JPS61137126A - Optical switch - Google Patents

Abstract

PURPOSE:To simplify the constitution of a total reflection type optical switch and to reduce its size and thickness by arranging a medium which has a variable refractive index between transparent substrates of specific-shape structure, and controlling the transmission and reflection of incident luminous flux. CONSTITUTION:The medium 2 having a variable refractive index is arranged between the transparent substrates 1 of plural-triangle structure which has pitch smaller than the diameter of luminous flux and is of such size that incident luminous flux is not refracted across transparent electrodes 3, and the transmission and reflection of luminous flux are controlled from total reflection to total transmission according to variation in the refractive index of the medium corresponding to feeding to electrodes and the tilt angle of triangle structure parts. Consequently, the constitution of the total reflection type optical switch array is simplified and reduced in size and thickness.

Description

[Detailed description of the invention] (1) Technical field The present invention relates to optical switches.

(2) Prior Art Conventionally, there have been optical switches that utilize the electro-optic effect, thermo-optic effect, and magneto-optic effect of crystals such as LiNbO3, or the electro-optic effect and thermo-optic effect of liquid crystals.

Although optical switches using crystals have excellent response speed, they have problems with luminous flux utilization efficiency, contrast ratio, and drive voltage, while optical switches using liquid crystals have a simple configuration and excellent contrast ratio. On the other hand, there were problems with response characteristics and luminous flux utilization efficiency.

Technical Research Report 0QE81-116, Optical Society Op America Spring 1980 Issue P, 147
As shown in
By filling liquid crystal between electrodes that have been subjected to orientation treatment such as oblique evaporation treatment such as gFz, and controlling the orientation direction of the liquid crystal using an electric field, the refractive index perceived by the incident light is changed, resulting in total reflection and total reflection of the luminous flux. There are some that perform transmission switching.

Therefore, methods such as using a trapezoidal substrate, coupling with an optical fiber, or attaching separate input/output prisms have been used. Therefore, the scope of use is limited to ordinary optical switches between fibers, etc., and total reflection type optical switches cannot be used in optical shutter arrays for displays, liquid crystal printers, etc.

(3) Summary of the invention The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples, and to provide a total internal reflection type optical switch that is simple, can be made thin, and can be used in a wide range of applications. In order to achieve this, the optical switch according to the present invention has a configuration in which a variable refractive index medium is arranged between transparent substrates, at least one of which has a plurality of triangular structures, and the pitch of the triangular structures is smaller than the diameter of the incident light beam. Depending on what you do, there may be more than one. Therefore, it is possible to reflect the incident light beam on a minute slope, and also to make the light beam perpendicularly incident on the substrate, thereby achieving a thinner device.

However, the triangular structure must be large enough to prevent the incident light beam from being diffracted. The transparent substrate may have various configurations depending on the means for controlling the refractive index of the variable refractive index medium used.

For example, when a liquid crystal is used as the variable refractive index medium, the transparent substrate can be composed of a transparent electrode or a transparent electrode and a transparent insulator. As a variable refractive index medium other than liquid crystal, 0
074,02H50H.

PMMA, those that change with heat such as T101, LiNb01. LiTaO5, KDP, ADP,
PLZT.

Zllo, BaTits + B50r Ba2Na
Those that change due to electric field such as Nbsets, MnB1.
Things that change due to magnetic fields such as EuO, O8! By controlling the refractive index of the variable refractive index medium, the light incident on the optical switch is directed to the interface between the slope having a predetermined inclination angle and the variable refractive index medium. The light intensity is modulated from total transmission to total reflection.

A variable refractive index medium 2 whose refractive index can be controlled by heat is placed on the same surface as the heater 4. Also, Figure 1 (
The optical switch B) is a miniaturized version of the sloped structure of the side substrates 1. Each side substrate 1 has a plurality of triangular structures, and a transparent electrode 3 is formed by vapor deposition etc. between the two side plates. A variable refractive index medium 2 is arranged. Further, the angle of inclination of the triangle is made to form an appropriate predetermined angle by considering the total reflection rule r1: formula derived from Snell's law.

Figure 2 shows an electric field controlled optical switch and its functions.The basic configuration is the same as the element in Figure 1 (0), but a transparent insulator 5 is further provided on top of the transparent electrode 3, and the refractive index is variable. Liquid crystal 6 is used as the medium. Similarly, as the transparent electrode 3, ■
TO, 5n02°In, 0. transparent insulator 51
This is glass Si02, SiO, MgF22 A
120m> Materials such as TiO2 and various optical glasses and optical plastics can be used for the transparent substrate 1. or,
As the liquid crystal 6, nematic liquid crystals having positive dielectric properties, 9 smectic liquid crystals having ferroelectric properties, etc. are widely used.Hereinafter, the functions of the optical switch according to the present invention will be explained using the optical switch shown in FIG. . In Figure 2, 7
8 represents incident light, 8 represents reflected light, 9 represents transmitted light, and 10 represents power source. Similarly, a nematic liquid crystal is used for the liquid crystal 6, and the sawtooth wavefront shown in FIG. There is.

When a light flux polarized in the sawtooth wavefront groove direction (perpendicular to the incident surface) is perpendicularly incident on this optical switch, in a static state, the polarization direction of the incident light 7 is in the alignment direction of the liquid crystal 6, that is, in the sawtooth wavefront groove direction. Consistent with this, the effective refractive index of the liquid crystal 6 with respect to the incident light 7 becomes the extraordinary refractive index n6. Here, transparent substrate 1. transparent °
Electrode 3. By matching the refractive index of the transparent insulator 5 and the extraordinary refractive index n6 of the liquid crystal 6, all of the incident light 7 becomes transmitted light 9 and is emitted as shown in FIG. 2(A). Next, when an electric field is applied between the transparent electrodes 3, the liquid crystal 6 begins to tilt in the direction of the electric field, and when the amount of electric field reaches a predetermined value, the liquid crystal 6 is aligned in the direction of the electric field (parallel to the plane of incidence). , the refractive index of the liquid crystal 6 with respect to the incident light 7 is the ordinary refractive index no. At this time, the incident light 7 will be incident on the liquid crystal 6 at the tilt angle θ of the plurality of slopes, and if the following equation (1) is satisfied, the incident light 7 will be transparent as shown in Figure 2 (B). It is totally reflected at the interface between the insulator 5 and the liquid crystal 6 and becomes n'C reflected light 8.

sin θ > n 6/n g ””・・”
- (1) Here, transparent insulator 5. Transparent electrode 3. The refractive index of the transparent substrate 1 is unified to ng. However, transparent 1 pole 3
．． If the thickness of the transparent insulator 5 is sufficiently small compared to the wavelength of the incident light 7, the refractive forces of the transparent electrode 3 and the transparent insulator 5 can be ignored. At this time, the conditions for total transmission and total reflection are mainly determined by the refractive index of the transparent substrate 1 and the liquid crystal 6 and the inclination angles of the plurality of slopes. Furthermore, by appropriately adjusting the amount of applied electric field, it is possible to control the amount of transmitted light. In the same way, in consideration of luminous flux utilization efficiency and prevention of ghost sources,
It is better to provide an anti-reflection film on the light output surface.

The process of creating this optical switch and the results of performance evaluation are shown below.

FIG. 3 is a three-dimensional view of the present optical switch, in which 11 indicates an extraction electrode, 12 indicates a slope structure region, and other numbers are the same as in FIG. 2.

La5FO3 glass (manufactured by Antifreeze Optical Glass Manufacturing Co., Ltd.)

20 x 30 x 2 mm", refractive index 1.80 for A-63281). After polishing both sides to a flatness within a few knee-ton rings, methanol, trichlene,
Ultrasonic cleaning with acetone and pure water, followed by nitrogen gas ζ
After drying, baking was performed in nitrogen at 120° C. Cl2O for minutes. Next, one side of the light incident area (10X1
0mffl) using a ruling machine to set the apex angle 60',
A sawtooth wavefront with a pitch of 0.5 mm was formed, and an ITO film was formed to a thickness of 200°, 1 by ion blating. The IT'O film had a sheet resistance of 16 Ω/sq and a refractive index of 1.80 at a wavelength of 6328. After etching the ITO film to form an electrode shape,
From the electron beam evaporation method ζ, except for the extraction electrode part A
A J*Os film was obliquely deposited to a thickness of 100 OA to provide electrical insulation from the counter electrode surface and to provide a remaining mass for alignment of the liquid crystal. The film thickness is 5000mm on the extraction electrode part. (An Al'tIL pole is formed, and an anti-reflection MgFM film is coated on the back surface of the transparent substrate.)
A film was formed to a thickness of 146 people.

Subsequently, a substrate having a sawtooth wavefront similar to that described above was manufactured using La5F03 glass. However, if the two boards are
As shown in the figure, one sawtooth wave surface is concave and the other is convex in order to engage with each other. Further, as a single-sided ζ spacer, 810 snow f1% was formed to a thickness of 7 μm around the sawtooth wave front.

The two substrates were placed opposite each other at the toothed wavefront region 12, filled with liquid crystal, and sealed. The liquid crystal used was a positive dielectric liquid crystal R,0-TN200 (manufactured by Rossi Gu).

Wavelength: n 6 = 1.53 * n for 6328 people
e −1, 80). Finally, the lead wire was pulled out and bonded to the Ill pole 11, and connected to the power source 8 to create the optical switch shown in FIG. 4.

When a He-Ne laser beam (J-63281) polarized in the groove direction of the sawtooth wavefront is perpendicularly incident on the substrate surface of this optical switch, the incident light passes through the optical switch in a static state. The transmitted light was 9, and the ratio of the transmitted light to the incident light reached 95q6 or more. Also, 10 Vppt I
When a rectangular AC electric field of K)iz was applied, the incident light was totally reflected, and the ratio of transmitted light 9 to incident light 7 was 0.5% or less. Similarly, the light source is not limited to lasers, and white light sources such as LEDs, halogen lamps, and fluorescent lights can also be used.

(5) As described in detail, the optical switch according to the present invention has a simple configuration, is compact, and is easy to connect to each volatile device.
It is an optical switch with advanced functions.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the basic configuration of an optical switch according to the present invention. Figure 2 is a diagram showing an electric field type optical switch and its functions. FIG. 3 is a three-dimensional view of the optical switch shown in FIG. 2.

Claims (1)

[Claims] A refractive index variable medium is disposed between transparent substrates in which at least one of the substrates has a plurality of triangular structures, and the pitch of the triangular structures is smaller than the diameter of the incident light beam, and the refractive index of the refractive index variable medium is controlled. An optical switch characterized in that transmission and reflection of an incident light beam is controlled at an interface between the plurality of slopes of the triangular structure and the refractive index variable medium.