JPH0748096B2 - light deflection element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for changing and controlling the direction of light or for displacing and controlling the focal point of light.

BACKGROUND ART Regarding the prior art, see, for example, "Optical Integrated Circuits (Hiroshi Nishihara)"
This _explanation will be based on the acousto-optical black cell using _{a LiNbO3} waveguide described on page 328 of "Ohmsha et al." and the SAW optical deflector shown in a lecture at the 35th Joint Conference on Applied Physics, 28a- _ZQ -4. Figure 1 shows the configuration of a conventional optical deflector. A Ti _- diffused waveguide layer 28 is formed on a _LiNbO3 substrate _27. Laser light 30 incident on an input prism 29 becomes guided light 31 propagating within the waveguide layer 28. The guided light 31 is split by a SAW optical deflector 32 into transmitted guided light 33 and diffracted guided light 34, which are then emitted by an output prism 35 as transmitted light 36 and diffracted light 37, respectively. The diffraction angle of the diffracted guided light 34 is determined by the pitch of the acoustic waves 38 generated by the SAW optical deflector 26. The diffraction angle of the diffracted guided light 34, i.e., the radiation direction of the diffracted light 37, can be changed by applying an electrical signal to the SAW optical deflector 32.

However, such conventional optical deflection elements have the following problems: The change in the diffraction angle caused by the SAW optical deflection element 32 is small, and it is not possible to deflect light significantly. Also, it is the diffracted light that is deflected, and the energy utilization efficiency of this light relative to the input light 30 is low.

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a novel light deflecting element that can deflect light to a large extent and has high energy utilization efficiency.

That is, the present invention is characterized in that a conductive thin film is formed on a substrate, a waveguide layer is formed by sandwiching a transparent layer on the conductive thin film, a transparent substrate with a transparent conductive thin film formed on the surface is tightly attached to the waveguide layer with liquid crystal sandwiched between them, a periodic structure is formed in the waveguide layer along the propagation direction of the guided light, the guided light is radiated by this periodic structure to become radiated light, and the direction of the radiated light can be controlled by applying a voltage signal between the conductive thin film and the transparent conductive thin film.In addition, the optical deflector element is characterized in that a means for aligning the liquid crystal is formed on the surface of the waveguide layer or the transparent conductive thin film, and the alignment direction is parallel or perpendicular to the propagation direction of the guided light.

The periodic structure is concentric, the guided light propagates perpendicular to the periodic structure, the light emitted from the waveguide layer is focused at one or several focusing points outside the waveguide layer, and the position of the focusing points can be changed by applying a voltage signal. Alternatively, the conductive thin film or transparent conductive thin film can be divided into many regions, and the position of the focusing point can be changed by applying a voltage signal to each divided region independently.

Brief Description of the Drawings: Figure 1 is a diagram illustrating the principle of a conventional optical deflection element, Figure 2 is a cross-sectional configuration diagram of an optical deflection element according to an embodiment of the present invention, Figures 3(a) and 3(b) are diagrams illustrating amplitude modulation of a signal wave in the optical deflection element, Figures 4(a), 4(b), and 4(c) are diagrams illustrating changes in the liquid crystal alignment direction and changes in refractive index distribution due to an amplitude modulation signal according to the present invention, Figures 5(a) and 5(b) are diagrams illustrating the relationship between the amplitude modulation signal amplitude v and the equivalent waveguide layer thickness Teff and the relationship between the equivalent waveguide layer thickness Teff and the equivalent refractive index N according to the present invention, Figure 6
Figures (a) and (b) are explanatory diagrams showing the polarization effect due to the refractive index anisotropy of liquid crystal, Figure 7 is a cross-sectional configuration diagram of the optical deflection element in the second embodiment of the present invention, Figure 8 is an explanatory diagram of the optical deflection element in the third embodiment of the present invention, Figure 9 is a cross-sectional explanatory diagram showing an embodiment for propagating guided light in a radial direction from the center in the third embodiment of the present invention, and Figure 10 is an explanatory diagram of the optical deflection element in the third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described with reference to Figs. 2 to 10. Fig. 2 is a cross-sectional view of the optical deflector element in a first embodiment of the present invention. As shown in Fig. 2, a conductive thin film 2 and a transparent layer 3 are formed on a substrate 1, with a transparent layer 4 having a higher refractive index than transparent layer 3 sandwiched between them. A grating 3G is formed on transparent layer 3, and a transparent alignment film 4P made of polyimide or the like is formed on the surface of transparent layer 4. The transparent layer 4 functions as a waveguide layer in combination with the transparent alignment film 4P.
A transparent conductive thin film 6 made of ITO or the like is formed on the surface of the transparent substrate 7, and is in close contact with the transparent alignment film 4P, sandwiching the liquid crystal 5 therebetween. The guided light 8 guided through the waveguide layers 4, 4P is divided by the grating 3G into light 9 radiated toward the liquid crystal 5 and light 9' radiated toward the substrate 1, and the radiated light 9' is reflected by the conductive thin film 2 or the surface of the substrate 1 and overlaps with the radiated light 9. The diffraction angle θ of the radiated light 9 (the angle normal 10 to the substrate surface, expressed as the angle when it is finally radiated into the air layer) is given by the following equation:

sin θ=N+qλ/Λ (1) where λ is the wavelength of the laser light, N is the equivalent refractive index of the waveguide, Λ is the pitch of the grating, and q is the coupling order, which is −1 in the case of two-beam coupling.

The alignment film 4P is rubbed in the propagation direction of the guided light 8 or in a direction perpendicular to this direction, and the alignment direction of the liquid crystal near the surface of the alignment film also coincides with this rubbing direction. A signal wave generated by a signal wave generator 11 is amplitude-modulated by an amplitude modulator 12, and the resulting amplitude-modulated signal is applied between the conductive thin film 2 and the transparent conductive thin film 6. Alternatively, the liquid crystal alignment means may be applied to the surface of the transparent conductive thin film 6.

3(a) and (b) show how the signal wave 13 is amplitude-modulated to become the amplitude-modulated signal 14, and the envelope waveform of the amplitude-modulated signal 14 oscillates around an amplitude v _A. Although it is preferable to amplitude-modulate the voltage signal applied to the electrodes as in this embodiment due to the problem of hydrolysis of the liquid crystal, the signal wave 13 may also be applied directly to the electrodes.

4(a), (b), and (c) show the change in the alignment direction due to the amplitude modulation signal and the change in the refractive index distribution in the normal direction. Generally, the liquid crystal 5 exhibits refractive index anisotropy, and its refractive index _nO for ordinary light is smaller than its refractive index _nE for extraordinary light. The alignment direction changes in the plane including the substrate normal 10 (x-axis direction) and the rubbing direction (z-axis direction).
1A, 1B, and 1C show the case where the amplitude of the amplitude modulation signal 14 is small, and the alignment direction of the liquid crystal molecules 5A is parallel to the surface of the alignment film 4P. Therefore, the guided wave 8 in the TM mode is aligned in the rubbing direction (z
If the guided light propagates in the x-axis direction or in the direction perpendicular to it (the y-axis direction, i.e., the direction perpendicular to the paper), the refractive index of the liquid crystal 5 for the guided light is equal to the refractive index n _O for ordinary light. Therefore, the refractive index distribution of the liquid crystal 5 along the x-axis is almost uniform, n _O
If the film thickness of the transparent layer 4 is _tF , the equivalent waveguide thickness of the waveguide layer is expressed as the sum of _tF and the width of the two evanescent lights, and if the width of the evanescent light leaking from the waveguide layer into the liquid crystal is _ta and the width of the evanescent light leaking into the transparent layer 3 is _t0 , then Teff = _t0 + _tF + _tb .
Generally, the propagation loss of guided light propagating through liquid crystal is 20 to 30
Although the loss is large at dB/cm, the ratio of the amount of evanescent light in the liquid crystal to the amount of total guided light is small, so the propagation loss of the entire guided light is small.

On the other hand, if the TE mode guided light 8 propagates in the direction perpendicular to the orientation direction (the y-axis direction), the refractive index of the liquid crystal 5 for the guided light is equal to the refractive index _nE for the extraordinary light. Therefore, the refractive index distribution of the liquid crystal 5 along the normal direction is distribution 18a'. In this case, the width of the evanescent light of the guided light seeping out from the waveguide layer into the liquid crystal is defined as t _a ', and the width of the evanescent light seeping out into the transparent layer 3 is defined as t ₀ '.

FIG. 4(b) shows the case where the amplitude of the amplitude modulation signal 14 is increased, and the alignment direction of the liquid crystal molecules is changed to the alignment film as shown in FIG. 5B'.
The liquid crystal molecules 5B near the alignment film 4P are oriented in the direction perpendicular to the surface (x-axis direction). However, the alignment retention force of the alignment film 4P is strong, and the liquid crystal molecules 5B near the alignment film 4P are not oriented in the normal direction sufficiently. Therefore, if the TM mode guided light 8 propagates in the z-axis or y-axis direction, the refractive index of the liquid crystal 5 for the guided light is close to the refractive index _nE for extraordinary light near the transparent conductive thin film 6, and close to the refractive index _nO for ordinary light near the alignment film surface. Therefore, in the normal direction (x-axis direction),
The refractive index of the liquid crystal 5 along the y-axis shows a distribution of 18b. In this case, if the width of the evanescent light that the guided light leaks out of the waveguide layer into the liquid crystal is _tb , then _tb > _ta . On the other hand, if the guided light 8 in the TE mode propagates in the y-axis direction, the refractive index of the liquid crystal 5 for the guided light is
The refractive index of the liquid crystal 5 along the normal direction (x-axis direction) is close to the refractive index _nO for ordinary light near the transparent conductive thin film 6, and close to the refractive index _nE for extraordinary light near the surface of the alignment film. Therefore, the refractive index of the liquid crystal 5 along the normal direction (x-axis direction) shows a distribution of 18b'. In this case, the width of the evanescent light that leaks from the waveguide layer into the liquid crystal is defined as _tb '.
Then, t _b '<t _a '.

FIG. 4(c) shows the case where the amplitude of the amplitude modulation signal 14 is further increased, and the refractive index distributions 18b and 18b' are 18c and 18c', respectively.
The widths of the evanescent light, t _b and t _b ′, are t _c and t _c ′, respectively.
and satisfies t _c > t _b and t _c ′ < t _b ′.

Therefore, when the TE mode guided light 8 propagates in the y-axis direction, the relationship between the amplitude modulated signal amplitude v and the equivalent waveguide layer thickness Teff is as shown in Figure 5(a).
When the amplitude v is small (v<v ₀ ), the film thickness Teff is t ₀ + t _F +
_Conversely , when the amplitude v exceeds _v1 , Teff = _t0 +
t _F + t _c '. When _{v 0} < v < v ₁ , as the amplitude v increases,
Therefore, when the amplitude v is varied around _vA as shown by waveform 14, Teff becomes waveform 15 which varies around _t0 + _tF + _tb '.

FIG. 5(b) shows the relationship between the equivalent waveguide layer thickness Teff and the equivalent refractive index N. The equivalent refractive index N increases with the increase in the film thickness Teff _.
The curve 16 monotonically increases from n _B (when the refractive index n _B of the transparent layer 3 is larger than n _O ) to the refractive index n _F of the waveguide layer. As described above, the waveform 15 whose width Teff fluctuates around t ₀ + t _F + t _b ′ is
, the equivalent refractive index N shows a waveform 17 that fluctuates around N _A.

As shown in formula (1), a change in the equivalent refractive index N appears as a change in the diffraction angle θ, so a change in Teff changes the diffraction angle of the emitted light, i.e., changing the amplitude v of the amplitude modulation signal changes the diffraction angle of the emitted light. The expected variation range of the equivalent refractive index N due to a change in the amplitude v of the amplitude modulation signal is about ( _nF - _nO ) x (0.1 to 0.3). If a variation range of 0.1 is obtained, the diffraction angle θ will have a center of variation of the diffraction angle of θ.
= 45 degrees, a deflection of about 10 degrees is possible. In addition, since it utilizes the change in the alignment direction of the liquid crystal near the surface of the waveguide layer, which has a strong alignment retention force, the response of the deflection is also fast.

Although FIG. 5 has been described taking as an example the case where the guided light of TE mode propagates in the direction perpendicular to the orientation direction (y-axis direction), the same applies when the guided light 8 of TM mode propagates in the orientation direction (z-axis direction) or in the direction perpendicular thereto (y-axis direction). When the amplitude v of the amplitude modulation signal 14 is less than _v0 , Teff= _t0 + _tF +
t _a , when the amplitude v exceeds v ₁ , Teff = t ₀ + t _F + t _o , v ₀ < v <
When v is ₁ , Teff increases monotonically as the amplitude v increases. When the amplitude v is varied around v _A as shown in waveform 14, Teff increases as shown in waveform 14.
Similar to 15, the waveform fluctuates around t ₀ +t _F +t _b . In other words, deflection of the synchrotron radiation can be achieved in the same way by controlling the amplitude modulation signal.

Generally, the greater the ratio of the amount of evanescent light to the amount of guided light, the greater the degree of fluctuation in the equivalent refractive index. Therefore, if n _O > n _B , the equivalent refractive index of the guided light is likely to change, and the fluctuation in the equivalent refractive index is most effective when n _E > n _F.

FIG. 6 is an explanatory diagram showing the influence of the refractive index anisotropy of the liquid crystal on the deflection of the guided light and the emitted light.
indicates the movement of the guided light beam, and as shown in 8E, the light wave penetrates into the liquid crystal. Furthermore, the emitted light 9 is generally a beam of light that crosses the liquid crystal at an angle. In Figure 6(b), 5D, 5E, and 5G are all index ellipsoids that represent the refractive index anisotropy of the liquid crystal. These correspond to 5A, 5B', and 5B in Figure 4, respectively. They are represented by a major axis of length _nE and two minor axes (length _nO ) perpendicular to the major axis, with the major axes lying in the xz plane. If the guided light is TE mode light traveling in the z direction, its electric field vector is in the y axis (perpendicular to the paper), while if it is TM mode light, its electric field vector is in the x axis. If the guided light is TM mode light traveling in the y axis, its electric field vector is in the z direction, and if it is TM mode light, its electric field vector is in the x direction. Generally, the polarization effect on linearly polarized light propagating through a medium with refractive index anisotropy is determined by the relative positions of the elliptical cut of the index ellipsoid along a plane perpendicular to the light propagation direction and the plane of vibration of the linearly polarized light.
In other words, if the vibration plane and the major axis of the cut ellipse are parallel or perpendicular to each other, the light remains linearly polarized without being affected by polarization, but if they are not parallel or perpendicular, it becomes elliptically polarized. Therefore, when the refractive index ellipsoid is 5D, the vibration plane of the guided light of the TM mode propagating in the z-axis or y-axis direction and the TE mode propagating in the z-axis direction is perpendicular to the major axis of the cut ellipse, so the linear polarization of their evanescent light (light wave 8E leaking into the liquid crystal) is maintained, and the vibration plane of the guided light of the TE mode propagating in the y-axis direction is parallel to the major axis of the cut ellipse, so the linear polarization of the evanescent light is also maintained. Therefore, the evanescent light that passes through the liquid crystal layer and returns to the waveguide layer remains in its original mode, and there is no polarization effect from the liquid crystal. Similarly,
The linear polarization of the radiated light 9 from the guided light of the TM mode propagating in the z-axis or y-axis direction and the TE mode propagating in the z-axis direction is maintained, and the linear polarization of the radiated light from the guided light of the TE mode propagating in the y-axis direction is also maintained.

In contrast, the refractive index ellipsoid is z in the xz plane as shown in 5G.
When the waveguide is tilted relative to the axis, the evanescent wave of the guided light propagating in the z-axis direction maintains linear polarization regardless of whether it is in TE or TM mode, but the evanescent wave propagating in the y-axis direction is affected by polarization and becomes elliptically polarized in both TE and TM modes.
Similarly, the emitted light from the guided light propagating along the z-axis maintains linear polarization regardless of whether it is in TE or TM mode, but the emitted light from the guided light propagating along the y-axis maintains linear polarization regardless of whether it is in TE or TM mode.
Both the TM and TM modes are affected by polarization and generally become elliptically polarized.

Therefore, the refractive index ellipsoid is tilted with respect to the z axis, and the guided light is
When propagating along the axis, the guided light splits into TE and TM modes, and each of these modes emits elliptically polarized light with different diffraction angles. As explained in Figure 5(a), in the TE mode, Teff decreases monotonically with increasing amplitude v, where _v0 <v< _v1 , whereas in the TM mode, it increases monotonically. That is, for the same applied signal, the polarity of Teff fluctuations in the TE and TM modes is different, and the polarization directions of the emitted light are also opposite. Therefore, when the guided light splits into TE and TM modes, two emitted lights with similar radiation angles are generated, and the polarization directions of these emitted lights are opposite to each other when a voltage signal is applied. This is undesirable as a polarizer, and the guided light should be aligned along the orientation direction (z-axis). Note that the refractive index of the liquid crystal for TE mode guided light propagating along the z-axis remains n _o even when the orientation direction of the liquid crystal changes in the xz plane, and therefore the emitted light cannot be polarized; therefore, the guided light must be in TM mode.

7 shows a cross-sectional view of the optical deflector element according to the second embodiment of the present invention. A concave-convex grating 1G is formed on a substrate 1, and a conductive thin film 2 and a transparent layer 3 are formed on top of it, with a waveguide layer 4 having a higher refractive index than the transparent layer 3 sandwiched therebetween.
A transparent conductive thin film 6 such as ITO is formed on the surface of the transparent substrate 7, and is in close contact with the waveguide layer 4 with the liquid crystal 5 sandwiched between them. Since the combined thickness of the conductive thin film 2, transparent layer 3, and waveguide layer 4 is thin, the surface of the waveguide layer 4 has a concave-convex grating.
The grating 4G remains, which radiates the guided light 8 in the waveguide layer and also functions to align the liquid crystal molecules in the liquid crystal. In this case, since the guided direction corresponds to the case where the light propagates in a direction perpendicular to the alignment direction, problems such as mode separation of the guided light and the polarization effect of the radiated light occur, but since the grating 4G, which is the radiation means for the guided light, can also be used as the alignment means for the liquid crystal, no alignment means such as polyimide is required, and the configuration is simplified.
In the second embodiment, the uneven grating may be located on the surface of the conductive thin film 2, the transparent layer 3, or the like.

FIG. 8 is an explanatory diagram of an optical deflector element according to a third embodiment of the present invention. The cross-sectional configuration is the same as that of the first embodiment.
The grating 3G in the first embodiment is concentric with the point O as the center, and the guided light 8 is guided through the grating 3G
By modulating the grating pitch and forming the waveguide layer, the light emitted from the waveguide layer is focused at a focusing point F outside the waveguide layer.
The deflection of the emitted light caused by a voltage signal applied between acts as a displacement of the focal point F along a line OF.

9 shows an example of the third embodiment for propagating guided light 8 perpendicular to the concentric grating 3G. Light emitted from a semiconductor laser 19 is collimated by a condenser lens 20 and passes through a quarter-wave plate 21 to become circularly polarized light 22. A conductive thin film 2 and a transparent layer 3 are sandwiched between them on a substrate 1, and a waveguide layer 4 having a higher refractive index than the transparent layer 3 is formed thereon. A concentric grating 23 with a concave-convex shape is formed on the surface of the waveguide layer using photoresist or the like, and the circularly polarized light 22 is input-coupled into the waveguide layer 4 by this concentric grating coupler 23, becoming guided light 8 propagating in the radial direction.

10 is an explanatory diagram of an optical deflector element according to a fourth embodiment of the present invention. As in the third embodiment, the grating 3G is concentrically arranged with the point O as the center, and the guided light 8 propagates perpendicular to the grating 3G, and the light emitted from the waveguide layer is focused at a focusing point F outside the waveguide layer.
Alternatively, the transparent conductive thin film 6 is divided into a number of regions, such as 24A, 24B, 24C, and 24D, by straight lines along the radial direction (diameter direction), and a voltage signal can be applied to each region independently. The magnitude of the voltage signal applied to each region can be expressed using a hollow cylinder with the grating surface 3G as its bottom surface. The height of a point on the circumference of a cut 25 of the hollow cylinder cut by a plane relative to the grating surface 3G (for example, the heights of points 25A and 26B, which are the feet of a perpendicular to the bottom surface 3G, are expressed as follows:
The distance between 25B and 26B (the distance between 25B and 26B) is the amplitude v of the amplitude modulation signal applied to the divided area corresponding to the point on the circumference.
The line connecting A and 25B passes through the center of the cut 25 and the cut plane 25 and the bottom
3G. When the cut edge 25 is not parallel to the base 3G, the focal point moves from point F to point F' in the plane including points 25A, 25B, 26A, and 26B. That is, the height of the cut edge is related to the displacement of the focal point along the optical axis OF, while the inclination of the cut edge is related to the displacement of the focal point in the direction perpendicular to the optical axis OF. Thus, while the focal point in the third embodiment could only be displaced along the straight line OF, it can now be displaced to any position by independently applying voltage signals to multiple regions such as 24A, 24B, 24C, and 24D. Note that other methods of dividing the conductive thin film 2 or the transparent conductive thin film 6 are possible, and dividing along straight lines along the radial direction is not necessarily required.

INDUSTRIAL APPLICABILITY As described above, in the optical deflection element of the present invention, the orientation direction of the liquid crystal in the vicinity of the surface of the waveguide layer is changed by a voltage signal applied between the conductive thin film and the transparent conductive thin film,
The refractive index of the liquid crystal for the guided light changes, changing the equivalent refractive index of the guided light, and the diffraction angle of the light emitted from the waveguide layer, so it functions as a deflector for the emitted light, and the polarization width is large. In addition, since it utilizes the change in the orientation direction of the liquid crystal near the surface of the waveguide layer, which has a strong orientation retention force, the response of the polarization is fast. Furthermore,
All of the guided light is emitted toward the liquid crystal and substrate sides. The light radiated toward the substrate side is reflected by the conductive thin film on the substrate surface and overlaps with the light radiated toward the liquid crystal side, increasing the amount of light radiated toward the liquid crystal side and improving the efficiency of energy utilization of the deflected light. On the other hand, if the periodic structure is concentric, the guided light propagates perpendicular to the periodic structure, and the light radiated from the waveguide layer is focused at a focusing point outside the waveguide layer, the deflection of the radiated light caused by a voltage signal applied between the conductive thin film and the transparent conductive thin film can be used to displace the focusing point. In particular, by dividing the conductive thin film or transparent conductive thin film into multiple regions and applying voltage signals independently, it is possible to displace the focusing point to any desired position. Due to these effects, the present invention is extremely useful in practical applications as a novel deflection element and variable-focus element.

──────────────────────────────────────────────────── Continued from the front page (72) Inventor: Junichi Asada 6-9-39 Minami-Kasugaoka, Ibaraki City, Osaka Prefecture

Claims (10)

[Claims] [Claim 1] An optical deflection element comprising: a conductive thin film formed on a substrate; a waveguide layer for propagating guided light formed on said conductive thin film either directly or via a transparent layer; a transparent substrate having a transparent conductive thin film formed on its surface and a liquid crystal sandwiched between them being tightly attached to said waveguide layer; a periodic structure formed in said waveguide layer along the propagation direction of the guided light; said periodic structure causing said guided light to be radiated as radiated light; a means for orienting said liquid crystal in said waveguide layer; and a voltage signal applied between said conductive thin film and said transparent conductive thin film to change the direction of the radiated light. [Claim 2] An optical deflection element comprising: a conductive thin film formed on a substrate; a waveguide layer for propagating guided light formed on said conductive thin film either directly or via a transparent layer; a transparent substrate having a transparent conductive thin film formed on its surface and a liquid crystal sandwiched between them is tightly attached to said waveguide layer; a periodic structure is formed in said waveguide layer along the propagation direction of the guided light, and said guided light is radiated as radiated light by this periodic structure; said periodic structure is formed as uneven grooves on the surface of the waveguide layer; said periodic grooves serve as an orientation means for orienting the liquid crystal; and a direction of the radiated light is changed by applying a voltage signal between said conductive thin film and said transparent conductive thin film. 3. The optical deflection element according to claim 1, wherein the refractive index of said conductive layer is greater than the refractive index of said liquid crystal for ordinary light. 4. The liquid crystal according to claim 1, wherein the refractive index of said liquid crystal for ordinary light is greater than the refractive index of said transparent layer.
4. The optical deflection element according to claim 2 or 3. 5. The optical deflection element according to claim 1, wherein the voltage signal is an amplitude-modulated wave. 6. The optical deflection element according to claim 1, wherein the direction of alignment of said liquid crystal by said alignment means is parallel or perpendicular to the propagation direction of said guided light. 7. The optical deflection element according to claim 6, wherein said guided light is in TM mode when the alignment direction of said liquid crystal by said alignment means is parallel to the propagation direction of said guided light. 8. The optical waveguide according to claim 7, wherein the periodic structure is a concentric circular or spiral structure, and the guided light propagates perpendicular to the periodic structure.
8. The optical deflector according to claim 1, wherein the light emitted from said waveguide layer is focused at one or more focusing points outside said waveguide layer, and the positions of said focusing points are changed by said voltage signal. [Claim 9] An optical deflection element as described in claim 8, characterized in that the conductive thin film or transparent conductive thin film is divided into many regions and the position of the focusing point is changed by independently applying a voltage signal to each divided region. 10. The optical deflection element according to claim 9, wherein the divided regions are sector-shaped and are partitioned by dividing lines along the propagation direction of the guided light.