WO2009147922A1 - Optical switch - Google Patents

Abstract

An optical switch includes electrode portions (13a, 13b) arranged inside an electro-optical crystal so as to control voltage supply to the electrode portions (13a, 13b), thereby performing switching between the reflection state and the transmission state for the light incident to the electro-optical crystal.  Gap portions (1a, 1b) are formed in a region adjacent to the end portions of the regions of the electrode portions (13a, 13b) at least along a part of the end portions.

Description

Light switch

The present invention relates to an optical switch that switches between reflection and transmission of incident light by applying an electric field to an electro-optic crystal.

As an example of an optical switch using the electro-optic effect, there is a light modulation device described in Japanese Patent Application Laid-Open No. 2006-293018 (hereinafter referred to as Patent Document 1). This light modulation device has a resonator structure in which an optical crystal plate made of an electro-optic crystal is sandwiched between a first reflective layer and a second reflective layer. First and second electrodes are formed on the surface of the optical crystal plate. The first and second electrodes are comb-shaped electrodes in which a plurality of linear electrodes are arranged in parallel at equal intervals, and linear electrodes corresponding to the comb teeth are alternately arranged.

Light enters from the second reflective layer side. The incident light is repeatedly reflected in the resonator (the first reflective layer and the second reflective layer), and then emitted outward from the surface of the first reflective layer. By applying a voltage between the first and second electrodes, an electric field is generated between these electrodes, and the refractive index of the optical crystal plate changes due to the electric field. When the refractive index of the optical crystal plate changes, the resonance wavelength of the resonator shifts to a longer wavelength side than before the change of the refractive index, and as a result, the reflectance of the resonator changes.

The intensity of the output light from the resonator is proportional to the reflectance of the resonator. Therefore, the intensity of the output light of the resonator can be changed by applying a voltage between the first and second electrodes to change the reflectance of the resonator. Thereby, light modulation becomes possible.

In an optical switch that changes the refractive index of a crystal by applying an electric field (electric field) to an electro-optic crystal as described in Patent Document 1, an electric field-induced strain generated by applying an electric field (electric field) to the crystal, so-called Due to electrostriction, the crystal near the electrode portion expands and contracts during the switch operation. If the period of expansion / contraction (determined by the frequency of the AC voltage applied between the electrodes) matches the resonance frequency inherent in the electro-optic crystal structure, the electro-optic crystal excessively expands and contracts, and as a result, the electrodes Crystal breakage such as cracks may occur in the crystal region near the portion.

An object of the present invention is to provide an optical switch that can solve the above-mentioned problems.

In order to achieve the above object, an optical switch according to the present invention includes an electrode part in an electro-optic crystal, and reflects and transmits light incident on the electro-optic crystal by controlling voltage supply to the electrode part. An optical switch in which the state is switched to a region adjacent to an end portion of the electrode forming region in which the electrode portion is formed inside the electro-optic crystal, and at least a part of the end portion of the electrode forming region. A void portion is formed along.

It is a top view of the principal part of the optical switch which is the 1st Embodiment of this invention. FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. It is a schematic diagram which shows the refractive index change area | region formed at the time of the electric field application of the optical switch shown to FIG. 1A. It is sectional drawing which shows the modification of the optical switch which is the 1st Embodiment of this invention. It is a top view of the optical switch which is the 2nd Embodiment of this invention. FIG. 4B is a cross-sectional view taken along line AA in FIG. 4A. It is a schematic diagram which shows the positional relationship of the electrode part in the advancing direction of incident light. It is a top view of the optical switch which is the 3rd Embodiment of this invention. FIG. 6B is a cross-sectional view taken along line AA in FIG. 6A. FIG. 6B is a cross-sectional view taken along line BB in FIG. 6A. It is a figure for demonstrating the temperature control function of the optical switch which is the 3rd Embodiment of this invention. It is a top view of the optical switch which is the 4th Embodiment of this invention. FIG. 7B is a cross-sectional view taken along line AA in FIG. 7A. FIG. 7B is a cross-sectional view taken along line BB in FIG. 7A. It is a top view of the optical switch which is the 5th Embodiment of this invention. FIG. 8B is a cross-sectional view taken along line AA in FIG. 8A. FIG. 8B is a sectional view taken along line BB in FIG. 8A. It is a figure for demonstrating the temperature control function of the optical switch which is the 5th Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is sectional process drawing for demonstrating the electrode formation method of the optical switch of the 3rd Embodiment of this invention. It is a schematic diagram which shows an example of an image display apparatus. 1 is a schematic diagram illustrating an example of an image forming apparatus.

1a, 1b Cavity 10, 11 Optical crystal plate 13a, 13b, 14a, 14b Electrode part

(First embodiment)
FIG. 1A is a top view of the optical switch according to the first embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA in FIG. 1A.

As shown in FIGS. 1A and 1B, the optical switch has a structure in which an optical crystal plate 10 and an optical crystal plate 11 having electrode portions 13a and 13b formed on the surface are laminated. The optical crystal plates 10 and 11 are made of a crystal having an electro-optic effect (electro-optic crystal).

Each of the electrode portions 13a and 13b is a comb-shaped electrode having a plurality of linear electrodes arranged at equal intervals and having a main cross section having the maximum area in the same plane. In the electrode portion 13a and the electrode portion 13b, the linear electrodes are alternately arranged, and the intervals between the linear electrodes are equal. The optical crystal plate 10 is affixed to the surface of the optical crystal plate 11 so as to cover the portion where the linear electrodes corresponding to the comb teeth of the electrode portions 13a and 13b are formed. Note that the intervals between the linear electrodes are not only in a state where the distances between the linear electrodes are completely matched, but also in a state where the spacing between the linear electrodes is shifted due to a manufacturing error or the like. Is also included. That is, the distance between the linear electrodes may be equal so that a refractive index change region for reflecting incident light can be formed.

FIG. 1A is a perspective view showing a state in which the electrode portions 13a and 13b formed on the surface of the optical crystal plate 11 are viewed from the optical crystal plate 10 side. When viewed from the direction perpendicular to the surface of the optical crystal plate 10, the region where the linear electrodes of the electrode portions 13a and 13b are alternately arranged (electrode formation region) is long in the width direction of the linear electrode. The shape electrode has a shorter length direction.

Void portions 1a and 1b are formed along both ends in the longitudinal direction of the electrode forming region. As shown in FIG. 1B, the gaps 1a and 1b are cavities that have a square cross-sectional shape and extend in a certain direction. The depths, lengths, and widths of the gaps 1a and 1b are appropriately set in consideration of the size of crystal expansion and contraction due to electrostriction induced by the electric field from the electrode parts 13a and 13b. In the example shown in FIG. 1B, the depth and length of the gaps 1a and 1b are set to be substantially the same as the depth and length of the linear electrode.

An optical switch is formed by laminating the optical crystal plates 10 and 11 shown in FIGS. 1A and 1B under high temperature and high pressure. The optical crystal plates 10 and 11 bonded together under high temperature and high pressure can be regarded as one optical crystal (specifically, an electro-optical crystal). That is, by bonding the optical crystal plates 10 and 11 under high temperature and high pressure, an electro-optical crystal having an electrode portion therein can be formed.

In this optical switch, when a voltage is applied between the electrode portions 13a and 13b, the refractive index of the crystal in the vicinity of the electrode including the electrode portions 13a and 13b changes due to the electro-optic effect.

FIG. 2 schematically shows a refractive index change region formed in the electrode vicinity region including the electrode portions 13a and 13b. When a voltage is applied between the electrode portions 13a and 13b, an electric field is generated between adjacent linear electrodes, and the refractive index of the crystal in the electrode vicinity region including each linear electrode changes due to the electric field. The region where the refractive index has changed is the refractive index changing region 16 shown in FIG. Incident light is totally reflected at the interface (refractive index interface) between the refractive index changing region 16 and the surrounding crystal region. The incident angle of the incident light is desirably set so as to satisfy a condition that allows total reflection at the interface.

Note that FIG. 2 shows a state in which incident light enters the refractive index change region from the left side toward the drawing and the reflected light goes to the right side. However, in order to further improve the light utilization efficiency, Is preferably configured so that it enters the refractive index change region from the front side (or back side) toward the drawing and the reflected light goes to the back side (or front side).

In addition, when an opaque material is used as the electrode, the electrode itself blocks a part of the incident light, so that the light use efficiency is reduced accordingly. The use efficiency of light can be improved by making an electrode into a transparent electrode.

When a voltage is applied to the electrode portions 13a and 13b, the refractive index change region 16 is formed, so that the incident light is totally reflected at the interface of the refractive index change region 16. On the other hand, when the supply of voltage to the electrode portions 13a and 13b is stopped, the refractive index changing region 16 is not formed, and the incident light passes through the electrode portions 13a and 13b as it is.

The optical switch can be switched between a first state in which incident light is reflected and a second state in which incident light is transmitted. In the first state, a voltage is applied to the electrode portions 13a and 13b to form a refractive index change region, and incident light is reflected at the refractive index interface of the refractive index change region. In the second state, voltage supply to the electrode portions 13a and 13b is stopped. Since the refractive index change due to the electro-optic effect does not occur in the region including the electrode portions 13a and 13b by stopping the voltage supply, the incident light is transmitted between the electrode portions 13a and 13b.

In the above switch operation, the crystal stretches due to electrostriction. Crystal expansion and contraction due to electrostriction occurs in each of the length direction, the width direction, and the thickness direction of the electrode formation region including the electrode portions 13a and 13b. Larger than the direction of. In the present embodiment, the gap portions 1a and 1b are formed along both end portions in the length direction of the electrode formation region, and stress generated by expansion and contraction in the length direction of the electrode formation region is caused by the gap portions 1a and 1b. Absorbed. Thereby, generation | occurrence | production of the crystal breakage by electrostriction can be suppressed.

As described above, in the present embodiment, attention is paid to the fact that the crystal expansion and contraction caused by electrostriction is greatest in the length direction of the electrode formation region, and the gaps 1a and 1b are formed in the length direction of the electrode formation region. It is provided at both ends. Thereby, the stress produced by crystal expansion and contraction can be absorbed efficiently.

Note that the void portion may be provided at one of the end portions in the length direction of the electrode formation region as long as crystal breakage can be reliably suppressed.

In addition, the number of gaps provided for one end may be two or more. For example, in the configuration shown in FIG. 1A, a plurality of gaps 1a and 1b may be arranged in parallel in the longitudinal direction of the electrode formation region.

Furthermore, a material softer than the electrode material of the electrode portions 13a and 13b may be filled in the gap portion.

Furthermore, since the magnitude of electrostriction is proportional to the electric field strength, the thickness of the gap is the thickness of the refractive index change region formed by applying a voltage to the electrode portions 13a and 13b (or its thickness). It is desirable to set a value close to that).

Further, as shown in FIG. 3, the gaps 1a and 1b may be formed on both of the optical crystal plates 10 and 11. The cross-sectional structure shown in FIG. 3 corresponds to the cross section taken along line AA in FIG. 1A.

Further, the gap may be provided at each end of the electrode formation region.

(Second Embodiment)
4A is a top view of an optical switch according to the second embodiment of the present invention, and FIG. 4B is a cross-sectional view taken along line AA in FIG. 4A.

As shown in FIGS. 4A and 4B, the optical switch includes an optical crystal plate 10, an optical crystal plate 11 having electrode portions 13a and 13b formed on the surface, and an optical crystal having electrode portions 14a and 14b formed on the surface. It has a structure in which the plate 12 is laminated. The optical crystal plates 10 to 12 are made of crystals having an electro-optic effect.

In the optical crystal plate 11, gaps 1a and 1b are formed at both ends in the longitudinal direction of the electrode forming region including the electrode parts 13a and 13b. These electrode portions 13a and 13b and the gap portions 1a and 1b are the same as those formed in the optical switch of the first embodiment.

The electrode portions 14a and 14b are comb electrodes similar to the electrode portions 13a and 13b, and the linear electrodes are alternately arranged. The intervals between the linear electrodes of the electrode portions 14a and 14b are equal intervals, and are the same as the intervals between the linear electrodes of the electrode portions 13a and 13b. In the optical crystal plate 12, gaps 2a and 2b are formed at both ends in the longitudinal direction of the electrode forming region including the electrode portions 14a and 14b.

The optical crystal plate 10 is attached to the surface of the optical crystal plate 11 so as to cover the portion where the linear electrodes corresponding to the comb teeth of the electrode portions 13a and 13b are formed. The optical crystal plate 11 to which the optical crystal plate 10 is attached is attached to the surface of the optical crystal plate 12 so as to cover the portion where the linear electrodes corresponding to the comb teeth of the electrode portions 14a and 14b are formed.

FIG. 4A is a perspective view showing a state where the electrode portions 13a and 13b formed on the surface of the optical crystal plate 11 are viewed from the optical crystal plate 10 side. When viewed from the direction perpendicular to the surface of the optical crystal plate 10, the first electrode formation region composed of the electrode portions 13a and 13b is slightly shifted from the second electrode formation region composed of the electrode portions 14a and 14b. Is formed. However, as shown in FIG. 4B, when viewed from the direction perpendicular to the cross section of the optical crystal plates 10 to 12 cut along the line AA in FIG. 4A, the position of each linear electrode of the electrode portions 13a and 13b, and the electrode The positions of the linear electrodes of the portions 14a and 14b are the same.

Further, the first and second electrode forming regions are sequentially arranged in the traveling direction of the incident light. That is, the first and second electrode formation regions are located on the optical path. When the first and second electrode formation regions are viewed along the traveling direction of the incident light, the first and second electrode formation regions are electrode surfaces composed of a plurality of linear electrodes in the electrode portions of each region ( Alternatively, they are laminated so that the surfaces on which the electrode portions are formed are parallel to each other.

FIG. 5 is a schematic diagram showing the positional relationship between the electrode portions 13a and 13b and the electrode portions 14a and 14b in the traveling direction of incident light. The cross section shown in FIG. 5 is a cross section taken along line BB of FIG. 4A.

As shown in FIG. 5, the first electrode formation region composed of the electrode portions 13a and 13b and the second electrode formation region composed of the electrode portions 14a and 14b are sequentially arranged along the traveling direction of the incident light. When viewed along the traveling direction of the incident light 15, the linear electrodes of the electrode portions 13a and 13b overlap the linear electrodes of the electrode portions 14a and 14b.

An optical switch is formed by bonding the optical crystal plates 10 to 12 shown in FIGS. 4A and 4B under high temperature and high pressure. The optical crystal plates 10 to 12 bonded together under high temperature and high pressure can be regarded as one optical crystal (specifically, an electro-optical crystal). That is, by bonding the optical crystal plates 10 to 12 under high temperature and high pressure, an electro-optical crystal having a plurality of electrode portions (a plurality of electrode formation regions) inside can be formed.

In this optical switch, as shown in FIG. 5, light is incident on the electrode surface (or electrode forming surface) at an incident angle θ. Here, the electrode surface (or electrode formation surface) is parallel to the interface (refractive index interface) between the refractive index changing region 16 and the surrounding crystal region shown in FIG. 2, and the incident angle θ is Satisfying conditions that allow total reflection. Further, the incident angle is an angle formed by a perpendicular (normal line in the case of a curved surface) set up at an incident point of the electrode surface (or electrode forming surface) and an incident light beam.

In the optical switch, the switching operation is performed by switching between a first state in which incident light is reflected and a second state in which incident light is transmitted. In the first state, a voltage is applied between the electrode portions 13a and 13b to form the first refractive index changing region, and a voltage is applied between the electrode portions 14a and 14b to set the second refractive index changing region. Then, the incident light is reflected in these refractive index changing regions. In the second state, voltage supply to the electrode portions 13a and 13b and the electrode portions 14a and 14b is stopped. By stopping the voltage supply, the refractive index change due to the electro-optic effect does not occur in each of the electrode portions 13a and 13b and the electrode portions 14a and 14b, so that the incident light passes through these regions.

Note that the refractive index interface of the refractive index changing region partially includes a region that does not satisfy the condition of total reflection, and a part of the incident light is transmitted through this region. The range of the region that does not satisfy the total reflection condition depends on the interval between the linear electrodes and the magnitude of the applied voltage (the magnitude of the electric field).

In the optical switch of the present embodiment, incident light is reflected at the refractive index interface of the first refractive index change region formed by applying a voltage to the electrode portions 13a and 13b, and is further applied to the electrode portions 14a and 14b. The light transmitted through the first refractive index changing region is reflected at the refractive index interface of the second refractive index changing region formed by applying a voltage. Thereby, it is possible to obtain a high extinction ratio.

The extinction ratio can be further improved by setting the number of electrode forming regions (the number of refractive index changing regions) formed along the traveling direction of incident light to three or more. However, when the number of electrode formation regions (refractive index changing regions) is increased, the number and capacity of the electrodes increase accordingly, which is not desirable from the viewpoint of power saving and miniaturization. The number of electrode forming regions (refractive index changing regions) is desirably determined in consideration of the relationship between the extinction ratio and power saving and miniaturization.

Also in the optical switch of this embodiment, as in the case of the first embodiment, during the switch operation, in the electrode formation regions of the electrode portions 13a and 13b and the electrode portions 14a and 14b, crystals due to electrostriction Expansion and contraction occurs. The gap portions 1a and 1b are formed at both ends in the length direction of the electrode formation regions of the electrode portions 13a and 13b, and stress generated by expansion and contraction in the length direction of the electrode formation regions is absorbed by the gap portions 1a and 1b. Is done. Similarly, the gap portions 2a and 2b are formed at both ends in the length direction of the electrode formation regions of the electrode portions 14a and 14b, and the stress generated by the expansion and contraction in the length direction of the electrode formation region is the gap portion. Absorbed by 2a and 2b. This suppresses the occurrence of crystal breakage due to electrostriction.

(Third embodiment)
When the refractive index is changed by applying an electric field to the electro-optic crystal, the change in the refractive index of the crystal depends on the temperature of the crystal. When the magnitude of the change in refractive index changes with temperature, the intensity of output light from the optical switch also changes. In order to make the operation of the optical switch more stable, it is necessary to maintain the temperature of the region where the refractive index change of the electro-optic crystal (the region where the state is switched by transmission and reflection) within an appropriate temperature range. Here, as a third embodiment of the present invention, the occurrence of crystal breakage due to electrostriction can be suppressed, and a region where the refractive index change occurs can be maintained within a certain temperature range. An optical switch having a structure will be described.

6A is a top view of an optical switch according to a third embodiment of the present invention, FIG. 6B is a cross-sectional view taken along line AA in FIG. 6A, and FIG. 6C is a cross-sectional view taken along line BB in FIG. is there.

The optical switch according to the present embodiment is mainly different in the configuration of the gap from the configuration of the optical switch according to the first embodiment. The structures of the electrode portions 13a and 13b are the same as the configuration of the optical switch of the first embodiment.

FIG. 6A is a perspective view of the state where the electrode portions 13a and 13b formed on the surface of the optical crystal plate 11 and the gap portion 1 provided around the electrode portions 13a and 13b are viewed from the optical crystal plate 10 side. Has been shown. As shown in FIG. 6A, when viewed from the direction perpendicular to the electrode surface, the gap 1 is provided so as to surround the electrode formation region in which the electrode portions 13a and 13b are formed.

The gap portion 1 intersects with the electrode portions 13a and 13b. As shown in FIG. 6C, the cross-sectional shape of the space 1 where the gap 1 intersects the electrodes 13a and 13b is a C shape. The gap 1 is filled with a metal material having a lower hardness (softer) than the electrode material of the electrode portions 13 a and 13 b, thereby forming a metal layer 4. As the material of the metal layer 4, it is desirable to use a soft metal material that is easy to pass heat, such as a metal material such as gold or aluminum. In the cross section shown in FIG. 6C, an insulating layer 10 a is formed between the electrode portion 13 a and the gap portion 1, and an insulating layer 10 b is formed between the electrode portion 13 b and the gap portion 1. For example, after vapor-depositing a metal material to be a metal layer, etching is performed on a portion that intersects the electrode portion of the metal layer, and a material to be an insulating layer is deposited thereon, and a surface thereof is polished. Layers 10a and 10b are formed. The insulating layers 10a and 10b may be formed of any material as long as the electrode portions 13a and 13b and the metal layer 4 can be insulated. For example, the insulating layers 10 a and 10 b may be formed of the same material as the optical crystal plate 10. In addition, when the electrode parts 13a and 13b and the metal layer 4 do not contact, it is not necessary to provide the insulating layers 10a and 10b.

A part of the metal layer 4 is exposed to the outside on the surface of the optical crystal plate 11 (the surface not covered with the optical crystal plate 10), and the temperature control element 3 is formed on the exposed surface.

The temperature control element 3 includes a thermoelectric conversion element typified by a Peltier element and a temperature sensor. The thermoelectric conversion element is provided such that its heat generating surface is in contact with the exposed surface of the metal layer 4. The thermoelectric conversion element generates heat when supplied with current. When the thermoelectric conversion element generates heat, the metal layer 4 is heated by the heat energy from the heat generating surface. When the metal layer 4 is heated, the temperature in the vicinity region (including the electrode formation region of the electrode portions 13a and 13b) rises.

Also, the thermoelectric conversion element has a heat absorption function that absorbs heat energy from a portion in contact with the heat generating surface. Specifically, in a Peltier device that is a thermoelectric conversion device, when a direct current is passed, one surface absorbs heat and heat is generated on the opposite surface. When the polarity of the current is reversed, the relationship is reversed. Thereby, heat absorption becomes possible.

* Based on the output of the temperature sensor, the temperature of the region where the thermoelectric conversion element is provided is detected. Based on this detected temperature, the temperature of the electrode forming region can be estimated. Based on the relationship between the temperature of the region where the thermoelectric conversion element is provided and the estimated temperature of the electrode formation region, a threshold value for maintaining the electrode formation region at a constant temperature is determined in advance. When the detected temperature is lower than the threshold value, the heat generation operation by the thermoelectric conversion element is performed. When the detected temperature is equal to or higher than the threshold value, an endothermic operation by the thermoelectric conversion element is performed. By this operation, the temperature of the electrode formation region can be maintained within a certain temperature range.

As shown in FIG. 6D, the temperature control element 3 is connected to the temperature control unit 50. The temperature control unit 50 is a circuit that controls current supply to the thermoelectric conversion element of the temperature control element 3. The output of the temperature sensor of the temperature control element 3 is supplied to the temperature control unit 50. When the temperature detected by the temperature sensor is less than the threshold value, the temperature control unit 50 causes the thermoelectric conversion element to generate heat, and when the detected temperature is equal to or higher than the threshold value, the temperature control unit 50 causes the thermoelectric conversion element to perform an endothermic operation. Thereby, the temperature of the region near the metal layer 4 (including the electrode formation regions of the electrode portions 13a and 13b) is maintained within a certain temperature range.

In the optical switch of the present embodiment, by controlling the current supply to the temperature control element 3, the temperature of the region in the vicinity of the metal layer 4 (including the electrode formation regions of the electrode portions 13a and 13b) is set within a certain temperature range. Maintain within. In this state, the switch operation is performed by controlling the supply of voltage to the electrode portions 13a and 13b. Thereby, output light with a constant intensity can be obtained.

In the above switch operation, the crystal stretches due to electrostriction. Since the metal layer 4 formed in the space 1 is made of a metal material having a low hardness (soft), it functions as an elastic means. Therefore, the stress generated by crystal expansion and contraction is absorbed by the elastic metal layer 4. Thereby, generation | occurrence | production of the crystal breakage by electrostriction can be suppressed.

Further, in the optical switch of the present embodiment, a temperature control metal layer is formed using a gap for strain absorption. Such a structure is simpler than a structure in which a gap for strain absorption and a metal layer for temperature control are formed in different regions.

The gap 1 including the metal layer 4 is not limited to the configuration shown in FIGS. 6A to 6C. The void portion 1 including the metal layer 4 can maintain the temperature of the region including the electrode portions 13a and 13b within a certain temperature range, and can suppress the occurrence of crystal breakage due to electrostriction. Any structure may be used. For example, the void portion 1 may be constituted by a plurality of void portions formed along the end portion of the electrode formation region, and each of the void portions may be filled with a metal material. In this case, a part of the metal layer in each gap is exposed, and a temperature control element is provided on each exposed surface. And the temperature of the area | region containing electrode part 13a, 13b is maintained within a fixed temperature range by performing operation | movement of the heating or heat absorption with respect to each metal layer by each temperature control element. The stress generated by the crystal expansion and contraction is absorbed by the elastic metal layer formed in each gap.

Further, the exposed surface of the metal layer 4 and the position of the temperature control element 3 are not limited to those shown in FIGS. 6A to 6C. The exposed surface of the metal layer 4 and the position of the temperature control element 3 can be appropriately set.

Furthermore, a plurality of portions of the metal layer 4 may be exposed and a temperature control element may be provided on each exposed surface. By performing heating or endothermic operation on the metal layer 4 at a plurality of exposed surfaces, temperature control of the region including the electrode portions 13a and 13b can be performed efficiently.

In addition, the optical crystal plates 10 and 11 are transparent above the phase transition temperature at which the crystal structure changes, and are electro-optic crystals that can obtain a large refractive index near the phase transition temperature, such as KTN (potassium niobate tantalate: KTa). _1-x Nb _x O ₃ ). In this case, the temperature control element 3 performs heating or endothermic operation on the metal layer 4 to maintain the temperature of the region including the electrode portions 13a and 13b of the optical crystal plates 10 and 11 at or above the phase transition temperature. More desirably, the temperature of the region including the electrode portions 13a and 13b of the optical crystal plates 10 and 11 is maintained at or above the phase transition temperature and in the vicinity of the phase transition temperature. In this state, the switch operation is performed by controlling the supply of voltage to the electrode portions 13a and 13b. By maintaining the electro-optic crystal in a transparent state, the amount of light transmitted through the electro-optic crystal is increased, and the extinction ratio can be increased accordingly.

When the electro-optic crystal is maintained at a temperature equal to or higher than the phase transition temperature, the upper limit value of the temperature control range is set within the range in which the optical switch operates in consideration of the temperature dependence of the refractive index of the electro-optic crystal. . Specifically, the upper limit value of the temperature control range is determined as follows.

When the temperature of the electro-optic crystal rises, the refractive index of the electro-optic crystal changes, and accordingly, the critical angle when incident light is totally reflected at the refractive index interface in the refractive index changing region also changes. For this reason, for example, when the incident angle of the incident light with respect to the refractive index interface is set to a critical angle at the phase transition temperature, the set incident angle becomes smaller than the critical angle when the critical angle changes due to the temperature rise. In this case, incident light is not totally reflected at the refractive index interface of the refractive index change region, but is transmitted through the refractive index change region, and as a result, the optical switch does not operate. Therefore, the upper limit value of the temperature control range is a temperature at which the critical angle does not exceed the set incident angle. The temperature condition where the critical angle does not exceed the set incident angle can be defined by the parameters of the distance between the linear electrodes, the magnitude of the applied voltage, and the incident angle.

The strain absorption structure and the temperature control structure using the void portion 1 including the elastic metal layer 4 of the optical switch of the present embodiment described above are the optical switches described in the second embodiment, that is, incident light. The present invention can be applied to an optical switch in which a plurality of refractive index changing regions are formed along the traveling direction. In this case, the strain absorption structure and the temperature control structure are provided for each refractive index change region.

Moreover, not only the heat absorption by the thermoelectric conversion element, but also the metal layer 4 itself has a heat dissipation action. Specifically, the thermal energy from the region near the metal layer 4 (including the electrode formation regions of the electrode portions 13a and 13b) is transmitted through the metal layer 4 and released from the exposed surface of the metal layer 4 to the external space. . Due to the release of the thermal energy, the temperature of the region near the metal layer 4 (including the electrode formation regions of the electrode portions 13a and 13b) decreases. In order to efficiently dissipate heat, it is desirable to increase the area of the exposed surface of the metal layer 4. From the viewpoint of cooling the electrode formation region, the heat dissipation structure by the metal layer 4 is effective.

(Fourth embodiment)
7A is a top view of an optical switch according to a fourth embodiment of the present invention, FIG. 7B is a sectional view taken along line AA in FIG. 7A, and FIG. 7C is a sectional view taken along line BB in FIG. 7A. is there.

The optical switch of the present embodiment has the same configuration as the optical switch of the third embodiment except that the configuration of the gap is different. 7A shows a state in which the electrode portions 13a and 13b formed on the surface of the optical crystal plate 11 and the gap portions 1c and 1d provided around the electrode portions 13a and 13b are viewed from the optical crystal plate 10 side. It is shown in perspective. As shown in FIG. 7A, when viewed from the direction perpendicular to the electrode surface, the gaps 1c and 1d are provided along the end portions of the electrode formation region where the electrode parts 13a and 13b are formed. Part of the portions 1c and 1d is formed along both ends in the longitudinal direction of the electrode formation region, and is disposed so as to face each other.

A metal layer 4a is formed in the gap 1c. The metal layer 4a is formed in a region on the side of the electrode portions 13a and 13b in a portion along the end in the longitudinal direction of the electrode forming region of the gap portion 1c. Similarly, a metal layer 4b is formed in the gap 1d. In the portion along the longitudinal end of the electrode forming region of the gap 1d, the metal layer 4a is formed in a region on the electrode portions 13a and 13b side. The gap 1d intersects with the electrode portion 13b as shown in FIG. 7C. The cross-sectional shape of the intersection of the gap 1d with the electrode 13b is C-shaped. At this intersection, an insulating layer 10c is formed between the electrode portion 13b and the metal layer 4b. The insulating layer 10c may be formed of any material as long as the electrode portion 13b and the metal layer 4b can be insulated. For example, the insulating layer 10 c may be formed of the same material as the optical crystal plate 10.

The metal layers 4a and 4b may be formed of the same electrode material as the electrode material of the electrode portions 13a and 13b, but more preferably, a metal material that easily conducts heat, for example, a metal material such as gold or aluminum. . When the metal layers 4a and 4b and the electrode portions 13a and 13b are formed of the same metal material, the metal layers 4a and 4b and the electrode portions 13a and 13b can be formed by the same formation process.

A part of the metal layer 4a is exposed to the outside on the surface of the optical crystal plate 11 (the surface not covered with the optical crystal plate 10), and the temperature control element 3a is formed on the exposed surface. Similarly, a part of the metal layer 4b is also exposed to the outside, and the temperature control element 3b is formed on this exposed surface.

The temperature control elements 3a and 3b have the same configuration as the temperature control element 3 shown in FIG. 6A, and include a thermoelectric conversion element typified by a Peltier element and a temperature sensor. Although not shown, thermoelectric conversion elements and temperature sensors provided in each of the temperature control elements 3a and 3b are connected to a temperature control unit. The temperature control unit corresponds to the temperature control unit 50 shown in FIG.

When the temperature detected by the temperature sensor of the temperature control element 3a is less than the threshold value, the temperature control unit causes the thermoelectric conversion element of the temperature control element 3a to perform a heat generation operation. When the detected temperature is equal to or higher than the threshold value, the temperature control unit The heat absorption operation by the thermoelectric conversion element of the element 3a is performed. Similarly, the temperature control unit causes the thermoelectric conversion element to perform a heat generation operation when the temperature detected by the temperature sensor is less than the threshold for the temperature control element 3b, and when the detected temperature is equal to or higher than the threshold, The endothermic operation is performed. Thereby, the temperature of the area | region (including the electrode formation area | region which consists of electrode parts 13a and 13b) near the metal layers 4a and 4b is maintained within a fixed temperature range.

In the optical switch of the present embodiment, the temperature of the region including the electrode portions 13a and 13b of the optical crystal plates 10 and 11 is kept constant by heating or absorbing the metal layers 4a and 4b with the temperature control elements 3a and 3b. Maintain within the temperature range of. In this state, the switch operation is performed by controlling the supply of voltage to the electrode portions 13a and 13b. Thereby, output light with a constant intensity can be obtained.

In the above switch operation, the crystal stretches due to electrostriction. The stress generated by the crystal expansion and contraction is absorbed by the hollow portions in the void portions 1c and 1d. Thereby, generation | occurrence | production of the crystal breakage by electrostriction can be suppressed.

Further, in the optical switch of the present embodiment, a temperature control metal layer is formed using a gap for strain absorption. Such a structure is simpler than a structure in which a gap for strain absorption and a metal layer for temperature control are formed in different regions.

The gaps 1c and 1d including the metal layers 4a and 4b are not limited to the configurations shown in FIGS. 7A to 7C. The void portions 1c and 1d including the metal layers 4a and 4b can maintain the temperature of the region including the electrode portions 13a and 13b within a certain temperature range, and suppress the occurrence of crystal breakage due to electrostriction. Any structure can be used as long as it is possible. For example, one or a plurality of voids may be formed along the end of the electrode formation region, and the metal layer may be formed on the side wall on the electrode formation region side in the void.

In the present embodiment, the metal layer is used for the purpose of controlling the temperature of the region including the electrode part. In order to efficiently control the temperature, the metal layer is desirably provided on the side wall on the region side of the electrode portion in the gap.

Further, the exposed surfaces of the metal layers 4a and 4b and the positions of the temperature control elements 3a and 3b are not limited to those shown in FIGS. 7A to 7C. The exposed surfaces of the metal layers 4a and 4b and the positions of the temperature control elements 3a and 3b can be set as appropriate.

Furthermore, in each of the metal layers 4a and 4b, a plurality of locations may be exposed and a temperature control element may be provided on each exposed surface. By performing heating or heat absorption on the metal layer at a plurality of exposed surfaces, the temperature of the region including the electrode portions 13a and 13b can be efficiently controlled.

Also in this embodiment, as in the case of the third embodiment, the optical crystal plates 10 and 11 may be made of an electro-optical crystal (for example, KTN) that becomes transparent at a phase transition temperature or higher. In this case, by causing the temperature control elements 3a and 3b to perform heating or endothermic operation on the metal layers 4a and 4b, the temperature of the region including the electrode portions 13a and 13b of the optical crystal plates 10 and 11 is changed to the phase transition temperature. Maintain above. More desirably, the temperature of the region including the electrode portions 13a and 13b is maintained at or above the phase transition temperature and in the vicinity of the phase transition temperature. In this state, the switch operation is performed by controlling the supply of voltage to the electrode portions 13a and 13b. By maintaining the electro-optic crystal in a transparent state, the amount of light transmitted through the electro-optic crystal is increased, and the extinction ratio can be increased accordingly. When the electro-optic crystal is maintained at a temperature equal to or higher than the phase transition temperature, the upper limit value of the temperature control range is as described in the third embodiment.

The strain absorption structure and the temperature control structure using the gaps 1c and 1d including the metal layers 4a and 4b of the optical switch of the present embodiment described above are the optical switches described in the second embodiment, that is, incident light. The present invention can be applied to an optical switch in which a plurality of refractive index changing regions are formed along the traveling direction of light. In this case, the strain absorption structure and the temperature control structure are provided for each refractive index change region.

(Fifth embodiment)
8A is a top view of an optical switch according to a fifth embodiment of the present invention, FIG. 8B is a sectional view taken along line AA in FIG. 8A, and FIG. 8C is a sectional view taken along line BB in FIG. 8A. is there.

The optical switch of the present embodiment has the same configuration as the optical switch of the third or fourth embodiment except that the configuration of the gap is different. FIG. 8A is a perspective view of the state where the electrode portions 13a and 13b formed on the surface of the optical crystal plate 11 and the gap portion 1e provided around the electrode portions 13a and 13b are viewed from the optical crystal plate 10 side. Has been shown. As shown in FIG. 8A, when viewed from a direction perpendicular to the electrode surface, the gap 1e is provided so as to surround the electrode formation region in which the electrode portions 13a and 13b are formed.

8B and 8C, in order to clarify the region of the gap 1e, the gap 1e is indicated by a vertical line region. The gap 1e intersects the electrode portion 13b. As shown in FIG. 8C, the cross-sectional shape of the space 1e intersecting with the electrode portion 13b is a C shape. An insulating layer 10d is formed on the electrode portion 13b at the intersection. That is, the insulating layer 10d is formed so as to cover the exposed surface of the electrode portion 13b in the gap portion 1e, so that, for example, a part of the electrode portion 13b is exposed to the fluid flowing in the gap portion 1e. , To suppress deterioration of the portion due to corrosion or the like. The insulating layer 10d may be formed of any material as long as the portion of the electrode portion 13b exposed in the gap portion 1e can be protected. For example, the insulating layer 10d may be formed of the same material as the optical crystal plate 10.

Also, as shown in FIG. 8B, one end of the gap 1e is formed across both the optical crystal plates 10 and 11, and this portion communicates with a space outside the optical crystal plate. 1 opening is formed. The other end of the gap 1e is also formed across both the optical crystal plates 10 and 11, and a second opening communicating with the space outside the optical crystal plate is formed in this portion. ing. Here, the first opening communicates with the inflow portion 5a, and the second opening communicates with the outflow portion 5b.

As shown in FIG. 8D, the inflow part 5a is connected to the jet outlet of the fluid supply part 51 via a flow path, and the outflow part 5b is connected to the fluid recovery port of the fluid supply part 51 via a flow path. Yes. The fluid supply part 51 supplies the fluid (gas or liquid) maintained within a certain temperature range from the inflow part 5a, and collects the supplied fluid from the outflow part 5b. The fluid maintained in a certain temperature range circulates in the gap 1e, whereby the temperature of the electrode forming regions of the electrode portions 13a and 13b can be maintained in the certain temperature range.

In the optical switch of the present embodiment, the temperature of the region including the electrode portions 13a and 13b of the optical crystal plates 10 and 11 is set to a constant temperature by supplying the fluid maintained in the constant temperature range into the gap 1e. Keep within range. In this state, the switch operation is performed by controlling the supply of voltage to the electrode portions 13a and 13b. Thereby, output light with a constant intensity can be obtained.

In the above switch operation, the crystal stretches due to electrostriction. The stress generated by this crystal expansion and contraction is absorbed by the gap 1e. Thereby, generation | occurrence | production of the crystal breakage by electrostriction can be suppressed.

Further, in the optical switch of the present embodiment, a fluid supply path for temperature control is formed using a gap portion for strain absorption. Such a structure is simpler than a structure in which a gap for strain absorption and a fluid supply path for temperature control are formed in different regions.

Note that the gap 1e is not limited to the configuration shown in FIGS. 8A to 8C. As long as the gap 1e can maintain the temperature of the region including the electrode portions 13a and 13b within a certain temperature range and can suppress the occurrence of crystal damage due to electrostriction, It is good also as a structure.

Also in this embodiment, as in the case of the third embodiment, the optical crystal plates 10 and 11 may be made of an electro-optical crystal (for example, KTN) that becomes transparent at a phase transition temperature or higher. In this case, the temperature of the region including the electrode portions 13a and 13b of the optical crystal plates 10 and 11 is maintained above the phase transition temperature. More desirably, the temperature of the region including the electrode portions 13a and 13b is maintained at or above the phase transition temperature and in the vicinity of the phase transition temperature. In this state, the switch operation is performed by controlling the supply of voltage to the electrode portions 13a and 13b. By maintaining the electro-optic crystal in a transparent state, the amount of light transmitted through the electro-optic crystal is increased, and the extinction ratio can be increased accordingly. When the electro-optic crystal is maintained at a temperature equal to or higher than the phase transition temperature, the upper limit value of the temperature control range is as described in the third embodiment.

The strain absorption structure and the temperature control flow path structure using the gap portion 1e of the optical switch of the present embodiment described above are the optical switch described in the second embodiment, that is, along the traveling direction of incident light. It can be applied to an optical switch in which a plurality of refractive index changing regions are formed. In this case, the strain absorption structure and the temperature control channel structure are provided for each refractive index change region.

[Electrode formation method]
The optical switch of each embodiment described above can be formed using an existing semiconductor process.

9A to 9I are cross-sectional process diagrams showing one procedure of the electrode forming method of the optical switch according to the first embodiment of the present invention.

First, a resist 91 is applied to the surface of the electro-optic crystal 90 (step of FIG. 9A). Next, the mask 92 on which the electrode pattern is formed is used to mask the surface coated with the resist 91, and the coated surface is exposed (step of FIG. 9B). Next, the exposed portion of the resist 91 is removed (step of FIG. 9C).

Next, the exposed surface of the electro-optic crystal 90 is etched using the resist 91 from which the exposed portion has been removed as a mask (step of FIG. 9D). The etching material is hydrogen fluoride or the like. After the etching, a resist is applied to a region that becomes a void (step of FIG. 9E).

Next, using the resist 91 used as a mask in the step of FIG. 9D and the resist applied in the step of FIG. 9E as a mask for vapor deposition, an electrode material (gold, platinum, etc.) is applied to the etched portion of the electro-optic crystal 90. ) Is deposited to form the electrode 93 (step of FIG. 9F). Thereafter, the resist used as a mask for vapor deposition is removed (step of FIG. 9G).

Next, those surfaces are polished so that the surface of the electro-optic crystal 90 and the surface of the electrode 93 are at the same height (step in FIG. 9H).

Finally, the surface of the electro-optic crystal 90 on which the electrode 93 is formed and one surface of the electro-optic crystal 94 are brought into close contact under high temperature and high pressure conditions, thereby bonding the electro-optic crystals 90 and 94 (see FIG. 9I step). In this bonding step, the surfaces to which the electro-optic crystals 90 and 94 are bonded are processed into surfaces having sufficient flatness.

As described above, the optical switch shown in FIGS. 1A and 1B can be realized by applying the processes of FIGS. 9A to 9I.

When forming the optical switch of the second embodiment of the present invention, first, by applying the steps of FIGS. 9A to 9I, the electrode portions 13a and 13b and the gaps as shown in FIGS. 4A and 4B are applied. A structure in which the optical crystal plate 10 is bonded to the surface of the optical crystal plate 11 on which the portions 1a and 1b are formed is formed. Further, by applying the steps of FIGS. 9A to 9I, the optical crystal plate 12 in which the electrode portions 14a and 14b and the gap portions 2a and 2b are respectively formed is formed. The surface of the optical crystal plate 12 on which the electrode portions 14a and 14b and the gap portions 2a and 2b are formed and the surface of the optical crystal plate 11 on which the electrode portions 13a and 13b and the gap portions 1a and 1b are formed. The opposite surface is stuck together under high temperature and high pressure conditions.

In this bonding step, the positions of the electrode portions 13a and 13b and the gap portions 1a and 1b on the optical crystal plate 11 side and the positions of the electrode portions 14a and 14b and the gap portions 2a and 2b on the optical crystal plate 12 side are determined. It is necessary to adjust precisely. In particular, in the alignment of the electrode portions, when the electrode portions are viewed along the traveling direction of the incident light, the positions of the linear electrodes of the electrode portions are matched. Further, the surfaces of the optical crystal plates to be bonded to each other are processed into surfaces having sufficient flatness.

FIGS. 10A to 10H are cross-sectional process diagrams showing one procedure of the electrode forming method of the optical switch according to the third embodiment of the present invention.

First, a resist 91 is applied to the surface of the electro-optic crystal 90 (step of FIG. 10A). Next, the mask 92 on which the electrode pattern is formed is used to mask the surface coated with the resist 91, and the coated surface is exposed (step of FIG. 10B). Next, the exposed portion of the resist 91 is removed (step of FIG. 10C).

Next, the exposed surface of the electro-optic crystal 90 is etched using the resist 91 from which the exposed portion has been removed as a mask (step of FIG. 10D). The etching material is hydrogen fluoride or the like.

Next, an electrode material (gold, platinum, etc.) is deposited on the etched portion of the electro-optic crystal 90 to form an electrode 93 and a metal layer 95 (step of FIG. 10E), and then the resist 91 is removed (FIG. 10). 10F step). The electrode 93 is the electrode portions 13a and 13b shown in FIG. 6A. The metal layer 95 is a portion formed on the optical crystal plate 11 side of the metal layer 4 shown in FIG. 6A.

Next, those surfaces are polished so that the surface of the electro-optic crystal 90 and each surface of the electrode 93 and the metal layer 95 have the same height (step of FIG. 10G). Thereby, the optical crystal plate 11 shown in FIG. 6A is obtained.

Next, the electro-optic crystal 94 corresponding to the optical crystal plate 10 on which a part of the metal layer 4 is formed as shown in FIG. 6C is formed by applying the above-described steps of FIGS. 10A to 10G. 6C, insulating layers corresponding to the insulating layers 10a and 10b formed at the intersections of the electrode portions 13a and 13b and the metal layer 4 are formed in the corresponding regions of the electro-optic crystal 94.

Finally, the surface of the electro-optic crystal 90 on which the electrode 93 and the metal layer 95 are formed and the surface of the electro-optic crystal 94 on which a part of the metal layer is formed are brought into close contact under high temperature and high pressure conditions. Then, the electro-optic crystals 90 and 94 are bonded together (step of FIG. 10H). In this bonding step, the surfaces to which the electro-optic crystals 90 and 94 are bonded are processed into surfaces having sufficient flatness.

As described above, the optical switch shown in FIGS. 6A to 6C can be realized by applying the processes of FIGS. 10A to 10H.

When forming the optical switch of the fourth embodiment of the present invention, first, by applying the steps of FIGS. 9A to 9H, the electrode portions 13a and 13b, the gap portion 1a, as shown in FIG. Then, an optical crystal plate in which a part of the gap 1b is formed is formed.

Next, a resist mask pattern for forming a metal layer is formed on the surface of the optical crystal plate on which the electrode part and the gap part are formed, and a metal material (gold, platinum, etc.) is deposited on the exposed surface. Then, a metal layer is formed, and then the resist mask pattern is removed. Then, those surfaces are polished so that the surface of the optical crystal plate and the surface of the metal layer have the same height. Thereby, the optical crystal plate 11 shown in FIG. 7A is obtained.

Next, the optical crystal plate 10 on which a part of the metal layer 4b is formed as shown in FIG. 7C is formed by applying the processes of FIGS. 10A to 10G. Further, as shown in FIG. 7C, an insulating layer corresponding to the insulating layer 10c formed at the intersection of the electrode portion 13b and the metal layer 4b is formed in a corresponding region of the optical crystal plate 10.

Finally, the optical crystal plates 10 and 11 are brought into close contact under high temperature and high pressure conditions. In this bonding step, the surface to be bonded of the optical crystal plate is processed into a surface having sufficient flatness. In this manner, the optical switch shown in FIGS. 7A to 7C can be realized.

When forming the optical switch of the fifth embodiment of the present invention, first, by applying the steps of FIGS. 9A to 9H, the electrode portions 13a and 13b and the gap portion 1e as shown in FIG. A part of the optical crystal plate 11 is formed.

Next, by applying the steps shown in FIGS. 9A to 9D, a part of the gap 1e shown in FIG. 8A is formed on one surface of the optical crystal plate. Then, the resist pattern is removed, and the optical crystal plate 10 in which a part of the gap 1e is formed as shown in FIG. 8C is formed. Further, as shown in FIG. 8C, an insulating layer corresponding to the insulating layer 10d formed at the intersection of the electrode portion 13b and the gap portion 1e is formed in a corresponding region of the optical crystal plate 10.

Finally, the optical crystal plates 10 and 11 are brought into close contact under high temperature and high pressure conditions. In this bonding step, the surface to be bonded of the optical crystal plate is processed into a surface having sufficient flatness. In this way, the optical switch shown in FIGS. 8A to 8C can be realized.

The optical switch of the present invention can be applied to an optical communication device, an image display device, an image forming device, and the like. Hereinafter, an image display apparatus and an image forming apparatus will be described as application examples of the optical switch.

[Image display device]
A configuration of an image display device including the optical switch of the present invention will be described.

FIG. 11 is a schematic diagram showing an example of an image display device. This image display device includes laser light sources 102, 103, 104, collimator lenses 105, 106, 107, reflection mirror 108, dichroic mirrors 109, 110, horizontal scanning mirror 115, vertical scanning mirror 116, and optical switches 118, 119, 120. Has a housing 100 containing the. The optical switches 118, 119, and 120 are the optical switches of the present invention.

A collimator lens 105, an optical switch 118, and a reflection mirror 108 are sequentially arranged in the traveling direction of the laser light from the laser light source 102. A parallel light beam from the collimator lens 105 enters the optical switch 118. The optical switch 118 operates according to a control signal supplied from a control unit (not shown). During a period in which the control signal is on (voltage supply period), a voltage is applied to the electrode portion of the optical switch 118 to form a refractive index change region, so that incident light is reflected in the refractive index change region. This reflected light deviates from the optical path toward the reflecting mirror 108. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 118 and travels toward the reflection mirror 108.

The collimator lens 106, the optical switch 119, and the dichroic mirror 109 are sequentially arranged in the traveling direction of the laser light from the laser light source 103. A parallel light beam from the collimator lens 106 enters the optical switch 119. In the optical switch 119, the same operation as that of the optical switch 118 is performed. During the period when the control signal is on (voltage supply period), incident light is reflected in the refractive index change region, and the reflected light deviates from the optical path toward the dichroic mirror 109. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 119 and travels toward the dichroic mirror 109.

The collimator lens 107, the optical switch 120, and the dichroic mirror 110 are sequentially arranged in the traveling direction of the laser light from the laser light source 104. A parallel light beam from the collimator lens 107 enters the optical switch 120. In the optical switch 120, the same operation as that of the optical switch 118 is performed. During a period in which the control signal is on (voltage supply period), incident light is reflected in the refractive index change region, and the reflected light deviates from the optical path toward the dichroic mirror 110. During a period in which the control signal is off (voltage supply stop period), incident light passes through the optical switch 120 and travels toward the dichroic mirror 110.

The dichroic mirror 109 is provided at a position where the light beam from the optical switch 119 and the light beam reflected by the reflection mirror 108 intersect. The dichroic mirror 109 has a wavelength selection characteristic that reflects light from the optical switch 119 and transmits light from the reflection mirror 108.

The dichroic mirror 110 is provided at a position where the light beam from the optical switch 120 and the light beam from the dichroic mirror 109 intersect. The dichroic mirror 109 has a wavelength selection characteristic that reflects light from the optical switch 120 and transmits light from the dichroic mirror 109.

The horizontal scanning mirror 115 is arranged in the traveling direction of the light beam from the dichroic mirror 110, and its operation is controlled by a horizontal scanning control signal from a control unit (not shown). The vertical scanning mirror 116 is disposed in the traveling direction of the light beam from the horizontal scanning mirror 115, and its operation is controlled by a vertical scanning control signal from a control unit (not shown).

As the laser light sources 102, 103, and 104, light sources that emit laser light of colors corresponding to the three primary colors R, G, and B are used. A color image can be displayed on the screen 117 by controlling on / off of the optical switches 118, 119, and 120 and controlling the horizontal scanning mirror 115 and the vertical scanning mirror 116.

[Image forming apparatus]
A configuration of an image forming apparatus including the optical switch of the present invention will be described.

FIG. 12 is a schematic diagram illustrating an example of an image forming apparatus. This image forming apparatus includes a housing 200, an fθ lens 223, and a photoreceptor 224. A laser light source 202, a collimator lens 205, a reflection mirror 208, a scanning mirror 222, and an optical switch 218 are accommodated in the housing 200. The optical switch 218 is the optical switch of the present invention.

A collimator lens 205, an optical switch 218, and a reflection mirror 208 are sequentially arranged in the traveling direction of the laser light from the laser light source 202. A parallel light beam from the collimator lens 205 enters the optical switch 218. The optical switch 218 operates in accordance with a control signal supplied from a control unit (not shown). During a period in which the control signal is on (voltage supply period), a voltage is applied to the electrode portion of the optical switch 218 to form a refractive index change region, so that incident light is reflected in the refractive index change region. This reflected light deviates from the optical path toward the reflecting mirror 208. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 218 and travels toward the reflection mirror 208.

The scanning mirror 222 is arranged in the traveling direction of the light beam from the reflection mirror 208, and its operation is controlled by a scanning control signal from a control unit (not shown). Light from the scanning mirror 222 is applied to the photoconductor 224 via the fθ lens 223.

By turning on / off the optical switch 218 and controlling the scanning mirror 222, an image can be formed on the photosensitive member 224.

According to the present invention as described above, when crystal expansion / contraction due to electrostriction occurs, stress generated by the crystal expansion / contraction is absorbed by the voids, so that the occurrence of crystal breakage can be suppressed.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and operation of the present invention without departing from the spirit of the present invention.

In the optical switch of each embodiment, it is desirable to form the gap so as to be out of the optical path of the incident light.

In addition to KTN, lithium niobate having a phase transition temperature (lithium niobate) or the like may be used as the electro-optic crystal. In this case as well, the same operational effects as when KTN is used can be obtained.

The optical switch of each embodiment can be applied to all optical modulation devices.

This application claims priority based on Japanese Patent Application No. 2008-148141 filed on June 5, 2008, the entire disclosure of which is incorporated herein.

Claims (12)

1. An optical switch comprising an electrode part inside an electro-optic crystal, and the state of reflection and transmission with respect to light incident on the electro-optic crystal can be switched by controlling voltage supply to the electrode part,
   In the electro-optic crystal, in the region adjacent to the end of the electrode forming region where the electrode portion is formed, a gap is formed along at least a part of the end of the electrode forming region. switch.
2. 2. The optical switch according to claim 1, wherein the gap is formed along at least one of end portions in the longitudinal direction of the electrode formation region.
3. 3. The optical switch according to claim 1, wherein the gap portion communicates with a space outside the electro-optic crystal.
4. A metal layer made of a metal material whose hardness is lower than that of the metal material constituting the electrode part is provided in the gap, and a part of the metal layer is exposed to the outside of the electro-optic crystal. The optical switch according to item.
5. 4. The light according to claim 3, further comprising a metal layer provided on a side wall on the electrode formation region side in the gap, wherein a part of the metal layer is exposed to the outside of the electro-optic crystal. switch.
6. The optical switch according to claim 5, wherein the metal layer is made of the same metal material as that of the electrode part.
7. A thermoelectric conversion element that is provided in an exposed portion of the metal layer and generates heat or absorbs heat according to the polarity of the supplied current;
   A temperature sensor provided in a region where the thermoelectric conversion element is formed, and detecting a temperature of the region;
   The temperature control part which controls supply of the electric current to the said thermoelectric conversion element so that the temperature detected by the said temperature sensor may be maintained within a fixed temperature range, The range 4th-6th Claim The optical switch according to any one of the above.
8. The optical switch according to claim 7, wherein the temperature controller maintains at least the temperature of the electrode formation region at a temperature equal to or higher than a phase transition temperature of the electro-optic crystal.
9. The gap includes first and second openings communicating with a space outside the electro-optic crystal,
   A fluid supply unit that supplies a fluid from the first opening, collects the supplied fluid from the second opening, and maintains a temperature of the fluid in a certain temperature range. 4. The optical switch according to any one of items 1 to 3 in the range.
10. 10. The optical switch according to claim 9, wherein the fluid supply unit maintains at least a temperature of the electrode formation region at a temperature equal to or higher than a phase transition temperature of the electro-optic crystal.
11. The said electrode part consists of several linear electrodes arrange | positioned in parallel and the main cross section which becomes the largest area is arrange | positioned in the same plane, In any one of Claims 1-10. The optical switch described.
12. A plurality of the electrode portions are provided inside the electro-optic crystal,
    The plurality of electrode portions are arranged such that electrode surfaces constituted by the plurality of linear electrodes are parallel to each other, and the gap portion is formed in each of the plurality of electrode portions. The optical switch according to claim 11.

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