JP3218111B2 - Light deflection element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflecting element used in laser printers, optical scanning devices, bar code readers, optical scanners, optical pickups, etc., which can continuously change the propagation direction of light.

[0002]

2. Description of the Related Art Conventionally, in an optical deflection element used in the above-mentioned field, three kinds of methods have been mainly employed in order to continuously change the propagation direction of light. The first method is to rotate a polyhedral mirror (polygon).
The third method is a method by rotating a hologram, and the third method is a method by vibrating a mirror (galvano mirror). However, in the first, second, and third methods, it is necessary to physically move the substance, and there are problems such as difficulty in miniaturization and lack of reliability.

A fourth method has been devised as the most promising method for solving the above problems. A fourth method is a method using Bragg reflection by a medium that causes a periodic refraction change by an acousto-optic effect (IEEE Transact).
ions on Circuit and System
ms, Vol. CAS-26, p1072 (197
9)). This method will be described based on the light deflection element shown in FIG.

This light deflecting element is made of lithium niobate (L
An optical waveguide 32 formed by Ti diffusion and a comb-shaped electrode 3 formed on the optical waveguide are formed on the entire surface of the iNbO ₃ ) substrate 31.
3 is provided. In the comb-shaped electrode 33, the distance between the electrodes varies depending on the location and is curved.

In the light deflecting element of the present method, the comb-shaped electrode 33 forms LiNbO _3, which is a material having an acousto-optic effect.
To generate a compression wave. As shown, when the frequency of the applied AC voltage is low, the compression wave W having a long wavelength is generated at the position of R. The position R is specified because the electrode spacing of the comb-shaped electrodes 33 is different as described above, and thus the position where the generated compression wave resonates is specified. When light enters A at an appropriate angle theta _A to the compression wave W, diffract light efficiently by Bragg diffraction, and generates a diffracted wave B. When the frequency of the AC voltage is increased, the resonance position changes from R to R ', and a compression wave W' is generated. The wavelength of the compression wave W ′ is higher than the wavelength of the compression wave W. The incident angle θ _B that is diffracted efficiently is also different from the angle θ _A.

[0006] The incident angle at which the diffraction occurs efficiently is determined by the wavelength of the compression wave. The wavelength of the compression wave is determined by the material characteristics such as the refractive index of the material having the acousto-optic effect and the propagation speed of the sound wave, and the frequency of the AC voltage applied to the comb-shaped electrode. Therefore, if the type of the material having the acousto-optic effect is determined, the incident angle at which diffraction occurs efficiently is determined by the frequency of the applied AC voltage. That is, if the frequency of the applied AC voltage is changed, the diffraction direction changes, and light deflection is realized.

In Bragg diffraction, since the diffraction efficiency is high only in a very narrow range where the Bragg condition is satisfied, the deflection angle becomes narrow. However, since the comb-shaped electrode 33 is curved as described above, the deflection angle increases. That is, the comb-shaped electrode 33 is curved so that the propagation direction that changes according to the change in the frequency of the compressional wave increases.

In the fourth method, the deflection angle can be easily controlled by controlling an externally applied electric signal. In addition, there is no mechanically moving part, and miniaturization is possible.

[0009]

In the optical deflecting element according to the fourth method, a large alternating current flows, so that the power consumption is large. Therefore, even if the element itself is small, it is difficult to reduce the size of peripheral devices such as a power supply. In addition, there are many practically difficult problems such as the need to obtain impedance matching in a wide frequency range, and the technology has not been put to practical use.

The present invention has been made in view of the above problems, and has as its object to provide an optical deflecting element which consumes less power, is small in size including peripheral devices, and has a large deflection range.

[0011]

According to the present invention, there is provided an optical deflecting element comprising:
A laminated body entirely curved, comprising two or more layers concentrically laminated in a certain order so as to have an optical period, and at least one layer made of a variable refractive index material; There is provided a refractive index changing means for deflecting light incident on the curved surface of the laminate by changing the refractive index of the layer made of a material, thereby achieving the above object.

The variable-refractive-index material is an electro-optic effect material, the layer sandwiching the layer made of the variable-refractive-index material is a conductor, and the refractive-index changing means includes a layer made of the variable-refractive-index material. A potential difference may be applied to the sandwiched layer.

[0013] The variable refractive index material is a semiconductor material,
The refractive index changing means may inject a current into the layer made of the variable refractive index material.

[0014]

In the light deflecting element of the present invention, the optical period of the laminate is changed by changing the refractive index of at least one layer of the laminate having the optical period. As a result, the angle at which the light incident on the light polarizing element is most efficiently diffracted changes according to this change.

The laminate is constituted so as to include a layer made of an electro-optic effect material and a layer made of a conductor, and by applying a voltage to the layer made of the conductor, the layer made of the electro-optic effect material is refracted. Change the rate. As a result, the optical period of the laminate changes, and the angle at which light incident on the light polarizing element is most efficiently diffracted changes according to the change. In this configuration, almost no current needs to flow just by applying a voltage, so that the power consumption is significantly reduced as compared with the related art.

When at least one layer constituting the laminate is used as a semiconductor material and an electric current is applied to a layer made of the semiconductor material, the refractive index of the layer changes and the optical period of the laminate changes. As a result, the angle at which light incident on the light polarizing element is most efficiently diffracted changes.

Further, since the laminated body is curved, the incident light on the laminated body is substantially changed in the incident angle and is reflected at an optimum position, so that the light is combed as in the fourth method. There is no need to adjust the spacing of the mold electrodes.

[0018]

Embodiments of the present invention will be described below.

(First Embodiment) FIG. 1 is a perspective view of a light deflecting element according to a first embodiment of the present invention. The light deflecting element includes a columnar substrate 11 having curved side surfaces and a plurality of transparent conductive I / O layers alternately stacked on the curved side surfaces.
TO film 12 and a plurality of LiNbO having a large electro-optic effect
_{And three} films 13. Each layer 12 and 13 formed on this curved side surface is a part of a concentric circle.
The ITO film 12 and the LiNbO ₃ film 13 are concentric. The ITO films 12 are alternately connected to a power supply V and a ground G so that an electric field is applied to the LiNbO ₃ film 13.

The principle of operation of the light deflecting element having the above configuration will be described. In this light deflecting element, light having different refractive indexes, that is, the ITO film 12 and the LiNbO ₃ film 13 are periodically laminated, so that light incident on the light deflecting element is diffracted.

The optical period Λ between the ITO film 12 and the LiNbO ₃ film 13 is such that the thickness of the LiNbO ₃ film 13 is d ₁ , the refractive index is n ₁ , the thickness of the ITO film 12 is d ₂ , and the refractive index is If n ₂ , it is expressed by Equation 1.

[0022]

(Equation 1)

As a result, the Bragg condition for the light incident on the present light deflection element is expressed by Equation 2.

[0024]

(Equation 2)

Here, λ is the wavelength of the incident light. The angle θ is an angle in the LiNbO ₃ film 13,
Considering the refraction at the interface with the TO film 12, the actual incident angle θ ′ becomes smaller.

When the refractive index n ₁ of the LiNbO ₃ film 13 is changed by changing the voltage V applied to the ITO film 12, the period Λ changes according to Equation 1. As a result, the incident angle θ that satisfies the Bragg condition changes according to Equation 2, so that the diffraction angle changes and light is deflected.

Further, the ITO film 12 and the LiNbO ₃ film 1
Since 3 is curved, the light incident on the light polarizing element passes through positions at different incident angles. As a result, FIG.
As shown in the voltage V, the diffracted light B is generated for example at the position R when the voltage V _1, when the voltage V ₂ different voltages V to the voltage V _1, the position R which is different from the position R 'A diffracted light B' is generated.

In this embodiment, the electro-optic effect is used to change the refractive index n ₁ of the LiNbO ₃ film 13. However, no current flows through the LiNbO ₃ film 13 and therefore the power consumption is the lowest.

(Second Embodiment) FIG. 2 is a perspective view showing a light deflecting element according to a second embodiment of the present invention. This optical deflection element comprises, for example, a semi-insulating GaAs substrate 21 having curved side surfaces, an undoped In _0.52 Al _0.48 P layer 22 and an n-type In _0.52 (G
aAl) _0.48 P layer 23 and electrodes 24a and 24b formed on both side surfaces adjacent to the curved side surface.

The light deflecting element having such a structure is formed on a flat semi-insulating GaAs substrate 21 by, for example, molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD).
Undoped In _0.52 Al _0.48 P layer 22
And n-type In _0.52 (GaAl) _0.48 P layers 23 are alternately stacked. At this time, the undoped In _0.52
Al _0.48 P layer 22 and n-type In _0.52 (GaAl) _0.48 P
When the lattice constant of the layer 23 is set to a composition slightly larger than the lattice constant of the GaAs substrate 21, as shown in FIG.
The GaAs substrate 21 is warped, and the stacked surface becomes a curved side surface.

In this light deflecting element, when a voltage is applied to the electrodes 24a and 24b provided on both side surfaces, the n-type In _0.52 (GaAl) having a low resistance sandwiched between the undoped In _0.52 Al _0.48 P layers 22 having a high resistance. _0.48 The refractive index of the P layer 23 changes, and incident light can be deflected by the same principle as in the first embodiment.

In the present embodiment, since the current injection is used to change the refractive index, the rate of change of the refractive index can be increased as compared with the first embodiment, so that the deflection angle can be increased. However, the power consumption is higher than in the first embodiment.

In the above embodiment, two types of films are deposited, but the types of films are not limited to two. Since the deflection angle depends on the thickness of the layer where the refractive index changes, for example, even in the case of a structure in which three types of films are deposited, if the thickness of the layer where the refractive index changes is constant, two types The same effect as in the case of the structure in which the film is deposited can be obtained.

[0034]

As is clear from the above description, according to the optical deflecting element of the present invention, the power consumption is small and the deflecting range is large. Therefore, peripheral devices such as a power supply can be reduced in size, and the entire device can be reduced in size.

[Brief description of the drawings]

FIG. 1 is a perspective view of a light deflection element according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a light deflection element according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a conventional light deflection element.

[Explanation of symbols]

Reference Signs List 11 substrate 12 ITO film 13 LiNbO ₃ film 21 semi-insulating GaAs substrate 22 undoped In _0.52 Al _0.48 P layer 23 n-type In _0.52 (GaAl) _0.48 P layer 24a, 24b Electrode

Claims (3)

(57) [Claims] An overall curved laminate comprising two or more layers concentrically laminated in a certain order so as to have an optical period, and at least one layer made of a variable refractive index material. An optical deflecting element comprising: a refractive index changing unit that deflects light incident on a curved surface of the laminate by changing a refractive index of a layer made of the variable refractive index material. 2. The variable-refractive-index material is an electro-optic effect material, a layer sandwiching the layer made of the variable-refractive-index material is a conductor, and the refractive-index changing means is made of the variable-refractive-index material. 2. The optical deflecting element according to claim 1, wherein a potential difference is applied to the layers sandwiching the layers. 3. An optical deflecting element according to claim 1, wherein said variable refractive index material is a semiconductor material, and said refractive index changing means injects a current into a layer made of said variable refractive index material.