surface and near the lower surface. The reflow is usually performed at a temperature of 850 ° C. or higher, and even if the surface of the upper clad 23 of the optical waveguide 2 is reflowed at this time, the characteristics of the optical waveguide 2 are not significantly affected. On the other hand, since the verticality of the end face 24 may be impaired due to reflow, it is desirable to heat only the reflection mirror forming member 7a. To ensure local heating for this, for example C
Irradiation with a gas laser beam such as O ₂ or Ar, or using an ordinary heater. In this way, the reflection mirror 7 is formed.

According to such a method of manufacturing an optical circuit, it is not necessary to adjust the position of the optical axis of the reflection mirror 7, so that the cost can be reduced, and highly accurate position setting can be easily realized. In addition, the reflection mirror 7 made of a quartz material
Can be produced in large quantities and easily using a lithographic process, resulting in low cost. In addition, the reflection mirror 7
1 is directly formed on the Si substrate 1, and therefore, the position variation does not occur even with respect to temperature variation, vibration impact, etc., as compared with the first embodiment of FIG. Can be established.

[0020]

As described above, according to the present invention, the same Si member as the Si substrate is anisotropically etched by Si, or the reflecting surface is formed in the same hierarchical structure as the optical waveguide formed of the quartz member on the Si substrate. Form the reflection mirror that has been arranged, S
In the case of i anisotropic etching, the Si substrate and the reflection mirror have a concavo-convex shape that can be fitted, and in the case of a hierarchical structure, the light is emitted from the optical waveguide to the upper portion by the reflection mirror by forming it as a solid element. A highly efficient optical circuit that can be optically coupled to an optical component such as a backside or front-illuminated type semiconductor detector can be realized at low cost, and it is extremely reliable against temperature fluctuations and vibration shock. It has an effect that an optical circuit that can realize a circuit and a manufacturing method thereof can be realized.

[Brief description of drawings]

FIG. 1 is a side view showing a structure of an optical circuit according to a first embodiment of the present invention.

FIG. 2 is a side view showing the structure of an optical circuit according to a second embodiment of the present invention.

FIG. 3 is a process drawing of an example of a method for manufacturing an optical circuit of the present invention.

FIG. 4 is a plan view showing the structure of a conventional optical circuit.

FIG. 5 is a side view showing the structure of a conventional optical circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Optical waveguide 3 Reflective mirror 4 Convex shaped portion 5 Concave shaped portion 6 Reflected light 7 Reflective mirror 8 Reflected light 9 Substrate 10 Optical waveguide 11 Optical fiber 12 Semiconductor light source 13a, 13b Semiconductor photodetector 14a, 15b Receiver circuit electron Device 15 Optical power branching or optical wavelength functional optical circuit.

Claims (3)

[Claims] 1. In an optical circuit in which an optical waveguide is formed on a Si substrate and the emitted light from the optical waveguide is converted into an optical axis, a reflection mirror for reflecting the emitted light from the optical waveguide is made of Si.
A reflection mirror formed of a Si member having a reflection surface formed by anisotropic etching coated with a reflection film, and a reflection mirror formed of the Si member by Si anisotropic etching;
A concave portion is formed on one of the i substrates, and a convex portion that fits with the concave portion is formed on the other side, and the reflection mirror and the Si substrate are fitted and fixed through the concave and convex portions. An optical circuit characterized by the above. 2. In an optical circuit in which a silica-based optical waveguide is formed on a substrate and the output light from the silica-based optical waveguide is converted into an optical axis, a reflection mirror that reflects the output light from the silica-based optical waveguide has a cross section. It has a reflecting surface formed in an oblique shape as a substantially trapezoidal shape, and is coated with a reflecting film on the reflecting surface to form a solid by using the quartz member used when forming the quartz optical waveguide on the substrate. An optical circuit characterized by being formed into elements. 3. A method of manufacturing an optical circuit in which a silica-based optical waveguide is formed on a substrate and the output light from the silica-based optical waveguide is converted into an optical axis, and a reflection mirror that reflects the output light from the silica-based optical waveguide. Has a reflecting surface formed in an oblique shape with a substantially trapezoidal cross section, and the quartz member used when the reflecting surface is coated with a reflecting film to form the quartz optical waveguide on the substrate. A method for manufacturing an optical circuit, characterized in that the optical element is formed as a solid element by using, and is formed by reflowing the reflecting surface by heating.