JPS58125025A - Two-dimensional optical deflector - Google Patents

Abstract

PURPOSE:To extend the range of polarization, by changing the oscillation frequency for comb-shaped electrodes to not only deflect a Bragg-diffracted optical beam in the plane of a thin film optical waveguide but also change the refractive index of the thin film optical waveguide near an exit end face. CONSTITUTION:When comb-shaped electrodes 3 are driven with a certain frequency (f), surface acoustic waves SAW of a wavelength are generated on a thin film optical waveguide 2, and the refractive index is changed at a periodic pitch in the optical waveguide 2, and optical beam P1 of the waveguide which is incident at an angle theta to the wave surface becomes a Bragg-diffracted optical beam P2 reflected by the wave surface if the condition of an expressionIis satisfied. When the driving frequency (f) for comb-shaped electrodes 3 is changed to f+ or -DELTAf, the advance direction of the optical beam P2 is changed in the range of an angle DELTAtheta. That is, the oscillation frequency of a high frequency oscillator 7 is changed continuously in a certain range to change the advance direction of the optical beam P2 continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid thin film type two-dimensional optical deflector that avoids deflecting light propagating in a thin film guided waveguide in two dimensional directions by an acousto-optic effect and a thermo-optic effect. , relates to a device that allows a large deflection angle of a light beam due to the thermo-optic effect.

Currently, barcode readers and laser printers.

2. Description of the Related Art In various photoelectronic application devices such as facsimile machines, photoelectric deep wound devices, and optical memories, the need to two-dimensionally control the traveling direction of light beams such as laser beams is increasing. A two-dimensional optical deflector for this purpose conventionally deflects two-dimensional light 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. J to do
It's becoming a sea urchin. This type of mechanical optical deflector has movable parts, so it has disadvantages in terms of high speed and reliability, and the optical system is complicated, so it is necessary to reduce the size, cost, and align the optical axis. There are also problems in terms of ease of manufacture, including problems in terms of ease of manufacture, and there are also problems in terms of power consumption.

This invention was developed in view of the conventional problems mentioned above, and its basic purpose is to two-dimensionally control the traveling direction of a light beam using a compact solid thin film type device with no mechanically moving parts. The object of the present invention is to provide a two-dimensional optical deflector that can be controlled and is excellent in terms of high speed, reliability, and ease of manufacture.

Based on this basic objective, the present inventors first transmitted a light beam propagated into a thin film optical waveguide formed on the substrate surface.
The acousto-optic effect (Bragg diffraction phenomenon) due to surface acoustic waves generated from the comb-shaped electrode installed on this G-film guided waveguide, and the electric heat generation Thermo-optical effects controlled by the body (
We have developed a two-dimensional optical deflector that deflects the optical waveguide two-dimensionally due to the change in the refractive index of the optical waveguide, and have already filed a patent application for this.

The specific objects of this invention are as follows:
In the dimensional light deflector, especially it! To realize a two-dimensional optical deflector in which the temperature gradient near the output end face of the l-film optical waveguide can be increased, thereby increasing the deflection angle of the light beam due to the thermo-optic effect. It is in.

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 a substrate 1, a comb-shaped electrode 3 that propagates a surface acoustic wave SΔW onto the thin film optical waveguide 2, and a comb-shaped electrode 3 that receives an external optical beam PO. a light introduction section consisting of a grating coupler 4 that propagates the light beam P1 into the thin film optical waveguide 2 so as to form a Bragg angle with respect to the wavefront of the surface acoustic wave SAW; A direct current type 11' is provided on the output end face 2a of the thin film guided waveguide 2 from which the light beam P2 is outputted as a light beam P3 to the outside, and on the north edge of the thin film optical waveguide 2 near the output end face 2a. The comb-shaped By controlling the high-frequency oscillator 7 that drives the electrode 3 and changing the vibration frequency of the comb-shaped electrode 3, the light beam P2 that is Bragg-diffracted by the surface acoustic wave SΔW is deflected within the plane of the thin-film optical waveguide 2, and the above-mentioned By controlling the DC power supply 8 applied to the heat generating electrode 6 and changing its heat generation temperature, the refractive index of the thin film optical waveguide 2 near the output end face 2a is changed, and the light beam P3 emitted from the output end face 2a is changed. It is configured to be deflected in a direction perpendicular to the thin film optical waveguide 2. Note that the two-dimensional deflection of the light beam P3 emitted from the output end face 2a can be observed on a screen 9.
It is indicated by the dot above.

The substrate 1 is made of niobium sanlithium (L), which is a piezoelectric crystal.
, i N l) O! ) is made of a single crystal, titanium ([i) is thermally diffused on the surface of this crystal, and the temperature is 0°00 from the substrate 1.
3.-〇, a high refractive index of about 005 with a refractive index of about 2°2;
An i1 film optical waveguide 2 is formed. The heating element 5-pole 6 is formed by depositing a nickel-chromium alloy on the thin film guiding waveguide 2.

The comb-shaped electrode 3 is connected to the substrate 1- which constitutes the thin-film optical waveguide 2.
It is made using the lift-off method.

Further, as shown in the enlarged view of FIG. 3, the lower surface of the substrate 1 on the side of the output OiJ end surface 2a, that is, the lower surface of the side facing the heating electrode 6, is etched by means such as etching or polishing. It is partially cut, and the lower surface of the thin film optical waveguide 2 is exposed in the cut portion. What is the situation? Then, P1 to Sink 10 made of a material with high thermal conductivity are bonded to the cut part of this substrate 1, and this part (here, the thin film optical waveguide 2 is connected to heating electrode 6 and -1 to Sink 10). In other words, the thin film optical waveguide 2 is heated from its upper surface by the heat generating electrode 6, and its lower surface is radiated and cooled by the heat sink 10. Note that the heat sink 10 is formed with fins or the like. It is desirable to improve heat dissipation and cooling effects.

Next, the operation of the two-dimensional optical deflector having the above configuration will be described in detail. When the comb-shaped electrode 3 is driven at a certain frequency, a surface acoustic wave SAW of wavelength Δ is generated in the thin film optical waveguide 2.1-, as shown in FIG. This surface acoustic wave SA
W causes a periodic refractive index change with a pitch Δ in the thin film optical waveguide 2, and the wave of this refractive index change acts as a diffraction grating, and the light beam 1XP1 at a wavelength incident at an angle of 0 to the wavefront of this When the following equation is satisfied, the light beam 1)2 that is deflected by the wavefront and subjected to Bragg diffraction becomes louder.

θ-arcsin (λ/2Δ) Here, the propagation pattern 1 to 1 of the surface acoustic wave SAW is the X-direction component in FIG. When the frequency 1 is changed within a certain range to be f±Δr, the Bragg diffracted light beam P2
As shown in FIG. 2, the direction of travel changes within the range of Δθ within the plane of the thin film optical waveguide 2. Lee, 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, the substrate 1 made of a lithium niobate single crystal is a crystal whose refractive index changes depending on the temperature.

Therefore, when an appropriate voltage is applied to the heating electrode 6 from the DC power supply 8 to generate heat, the heat is transmitted to the A9 film leading waveguide 2, and the refractive index of the N9 leading waveguide 2 is increased by the heat. At this time, the larger the temperature rise, the larger the change in the refractive index, so the refractive index increases closer to the heating electrode 6. Fourth
The figure shows the relationship between the change in the refractive index of the thin film optical waveguide 2 at the direct F portion of the heating electrode 6 and the distance from the heating electrode 6. , B, and C as parameters.

As shown in the figure, the refractive index change Δ11 of the thin film optical waveguide 2 is
The closer the heating electrode 6 is, the larger the heating temperature becomes, and the higher the heating temperature of the photothermal electrode 6 is, the larger the heating temperature becomes. In other words, as shown in FIG. 3 when looking at the longitudinal cross section of the portion directly below the heating electrode 6, a graded increase in the refractive index occurs in the optical waveguide 2 immediately below the heating electrode 6 as shown by the dotted line, and the change in refractive index shown in A. f8i acts in the same way as Jζ where /rhythm is placed equivalently in the optical waveguide 2.

In general, just as the propagation direction of light is generally changed by a prism, by applying a voltage to the heating electrode 6, the equivalent prism is Due to the action, light beam 1]
2 is deflected upward when passing through this portion, and is emitted from the output end face 2a as a light beam P3. At that time,
The deflection angle Δα of the light beam P3 relative to straight light traveling parallel to the plane of the thin-film optical waveguide 2 depends on the degree of change in the refractive index of the optical waveguide 2 that acts as an equivalent prism, that is, the magnitude of the heating temperature by the heating electrode 6. Changes will occur accordingly. That is, by changing the voltage of the DC power supply 8 applied to the heating electrode 6, the light beam P3 emitted from the output OA end face 2a can be deflected in a direction perpendicular to the plane of the thin film optical waveguide 2.

By combining the deflection control by the high-frequency oscillator 7 and the deflection control by the DC power supply 8, the direction of travel of the light beam P3 emitted from the exit end face 2a is indicated by each dot on the screen 9. can be arbitrarily controlled two-dimensionally.

9- Here, in the present invention, the portion near the output end surface 2a of the 1fIJ film optical waveguide 2 is heated from the upper surface side by the heat generating electrode 6, and at the same time, the heat is radiated and cooled by the heat sink 10 from the lower surface side. It is possible to make the temperature gradient of the part very large. The fact that the temperature gradient directly under the electrode 6 can be easily increased means that the vertical deflection angle of the optical beam I\P3 can be increased due to the effect of the equivalent prism, and the temperature gradient directly under the electrode 6 can be increased. This means that the deflection angle of the light beam P3 can be greatly changed by a small change in voltage, resulting in high sensitivity.

As explained in detail above, the two-dimensional optical deflector according to the present invention utilizes the acousto-optic effect and the thermo-optic effect to direct the traveling direction of the light beam into the thin film optical waveguide formed on the substrate. It is dimensionally controlled, has no mechanically moving parts, and is superior in terms of high speed and reliability, and uses integrated circuit technology to achieve uniform control. It is possible to mass-produce products with the same characteristics, and it is possible to realize a small and inexpensive solid thin film type two-dimensional optical deflector.In particular, in this -10- invention, the heat sink is used to heat the lower part of the electric heating element. It is possible to increase the humidity gradient, thereby allowing a large deflection angle of the light beam due to the action of an equivalent prism due to the thermo-optic effect, and a two-dimensional optical deflector with a large deflection range due to the aperture.

[Brief explanation of drawings]

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 waves SΔW, and FIG. 3 is a diagram for explaining the deflection of a light beam due to the thermo-optic effect of a thin film optical waveguide, and Figure 4 shows the change in refractive index due to heat generation of the heating electrode in order to obtain the above-mentioned thermo-optic effect. It is a graph showing a relationship. 1... Substrate 2... Thin film optical waveguide 2a... Output end face 3... Comb-shaped electrode 4... ...Grating Kabra 6...
...Heating electrode 7...High frequency oscillator 8...DC power supply 9...Screen 10...Heat sink SAW・・・・・・Surface acoustic wave PO, P1. P2. P3・・・・・・・Light Beam Special W (Applicant Tateishi Electric Co., Ltd. 1-17--1

Claims (1)

[Claims] (1) A thin-film optical waveguide formed on the substrate surface, a comb-shaped electrode that propagates a surface acoustic wave on the U-film optical waveguide, and a light beam directed above the surface at a Bragg angle with respect to the wavefront of the surface acoustic wave. A pre-introduction part for propagation into the thin film optical waveguide, an output end face of the thin film optical waveguide from which the light beam Bragg-diffracted by the surface acoustic wave is outputted to the outside, and an edge 1 of the thin film optical waveguide near the output end face. A heat sink is provided on the side of the optical waveguide so as to sandwich the thin film optical waveguide between the electric heating element and the electric heating element. By changing the black-diffracted light beam, the light beam is deflected within the plane of the thin-film guiding waveguide, and by changing the heat generation temperature of the electric heating element, the refractive index of the thin-film guiding waveguide near the output end face can be changed. A two-dimensional optical deflector, characterized in that the light beam emitted from the output end face is deflected in a direction perpendicular to the optical waveguide surface at the end of the R? film.