JPH04121713A - Optical deflecting element - Google Patents

Abstract

PURPOSE:To allow light deflection in many directions at a high speed by arranging plural comb-shaped electrodes on an optical waveguide so as to successively generate Bragg diffractions. CONSTITUTION:Since an LiNbO3 substrate 1 has an electrooptical effect, the refractive index of the optical waveguide 2 changes by impressing a voltage between electrodes 4a and 4b. The light Pi which propagates in the optical waveguide 2 and progresses to the place of the electrodes 4 is diffracted at a prescribed angle and is made into diffracted light Pd if the grating space of the diffraction gratings by the comb-shaped electrode 4 is as determined that the wavelength of the refractive index Pi and the incident angle satisfy the Bragg diffraction conditions. The incident light Pi advances rectilinear to provide the transmitted light Pt when the voltage is not impressed to the electrodes 4. The control of the propagation direction of light in two ways is possible if the impression of the voltage is controlled by a switch 6. The progressing direction of light is controlled in the direction of 2n if n-pieces of the electrodes 4 are used.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflection element that utilizes the electro-optic effect to control the traveling direction of light propagating within a leading waveguide by an externally applied voltage.

Conventional technology and its problems Optical deflection elements that control the traveling direction of light include a rotating polygon mirror scanner that deflects light by rotating a polygon mirror, and a hologram scanner that deflects light by rotating a hologram disk. disk scanner.

There are galvanometer deflection scanners that use galvanometers. However, since these optical deflection elements control the traveling direction of the light by mechanically rotating a mirror, hologram disk, etc., there is a limit to high-speed optical deflection due to the inertia of the mirror etc. As the equipment becomes larger,
It is difficult to achieve miniaturization. Poor durability. There is a problem.

In order to solve the above problems, we have developed a light beam polarizer that deflects light by applying a voltage to a crystal with an electro-optic effect and changes the refractive index, and a Bragg-wave polarizer that uses surface acoustic waves to propagate on a leading waveguide. There are Bragg modulation circuits that utilize the acousto-optic effect to deflect light through diffraction. However, in these optical deflection elements, the deflection angle is small and the number of resolution points is small, so they are not practical.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION An object of the present invention is to provide a compact optical deflection element that can achieve high-speed and multidirectional optical deflection and has excellent durability.

Structure 1 of the Invention Functions and Effects The optical deflection element according to the present invention has a plurality of <゛It is characterized by a square shaped electrode.

According to this invention, when a voltage is applied to the comb-shaped electrodes on the leading waveguide, the refractive index of the optical waveguide changes due to the electro-optic effect. This refractive index change differs depending on the direction of the electric field. In comb-shaped electrodes, the direction of the electric field alternates in each region between the electrodes. For this reason, regions with a relatively high refractive index and regions with a relatively low refractive index are alternately formed in the leading waveguide, forming a gradient index diffraction grating. The light propagating through the leading waveguide is subjected to Bragg diffraction by this diffraction grating. When no voltage is applied to the comb-shaped electrodes, light travels straight without being diffracted. In this way, the traveling direction of light can be controlled in two directions with one comb-shaped electrode. Therefore, by arranging n comb-shaped electrodes in a fixed direction on the leading waveguide, the traveling direction of light can be controlled in the 2n direction.

The optical deflection element according to the present invention utilizes the electro-optic effect, so high-speed deflection is possible.

Furthermore, by appropriately shaping the comb-shaped electrodes, optical deflection with a high signal-to-noise ratio can be achieved even with a low driving voltage.

Furthermore, since the optical waveguide and comb-shaped electrodes are formed of a material that has an electro-optic effect, it is easy to miniaturize the device and its durability is improved.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an embodiment of the present invention, and is a perspective view of a light deflection element.

Y-cut LiNb0. An optical waveguide layer 2 is formed on a substrate 1 by thermally diffusing Ti. The optical waveguide layer 2 is TE
Its thickness is adjusted to provide a single mode leading wavepath for propagating the mode of light. A SiO2 film 3 is formed on this optical waveguide layer 2 by sputtering. Further, on the 5in2 film 3, a comb-shaped electrode 4 consisting of two electrodes 4a and 4b alternately arranged at a predetermined interval is formed by photolithography. A plurality of comb-shaped electrodes 4 are arranged in rows. As shown in FIG. 3, each of these comb-shaped electrodes 4 is connected to a DC power source 5 via a switch 6 between the electrodes 4a and 4b.

Since the LiNb0i substrate 1 has an electro-optic effect, the electrode 4
By applying a voltage between a and 4b, the leading wave layer 2
The refractive index of changes. The change in refractive index differs depending on the direction of the electric field in the leading wave layer 2.

Referring to FIG. 2, if the refractive index of the substrate 1 is n, the refractive index increases by Δn in the region D1 between the electrodes 4a and 4b, and n
+Δn, and in the region Dd adjacent thereto, the refractive index decreases to n-Δn. Therefore, regions D1 with a high refractive index and regions Dd with a low refractive index are periodically formed in the optical waveguide layer 2. As a result, a gradient index diffraction grating is created in the leading wave layer 2.

Referring again to FIG. 3, if the grating spacing of the diffraction grating formed by the comb-shaped electrode 4, the wavelength of the incident light P1, and its angle of incidence with respect to the diffraction grating are determined so as to satisfy the Bragg diffraction conditions, the leading wave layer The light P1 propagating through the comb-shaped electrode 4 is diffracted at a predetermined angle by Bragg diffraction and becomes a diffracted light Pd. When no voltage is applied to the comb-shaped electrodes 4, no diffraction grating is generated in the leading wave layer 2, so the incident light Pi is not diffracted and travels straight through the portion where the electrodes 4 are formed to become transmitted light Pt. By forming the comb-shaped electrodes 4 on the optical waveguide layer 2 in this manner and controlling the application of voltage with the switch 6, the propagation direction of light can be controlled in two directions. If n comb-shaped electrodes 4 are arranged and formed on the optical waveguide layer 2 and the light is sequentially diffracted, the traveling direction of the light can be controlled in the 2° direction. Actually, as shown in Fig. 1, Y cut L i N b O3
A leading wave layer 2 and four pairs of comb-shaped electrodes 4 are formed on a substrate 1.

5 for the X axis. When light was incident at an angle of l@, the light could be emitted to 16 different points by changing the combination of whether or not a voltage was applied to the four pairs of comb-shaped electrodes 4.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the optical deflection element, and FIG. 2 is a plan view showing how the refractive index changes with the application of voltage. FIG. 3 is a plan view showing how incident light is controlled in two directions. 1...L i N b 03 board. 2... Optical waveguide layer. 4...Comb-shaped electrode. that's all

Claims (1)

[Claims] An optical deflection element in which a plurality of comb-shaped electrodes are formed on an optical waveguide made of a material with an electro-optic effect, arranged so as to sequentially cause Bragg diffraction in the light propagating through the optical waveguide.