JPS58130327A - Two-dimensional optical deflector - Google Patents

Abstract

PURPOSE:To control the advancing directions of light beams two-dimensionally with a small-sized device of solid-state thin film type by deflecting the light beams propagating in optical waveguides of thin films in the direction perpendicular to the plane in the waveguides by an electrooptic effect or the like. CONSTITUTION:The advancing direction of a light beam P2 is changed continuously by changing the oscillation frequency of a high frequency oscillator 7 continuously in a certain range. When DC voltage is applied between electrodes 6, 6, a refractive index is generated in the crystal parts and changes according to the DC voltage. The light beam P3 can be deflected in the direction perpendicular to the plane of optical waveguides 2 of thin films by changing the voltage to be applied to the electrodes 6. The advancing directions of the light beams are controlled two-dimensionally with the small-sized device of solid state thin film type by combining the deflection control by the oscillator 7 and the deflection control by a DC power source 8 in the above-mentioned manner.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid thin film type two-dimensional optical deflector that deflects a light beam in two-dimensional directions using a VA film tipped optical waveguide acousto-optic effect or electro-optic effect.

Currently, Berni'-Dorida, Leli°-linta.

In various optoelectronic applied devices such as facsimiles, photoelectric flaw detection devices, and optical memories, there is an increasing need to two-dimensionally control the traveling direction of a light beam such as a laser beam. A two-dimensional beam width director for this purpose has conventionally been developed by mechanically displacing a part of an optical system through which a light beam passes, such as a set of rotating mirrors or a set of vibrating mirrors. It is designed to deflect. This type of mechanical optical deflector has moving parts, so it has drawbacks in terms of high speed and reliability, and the optical system is complicated, so it is difficult to manufacture, including miniaturization, cost reduction, and optical axis alignment. There are problems in terms of ease of use, etc., and there are also problems in terms of power consumption.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to be able to two-dimensionally control the traveling direction of a light beam using a small solid-state thin film type device with no mechanically movable parts. , and high speed.

It is an object of the present invention to provide a two-dimensional optical deflector that is excellent in terms of reliability and ease of manufacture.

In order to achieve the above object, the present invention deflects a light beam propagating in a thin film optical waveguide within the plane of the waveguide by causing Bragg diffraction by a surface acoustic wave propagating on the waveguide. , the Bragg-diffracted light beam is emitted to the outside from an exit grating formed on the waveguide, and the refractive index of a portion of the waveguide where the exit grating is formed is changed by an electro-optic effect or a thermo-optic effect. The optical waveguide is characterized in that the light beam emitted from the output grating is deflected in a direction perpendicular to the plane of the waveguide.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a perspective view showing the configuration of a two-dimensional optical deflector according to the present invention. This optical deflector includes a thin film optical waveguide 2 formed on one surface of a substrate, and a surface acoustic wave S
A comb-shaped electrode 3 that propagates the AW and a light beam PO from the outside.
The light beam P1 is then propagated into the thin film guiding waveguide 2 at a Bragg angle with respect to the wavefront of the surface acoustic wave SAW. an output grating 5 formed on the upper surface of the thin film guiding waveguide 2 in order to output the optical beam P2 to the outside as a optical beam P3; and a variable refractive index that changes the refractive index of the thin film guiding waveguide 2 in the portion where the output grating 5 is formed. A pair of electrodes 6 provided on the waveguide 2 on both sides of the output grating 5 are provided as means, and the vibration frequency of the comb-shaped electrode 3 is changed by controlling a high-frequency oscillator 7 that drives the comb-shaped electrode 3. deflects the light beam P2 Bragg diffracted by the surface acoustic wave SAW within the plane of the thin film optical waveguide 2, and controls the output voltage of the DC power supply 8 that applies a voltage between the pair of electrodes 6. causing a refractive index change in the thin film optical waveguide 2 in the area where the exit grating 5 is formed, due to the electro-optic effect;
It is configured to deflect the light beam P3 output from the output grating 5 in a direction perpendicular to the 2 surfaces of the thin film optical waveguide. Note that the two-dimensional deflection of the light beam P3 emitted from the output grating 5 is shown by dots on the screen 9.

The substrate 1 is made of a lithium niobate single crystal, which is a piezoelectric crystal, and titanium is thermally diffused onto the surface of the crystal to form an AM optical waveguide 2 having a refractive index about 0.003 to 0.005 higher than that of the substrate 1. are doing. The comb-shaped electrode 3 forms a thin film optical waveguide 2 and is made on the ICM board 1 using a lift-off method.

The above entrance grating 4 and exit grating 5
is made by forming silicon oxide or the like in a predetermined pattern at a predetermined position on the thin film guiding waveguide 2 by, for example, the CVD method.

The electrode 6 is formed by depositing an electrode metal such as aluminum at a predetermined position of the thin film optical waveguide 2.

Next, the operation of the -F-type two-dimensional optical deflector will be described in detail. When the comb-shaped electrode 3 is driven at a certain frequency f,
As shown in FIG. 2, a surface acoustic wave SAW with a wavelength is generated on the thin film optical waveguide 2. This surface acoustic wave SAW causes a periodic refractive index change in the pitch in the Ill optical waveguide 2, and the wave of this refractive index change acts as a diffraction grating,
A light beam P1 of wavelength Δ that is incident on this wavefront at an angle θ is reflected by the wavefront and becomes a Bragg-diffracted light beam P2 when the following equation is satisfied.

θ−arcsin (λ/2△) Here, the propagation vector of the surface acoustic wave SAW is
By having not only a directional component but also a 7-directional acid component, the driving frequency f of the comb-shaped electrode 3 can be changed within a certain range to achieve "±
When Δf, the traveling direction of the Bragg-diffracted light beam P2 is as shown in FIG.
It changes within a range of Δθ in a plane. That is, by continuously changing the oscillation frequency of the high-frequency oscillator 7 within a certain range, the traveling direction of the light beam P2'' can be continuously changed.

Further, due to the electro-optical effect of the substrate 1 made of lithium niobate single crystal, when a DC voltage is applied between the electrodes 6, 6,
A change in the refractive index occurs in the crystal part between the electrodes 6.6. This refractive index change occurs in the surface portion of the thin film optical waveguide 2 where the output grating 5 is formed. As shown in an enlarged view in FIG. 3, the refractive index change of the surface portion 2a of the WI film guiding waveguide 2 formed with the Bj radiation grating 5 is as follows: Therefore, the output angle of the light beam P3 output from the output grating 5 changes due to the change in the refractive index of the portion 2a. This change in the output angle is caused by the change in the part 2 of the thin film optical waveguide 2.
It changes depending on the degree of change in the refractive index of a. The degree of this refractive index changes depending on the DC voltage applied to the electrode 6.6. Therefore, DC electricity I! By changing the output voltage of 8 within a certain range, the output angle of the output light beam P3 can be changed within a certain range Δα. That is, by changing the voltage of the DC power supply 8 applied to the electrode 6, the light beam P3 emitted from the output crating 5 can be deflected in a direction perpendicular to the plane of the thin film optical waveguide 2.

As mentioned above, by combining the deflection control by the high frequency oscillator 7 and the deflection control by the DC power supply 8, the traveling direction of the light beam P3 can be arbitrarily controlled two-dimensionally as shown by the dots on the screen 9. can do.

In addition, as a refractive index variable means for changing the refractive index of the III film optical waveguide 2 in the forming part of the output grating 5, in the above embodiment, a DC voltage is applied between the electrodes 6, 6 to change the refractive index due to the electro-optic effect. However, the present invention is not limited to this, and since the substrate 1 made of lithium niobate single crystal is a crystal that exhibits a thermo-optic effect whose refractive index changes depending on IFi, it is possible to The necessary refractive index change can also be caused by providing an electric heating element that heats the above-mentioned portion 2a of the wave path 2 and changing the heating temperature thereof.

Further, in the above embodiment, the output grating is formed of a different material on the thin film optical waveguide, but the present invention is not limited to this, and the grating may be formed directly on the surface of the thin film optical waveguide. . Furthermore, the shape of the grating is not limited to the rectangular wave shape shown in the figure (although it is of course possible to use a sine wave or sawtooth wave shape).

As explained in detail above, the two-dimensional optical deflector according to the present invention uses the acousto-optic effect, electro-optic effect, and thermo-optic effect in the illumination optical waveguide formed on the substrate to control the traveling direction of the light beam. It is two-dimensionally controlled,
There are no mechanically moving parts like in the past, making it superior in terms of speed and reliability, and using optical integrated circuit technology, products with uniform characteristics can be produced in large quantities. A compact and inexpensive solid thin film type two-dimensional optical deflector can be realized.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the overall configuration of a two-dimensional optical deflector according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the Bragg diffraction phenomenon of a light beam due to surface acoustic wave SAW, and FIG. 3 FIG. 2 is a diagram for explaining the deflection of a light beam due to a change in refractive index of a portion where an output grating is formed in a thin film optical waveguide. １・・・・・・・・・Board 2・・・・・・・・・WI! s optical waveguide 2a...
・Part that causes refractive index change, 3...Comb-shaped electrode 4...Incidence grating 5...
...Exit grating 6... Electrode 7... High frequency oscillator 8... DC power supply 9...・Screen SAW・・・・・・Surface acoustic wave PO, P1. P2. P3・・・・・・Light beam patent applicant Tateishi Electric Co., Ltd.

Claims (1)

[Claims] <1> A thin film optical waveguide formed on a substrate surface, a comb-shaped electrode for propagating a surface acoustic wave on the thin film optical waveguide, and a comb-shaped electrode that is at a Plack angle with respect to the wavefront of the surface acoustic wave. a light introduction section for propagating a light beam into the S-type optical waveguide; and a 1C output grading formed on the upper surface of the thin-film optical waveguide for emitting the light beam that has been 1-lag diffracted by the surface acoustic wave to the outside. and a refractive index variable means for changing the refractive index of the thin film leading waveguide in the formation portion of the exit grating, and by changing the vibration frequency of the comb-shaped electrode, the Bragg-diffracted light beam is directed to the WI leading light guide. Deflecting within the wave path plane and 1. Two-dimensional optical deflection characterized in that the light beam emitted from the output cladding is deflected in a direction perpendicular to the surface of the thin film optical waveguide by changing the refractive index of the portion using a refractive index variable means. vessel. (2) The refractive index variable means includes an electrode provided near the output grade ink forming portion of the Ill optical waveguide, and by applying a voltage to this electrode, an electro-optic effect is applied to the thin film optical waveguide. 2. A two-dimensional optical deflector according to claim 1, which causes a change in refractive index.