JPH10133044A - Plane light circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To limit the dimension of a substrate in a light advancing direction, to constitute the light incidence/exit face of a plane light circuit on one face and to miniaturize the plane light circuit by sticking a mirror to the opposite face to the incident face of the circuit. SOLUTION: Two optical waveguides 2, 2' and an waveguide independent 3dB coupler 3 are arranged on the center of an optical substrate 1, the waveguides 2, 2' are folded on the right side end face of the substrate 1 and an independently formed reflection mirror 4 is stuck to the end face of the substrate 1 which is on the opposite side of an incident port 1 so as to guide light to the left side end face which is the same side as the incident port. When the incident light A arrives at the coupler 3, the light is separated into to two light components A1, B2 by the characteristics of the coupler 3. The light components A1, B2 are respectively attenuated by 3dB from the light A. The light components A1, B2 are respectively advanced through the waveguides 2, 2', made incident upon the mirror 4 on the right ends 5, 5' of the plane light circuit and reflected by the mirror 4 and the reflected light components are respectively advanced through the waveguides 2, 2' and projected from respective exit ports O1, O2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar optical circuit for splitting light by using a wavelength-independent 3 dB coupler, a wavelength separation coupler, and a wavelength separation filter, and more particularly, to a mirror on a surface opposite to an entrance port of a planar optical circuit. The present invention relates to an attached planar optical circuit.

[0002]

2. Description of the Related Art Since the introduction of an optical cable as a communication trunk, the communication quality has been improved and the communication capacity has been dramatically increased, so that the communication cost has been greatly reduced. Networking of computers, e-mail,
The demand for high-speed and large-capacity communication such as image communication has been increasing year by year, and as a result, the demand for optical components used for optical transmission has increased significantly. As an example of the optical device used for the optical transmission, there is a planar optical circuit shown in FIG. 3, which is a schematic plan view in which an optical waveguide is particularly greatly enlarged for easy understanding. The planar optical circuit shown in FIG. 3 is a device that splits light using an optical waveguide 11 formed on an optical substrate 10 made of quartz or the like.
The light travels along. Incident light A is wavelength independent 3dB
The output light A1 and B1 are separated by the coupler 12, and the light A1 (B1) is further separated into the output light A11 (B11) and A12 (B12) by the 3-dB Y branch circuit 13, and the output ports O1, O2, Outgoing light is obtained from O3 and O4. The same applies to the case where light is incident from the incident port I2.

Here, the wavelength-independent 3 dB coupler 12 will be described. As is well known, when the optical waveguides 11 and 11 'are arranged close to each other as shown in FIG. 3, optical coupling occurs to form a directional coupler. At this time, the material, structure, etc. of the optical waveguides 11 and 11' are used. And by appropriately selecting the length of the coupling portion, the outgoing light A
The wavelength-independent 3 dB coupler 12 in which 1, B1 is attenuated by そ の, that is, 3 dB. FIG.
Since the 3dBY branch circuit 13 has the same material and the same structure of the waveguide in a Y-shape, the incident light A1 (B1) is equally divided into the outgoing light A11 (B11) and A12 (B12) and is incident. The light A1 is attenuated by 即 ち, that is, 3 dB, respectively.

Here, an example of a method of manufacturing a planar optical circuit will be described according to the sequence of steps (4-1 to 4-10) shown at the left end of FIG. First, a lower clad film having a thickness of about 25 μm is formed on a substrate such as quartz which is a substrate of a planar optical circuit by Si.
It is formed using O2. The component weight ratio (99% S
A core film of iO2 + 1% TiO2) is formed with a thickness of about 8 μm, and a Si film is formed thereon with a thickness of about 2 μm. S
After performing photoresist patterning on the i film formation, etching is performed to remove unnecessary portions. Further, an upper clad film of SiO2 is formed on the formed pattern for about 25 minutes.
μm is formed. Thereafter, the optical fiber is cut with a cutter or the like, and the optical cable connection terminals are adhered and housed in a case to form a planar optical circuit. In addition, a groove shown in 4-8 is formed according to the function of the optical device, a filter of a dielectric multilayer film having a thickness of several tens of μm shown in 4-9 is inserted into the groove, and an optical cable connection terminal is adhered. To form a planar optical circuit.

As described above, the optical waveguide is composed of a surrounding clad part and a core core part.
2 and the core portion is made of (99% SiO2 + 1% TiO
Since it is formed in 2), the light wave is confined and propagated in a linear core portion having a large refractive index as is well known.
This phenomenon can be easily understood by considering the total reflection of light.

[0006]

However, in the method of splitting light as shown in FIG. 3, the light incident / exit surfaces exist on two opposing surfaces. As a result, as shown in FIG. There is a problem that the optical device using the planar optical circuit cannot be reduced in size because it is necessary to arrange connectors on both sides of the planar optical circuit. The present invention has been made in view of the above, and has a light entrance / exit surface of one.
It is an object of the present invention to provide an optical device using a more compact planar optical circuit by making the planar optical circuit smaller by using a plane.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to claim 1 of the present invention is directed to an optical waveguide formed by depositing a dielectric film on an optical substrate in multiple layers and etching the same, In a planar optical circuit having a 3 dB coupler or a wavelength separation coupler, a mirror is attached to a surface of the planar optical circuit opposite to the incident surface. According to a second aspect of the present invention, there is provided the planar optical circuit according to the first aspect, wherein a wavelength separation filter or a wavelength-independent half mirror is provided in the optical waveguide immediately after the light incident port.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a plan view of one embodiment of the planar optical circuit according to the present invention. The actual dimensions of the optical waveguide 2 are extremely small, both about 8 μm in thickness and width, but are enlarged for easy understanding. It is shown in FIG. The formation of the optical planar circuit of FIG. 1 is the same as the above-mentioned conventional formation method. A lower clad film having a thickness of approximately 25 μm is formed on an optical substrate 1 of quartz or the like using SiO 2, and the component weight ratio is formed thereon. Forms a core film of (99% SiO 2 + 1% TiO 2) with a thickness of approximately 8 μm. Further, an Si film is formed thereon to a thickness of approximately 2 μm, and a photoresist is patterned on the film, followed by etching to remove unnecessary portions. Further, an upper clad film of SiO2 is formed on the formed pattern in a thickness of 25 μm and then cut by a cutter or the like to manufacture a planar optical circuit. The planar optical circuit shown in FIG. 1 has two optical waveguides 2, 2 ′ formed through the above-described steps.
And a wavelength-independent 3 dB coupler 3 are arranged at the center of the optical substrate 1 and the waveguides 2 and 2 'are turned back at the right end surface of the optical substrate 1 in the drawing to guide light to the same left end surface as the incident port in the drawing. As described above, the reflection mirror 4 separately formed is bonded to the end face of the optical substrate 1 opposite to the incident port.

The operation of the planar optical circuit shown in FIG. 1 will be described. Light may be incident from either of the incident ports I1 and I2, but the case where the light is incident from the incident port I1 will be described here. The incident light A travels along the optical waveguide 2 and, when reaching the wavelength-independent 3 dB coupler 3, is separated into two lights A1 and B2 by the characteristics of the coupler. At this time, as described above, the light A1 and the light A2 are each 3 dB relative to the light A.
Decay. The lights A1 and B1 travel through the optical waveguides 2 and 2 ', respectively, and enter the reflection mirrors at the right ends 5 and 5 of the planar optical circuit.
The light is reflected, travels through the optical waveguides 2 and 2 ′, and is emitted from the emission ports O1 and O2. Further, even when light is incident from the incident port I2, the incident light can be separated in the same manner as described above. In some cases, incident light is introduced from both of the input ports I1 and I2 and used.
Are referred to as 2 × 2 optical waveguides. With this configuration, all incoming and outgoing light can be handled only on the left side of the planar optical circuit in the figure.

FIG. 2 shows another embodiment of the planar optical circuit for separating light, which is for guiding the wavelength-independent half mirror 6 and the light reflected from the half mirror 6 to the optical waveguide of the planar optical circuit of FIG. Are added. The half mirror 6 is an optical device for laminating a dielectric film in multiple layers on an optical substrate and separating the ratio of transmitted light to reflected light to incident light to approximately 1: 1. In explaining the operation of FIG. 2, light may be incident from any of the incident ports I1 and I2.
Consider a case where light is incident from I1. Injection port I1
The light A incident from the light source is almost equally separated into the light A1 and the light B1 by the wavelength-independent half mirror 6, and the light B1 is emitted from the emission port O2. On the other hand, the light A1 travels through the optical waveguide 2 to reach the wavelength-independent 3 dB coupler 3, where the light A2 is attenuated by 3 dB with respect to the incident light A1 due to the characteristics of the coupler.
And C2. The separated lights A2 and C2 are reflected by a reflection mirror 4 attached on the opposite side of the plane optical circuit from the entrance port.
, And again travels through the optical waveguide 2 to reach the emission ports O1 and O4. Also, the input port I2
The same applies to the case where the light is made incident from the above, except that the light is emitted from the emission port O3 instead of the emission port O2. This is a so-called 1 × 3 optical waveguide. In some cases, incident light is introduced from both of the input ports I1 and I2. In this case, a 2 × 4 optical waveguide is used. With such a configuration, it is possible to realize a planar optical circuit that can process a large number of incoming and outgoing lights only at one end surface.

Further, it is needless to say that a 1 × 2 optical waveguide can be constituted by replacing the wavelength-independent 3 dB coupler 3 with a 3 dBY branch circuit in FIG.

[0012]

According to the present invention, as described above, since the mirror and the half mirror are used, the size of the substrate in the light traveling direction is limited and the light input / output surface of the planar optical circuit is formed as one surface. It is only necessary to form an optical cable terminal attached to the circuit on only one surface, so that the planar optical circuit and the optical device using the same can be greatly reduced in size.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing one embodiment of a planar optical circuit according to the present invention.

FIG. 2 is a schematic plan view showing another embodiment of the planar optical circuit according to the present invention.

FIG. 3 is a schematic plan view showing a conventional planar optical circuit.

FIG. 4 is a schematic view showing a step of forming a planar optical circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical substrate 2 optical waveguide 3 wavelength-independent 3 dB coupler 4 mirror 5 reflection point 6 half mirror I1, I2 incident port O1, O2 , O3, O4 ... Outgoing ports A, A1, A2, B, B1, C1, C2 ... Light Arrow ... Light traveling direction

Claims (2)

[Claims] 1. A planar optical circuit having an optical waveguide, a wavelength-independent 3 dB coupler or a wavelength separating coupler formed by attaching and etching a dielectric film in multiple layers on an optical substrate, opposite to the plane of incidence of the planar optical circuit. A planar optical circuit, characterized in that a mirror is attached to the surface of (1). 2. A planar optical circuit according to claim 1, wherein a wavelength separation filter or a wavelength-independent half mirror is provided in the optical waveguide immediately after the light incident port.