JPH04304433A - Optical switching element and its manufacture - Google Patents

Abstract

PURPOSE:To obtain the fast-response optical switch element which uses not heat effect, but light reaction for the operation principle of an optical switch. CONSTITUTION:In the manufacturing process of the optical switching element which is provided with a layer, varying in refractive index with control light, between optical waveguides of a coupler composed of the optical waveguides, the layer is formed by vapor-deposition or light-irradiating vapor-deposition. A photochromic compound is used preferably for the layer. The internal strain stress of the formed noncrystalline vapor-deposited film itself is 1-3 digits less than that of a conventional optical switch which requires a substrate heating process and postbaking and variation and a noise due to stress between the couplers are made small.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switching element in which light passing through a waveguide as a signal is controlled by another light irradiated onto a coupler, and a method for manufacturing the same.

0002

2. Description of the Related Art Optical switches are eagerly awaited for application to optical exchanges and uninterrupted optical line switching devices in the field of optical communications, and even as key components of optical computers. However, conventional optical switches have problems. This will be explained based on FIG. That is, FIG. 2 is a diagram illustrating a conventional optical switching element, and is a diagram of the conventional optical switching element viewed from above. In FIG. 2, 1 and 2 are optical waveguides made of quartz, 3 is a first optical coupler, 4 is a second optical coupler, 5 is a thin film heater, and 6 is a silicon substrate. As shown in FIG. 2, a heater 5 is attached to the silica-based optical waveguide between the couplers, and the length of the optical path between the couplers 3 and 4 in FIG. was used to switch between the cross state and the bar state by changing the .

0003

[Problems to be Solved by the Invention] Therefore, since the operating principle is thermal effects due to heating and natural cooling, the response speed is slow, and when used as an optical computer, compared to the calculation speed of existing ordinary computers. There were disadvantages such as inferiority. Furthermore, when a large number of optical switches are integrated in a small area, crosstalk due to heat between adjacent switches is unavoidable. In addition, conventional couplers and optical waveguides are made from, for example, a quartz layer deposited on a silicon substrate.
The manufacturing process was complicated, as it was patterned using an etching process, and a heater section had to be separately provided on the silicon substrate, resulting in many problems in terms of yield and cost. An object of the present invention is to provide an optical switching element that solves these problems and a method for manufacturing the same.

0004

[Means for Solving the Problems] To summarize the present invention, the first invention relates to an optical switching element, in which a refractive index is changed by control light between optical waveguides of a coupler made of optical waveguides. It is characterized by having a layer that changes. A second invention of the present invention relates to a method of manufacturing an optical switching element, and in the method of manufacturing an optical switching element of the first invention, a layer whose refractive index is changed by the control light is formed by vapor deposition. Alternatively, it is characterized in that it is formed by a light irradiation vapor deposition method.

The present invention provides a high-response-speed optical switching element in which the operating principle of the optical switch is not a thermal effect but a photoreaction by providing a layer in the optical coupler whose refractive index is changed by control light. Another object of the present invention is to provide a method for manufacturing an optical switching element in which a layer having a changing refractive index is manufactured by a simple method such as a vapor deposition method or a light irradiation vapor deposition method.

[0006] The switching principle differs from conventional optical switching elements in that the refractive index within the coupler is directly changed by control light rather than a thermal effect, and the manufacturing method is different from conventional optical switching elements in that a heater section must be provided. However, the difference is that it can be produced using a simple vapor deposition method or a light irradiation vapor deposition method.

[0007] It is preferable to use a photochromic compound as the layer whose refractive index changes according to the control light. Since this photochromism is self-retaining, there is no need to continuously apply electricity to the heater section to continuously apply heat, unlike conventional optical switches, and the difference is that power consumption can be reduced. Photorefractive materials such as ferroelectric crystals, which are inorganic materials, are well-known as materials whose refractive index changes when irradiated with light. In addition, photochromic materials are known to change their refractive index due to changes in their molecular structure.
By using these materials, the refractive index can be changed using control light. In addition, these organic photochromic materials can be produced using a simple vapor deposition method or a light irradiation vapor deposition method (patent application filed in 1983).
1-117406). From the above, optical switching, which is the object of the present invention, is made possible. An advantage of creating a layer with a variable refractive index in an optical coupler using a vapor deposition method or a light irradiation vapor deposition method is that, for example, when an organic substance is used as a material with a variable refractive index, when dispersed in a polymer film, etc. The concentration decreases, the refractive index change becomes smaller, and the switching efficiency decreases, but when fabricated using the vapor deposition method or the light irradiation vapor deposition method, the concentration is 100%, which dramatically increases the switching efficiency to the point where no further increase can be expected. It is to rise to.

[0008]

[Examples] The present invention will be explained in detail with reference to Examples below, but the present invention is not limited to these Examples.

Example 1 A method for manufacturing a layer whose refractive index is changed by control light in an optical coupler will be described. SiO2 on silicon substrate
was fabricated by sputtering, and an optical coupler with a waveguide structure was fabricated using a conventional method. On this coupler, adamantylidene fulgide (abbreviation: AF), which is a photochromic compound, was deposited at a vacuum degree of 1×10 −5 Torr and a deposition rate of 2 to 50 Å/sec. The molecular structural formula of AF is shown below.

0010

[Chemical formula 1]

An overview of the fabricated optical switching device is shown in FIG.
Shown below. That is, FIG. 1 is a diagram showing an outline of an optical switching element according to the present invention, in which 21 and 22 are optical waveguides made of quartz, and 23 is an AF whose refractive index is changed by control light.
Layer 24 is a silicon substrate. In this way, an optical switching element having an AF layer whose refractive index changes with control light inside the coupler was manufactured.

Example 2 An optical coupler having a waveguide structure was fabricated using the same method as in Example 1, and a photochromic compound, 1',3',3'-trimethyl-6-nitrospiro- [2H-1-benzopyran-2,2'-indoline] (abbreviation: NBPS) was produced by a light irradiation vapor deposition method. The molecular structural formula of NBPS is shown below.

[0013]

[Case 2]

[0014] NBPS becomes a microcrystalline opaque film that does not exhibit photochromism when used with a normal vapor deposition method, but it becomes a stable transparent film when formed using a light irradiation vapor deposition method (see the specification of Japanese Patent Application No. 117406/1986). Shows photochromism. The light irradiated during vapor deposition was ultraviolet light, and the other vapor deposition conditions were the same as in Example 1. FIG. 3 shows an outline of the optical switching device produced. That is, FIG. 3 is a diagram showing an outline of an optical switching element according to the present invention, in which 31 and 32 are optical waveguides made of quartz, 33 is an NBPS layer whose refractive index changes depending on the control light, and 34 is a silicon substrate. In this way, an optical switching element having an NBPS layer whose refractive index changes with control light inside the coupler was manufactured.

Example 3 A signal light (wavelength: 1.55 μm) was passed through the optical switching element manufactured in Example 1 from the right side of the waveguide 21 in FIG. Before the control light was irradiated, the signal light that had passed through the optical coupler was observed on the left side of the waveguide 21, and the signal light was not switched to the waveguide 22. When ultraviolet light was irradiated to 23 in FIG. 1 as control light, the signal light was immediately switched and observed on the left side of the waveguide 22, indicating that switching was successful. As a result of examining the switching speed, it was found that switching occurs within nanoseconds (1×10 −9 seconds). If visible light is further irradiated as control light,
The signal light was immediately switched and observed on the left side of the waveguide 21. This switching phenomenon could be repeated every time the control light was irradiated.

Example 4 Signal light (wavelength: 1.55 μm) was passed through the optical switching element manufactured in Example 2 from the right side of the waveguide 31 in FIG. Before the control light was irradiated, the signal light that had passed through the optical coupler was observed on the left side of the waveguide 31, and the signal light was not switched to the waveguide 32. When visible light was irradiated to 33 in FIG. 3 as control light, the signal light was immediately switched and observed on the left side of the waveguide 32, indicating that switching was successful. When ultraviolet light was further irradiated as control light, the signal light was immediately switched and observed on the left side of the waveguide 31. This switching phenomenon could be repeated every time the control light was irradiated.

[0017]

As described above, the present invention enables optical switching to be performed using control light, and has the advantage that the switching speed is theoretically faster than that of conventional optical switching elements. Furthermore, since photochromism is self-retaining, there is no need to continuously apply electricity to the heater section to continuously apply heat, unlike conventional optical switches, which has the advantage of reducing power consumption. The present invention using photochromism has a large refractive index change due to light, so
When designing an optical coupler, it is possible to have a large operating margin for the coupler, and it is possible to obtain an optical switch that operates stably against external noise such as heat and stress. In addition, it can be manufactured using vapor deposition method or light irradiation vapor deposition method, and does not require the complicated manufacturing process of conventional optical switching devices, which has advantages over conventional device manufacturing methods in terms of yield and cost. have. Optical switches fabricated by vapor deposition or light irradiation vapor deposition have less loss of waveguides due to contamination by dust and dirt than those produced by wet spin coating using a solvent. In addition, the internal strain stress of the fabricated amorphous vapor-deposited film itself is 1 to 3 orders of magnitude lower than that of conventional optical switches that require a substrate heating process and post-bake, reducing changes due to stress between couplers and noise. You can.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of an optical switching element according to the present invention.

FIG. 2 is a diagram illustrating a conventional optical switching element, and is a diagram of the conventional optical switching element seen from above.

FIG. 3 is a diagram showing an outline of an optical switching element according to the present invention.

[Explanation of symbols]

1, 2, 21, 22, 31 and 32: quartz optical waveguide, 3: first optical coupler, 4: second optical coupler, 5: thin film heater, 6, 24 and 34: silicon substrate, 23: AF layer whose refractive index changes according to control light, 33: NBPS layer whose refractive index changes according to control light

Claims (3)

[Claims] 1. An optical switching element characterized in that a layer whose refractive index is changed by control light is provided between the optical waveguides of a coupler made of optical waveguides. 2. The optical switching element according to claim 1, wherein a photochromic compound is used as the layer whose refractive index is changed by the control light. 3. The method for manufacturing an optical switching element according to claim 1, wherein the layer whose refractive index changes according to the control light is formed by a vapor deposition method or a light irradiation vapor deposition method. Production method.