JPH05142514A - Optical switching device - Google Patents

Abstract

PURPOSE:To provide the optical switching device of high efficiency which can be easily controlled electrically, in the optical switching device using a ferroelectric liquid crystal hologram. CONSTITUTION:In the optical switching device consisting of a liquid crystal hologram 20 for controlling the advance direction of light which is made incident on a ferroelectric liquid crystal display element by displaying a hologram pattern on the ferroelectric liquid crystal display element, an optical system for leading the light into the liquid crystal hologram 20, and a photodetector array 30 for photodetecting the light diffracted by the hologram 20, a mirror 40 is installed in an optical path between the hologram 20 and the photodetector array 30, and the mirror 40 has a function for inverting symmetrical diffracted images by the hologram 20, superposing them onto the prescribed photodetector array 30, and condensing them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an optical wiring of an optical switch or an optical information processing device, and more particularly to a structure of an optical switching device used for its optical control.

[0002]

2. Description of the Related Art Optical wiring technology using a three-dimensional space has been actively studied for the purpose of increasing the density of wiring of optical information processing and optical switching processing equipment. In order to realize this, it is important to develop an optical switching element for dynamically controlling the light direction and switching the optical connection between the functional elements.

As a method of constructing such an optical switching element, a method of using a rewritable hologram element has been proposed and actively studied. FIG. 3 shows an outline of the configuration of such an apparatus. In FIG. 3, an input light source array 10, a rewritable hologram 20, and a light receiving element array 30 are provided. The input light from the light source array 10 is controlled by the hologram 20, and a predetermined light receiving element in the light receiving element array 30 is received. Connected to the element.

The hologram 20 plays a central role in such an optical switching element. As a rewritable hologram material, a photochromic film, a photorefractive liquid crystal, a thermoplastic, a photopolymer and the like have long been known. However, all of them are optical writing, and there are problems that the writing takes a long time and that a complicated and precise optical system is required for writing. In order to overcome this problem, a liquid crystal hologram has been proposed in which a hologram pattern is displayed on a liquid crystal display element that can be easily written electrically and the direction of light is controlled. In particular,
The one using a ferroelectric liquid crystal display element is promising as a rewritable hologram used for an optical switching device because it can realize a fine pixel on the order of μm and can obtain a large deflection angle.

However, since the ferroelectric liquid crystal can display only two values, a symmetrical diffraction image is formed and the power is divided. Therefore, when an optical switching device is configured using diffracted light in a specific direction, there is a problem that the power of the optical signal becomes half or less and the efficiency becomes low.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to an optical switching device using a ferroelectric liquid crystal hologram,
An object of the present invention is to provide a highly efficient optical switching device that overcomes the problem of low efficiency and can be easily controlled electrically.

[0007]

The optical switching device of the present invention displays a hologram pattern on a ferroelectric liquid crystal display element so that the traveling direction of light incident on the ferroelectric liquid crystal display element is controlled. In a light switching device comprising a liquid crystal hologram element for controlling, an optical system for introducing light into the liquid crystal hologram, and a light receiving device array for receiving light diffracted by the hologram, an optical path from the hologram to the light receiving device array. A mirror is installed therein, the diffraction image by the hologram is inverted by the mirror, and the light is superimposed and condensed on a predetermined light receiving device. By this, the power-divided symmetrical diffracted lights are overlapped again, and the efficiency is improved.

In the optical switching device of the present invention, the installed mirror has a reflecting surface which is perpendicular to the hologram surface and parallel to the axis of symmetry of the diffraction image by the hologram, and the light is received from the mirror. A convex lens is installed between the element arrays, and a light receiving element is arranged on the focal plane of the convex lens. Since the reflecting surface of the mirror is perpendicular to the hologram surface and is parallel to the symmetry axis of the diffraction image by the hologram, the symmetrical diffracted lights are folded back and become lights parallel to each other. When this is introduced into the convex lens, it is superposed on the focal plane of the lens and focused. The converging position is determined by the directions of the diffracted lights that have become parallel lights. Therefore, even when the diffraction angle is changed by changing the pattern of the hologram, the light is focused on a predetermined light receiving element on the focal plane according to each diffraction angle. Further, the condensing position by the convex lens does not change regardless of the emitting position on the hologram. Therefore, even if the hologram becomes large, there is no deviation. Further, this also makes it possible to drive the hologram in a divided manner to perform multi-input optical control.

Further, in the optical switching device of the present invention, when the hologram diffraction image has two axes of symmetry, the installed mirror is perpendicular to the hologram surface,
Further, it has two reflecting surfaces parallel to the respective axes of symmetry. According to the present invention, when a hologram for two-dimensional direction control is formed by rectangular pixels as in the case of a ferroelectric liquid crystal element, a diffraction image having two line symmetry axes orthogonal to each other may be obtained. However, it provides a method of superposition in such a case. That is, with a mirror parallel to one symmetry axis, diffracted light symmetrical to one symmetry axis is made parallel, and with a mirror parallel to another symmetry axis, diffraction diffracted to another symmetry axis. Make the light parallel. When the parallel light beams thus obtained are condensed by a convex lens, they are all superposed, and the efficiency can be improved.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of the first embodiment of the present invention. A liquid crystal hologram 20 and a mirror 4 having a reflection surface perpendicular to the liquid crystal hologram 20 and including the line symmetry axis of the diffraction image of the hologram.
0, a convex lens 50 capable of simultaneously collecting light diffracted from the hologram and light reflected from the mirror.
And the light receiving element array 30 is installed on the focal plane thereof.

The liquid crystal hologram 20 has a structure in which the drive circuit 25 can independently control the input signal lights 11 and 12 introduced into each of the hologram areas 21 and 22 which are divided and driven. The respective signal lights are diffracted by being divided into symmetrical directions by the holograms of the respective regions. One of the lights is reflected by the mirror and introduced into the convex lens 50 in parallel with the light that is not reflected. At this time, as shown in FIG. 1, the diffraction angles are different in each hologram area. Since the convex lens 50 has a function of condensing the incident parallel light at a predetermined position on the focal plane, if a light receiving element is placed at this position, the lights divided by the hologram are superposed and condensed. Efficiency doubles. At this time, the focus position is determined by the direction of the diffracted light that has become parallel. Therefore, if this direction is controlled by the hologram, the light receiving element to be connected can be selected. For example, in FIG. 1, the signal light 11 is the light receiving element 31.
Further, the signal light 12 is connected to the light receiving element 35. This connection relationship is independently controlled by the hologram pattern and can be arbitrarily switched and connected to the light receiving elements 31, 32, 33, 34, and 35. Furthermore, the signal light 11
It is also possible to connect and 12 to the same light receiving element. From the above, with the configuration shown in FIG. 1, a highly efficient optical switching device can be realized.

In the above embodiment, the hologram is divided into two for the sake of simplicity, and two signal lights are controlled. However, if the number of divisions is further increased, more signal lights can be controlled. This constitutes a multi-input / multi-output optical switching device. Further, if an optical fiber is used as the light receiving element, it is possible to directly connect to the optical fiber.

When square pixels are arranged in a grid pattern like a ferroelectric liquid crystal element, if a hologram pattern is displayed and two-dimensional direction control is performed, the directions of two sides of the square are changed. A diffraction image with the axis of symmetry may be obtained.
In other words, if you try to control the light in a specific direction,
It becomes light in the direction.

The second embodiment shown in FIG. 2 is applied to such a case. As in the case of FIG. 1, the configuration of this device includes a liquid crystal hologram 20, a mirror 40, a convex lens 50, and a light receiving element array 30, but the mirror 4
It has an L-shape with two reflecting surfaces of which 0 is orthogonal, each surface is perpendicular to the hologram surface, and has a surface parallel to each symmetry axis of the diffraction image by the hologram. .

Incident light 13 incident on the hologram is divided into light in four directions 1, 2, 3 and 4 symmetrical with respect to the two mirror surfaces. The input light 2 travels straight as it is, and the optical input 1 and the input light 4 are reflected once by the mirror to become light parallel to the input light 2. The input light 3 is reflected twice by the mirror and becomes parallel to the light of the input light 2. This allows
Although the four light beams are parallel, they are imaged by the convex lens 50 by being superimposed on a predetermined light receiving device on the focal plane thereof. This can significantly improve efficiency. Further, since the light condensing position is determined by the direction of the parallel light, it can be controlled by the hologram. Further, since the condensing position is determined by the direction of the diffracted light regardless of the position on the hologram, it is effective even if the hologram is large, and it is also possible to control multi-input light by driving the hologram separately. Become.

[0016]

As described above, in the optical switching device of the present invention, since the diffracted lights whose powers are split are superimposed, the efficiency of the conventional optical switching device using the ferroelectric liquid crystal hologram is improved. It has the advantages of overcoming the problem of low, being easily controllable electrically and having high efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of an optical switching device using a conventional hologram.

[Explanation of symbols]

 1, 2, 3, 4 Diffracted light 10 Input light source array 11, 12, 13 Input signal light 20 Hologram 21, 22 Divided driven hologram area 25 Drive circuit 30 Light receiving element array 31, 32, 33, 34, 35 Light receiving element 40 Mirror 50 Convex lens

Claims (3)

[Claims] 1. A liquid crystal hologram element for controlling a traveling direction of light incident on the ferroelectric liquid crystal display element by displaying a hologram pattern on the ferroelectric liquid crystal display element, and introducing light into the liquid crystal hologram. And an optical switching device including a light receiving device array that receives light diffracted by the hologram, a mirror is installed in an optical path from the hologram to the light receiving device array. An optical switching device having a function of inverting a symmetrical diffraction image of a hologram, superimposing it on a predetermined light receiving device, and collecting the light. 2. The optical switching device according to claim 1, wherein the installed mirror has a reflecting surface that is perpendicular to the hologram surface and that is parallel to the symmetry axis of the symmetrical diffraction image of the hologram. An optical switching device, wherein a convex lens is provided between the mirror and the light receiving element array, and the light receiving element is arranged on the focal plane of the convex lens. 3. The optical switching device according to claim 2, wherein when the hologram diffraction image has two symmetry axes, the installed mirror is perpendicular to the hologram plane and parallel to each symmetry axis. An optical switching device having two reflecting surfaces.