JP2666836B2 - Solid state light deflector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical deflecting device, and more particularly to a technique for obtaining a large deflection angle. 2. Description of the Related Art Light deflection devices for deflecting light are used in devices such as laser beam printers and bar code readers. As such a light deflecting device, a polygon mirror, a hologram scanner, and the like are known. However, since each device has a mechanically movable portion such as a rotating mechanism and a driving device thereof, the device becomes complicated and large. Also, sufficient durability was not always obtained. On the other hand, a solid-state light deflecting element that deflects light by giving a change in the refractive index to a light transmission path by utilizing an electro-optic effect, an acousto-optic effect, a thermo-optic effect, or the like is conceivable.
According to such an optical deflecting element, there is an advantage that the device can be reduced in size and sufficient durability can be expected because there is no mechanically movable portion. However, according to the solid-state light deflecting element of this type,
Generally, there is a disadvantage that a sufficient deflection angle cannot be obtained yet. Means for Solving the Problems The present invention has been made in view of the above circumstances, and the gist of the present invention is to provide a two-dimensional optical waveguide formed on one surface of a substrate from a light source along one axis. A solid-state light deflecting device for imparting a relatively large deflection angle to propagating light, comprising: (a) provided at an output side portion of the substrate, for transmitting light propagating in a two-dimensional optical waveguide of the substrate; A second light deflecting unit that deflects by changing the refractive index of the optical waveguide, and (b) a light deflecting unit that is provided at the input side of the substrate and transmits light propagating in the two-dimensional optical waveguide of the substrate. A first light deflecting unit that deflects by changing a refractive index;
(C) provided on one surface of the substrate between the first light deflecting unit and the second light deflecting unit, wherein the light deflected by the first light deflecting unit is deflected by the first light deflecting unit. A plurality of three-dimensional optical waveguides leading to a position at which the distance from the one axis increases in accordance with the deflection angle, and (d) between the three-dimensional optical waveguide and the second optical deflector on one surface of the substrate. A Fresnel lens provided to make the light emitted from the three-dimensional optical waveguide incident on the second light deflection unit at an incident angle that increases according to the distance from the one axis. In this way, a three-dimensional optical waveguide and a Fresnel lens are provided between the first light deflecting unit and the second light deflecting unit on one surface of the substrate, and the light is deflected by the first light deflecting unit. The reflected light is guided by the three-dimensional optical waveguide to a position where the distance from one axis is increased according to the deflection angle, and is incident on the second light deflector by the Fresnel lens at an incident angle that is increased according to the distance from the one axis. Let me do. Accordingly, the deflection angle of the light emitted from the second light deflecting unit is an angle obtained by adding the incident angle of the incident light to the deflection angle due to the deflecting action of the second light deflecting unit itself. Even if the deflection angle is small, a large deflection angle can be obtained as a whole. According to the solid-state light deflecting device of the present invention, the first light deflecting unit and the second light deflecting unit that deflect light by changing the refractive index on the two-dimensional optical waveguide formed on one surface of the substrate; Since a three-dimensional optical waveguide for guiding the light deflected by the first optical deflector and a Fresnel lens for causing the light guided by the three-dimensional optical waveguide to enter the second optical deflector are provided, Adjustment is facilitated, and there is no mechanically movable part, so that the configuration is simple and small, and sufficient durability can be obtained. Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a two-dimensional optical waveguide 12 is provided on one surface of a substrate 10 made of an electro-optical material, for example, lithium niobate LiNbO ₃ crystal and having a thickness of about 0.5 mm. This optical waveguide
Numeral 12 has a higher refractive index than other portions of the substrate 10 so that the light is preferably guided by the property of confining the light in the thickness direction, and for example, diffuses Ti (titanium) from the surface of the substrate 10. As a result, it is formed in a relatively thin layer of about several μm. Note that, since only the refractive index of the substrate 10 differs from that of the optical waveguide 12 and the refractive index changes continuously, the boundary between them is indicated by a broken line. A semiconductor laser chip 14 is fixed to one end surface of the substrate 10, and a laser beam is emitted from the semiconductor laser chip 14 along the center line C of the substrate 10. This laser beam is converged to parallel light in the first Fresnel lens unit 16 while being guided in the optical waveguide 12, and is deflected to a predetermined deflection angle among a plurality of deflection angles in the first light deflection unit 18. Along with the deflection angle, a large number of three-dimensional optical waveguides 20a, 20b, 20cd,
Is guided to a position separated from the center line C by a distance corresponding to the deflection angle of the first light deflector 18 according to one of the above, and according to the distance from the center line C in the second Fresnel lens unit 22 The light is refracted at an angle and is deflected to a desired angle in the second light deflection unit 24. The first Fresnel lens portion 16 and the second Fresnel lens portion 22 are formed by locally increasing the refractive index in a Fresnel lens shape by a technique such as titanium diffusion or proton exchange. The first light deflection unit 18 includes electrodes 26 and 28 on the substrate 10.
30 is provided via a buffer layer 32. The buffer layer 32 is made of a transparent material having a smaller refractive index than the two-dimensional optical waveguide 12, such as SiO _{2, and} has a thickness of about several μm, and prevents absorption of light by the electrodes 26, 28, and 30. It is not necessarily provided. The electrodes 26 and 28 are located at a predetermined interval with the center axis C interposed therebetween, and the electrode 30 is oblique to the center axis C between the electrodes 26 and 28. For example, when the substrate 10 is a Y-cut crystal of LiNbO ₃ , the change Δn in the refractive index of the portion located between the electrodes 26 and 28 is given by the following equation (1). Δn = (1/2) _ne ³ r ₃₃ · E (1) where _ne is the refractive index of the substrate 10 for extraordinary light, and r ₃₃ is in the plane of the substrate 10. It is an electro-optic constant in a direction orthogonal to the central axis C. The distribution of the refractive index, that is, the distribution of the refractive index change Δn also changes according to the distribution of the electric field E.
When a ground voltage is applied to 26 and 28, the distribution of the electric field E and the change in the refractive index Δn on the lines AA, BB, and CC of the first optical deflection unit 18 are respectively shown in FIGS. As shown in FIG. For this reason, the laser beam traveling parallel to the central axis C has a different refractive index experienced by each part of the light beam, and is bent toward a higher refractive index. Therefore,
When the voltage applied between the electrode 30 and the electrodes 26 and 28 is changed stepwise, the first
The laser beam passing through the light deflecting unit 18 is deflected and made incident on one of the three-dimensional optical waveguides 20a, 20b, 20c,. The electric field E in FIGS. 2 to 4 is shown in a direction in which the downward direction in FIG. 5 is positive and the electrode 26 is on the right and the electrode 28 is on the left. Next, the three-dimensional optical waveguides 20a, 20b, 20c,... Are paths whose refractive index is further increased toward the center by diffusion of Ti or the like along a predetermined path for guiding light. As shown in the figure, the incident-side end is substantially parallel to a straight line connecting the output-side edges (right edges in the figure) of the electrodes 26 and 28 in the first light deflector 18. Thus, with the stepwise change in the deflection angle of the laser beam passing through the first light deflection unit 18, the three-dimensional optical waveguides 20a, 20b, and 20c positioned corresponding to the stepwise change in the deflection angle. , .. is incident on one of the ends. 3D optical waveguide 20
The end portions on the emission side of a, 20b, 20c,... are respectively disposed at a plurality of types of positions separated by a predetermined distance from the central axis C so as to guide the laser beam to the positions. That is, the three-dimensional optical waveguides 20a, 20b, 20c,.
Guides light to a position where the distance from the center line C increases in accordance with the deflection angle of the first light deflection unit 18. In addition,
In the figure, seven three-dimensional optical waveguides 20a, 20b, 20c,... Are drawn for easy understanding, but a larger number may be provided. The laser beam emitted from the end of the three-dimensional optical waveguide 20a, 20b, 20c,.
The light enters the Fresnel lens unit 22. The laser beam incident in this manner is refracted as shown in FIG. 6, so that the incident angle θi (the angle with respect to the center line C) on the second light deflection unit 24 is the tertiary Position of the end on the emission side of the original optical waveguides 20a, 20b, 20c,...
That is, it differs according to the distance from the center line C. That is, the second Fresnel lens 22 has a second light deflector with an incident angle that increases as the distance from the center line C increases.
Inject into 24. The second light deflecting unit 24 includes a large number (11 in this embodiment) of resistive heating elements provided on the same buffer layer 34 as the buffer layer 32 and having a similar resistance value in a stripe shape parallel to the center line C. Element 36
a, 36b, 36c, ... and their resistance heating elements 36a, 36b, 36
c, a common electrode 38 connected in common with one end of each of the plurality of electrodes 40 connected to the other end of the resistive heating element 36, respectively.
a, 40b, 40c,... Each resistance heating element 36a between the common electrode 38 and the electrodes 40a, 40b, 40c,.
When different voltages for generating heat are applied to the respective resistance heating elements 36a, 36b, 36c,.
Have similar resistance values, and each of these resistance heating elements 36
Since a, 36b, 36c,... are sequentially supplied with different powers from the ends thereof, different Joule heats are sequentially generated, so that the resistance heating elements 36a, 36b, 36 of the two-dimensional optical waveguide 12 are generated.
c, a temperature gradient which continuously changes in a direction intersecting with the traveling direction of the laser beam, that is, a direction perpendicular to the center line C, is formed in a portion located in the vicinity, and the refraction formed by this temperature gradient The laser beam passing through the second light deflecting unit 24 is deflected by an index gradient (a state in which the refractive index changes continuously). That is, the second light deflecting unit 24 continuously deflects the laser beam passing therethrough, and the laser beam passing through the second light deflecting unit 24 has the incident angle of the deflection angle of the second light deflecting unit 24. The substrate 10 can be emitted at a deflection angle (overall value) θ _{H to} which the sum is added. The resistance heating elements 36a, 36b, 36c,... Are formed by depositing a resistance material such as a nickel-chromium alloy or a cermet.
It is formed into a film using a method such as sputtering, the electrodes 26, 28, 30, 38 and 40a, 40b, 40
c, a conductive material such as aluminum is formed by the same method. On the emission side of the substrate 10, a correction lens 42 for converging the laser beam emitted from the substrate 10 in the thickness direction of the substrate 10 is provided. Hereinafter, the operation of the present embodiment will be described. The electrodes 26 and 28 and 30 are supplied from a control drive circuit (not shown).
A predetermined voltage selected from a plurality of levels of voltages is applied between the common electrode 38 and the electrodes 40a, 40b, 40
When sequentially different voltages of a predetermined magnitude corresponding to a desired deflection control angle are applied between c,.
The laser beam passing therethrough is deflected to a predetermined angle out of a plurality of stages, and the three-dimensional optical waveguides 20a, 20b, 20c,.
Are applied to one end of the one corresponding to the applied voltage and guided to the second Fresnel lens unit 22.
The laser beam guided in this manner is applied to the second optical deflection unit at an incident angle θ _i corresponding to the three-dimensional optical waveguide from which the laser beam is guided.
Together they are caused to enter the 24 where it receives a deflection corresponding to forming temperature gradient is caused to exit by a deflection angle theta _H. Here, the range of the deflection angle that can be continuously changed in the second light deflector 24 is not so large, but the second angle of the laser beam passing through the second light deflector 24 is small.
The angle of incidence with respect to the light deflecting unit 24 is to select one of a plurality of preset angles of the voltage applied between the electrodes 26 and 28 and the electrode 30, that is, the deflection angle in the first deflecting unit 18. The deflection angle θ _H as a whole can be continuously changed by combining the incident angle with the second light deflection unit 24 and the deflection angle in the second light deflection unit 24. Accordingly, it is the optical deflecting device and controllable range without mechanically moving parts with a large deflection angle theta _H is obtained. As described above, the present invention has been described with reference to the drawings showing one embodiment, but the present invention can be applied to other aspects. For example, the light is deflected by the thermo-optic effect in the second light deflecting unit 24 of the above-described embodiment, but the light is deflected by the light deflecting method by the electro-optic effect like the first light deflecting unit 18. May be deflected, or light may be deflected by another method, for example, utilizing an acousto-optic effect. Also, the first light deflecting unit 18 may use a light deflecting method using a thermo-optic effect or a deflecting method using an acousto-optic effect. The above is merely an embodiment of the present invention, and the present invention can be variously modified without departing from the spirit thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view illustrating the configuration of an embodiment of the present invention. FIGS. 2, 3, and 4 are views showing the electric field distribution and the refractive index distribution in the first light deflection unit in FIG. FIG. 5 is a diagram showing the relationship between the first light deflecting unit of FIG. 1 and the three-dimensional optical waveguide. FIG. 6 is a diagram showing a relationship between the three-dimensional optical waveguide of FIG. 1 and a second Fresnel lens. 10: substrate 12: two-dimensional optical waveguide 14: semiconductor laser chip (light source) 18: first optical deflector 20a, 20b, 20c: three-dimensional optical waveguide 22: second Fresnel lens (Fresnel lens) 24: second optical deflection Department

   ────────────────────────────────────────────────── ─── Continuation of front page        Panel     Referee Yukio Okada     Judge Yoshiyuki Kawakami     Judge Kimio Yoshino                (56) References Jikken Sho 51-32471 (JP, Y2)

Claims (1)

(57) [Claims] A solid-state light deflecting device that imparts a relatively large deflection angle to light propagating from a light source along one axis in a two-dimensional optical waveguide formed on one surface of a substrate, provided at an output side portion of the substrate. A second light deflecting unit that deflects light propagating in the two-dimensional optical waveguide of the substrate by changing a refractive index of the two-dimensional optical waveguide; A first light deflecting unit that deflects light propagating in the optical waveguide by changing a refractive index of the two-dimensional optical waveguide; and between the first light deflecting unit and the second light deflecting unit on one surface of the substrate. And a plurality of three-dimensional optical waveguides that guide the light deflected by the first light deflector to a position where the distance from the one axis increases according to the deflection angle deflected by the first light deflector. And the three-dimensional optical waveguide on one surface of the substrate And a Fresnel lens provided between the three-dimensional optical waveguide and the second light deflector, and configured to make the light emitted from the three-dimensional optical waveguide incident on the second light deflector at an incident angle that increases according to a distance from the one axis. And a solid-state light deflecting device.