JP5168076B2 - Optical switch, optical switch manufacturing method, image display apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to an optical switch that switches between a state of transmitting light and a state of reflecting light, and an image display device using the same.

  In the field of optical communications, an optical switch that switches light by applying an electric field to a crystal having an electro-optic effect (electro-optic crystal) to generate a refractive index change is known. As such an optical switch, there are waveguide type optical switches such as a directional coupler type optical switch and a Mach-Zehnder interferometer type optical switch. A directional coupler type optical switch utilizes the proximity effect of two waveguides. In the Mach-Zehnder interferometer type optical switch, a voltage is applied between the waveguides from the outside to generate a phase difference between the light propagating through the waveguides, and use the interference of the light. These waveguide-type optical switches can perform high-speed switching because control for generating a change in refractive index can be performed at high speed.

  In addition to the above, Patent Document 1 describes an optical switch using Bragg reflection. FIG. 23 shows the configuration of the optical switch.

  Referring to FIG. 23, the optical switch includes an optical waveguide layer having an electro-optic effect, and first and second electrode groups provided in the optical waveguide layer. Each of the first and second electrode groups is composed of a plurality of plate-like electrodes extending in the thickness direction of the optical waveguide layer. Each plate electrode is arranged at a constant interval. Each of the first electrode group and the second electrode group has a comb shape on a surface intersecting the thickness direction of the optical waveguide layer, and plate electrodes corresponding to the comb teeth are alternately arranged. Has been placed.

  In the above optical switch, a change in refractive index occurs in a region between adjacent plate electrodes by applying a voltage between the first and second electrode groups. As a result, a periodic refractive index change occurs in the optical waveguide layer. The portion where the periodic refractive index change occurs functions as a diffraction grating, and incident light is Bragg reflected. On the other hand, when the voltage application to the first and second electrode groups is stopped, the function as a diffraction grating is lost, so that incident light is transmitted through the region between the plate electrodes.

  Patent Document 2 describes an optical shutter element using translucent ceramics. As shown in FIG. 24, the optical shutter element has a convex portion 2 serving as a light transmitting portion at a predetermined position of the translucent ceramic substrate 1, and the surface of the translucent ceramic substrate 1 including the side surface portion of the convex portion 2. In addition, an electrode 3 made of a sputtered film such as aluminum is formed.

  The above optical shutter element is installed between two polarizers. Light having a polarization direction that has passed through one of the polarizers is incident from the incident surface 4 a of the translucent ceramic substrate and is emitted from the exit surface 4 b at the tip of the convex portion 2. Light incident from the incident surface 4a passes through the region where the electrode 3 is formed. When a voltage is applied between the electrodes 3, the polarization direction of incident light rotates by a predetermined angle. The light whose polarization direction has been rotated exits from the exit surface 4b and is blocked by the other polarizer. On the other hand, when the voltage application between the electrodes is stopped, the polarization direction does not rotate, so that the light emitted from the exit surface 4b passes through the other polarizer.

Patent Document 3 discloses a waveguide type optical switch. This waveguide type optical switch has an optical directional coupler composed of two optical waveguides formed on the surface of a substrate, and an electrode formed on each waveguide. Each electrode is formed in a groove formed on the substrate surface. Protrusions are provided in the region between the optical waveguides on the substrate surface.
Japanese Patent No. 2666805 (Japanese Patent Laid-Open No. 1-214827) Japanese Patent No. 3280106 (Japanese Patent Laid-Open No. 6-202054) JP-A-1-223432

  In an optical switch that performs optical switching by applying an electric field to an electro-optic crystal to cause a change in refractive index, there is a demand for higher power consumption and faster switching operation. In order to increase power consumption and switch operation speed, it is necessary to reduce interelectrode capacitance.

  Since the optical switch described in Patent Document 1 has a configuration in which a plurality of plate electrodes having a large area are embedded in an electro-optic crystal having a high dielectric constant, the capacitance between the electrodes is large. Therefore, it is difficult to achieve power saving and high speed operation.

  In the optical shutter element described in Patent Document 2, the electrode 3 is formed on the surface of the translucent ceramic substrate 1 including the side surface portion of the convex portion 2. Since the area of the electrode 3 is large and a substrate having a high dielectric constant is provided between the electrodes 3, the interelectrode capacitance is large. Therefore, it is difficult for the optical shutter element described in Patent Document 2 to achieve power saving and high speed operation.

  The optical switch described in Patent Document 3 is a waveguide type. The size of the waveguide is generally several μm. Depending on the intensity of the incident light, the optical density in the waveguide becomes extremely high, and the waveguide is damaged by the optical material that forms the waveguide. May end up. As described above, the optical switch described in Patent Document 3 has a problem that the optical damage resistance is low. In an image display device such as a laser display, for example, optical modulation is performed on high-power light of 100 mW or more, and thus an optical switch of such an image display device needs to have sufficient light damage resistance.

  As one method for improving the optical damage resistance, there is a method of switching a light beam having a large aperture (several tens to several hundreds μm). A waveguide type optical switch as described in Patent Document 3 Therefore, it is difficult to use as an optical switch for switching such a large-diameter light beam.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to have a high optical damage resistance, and to perform a switch operation for a large-diameter light beam at a high speed with less power, a method for manufacturing the same, and an image display using the same. An apparatus and an image forming apparatus are provided.

In order to achieve the above object, an optical switch according to the present invention includes an electro-optic crystal and an electrode portion including a plurality of electrodes arranged on the same plane, and the electro-optic is generated by an electric field generated by the electrode portion. An optical switch that switches between transmission and reflection of incident light incident on the electro-optic crystal by changing a refractive index of a part of the crystal, wherein the electro-optic crystal is interposed between electrodes constituting the electrode unit. Further, the electro-optic crystal has a side wall whose height from the plane is higher than that of the electrode, and at least a region to which an electric field from the electrode portion extends is formed of an optically homogeneous material , The electrodes include first and second electrodes having different polarities, and the first and second electrodes are alternately arranged .

  The image display apparatus of the present invention includes a light source, the above-described optical switch that modulates light from the light source, a scanning unit that scans an external screen with a modulated light beam from the optical switch, and external control. And a control unit that controls a modulation operation in the optical switch according to a signal.

  An image forming apparatus according to the present invention includes a light source, a photosensitive member, the above-described optical switch that modulates light from the light source, and a scanning unit that scans the photosensitive member with a modulated light beam from the optical switch. And a control unit for controlling a modulation operation in the optical switch in accordance with a control signal from the outside.

  According to the present invention, an electro-optic crystal having a side wall higher than that of the electrode is used, whereby the contact area between the electro-optic crystal having a high dielectric constant and the electrode can be reduced. Since the interelectrode capacitance can be reduced by reducing the contact area between the electro-optic crystal and the electrode, power saving and high speed operation can be achieved.

  In addition, unlike the waveguide type, since it is not necessary to confine light, the optical damage resistance can be improved as compared with the waveguide type optical switch. In addition, as compared with a waveguide type optical switch, it is possible to perform a switching operation for a light beam having a large aperture (several tens to several hundreds μm).

  Next, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1A is a schematic diagram illustrating a configuration of an optical switch according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view of the optical switch of FIG. 1A viewed from the exit surface side.

  As shown in FIG. 1A, the optical switch is formed by joining two electro-optic crystals 104 and 105 under high temperature and high pressure. As shown in FIG. 1B, in the electro-optic crystal after bonding, the junction interface between the electro-optic crystals 104 and 105 has a refractive index substantially equal and is continuous, so that it is regarded as one optically uniform electro-optic crystal. Can be tricked.

  The electro-optic crystals 104 and 105 are crystals having an electro-optic effect such as potassium tantalate niobate (KTN) and lithium niobate (LN).

  A plurality of grooves are formed in parallel on the surface of the electro-optic crystal 104 before bonding (surface bonded to the electro-optic crystal 105), and an electrode 106 is formed inside each groove. The electrode 106 is formed, for example, by depositing an electron conductor that can be an electrode member on the bottom of the groove. The thickness of the electrode 106 is smaller than the depth of the groove. For this reason, the surface of the electro-optic crystal 104 is in a state where the portion where the electrode 106 is formed is depressed. Portions other than the grooves on the surface of the electro-optic crystal 104 are sufficiently polished to be a flat surface.

  The surface of the electro-optic crystal 105 before bonding is sufficiently polished to be a flat surface, and this surface is bonded to the surface of the electro-optic crystal 104 on which the electrode 106 as described above is formed. In a state after bonding, an electrode portion 107 including a plurality of electrodes 106 is formed in the electro-optic crystal, and a depression portion on the surface of the electro-optic crystal 104 becomes a void portion 108 formed in the electro-optic crystal. . Due to the gap 108, the light transmission portion 109 between the electrodes 106 has a structure having a side wall 110. The electro-optic crystals 104 and 105 may be joined with a binder having the same refractive index.

  The plurality of electrodes 106 are arranged in parallel on the same plane, and are electrically connected to the external power source 111 so that the polarities of adjacent electrodes are different. Each electrode 106 is not in contact with the electro-optic crystal 105. Each electrode 106 is provided so as to extend from one end face of the joined electro-optic crystal toward the other end face. One end surface is an entrance surface and the other end surface is an exit surface.

  The same plane as used herein is not limited to the geometrically completely same plane, and may be a plane that includes manufacturing errors and has a range that allows the refractive index change region to be formed flat. .

  Next, the operation of the optical switch of this embodiment will be described.

  When no voltage is applied to the electrode portion 107, the refractive index does not change in the crystal region near the electrode 106, as shown in FIG. 1B. In this state, when the incident light 101 is incident from the incident surface of the electro-optic crystal, the incident light is transmitted through the light transmitting portion 109 and emitted to the outside as transmitted light 102 from the emitting surface.

  On the other hand, when a voltage is applied to the electrode portion 107, a refractive index change due to an electric field from the electrode 106 occurs in the crystal region in the vicinity of the electrode 106, as shown in FIG. 1C. For this reason, the refractive index changing portion 112 is generated in the crystal region near the electrode 106. The critical angle θm, which is a condition for total reflection of incident light, at the refractive index interface 113 between the refractive index changing portion 112 and the surrounding crystal region is the refractive index change amount Δn of the refractive index changing portion 112 and the electro-optic crystal. From the relationship with the refractive index n0 of 104 and 105, it is calculated by the following formula.

  Incident light having an incident angle greater than or equal to the critical angle θm is totally reflected at the refractive index interface 113 and is emitted to the outside as reflected light 103 from the emission surface. The outgoing direction of the reflected light 103 is different from the outgoing direction of the transmitted light 102.

  As described above, the transmission state and the reflection state can be switched by controlling the application of the voltage to the electrode portion 107, thereby enabling on / off control of light. Since the transmitted light 102 and the reflected light 103 have different emission directions, they can be easily separated.

  FIG. 2 is a diagram for explaining changes in refractive index and optical power with respect to applied voltage in the optical switch of the present embodiment. FIG. 2A is a graph showing a waveform of an applied voltage, where the horizontal axis indicates time and the vertical axis indicates voltage. FIG. 2B is a graph showing a change in refractive index in the vicinity of the electrode portion with respect to the applied voltage shown in FIG. 2A, in which the horizontal axis indicates time and the vertical axis indicates the refractive index. FIG. 2C is a graph showing changes in optical power with respect to the applied voltage shown in FIG. 2A. The horizontal axis indicates time, and the vertical axis indicates optical power. The value of the optical power is a value obtained by detecting the transmitted light 102 with a photodetector.

  When a voltage is applied to the electrode portion 107, the refractive index in the vicinity of the electrode 106 is mainly smaller than the refractive index in the surrounding area. For this reason, light incident on the refractive index interface 113 at an incident angle greater than the critical angle is totally reflected at the refractive index interface 113, and the power value of the transmitted light 102 detected by the photodetector is lowered.

  When the voltage applied to the electrode portion 107 is zero, no change in the refractive index in the region near the electrode 106 occurs. For this reason, incident light passes through the light transmission part 109 between the electrode parts 106 as it is, and the power value of the transmitted light 102 detected by the photodetector is higher than that at the time of voltage application.

  In the optical switch of the present embodiment described above, the electro-optic crystal has sidewalls 110 higher than the thickness of the electrodes 106 between the electrodes 106. According to this configuration, a part of the electrode 106 is exposed in the space (gap 108) partitioned by the side wall 110, and the exposed surface does not contact the electro-optic crystal. Therefore, the area where the electrode 106 is in contact with the electro-optic crystal can be reduced by the exposed surface. The interelectrode capacitance in this case is about 3/4 of the interelectrode capacitance when the entire electrode is in contact with the electro-optic crystal.

  The capacitance between electrodes is determined by parameters such as electrode length, electrode thickness, electrode spacing, dielectric constant of the material or space (vacuum / air) in contact with the electrode, spacing between the electrode and the side wall, etc. By appropriately optimizing, it is possible to further reduce the interelectrode capacitance.

  Further, the relationship among the power consumption P, the interelectrode capacitance C, and the maximum modulation operating frequency fmax at the time of high-speed operation in the optical switch of the present embodiment is expressed by the following Expression 2.

Here, f is an operating frequency and R is an output resistance.

  According to Equation 2, the power consumption P during high-speed operation is proportional to the interelectrode capacitance C. Therefore, the power consumption can be reduced by reducing the interelectrode capacitance C. Since the operating frequency fmax is inversely proportional to the interelectrode capacitance C, the operating frequency can be increased, that is, the switching operation can be speeded up by reducing the interelectrode capacitance C.

  FIG. 3 is a characteristic diagram showing the relationship between the electrode interval d and the electric field strength E generated between the electrodes when a voltage V is applied between the electrodes. According to this relationship, when the electrode distance d is reduced, the electric field strength E increases exponentially. In the optical switch of the present embodiment, since the distance between the electrodes 106 is about several μm to several tens of μm, a stronger electric field is generated in the electro-optic crystal portion between the electrodes with a small applied voltage, and the refractive index. A change part can be generated. Therefore, the voltage applied to the electrode portion can be lowered.

  As described above, in the optical switch of this embodiment, it is possible to reduce power consumption and increase the speed of the switch operation.

  Further, according to the optical switch of this embodiment, since the device alone can be operated as an optical switch, an external optical component such as a polarizer is not necessary, and accordingly, miniaturization and cost reduction can be achieved. .

  Furthermore, according to the optical switch of the present embodiment, heat generated when light is applied to the electrode unit 107 or a voltage is applied to the electrode unit 107 by the gap 108 formed in the electrode unit 107. It is possible to efficiently release the strain and heat generated in the. This can reduce the load on the crystal and prevent the crystal from being damaged, so that the durability and reliability can be improved.

  Next, desirable materials used for each part of the optical switch of the present embodiment and desirable setting conditions such as electrode length will be described.

In the optical switch of this embodiment, the electro-optic crystal includes an electro-optic crystal having a high Kerr constant, Pockels constant and refractive index, such as potassium tantalate niobate (KTN), lithium niobate (LiNbO ₃ ), LiTaO ₃ ( LT), KTiOPO ₄ (KTP) or the like is preferably used. This is because the refractive index change amount Δn is given by the following Equation 3, and therefore a large refractive index change can be obtained by using an electro-optic crystal having a high Kerr constant, Pockels constant, and refractive index.

  By optimizing the length of the electrode 106 according to the beam diameter of the incident light 101, the interelectrode capacitance can be further reduced. Specifically, the beam diameter in a plane including the vertical direction of the electrode surface (surface consisting of each electrode 106) and the traveling direction of the beam is r, the region in which the refractive index is changed by the electric field from the electrode portion, and its periphery The length of the electrode 106 is equal to or greater than the value of the electrode length L given by the following equation 4, where θm is the critical angle in the electro-optic crystal, which is the total reflection condition, at the refractive index interface with the region If it is.

  The width W of the electrode portion (the width of the lattice-like portion) may be equal to or greater than the beam width w in the horizontal direction with respect to the electrode.

  The film thickness (height) of each electrode 106 is desirably as uniform as possible, and the distance between each electrode 106 is desirably as uniform as possible. A relatively flat refractive index interface 113 can be formed by equalizing the film thickness and interval of each electrode 106. By making the refractive index interface 113 a relatively flat surface, the reflected light 103 travels in substantially the same direction without being scattered, and as a result, a decrease in extinction ratio due to the influence of the scattered light can be suppressed.

  In order to increase the light utilization efficiency, it is desirable that the traveling direction of the incident light 101 and the longitudinal direction of the electrode 106 be parallel to each other. In addition, since incident light needs to be incident at a shallow angle of about a critical angle, in a configuration in which the traveling direction of the incident light 101 intersects with the longitudinal direction of the electrode 106, the thickness of the groove portion where the electrode 106 is formed. May block light.

  The space 108 may be in a vacuum (reduced pressure state) or may be filled with air. For example, an electrode is deposited on the electro-optic crystal 104 or the electro-optic crystals 104 and 105 are attached in a vacuum chamber. In the attaching process, a process is performed to seal the gap 108. The space 108 can be evacuated. Since the dielectric constant in a vacuum (depressurized state) is lower than that of air, the interelectrode capacitance can be further reduced by making the space 108 vacuum. In addition, when the space 108 is evacuated, oxidation of the exposed surface of the electrode 106 can be suppressed.

  A material having a dielectric constant lower than that of the electro-optic crystal may be filled in the gap 108. FIG. 4 shows a structure in which a substance is filled in the gap in the configuration shown in FIG. 1B. The substance 401 filled in the gap is in contact with the electrode 106. The dielectric constant of the material 401 is lower than that of the electro-optic crystals 104 and 105. Accordingly, the interelectrode capacitance in this case is smaller than that of the structure in which the entire electrode 106 is covered with the electro-optic crystal.

  The substance 401 only needs to have a dielectric constant smaller than that of the electro-optic crystal, and may be a material having an insulating property (low dielectric constant), a material having a high thermal conductivity, or a material having a high thermal conductivity having an insulating property. 401 may be used. Examples of the insulating material having high thermal conductivity include an insulating graphite sheet and a silicone compound.

  In the case where a material having an insulating property (low dielectric constant) is used as the material 401, in addition to a reduction in interelectrode capacitance, the function of the material 401 to shield an electric field in a multi-electrode structure having a plurality of electrode portions described later work. By this electric field shielding function, mutual interference of electric fields between the electrode portions can be suppressed.

  In the case where a material having high thermal conductivity is used as the material 401, heat generated in the electrode portion 106 can be efficiently released when light is applied or voltage is applied.

  Further, by connecting the substance 401 having a high thermal conductivity to an external temperature adjusting device such as a Peltier element, the temperature of the region near the electrode portion of the electro-optic crystal can be controlled. According to this configuration, for example, an electro-optic crystal that is transparent above the phase transition temperature at which the crystal structure changes and can obtain a large refractive index near the phase transition temperature, such as potassium tantalate niobate (KTN), is used. In this case, the temperature in the region near the electrode part can be maintained at or above the phase transition temperature. 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.

  Further, in the optical switch of the present embodiment, the interelectrode capacitance can be reduced by designing based on the wavelength of light to be modulated. For display applications, it is particularly necessary to modulate visible light having a wavelength of 400 nm to 700 nm. In such a wavelength range, the refractive index and refractive index change amount of the electro-optic crystal are slightly different depending on the wavelength. For example, when potassium tantalate niobate (KTN) is used for the electro-optic crystal, the refractive index n and the kerr are calculated from the secondary electro-optic coefficient g11-g12, the vacuum dielectric constant ε0, and the relative dielectric constant εr of the electro-optic crystal. The constant s can be calculated by the following formula 5.

Assuming that the secondary electro-optic coefficient g11-g12 having a wavelength of 440 nm is 0.206, the refractive index n is 2.409 and the Kerr constant s is 4.67 × 10 ^{−15 according} to Equation 5. Assuming that the secondary electro-optic coefficient g11-g12 having a wavelength of 640 nm is 0.154, the refractive index n is 2.284 and the Kerr constant s is 3.49 × 10 ^{−15 according} to Equation 5. In addition, when a voltage of 5 V is applied between the electrodes having an interval of 5 μm, the refractive index change Δn is −0.033 in the case of light with a wavelength of 440 nm and −0.033 in the case of light with a wavelength of 640 nm, according to Equation 3. 0.021. According to Equation 1, the critical angle θm at the refractive index interface is 80.6 degrees in the case of light having a wavelength of 440 nm, and 82.3 degrees in the case of light having a wavelength of 640 nm. As can be seen from these calculated values, the critical angle also varies depending on the wavelength used.

  When laser light is used as incident light, the wavelength of the light to be used is determined, and therefore, the critical angle obtained from the refractive index of the electro-optic crystal and the amount of change in the refractive index, and the laser beam diameter r, are calculated using Equation 4. Using the electrode length L, an optical switch can be designed with the minimum necessary electrode length. As a result, an optical switch capable of high-speed modulation with low power consumption can be realized.

  In addition, when using light with a broad wavelength such as white light as the incident light, set the incident angle, electrode length, applied voltage, etc. of the incident light according to the light on the long wavelength side where the refractive index change is small. It is desirable to do.

  Next, the electrode forming method of the optical switch of this embodiment will be specifically described.

  FIGS. 5A to 5J are cross-sectional process diagrams showing one procedure of the electrode forming method of the optical switch.

  First, a resist 502 is applied to the surface of the electro-optic crystal 501 (step of FIG. 5A). Next, using the mask 503 on which the first pattern for electrode formation is formed, the surface coated with the resist 502 is masked, and the coated surface is exposed (step of FIG. 5B). Next, the exposed portion of the resist 502 is removed (step of FIG. 5C).

  Next, the exposed surface of the electro-optic crystal 501 is etched using the resist from which the exposed portion has been removed as a mask (step in FIG. 5D). The etching material is, for example, hydrogen fluoride.

  Next, a resist 502 is applied again (step in FIG. 5E), and the mask 504 on which the second pattern for electrode formation is formed is used to mask the surface on which the resist 502 is applied again. The coated surface is exposed (step of FIG. 5 (f)). The second pattern is slightly smaller than the first pattern of the mask 503 used in the step of FIG. Next, the exposed portion of the resist 502 is removed (step of FIG. 5G). 5E to 5G, a groove is formed on the surface of the electro-optic crystal 501, and the entire surface except the bottom of the groove is covered with a resist. That is, the side wall of the groove is covered with the resist.

  Next, an electrode material (gold, platinum, etc.) is deposited on the entire surface of the electro-optic crystal 501 where the grooves are formed by vapor deposition or sputtering (step in FIG. 5H). An electrode 505 is formed by the electrode material deposited on the bottom of the groove. The film thickness of the electrode 505 is made thinner than the etching amount (depth) of the electro-optic crystal performed in the step of FIG. Next, the resist 502 is removed, and the surface of the electro-optic crystal 501 is sufficiently polished to obtain a flat surface (step shown in FIG. 5I).

  Finally, the surface of the electro-optic crystal 501 on which the electrode 505 is formed is brought into close contact with the polished flat surface of another electro-optic crystal 506 under high temperature and high pressure conditions, 506 is attached (step of FIG. 5J). The electro-optic crystals 501 and 506 may be bonded with a binder having the same refractive index as these. In the bonding step, the surfaces to which the electro-optic crystals 501 and 506 are bonded are processed into surfaces having sufficient flatness.

  Through the steps (a) to (j) in FIG. 5 described above, the electrodes 106 and the gaps 108 as shown in FIG. 1A and the electro-optic crystals 104 and 105 can be bonded. Note that the electrode 106 formed by the steps (a) to (j) in FIG. The interelectrode capacitance in the structure in which the electrode 106 is not in contact with the side wall 110 is smaller than that in the structure in which the electrode 106 is in contact with the side wall 110. In a structure in which the electrode 106 does not contact the side wall 110, the interelectrode capacitance decreases as the distance between the electrode 106 and the side wall 110 increases. However, when the distance between the electrode 106 and the side wall 110 is increased, it is necessary to reduce the area of the transmissive portion 109, and as a result, the light utilization efficiency is lowered. Therefore, it is desirable to determine the distance between the electrode 106 and the side wall 110 in consideration of the light use efficiency.

  Next, another electrode forming method will be described. In this electrode formation method, a substance 401 having a dielectric constant smaller than that of the electro-optic crystal 501 is formed or pasted on the electrode 505 formed in the step of FIG. 5H (step of FIG. 6A). . The substance 401 is an insulating (low dielectric constant) substance, a high thermal conductivity substance, or a substance having both characteristics. After the formation of the substance 401, the resist is removed and the surface of the electro-optic crystal 501 is polished. Then, the electro-optic crystal 501 is bonded to the electro-optic crystal 506 under high temperature and high pressure conditions (step of FIG. 6B). The electro-optic crystals 501 and 506 may be bonded using a binder having a refractive index equivalent to that of the electro-optic crystal. Thus, the optical switch as shown in FIG. 4 can be manufactured.

  Next, still another electrode forming method will be described. In this electrode formation method, after the step of FIG. 5C, an electrode 507 is formed on the surface of the electro-optic crystal 501 and the resist is removed (step of FIG. 7A). Next, a groove deeper than the film thickness of the electrode 507 is formed in a region corresponding to the electrode 507 on the surface of another electro-optic crystal 508 by a process similar to the process of FIGS. (Step of FIG. 7B). Then, the surface on which the groove of the electro-optic crystal 508 is formed is polished to be a flat surface, and this surface is attached to the surface on which the electrode 507 of the electro-optic crystal 501 is formed (step of FIG. 7C). . In the attaching step, the electro-optic crystals 501 and 508 are aligned so that the electrode 507 is accommodated in the groove. In this way, an electrode structure as shown in FIG. 1A is obtained.

  Next, another electrode forming method will be described. In this electrode formation method, a groove for embedding an electrode is formed on the surface of the electro-optic crystal 509 by the same process as the process of FIGS. 5A to 5D, and the depth is approximately the same as the depth of the groove. After forming the electrode having a film thickness, the resist is removed. Next, the surface on which the electrode of the electro-optic crystal 509 is formed is polished into a flat surface. Next, a groove is formed on the surface of another electro-optic crystal 508 by a process similar to the process of (a) to (d) of FIG. The position of this groove corresponds to the position of the electrode of the electro-optic crystal 509, and its width is wider than the width of the electrode. Next, the surface on which the groove of the electro-optic crystal 508 is formed is polished to a flat surface, and this surface is attached to the surface on which the electrode of the electro-optic crystal 509 is formed. Thus, an optical switch having a structure in which a part of the electrode does not contact the electro-optic crystal as shown in FIG. 8 is obtained.

  In the optical switch of this embodiment, a plurality of electrode portions may be provided along the traveling direction of incident light. According to this multi-electrode structure, a high extinction ratio can be obtained.

  In order to realize a small optical switch that can suppress a light loss generated when light enters and exits at the end of the electro-optic crystal and obtains a high extinction ratio, a multi-electrode structure is desirable.

  FIG. 9A is a schematic diagram illustrating a configuration of an optical switch having a multi-electrode structure, and FIG. 9B is a cross-sectional view of the optical switch of FIG. 9A viewed from the exit surface side.

  As shown in FIG. 9A, the optical switch is obtained by joining three electro-optic crystals 104, 105, and 603 under high temperature and high pressure. In the electro-optic crystal after joining, the electro-optic crystals 104, 105, and 603 are joined. Each of the junction interfaces has a refractive index substantially the same and is continuous, so that it can be regarded as an optically uniform electro-optic crystal. The electro-optic crystals 104, 105, and 603 are crystals having an electro-optic effect such as potassium tantalate niobate (KTN) and lithium niobate (LN).

  The electro-optic crystal 104 includes an electrode unit 604. The electrode portion 604 has the same electrode structure as that shown in FIG. 1A and includes a plurality of electrodes 106. The thickness of each electrode 106 is thinner than the depth of the groove. The electro-optic crystal 105 includes an electrode unit 605. The electrode portion 605 has a structure similar to that of the electrode portion 604.

  The surface on which the electrode portion 604 of the electro-optic crystal 104 is formed is bonded to the surface opposite to the surface on which the electrode portion 605 of the electro-optic crystal 105 is formed. The surface of the electro-optic crystal 105 on which the electrode portion 605 is formed is bonded to the surface of the electro-optic crystal 603. The electro-optic crystals 104, 105, and 603 are joined under high temperature and high pressure conditions. Instead, the electro-optic crystals 104, 105, and 603 are bonded with a binder having a refractive index equivalent to that of the electro-optic crystals. And may be joined.

  As shown in FIG. 9B, after joining, the electrode portions 604 and 605 are arranged in parallel to each other, and the electrode and the gap portion constituting the electrode portion 604 are arranged in the electrode portion 605 in the direction in which the incident light 101 is transmitted. It overlaps with the electrode and the gap portion.

  In the optical switch having the multi-electrode structure described above, the switch operation in each of the electrode portions 604 and 605 is substantially the same as the electrode portion of the optical switch shown in FIG. 1A. When a voltage is applied to each of the electrode portions 604 and 605, as shown in FIG. 9C, a refractive index changing portion 606 is formed in the crystal region in the vicinity of the electrode portion 604, and the refractive index changing portion in the crystal region in the vicinity of the electrode portion 605. 607 is formed.

  In a state where a voltage is applied to each of the electrode portions 604 and 605, the incident light 101 enters the electro-optic crystal 104 while maintaining an incident angle that is greater than or equal to the critical angle. The incident light 101 reaches the refractive index changing unit 606, where it is divided into two light components, a first transmitted light component and a first reflected light component. The first transmitted light component that has passed through the refractive index changing unit 606 reaches the refractive index changing unit 607 disposed behind the refractive index changing unit 606, where the second transmitted light component and the second reflected light component are transmitted. The light component is again divided into two components. The first reflected light 602 reflected by the refractive index changing unit 606 is emitted from the emission surface of the electro-optic crystal 104 to the outside as reflected light 601. The second reflected light 602 reflected by the refractive index changing portion 607 is emitted as reflected light 602 from the emission surface of the electro-optic crystal 105 to the outside.

  On the other hand, when the voltage supply to the electrode portions 604 and 605 is stopped, the refractive index changing portions 606 and 607 are not formed, so that the incident light 102 is transmitted through a region between the electrodes constituting the electrode portions 604 and 605. This transmitted light is emitted as the transmitted light 102 from the emission surface of the electro-optic crystal 603 to the outside. The outgoing direction of the transmitted light 102 is different from the outgoing direction of the reflected lights 601 and 602.

  As described above, in the state where a voltage is applied to each of the electrode portions 604 and 605, the light that has been transmitted through the refractive index changing portion 606 in the preceding stage is incident on the refractive index changing portion 607 in the subsequent stage. By reflecting, the extinction ratio can be increased.

  If the incident angle, beam diameter, and interval between the electrode portions 604 and 605 are not set appropriately, the second reflected light from the refractive index changing portion 607 enters the electrode portion 604, which adversely affects the switching operation. And the extinction ratio may be reduced. In particular, when the interval between the electrode portions 604 and 605 is narrow, an unexpected refractive index change portion is generated between the electrode portions 604 and 605 due to the mutual interference of the electric fields generated at the electrode portions 604 and 605. In this case, there is a possibility that an appropriate extinction ratio cannot be obtained due to the effect of unexpected light scattering. For this reason, it is desirable that the interval between the electrode portions 604 and 605 be set such that mutual interference of electric fields does not occur. Experimentally, the interval between the electrode portions 604 and 605 is desirably set to be three times or more the interval between the electrodes constituting each electrode portion.

  Also, as shown in FIGS. 10A and 10B, a plurality of electrode portions 604 and 605 composed of electrodes having a length equal to or longer than the electrode length L shown in Formula 1 are arranged only on the optical path of the incident light 101. May be. Also in this case, in the state where a voltage is applied to each of the electrode portions 604 and 605, the light that has passed through the incident light 101 without being reflected by the preceding electrode portion 604 is reflected by the subsequent electrode portion 605. It is possible to increase the extinction ratio. By limiting the electrode formation region to a region through which light is transmitted, the area of the electrode can be further reduced. As a result, the interelectrode capacitance can be reduced as compared with the structure shown in FIG. 9A, and further improvement in power consumption and high speed operation can be achieved. Further, the amount of expensive electrode material used can be reduced, and the cost can be reduced.

  In the optical switch having the multi-electrode structure shown in FIGS. 9A and 10A, when a voltage is applied to the electrode portions 604 and 605, light is scattered at each refractive index changing portion, so that stray light is likely to be generated. An appropriate extinction ratio may not be obtained due to the influence of the generated stray light. For this reason, in an optical switch having a multi-electrode structure, it is necessary to suppress light scattering at the refractive index interface as much as possible. In order to form a flat refractive index interface, as in the case of an optical switch having a one-stage electrode structure, the plurality of electrodes forming the electrode section have a structure in which the height, film thickness, and electrode interval are uniform. It is desirable to be.

  As shown in FIG. 9B, when the positions of the electrodes of each electrode part are configured at the time of production, it is possible to prevent light from being reflected by the electrode part as much as possible. Can be raised.

  In addition, the electrode portion peripheral portion (void portion) that is not in contact with the electro-optic crystal may be filled with air, and an insulating (low dielectric constant) / high thermal conductivity substance (for example, insulating graphite sheet or silicone compound) ) May be formed.

  Next, a method for manufacturing the optical switch having the multi-electrode structure described above will be described. First, a plurality of electro-optic crystals 501 each having an electrode portion composed of a plurality of electrodes 505 are formed by the steps (a) to (i) in FIG. In this bonding, the surface on which the electrode portion of one electro-optical crystal is formed is bonded to the surface opposite to the surface on which the electrode portion of the other electro-optical crystal is formed. Finally, as shown in FIG. 11A, a plurality of electro-optic crystals 501 bonded together are attached to a polished flat surface of another electro-optic crystal 506.

  Next, another method for manufacturing an optical switch having a multi-electrode structure will be described. First, two electro-optic crystals 501 each having an electrode portion composed of a plurality of electrodes 505 are formed by the steps (a) to (i) in FIG. 5 and bonded together. In this bonding, the surface on which the electrode portion of one electro-optical crystal is formed is bonded to the surface on which the electrode portion of the other electro-optical crystal is formed. Thereby, a multi-electrode structure as shown in FIG. 11B is obtained. In this multi-electrode structure, an electrode formed on one electro-optic crystal and an electrode formed on the other electro-optic crystal are arranged to face each other, and a gap is formed between these electrodes. According to this structure, the capacitance between the electrodes can be reduced, and it is not necessary to attach another electro-optic crystal 506 shown in FIG. 11A, so that the cost can be reduced accordingly. Also in this case, it is desirable that the interval between the electrode portions be three times or more the interval between the electrodes 106.

  Next, an arrangement example when the optical switch of this embodiment is actually designed will be described. Here, an arrangement example using potassium tantalate niobate (KTN) and an arrangement example using lithium niobate (LN) will be described.

  First, the case where potassium tantalate niobate (KTN) is used for the electro-optic crystal will be described.

  The width of the incident light beam in the direction perpendicular to the electrode surface (surface comprising the electrodes 106) is 20 μm, and the width in the direction parallel to the electrode surface is 50 μm. The wavelength λ of the incident light is 640 nm, and the refractive index n of potassium tantalate niobate (KTN) in this case is 2.284.

  The electrode part is composed of ten electrodes 106 having a width w of 1 μm, and the interval x between the electrodes 106 is 5 μm. Each electrode 106 is in contact with a gap 108 having a depth of 1 μm.

  The refractive index change amount Δn is −0.0065 when a voltage of 5 V is applied to the electrode portion from the external power source 111. Under this condition, the critical angle θm when the incident light is totally reflected by the refractive index interface of the refractive index changing portion generated by the electric field application is 85.7 °. At this time, the incident angle of the incident light to the electro-optic crystal is 9.9 °.

  In order to reflect all the incident light having a diameter of 20 μm by the refractive index interface of the refractive index changing portion, the length of the electrode 106 needs to be 265 μm or more. At this time, the total interelectrode capacitance of the electrode portion is about 325 pF. On the other hand, when an electrode having the same shape and size as the electrode 106 is formed in the comparative structure having no void portion, it is approximately 405 pF. From this, it can be seen that according to this example, the interelectrode capacitance can be reduced to about 80% of the comparative structure.

  When an optical switch having a two-stage electrode structure is realized, if the thickness of the electro-optic crystal 105 is 20 μm, the distance between the electrode portions needs to be about 265 μm. For this reason, the total length of the electro-optic crystal is 795 μm or more, and the height of the electro-optic crystal is 60 μm or more.

  Next, the case where lithium niobate (LN) is used for the electro-optic crystal will be described.

  The width of the incident light beam in the direction perpendicular to the electrode surface is 20 μm, and the width in the direction parallel to the electrode surface is 50 μm. The wavelength λ of incident light is 640 nm, and the refractive index n of lithium niobate (LN) in that case is 2.284.

  The electrode part is composed of 14 electrodes 106 having a width w of 1 μm, and the interval x between the electrodes 106 is 3 μm. Each electrode 106 is in contact with a gap 108 having a depth of 1 μm.

  The refractive index change amount Δn when a voltage of 200 V is applied from the external power source 111 to the electrode part is −0.0067. Under this condition, the critical angle θm when the incident light is totally reflected by the refractive index interface of the refractive index changing portion generated by the electric field application is 85.6 °. At this time, the incident angle of the incident light to the electro-optic crystal is 10.1 °.

  In order to reflect all incident light having a diameter of 20 μm by the refractive index interface of the refractive index changing portion, the length of the electrode 106 needs to be 261 μm or more. The total interelectrode capacitance of the electrode part at this time is about 1.34 pF. On the other hand, when an electrode having the same shape and size as the electrode 106 is formed in the comparative structure having no void portion, it is about 1.63 pF. From this, it can be seen that according to this example, the interelectrode capacitance can be reduced to about 80% of the comparative structure.

  When an optical switch having a two-stage electrode structure is realized, if the thickness of the electro-optic crystal 105 is 20 μm, the interval between the electrode portions needs to be about 261 μm. For this reason, the total length of the electro-optic crystal is 783 μm or more, and the height of the electro-optic crystal is 60 μm or more.

  In the example shown in FIG. 9A and FIG. 10A described above, the optical switch including two electrode portions arranged in parallel along the traveling direction of incident light has been described. However, the number of electrode portions is not limited to this, There may be three or more. As the number of electrode portions arranged in parallel along the traveling direction of incident light increases, a higher extinction ratio can be obtained.

(Second Embodiment)
FIG. 12A is a schematic diagram illustrating a configuration of an optical switch according to a second embodiment of the present invention, and FIG. 12B is a cross-sectional view of the optical switch of FIG. 12A viewed from the exit surface side.

  As shown in FIG. 12A, the optical switch includes an electro-optic crystal 104 in which an electrode portion 107 including a plurality of electrodes 106 is formed. The electro-optic crystal 104 is a crystal having an electro-optic effect such as potassium tantalate niobate (KTN) or lithium niobate (LN).

  On the surface of the electro-optic crystal 104, a plurality of grooves are formed in parallel along the traveling direction of the incident light 101, and an electrode 106 is formed at the bottom of each groove. The electrode 106 is formed, for example, by depositing an electron conductor that can be an electrode member on the bottom of the groove. The thickness of the electrode 106 is smaller than the depth of the groove. The depth of the groove is equal to or greater than the length of the beam in the direction perpendicular to the electrode surface of incident light (surface comprising the electrodes 106).

  The plurality of electrodes 106 are arranged in parallel on the same plane, and are electrically connected to the external power source 111 so that the polarities of adjacent electrodes are different. Each electrode 106 is provided so as to extend from one end face of the electro-optic crystal 104 toward the other end face. One end surface is an entrance surface and the other end surface is an exit surface.

  The same plane as used herein is not limited to the geometrically completely same plane, and may be a plane that includes manufacturing errors and has a range that allows the refractive index change region to be formed flat. .

  Next, the operation of the optical switch of this embodiment will be described.

  When a voltage is applied to the electrode portion 107, a refractive index change due to the electric field from the electrode 106 occurs in the crystal region near the electrode 106, as shown in FIG. 12C. For this reason, the refractive index changing portion 112 is generated in the crystal region near the electrode 106. On the other hand, when no voltage is applied to the electrode portion 107, the refractive index changing portion 112 does not occur.

  FIG. 13A is a schematic view of the state of the optical switch viewed from the side when the voltage supply to the electrode unit 107 is stopped. When no voltage is applied to the electrode portion 107, the refractive index changing portion 112 does not occur, so that the incident light 101 passes through the light transmitting portion 109 between the electrodes 106 and is transmitted to the outside as the transmitted light 102 from the emission surface. Emitted.

  FIG. 13B is a schematic view of the state of the optical switch viewed from the side when a voltage is applied to the electrode unit 107. When a voltage is applied to the electrode portion 107, the incident light 101 is totally reflected at the refractive index interface 113 between the refractive index changing portion 112 and the surrounding crystal region. The reflected light from the refractive index interface 113 is emitted to the outside as reflected light 103 from the emission surface. The incident angle of the incident light 101 with respect to the refractive index interface 113 is not less than the critical angle.

  The optical switch of this embodiment can also obtain the same effects as those of the first embodiment.

  Since the outgoing direction of the transmitted light 102 is different from the outgoing direction of the reflected light 103, they can be easily separated.

  In the optical switch of this embodiment, the light transmitted through the electrode portion 107 is emitted from the emission surface through the lattice-shaped crystal region 801 below the electrode portion 107 of the electro-optic crystal 104. For this reason, it is not necessary to provide another electro-optic crystal for light emission (or light incidence) (for example, the electro-optic crystal 105 shown in FIG. 1A). Therefore, the step of attaching the electro-optic crystal is not required, and as a result, the manufacturing can be simplified and the cost can be reduced.

  Note that when the depth of the groove in which the electrode 106 is formed is less than the length of the beam in the direction perpendicular to the electrode surface of the incident light, a part of the beam is reflected by the end face of the electro-optic crystal, and thus transmitted. The light emission direction is different from the original direction. FIG. 14 is a schematic view of an optical switch having a groove depth less than the length of a perpendicular beam as viewed from the side when voltage supply to the electrode portion is stopped. Part of the light transmitted through the light transmitting portion 109 is reflected in the same direction as the reflected light 103 shown in FIG. 13B on the surface of the electro-optic crystal 104 on the side where the electrode portion 107 is formed. For this reason, the transmitted light 901 traveling in the same direction as the transmitted light 102 shown in FIG. 13A and the reflected light 902 traveling in the same direction as the reflected light 103 are respectively emitted from the exit surface, and the direction of the emitted light is not determined.

  From the above, a deep groove longer than the length of the beam in the direction perpendicular to the electrode surface of the incident light is necessary.

  In addition, the electrode portion peripheral portion (void portion) that is not in contact with the electro-optic crystal may be filled with air, and an insulating (low dielectric constant) / high thermal conductivity substance (for example, insulating graphite sheet or silicone compound) ) May be formed.

  Further, as shown in FIG. 15, a structure in which the direction of light incidence and emission is opposite to that shown in FIG. 12A may be adopted. In this case, the distance from the surface opposite to the side on which the groove of the electro-optic crystal is formed to the electrode portion 107 is equal to or longer than the length of the beam in the perpendicular direction of the electrode surface of the incident light.

  In a state where a voltage is supplied from the external power source 111 to the electrode unit 107, the incident light 101 having an incident angle greater than the critical angle is totally reflected by the refractive index changing interface 113 and reflected light 103 from the upper end face of the electro-optic crystal 104. Is emitted to the outside. When the voltage supply to the electrode unit 107 is stopped, the incident light 101 passes through the lower region of the electro-optical crystal 104 (the crystal region below the electrode unit 107), and transmits the transmitted light 102 from the lower end surface of the electro-optical crystal 104. Is emitted to the outside. Since the transmitted light 102 and the reflected light 103 have different emission directions, they can be easily separated.

  According to the optical switch of this embodiment, compared to the optical switch of the first embodiment, the electro-optic crystal 105 is unnecessary, and processes such as polishing and bonding are not required. Cost reduction can be achieved, and a small and thin optical switch can be realized.

  Also in the optical switch of this embodiment, a plurality of electrode portions may be provided along the traveling direction of incident light. According to this multi-electrode structure, a high extinction ratio can be obtained.

  FIG. 16A is a schematic diagram illustrating a configuration of an optical switch having a multi-electrode structure to which the second embodiment is applied, and FIG. 16B is a cross-sectional view of the optical switch of FIG. 16A viewed from the exit surface side.

  As shown in FIG. 16A, the optical switch is obtained by joining two electro-optic crystals 104 and 105 under high temperature and high pressure, and in the joined electro-optic crystal, the junction interface between the electro-optic crystals 104 and 105 Can be regarded as an optically uniform electro-optic crystal because the refractive indexes are substantially the same and continuous. The electro-optic crystals 104 and 105 are crystals having an electro-optic effect such as potassium tantalate niobate (KTN) and lithium niobate (LN).

  The electro-optic crystal 104 has an electrode portion 604 composed of a plurality of electrodes arranged in parallel on the same plane. The electrode portion 604 has the same electrode structure as that shown in FIG. 1A. The thickness of each electrode constituting the electrode portion 604 is thinner than the depth of the groove.

  The electro-optic crystal 105 has an electrode portion 605 including a plurality of electrodes arranged in parallel on the same plane. The electrode portion 605 has the same electrode structure as the electrode portion 107 shown in FIG. 12A. The thickness of each electrode constituting the electrode portion 605 is thinner than the depth of the groove. The depth of the groove is equal to or greater than the length of the beam incident on the electrode portion 605 in the direction perpendicular to the electrode surface.

  The surface on which the electrode portion 604 of the electro-optic crystal 104 is formed is bonded to the surface opposite to the surface on which the electrode portion 605 of the electro-optic crystal 105 is formed. The electro-optic crystals 104 and 105 are joined under high temperature and high pressure conditions. Instead, the electro-optic crystals 104 and 105 are joined using a binder having a refractive index equivalent to that of the electro-optic crystals. May be.

  As shown in FIG. 16B, after bonding, the electrode portions 604 and 605 are arranged in parallel to each other along the direction in which the incident light 101 is transmitted. In the direction in which the incident light 101 is transmitted, the electrode and the gap that constitute the electrode portion 604 overlap with the electrode and the gap that constitute the electrode portion 605.

  The multi-electrode structure optical switch in the first embodiment has a structure in which three electro-optic crystals are bonded together, whereas the multi-electrode structure optical switch in the present embodiment has two electro-optic crystals. The structure is such that crystals are bonded together, and the number of electro-optic crystals is one less than that of the first embodiment. Therefore, according to the optical switch having a multi-electrode structure according to the present embodiment, the manufacturing can be simplified, and the cost can be reduced because the number of electro-optic crystals is small. Can be realized.

  FIG. 17A is a schematic diagram illustrating a configuration of an optical switch having another multi-electrode structure to which the second embodiment is applied, and FIG. 17B is a cross-sectional view of the optical switch of FIG. 17A viewed from the exit surface side. .

  The optical switch shown in FIG. 17A is composed of one electro-optic crystal 104, and a plurality of parallel deep grooves are formed on each of the upper and lower surfaces of the electro-optic crystal 104. An electrode 106 is formed in each groove. As shown in FIG. 17B, an electrode portion 604 is formed by the plurality of electrodes 106 formed in each groove on the upper surface side, and an electrode portion 605 is formed by the plurality of electrodes 106 formed in each groove on the lower surface side. .

  The depth of the groove formed on the upper surface is equal to or greater than the length of the beam incident on the electrode portion 604 in the direction perpendicular to the electrode surface. The depth of the groove formed on the lower surface is equal to or longer than the length of the beam incident on the electrode portion 605 in the direction perpendicular to the electrode surface.

  According to the optical switch having another multi-electrode structure described above, since it can be formed by one electro-optic crystal, compared with the one shown in FIG. It is possible to reduce the size.

  Next, the electrode forming method of the optical switch of this embodiment will be specifically described.

  18A to 18H are cross-sectional process diagrams illustrating one procedure of the electrode forming method of the optical switch according to the present embodiment.

  First, a resist 502 is applied to the surface of the electro-optic crystal 501 (step of FIG. 18A). Next, using the mask 503 on which the first pattern for electrode formation is formed, the surface coated with the resist 502 is masked, and the coated surface is exposed (step of FIG. 18B). Next, the exposed portion of the resist 502 is removed (step of FIG. 18C).

  Next, the exposed surface of the electro-optic crystal 501 is etched using the resist from which the exposed portion has been removed as a mask (step in FIG. 18D). The etching material is, for example, hydrogen fluoride.

  Next, a resist 502 is applied again (step in FIG. 18E), and the surface to which the resist 502 is applied again is masked using the mask 504 on which the second pattern for electrode formation is formed. The coated surface is exposed (step of FIG. 18 (f)). The second pattern is slightly smaller than the first pattern of the mask 503 used in the step of FIG. Next, the exposed portion of the resist 502 is removed (step of FIG. 18G). These steps (e) to (g) in FIG. 18 are basically the same as the steps (e) to (g) in FIG. 5 described above. Through these steps, a groove is formed on the surface of the electro-optic crystal 501, and the entire surface except the bottom of the groove is covered with a resist. That is, the side wall of the groove is covered with the resist.

  Finally, an electrode material (gold, platinum, etc.) is deposited on the etched portion of the electro-optic crystal 501 by vapor deposition or sputtering to form the electrode 505, and then the resist 502 is removed (step of FIG. 18 (h)). ). Thus, the optical switch of this embodiment is obtained.

  In the case of the optical switch having the multi-electrode structure shown in FIG. 16A, two electro-optic crystals on which the electrodes 505 are formed are formed by the steps (a) to (h) in FIG. The groove of one electro-optic crystal is deeper than the thickness of the electrode, but shallower than the groove of the other electro-optic crystal. The depth of the groove of the other electro-optic crystal is equal to or greater than the length of the beam in the direction perpendicular to the electrode surface of the incident light. These two electro-optic crystals are bonded together.

  In the case of the optical switch having the multi-electrode structure shown in FIG. 17A, an electro-optic crystal having electrodes 505 formed on the upper surface and the lower surface is formed by the steps (a) to (h) in FIG. The grooves on the upper surface and the lower surface are deeper than the thickness of the electrode and have a depth equal to or greater than the length of the beam in the direction perpendicular to the electrode surface of the incident light.

  In the optical switch having the multi-electrode structure shown in FIG. 16A, the region incident on the first-stage electrode portion is not a lattice-like crystal region as compared to the optical switch having the multi-electrode structure shown in FIG. 17A. Accordingly, the light utilization efficiency is improved and a high extinction ratio can be obtained. In addition, since the optical switch having the multi-electrode structure shown in FIG. 16A is thinner than the multi-electrode structure shown in FIG. 17A, a small and thin optical switch can be realized.

  On the other hand, since the optical switch having the multi-electrode structure shown in FIG. 17A can be composed of a single electro-optic crystal, the cost can be reduced.

  Also in the optical switch of the present embodiment, the incident angle of the beam is not less than the critical angle θm given by the above-described equation 1. Further, the electrode length (same as the groove length) is set to be equal to or longer than the electrode length L given by Equation 4 described above. In Equation 4, r is the beam diameter in a plane including the normal direction of the electrode surface and the traveling direction of the beam. The width of the electrode portion (the width of the lattice portion) is equal to or greater than the width of the beam in the horizontal direction with respect to the electrode.

  Next, an arrangement example when the optical switch of this embodiment is actually designed will be described. Here, an arrangement example using potassium tantalate niobate (KTN) and an arrangement example using lithium niobate (LN) will be described.

  First, the case where potassium tantalate niobate (KTN) is used for the electro-optic crystal will be described.

  The width of the incident light beam in the direction perpendicular to the electrode surface is 20 μm, and the width in the direction parallel to the electrode surface is 50 μm. The wavelength λ of the incident light is 640 nm, and the refractive index n of potassium tantalate niobate (KTN) in this case is 2.284.

  The electrode part is composed of ten electrodes 106 having a width w of 1 μm, and the interval x between the electrodes 106 is 5 μm. Each electrode 106 is in contact with a gap 108 having a depth of 1 μm.

  The refractive index change amount Δn is −0.0065 when a voltage of 5 V is applied to the electrode portion from the external power source 111. Under this condition, the critical angle θm when the incident light is totally reflected by the refractive index interface of the refractive index changing portion generated by the electric field application is 86.1 °. At this time, the incident angle of the incident light to the electro-optic crystal is 9.0 °.

  In order to reflect all incident light having a diameter of 20 μm by the refractive index interface of the refractive index changing portion, the length of the electrode 106 needs to be 291 μm or more. At this time, the total interelectrode capacitance of the electrode portion is about 329 pF. On the other hand, when an electrode having the same shape and size as the electrode 106 is formed in the comparative structure having no void portion, it is approximately 432 pF. From this, it can be seen that according to this example, the interelectrode capacitance can be reduced to about 80% of the comparative structure.

  When an optical switch having a two-stage electrode structure is realized, if the thickness of the electro-optic crystal 105 is 20 μm, the interval between the electrode portions needs to be about 291 μm. For this reason, the total length of the electro-optic crystal is 873 μm or more, and the height of the electro-optic crystal is 60 μm or more.

  Next, the case where lithium niobate (LN) is used for the electro-optic crystal will be described.

  The width of the incident light beam in the direction perpendicular to the electrode surface is 20 μm, and the width in the direction parallel to the electrode surface is 50 μm. The wavelength λ of incident light is 640 nm, and the refractive index n of lithium niobate (LN) in that case is 2.284.

  The electrode part is composed of 14 electrodes 106 having a width w of 1 μm, and the interval x between the electrodes 106 is 3 μm. The electrode is formed in a deep groove having a depth of 20 μm.

  The refractive index change amount Δn is −0.0070 when a voltage of 200 V is applied from the external power source 111 to the electrode portion. Under this condition, the critical angle θm when the incident light is totally reflected by the refractive index interface of the refractive index changing portion generated by the electric field application is 85.5 °. At this time, the incident angle of the incident light to the electro-optic crystal is 10.3 °.

  In order to reflect all the incident light having a diameter of 20 μm by the refractive index interface of the refractive index changing portion, the length of the electrode 106 needs to be 256 μm or more. At this time, the total interelectrode capacitance of the electrode portion is about 1.26 pF. On the other hand, when an electrode having the same shape and size as the electrode 106 is formed in the comparative structure having no void portion, it is approximately 1.59 pF. From this, it can be seen that according to this example, the interelectrode capacitance can be reduced to about 80% of the comparative structure.

  When an optical switch having a two-stage electrode structure is realized, if the thickness of the electro-optic crystal 105 is 20 μm, the distance between the electrode portions needs to be about 256 μm. Therefore, the total length of the electro-optic crystal is 768 μm or more, and the height of the electro-optic crystal is 60 μm or more.

(Third embodiment)
FIG. 19A is a schematic diagram illustrating a configuration of an optical switch according to a third embodiment of the present invention, and FIG. 19B is a cross-sectional view of the optical switch of FIG. 19A viewed from the exit surface side.

  As shown in FIG. 19A, the optical switch includes an electro-optic crystal 104 in which an electrode portion 107 including a plurality of electrodes 106 is formed. The electro-optic crystal 104 is a crystal having an electro-optic effect such as potassium tantalate niobate (KTN) or lithium niobate (LN).

  On the surface of the electro-optic crystal 104, a plurality of grooves are formed in parallel along the traveling direction of the incident light 101, and an electrode 106 is formed at the bottom of each groove. The electrode 106 is formed, for example, by depositing an electron conductor that can be an electrode member on the bottom of the groove. The thickness of the electrode 106 is smaller than the depth of the groove. The depth of the groove is at least half of the length of the beam in the direction perpendicular to the electrode surface of incident light (surface comprising the electrodes 106).

  The same plane as used herein is not limited to the geometrically completely same plane, and may be a plane that includes manufacturing errors and has a range that allows the refractive index change region to be formed flat. .

  The plurality of electrodes 106 are arranged in parallel on the same plane, and are electrically connected to the external power source 111 so that the polarities of adjacent electrodes are different. Each electrode 106 is provided so as to extend from one end face of the electro-optic crystal 104 toward the other end face. One end surface is an incident surface, and the other end surface is an exit surface (exit end surface 1305).

  The end of the electro-optic crystal 104 on the side where the emission surface is formed has a portion (upper end) above the electrode portion 107 extending further in the direction of electrode extension than the emission end surface 1305, and the bottom surface of the extension end portion. The plane including 1302 is orthogonal to the plane including the emission end face 1305. The cross-sectional shape of the end when viewed from the side surface of the electro-optic crystal 104 is bowl-shaped. A mirror surface 1301 is formed on the lower surface 1302 of the extended end portion. The mirror surface 1301 is an optical thin film designed to reflect a highly reflective metal or light having a wavelength to be used. The lower surface 1302 and the mirror surface 1301 at the end are parallel to the lower surface 1304 of the electro-optic crystal 4.

  Also in this embodiment, the electrode portion peripheral portion (void portion) that is not in contact with the electro-optic crystal may be filled with air, and an insulating (low dielectric constant) / high thermal conductivity substance (for example, insulating graphite) Sheet or silicone compound) may be formed.

  Next, the operation of the optical switch of this embodiment will be described.

  When a voltage is applied to the electrode portion 107, a refractive index change due to an electric field from the electrode 106 occurs in the crystal region near the electrode 106, as shown in FIG. 19C. For this reason, the refractive index changing portion 112 is generated in the crystal region near the electrode 106. On the other hand, when no voltage is applied to the electrode portion 107, the refractive index changing portion 112 does not occur.

  FIG. 20A is a schematic view of the state of the optical switch viewed from the side when the voltage supply to the electrode unit 107 is stopped. When no voltage is applied to the electrode part 107, the refractive index changing part 112 does not occur, so that the incident light 101 passes through the light transmission part 109 (lattice crystal region 1303 between the electrodes) between the electrodes 106. .

  An outgoing end face 1305 and a lower face 1304 are arranged in the traveling direction of the light transmitted through the light transmitting portion 109. Since the refractive index difference between the electro-optic crystal and the atmosphere is large, light directed toward the lower surface 1304 out of the light transmitted through the light transmitting portion 109 is totally reflected by the lower surface 1304. An outgoing end face 1305 is disposed in the traveling direction of the reflected light.

  Of the light transmitted through the light transmitting portion 109, the light directed toward the emission end face 1305 is emitted as the transmitted light 102 from the emission end face 1305. On the other hand, the reflected light from the lower surface 1304 is emitted from the emission end surface 1305 toward the mirror surface 1301. The mirror surface 1301 is formed at the same height as the electrode portion 107 and in parallel with the lower surface 1304, and reflected light from the lower surface 1304 is reflected by the mirror surface 1301. The reflected light 1302 from the mirror surface 1301 travels in the same direction as the outgoing direction of the transmitted light 102.

  FIG. 20B is a schematic diagram of the state of the optical switch when a voltage is applied to the electrode unit 107 as viewed from the side. When voltage is applied to the electrode portion 107, the incident light 101 is totally reflected at the refractive index interface between the refractive index changing portion and the surrounding crystal region. The reflected light from the refractive index interface is emitted to the outside as reflected light 103 from the end face of the stretched end. In addition, the incident angle with respect to the refractive index interface of incident light is more than a critical angle.

  Since the outgoing direction of the transmitted light 102 is different from the outgoing direction of the reflected light 103, they can be easily separated. An optical switch operation is realized by utilizing the separation of the transmitted light 102 and the reflected light 103.

  The optical switch of this embodiment can also obtain the same effects as those of the first embodiment.

  Similarly to the second embodiment, the light transmitted through the electrode portion 107 is emitted from the emission surface through the lattice crystal region 1303 below the electrode portion 107 of the electro-optic crystal 104. For this reason, it is not necessary to provide another electro-optic crystal for light emission (or light incidence) (for example, the electro-optic crystal 105 shown in FIG. 1A). Therefore, the step of attaching the electro-optic crystal is not required, and as a result, the manufacturing can be simplified and the cost can be reduced.

  Further, in the optical switch of the second embodiment, it is necessary to form a deep groove that is longer than the length of the beam in the direction perpendicular to the electrode surface of the incident light. In the optical switch of this embodiment, the groove Can be reduced to about ½ that of the second embodiment. Therefore, according to the present embodiment, since the optical switch can be configured with an electro-optic crystal that is thinner than that of the second embodiment, a small and thin optical switch can be provided.

  Further, the electro-optic crystal 105 necessary for the optical switch of the first embodiment is unnecessary, and the etching amount of the electro-optic crystal can be reduced to about half compared with the optical switch of the second embodiment. In addition, since the processing is easy in view of the fact that steps such as polishing and pasting are unnecessary, manufacturing can be simplified and costs can be reduced.

  The optical switch of the present embodiment can be created by applying the optical switch manufacturing method of the first embodiment (steps (a) to (i) in FIG. 5). However, in the step of forming the groove for forming the electrode, when the resist-uncoated portion of the electro-optic crystal is etched with an etching material (such as hydrogen fluoride), the depth of the groove is a beam in the direction perpendicular to the electrode. Etching is performed so as to be about half of the length. At this stage, at the same time, a portion for forming the mirror surface is formed by etching. And in the vapor deposition process which forms an electrode, a mirror surface is formed simultaneously. Thereby, since an electrode and a mirror surface can be formed with few processes, manufacture can be simplified and cost reduction can be achieved.

  Moreover, after manufacturing the optical switch of the first embodiment or the second embodiment, the optical switch of this embodiment can also be manufactured by attaching the mirror surface to the same height as the electrode position.

In the optical switch of the present embodiment, the electrode portion and the mirror surface do not necessarily have to be formed at the same height, and the electrode portion and the mirror surface are parallel to each other, and the incident light exit surface of the electro-optic crystal. The length from the end on the side to the end on the exit surface side of the electrode portion is l, the height from the surface where the electrode portion is formed to the surface where the mirror surface is formed is H, and the refractive index boundary surface When the critical angle at is θm, the electrode part and the mirror surface are
H ≧ l / tan θm
It is only necessary to be formed so as to satisfy the above. If the mirror surface is formed parallel to the electrode part at a height that satisfies this conditional expression, the light reflected by the electrode part and the light transmitted through the electrode part can be separated, so that it can be used as an optical switch. It becomes possible. In addition, when l is 0, that is, when the distance between the electrode portion and the end portion of the electro-optic crystal is not separated, H is 0. In this case, the conditions are the same as when the electrode portion and the mirror surface are formed at the same height.

  Next, an arrangement example when the optical switch of this embodiment is actually designed will be described. Here, an arrangement example using potassium tantalate niobate (KTN) and an arrangement example using lithium niobate (LN) will be described.

  First, the case where potassium tantalate niobate (KTN) is used for the electro-optic crystal will be described.

  The width of the incident light beam in the direction perpendicular to the electrode surface is 20 μm, and the width in the direction parallel to the electrode surface is 50 μm. The wavelength λ of the incident light is 640 nm, and the refractive index n of potassium tantalate niobate (KTN) in this case is 2.284.

  The electrode part is composed of ten electrodes 106 having a width w of 1 μm, and the distance between the electrodes 106 is 5 μm. The electrode is formed in a groove having a depth of 10 μm.

  The refractive index change amount Δn is −0.0065 when a voltage of 5 V is applied to the electrode portion from the external power source 111. Under this condition, the critical angle θm when the incident light is totally reflected by the refractive index interface of the refractive index changing portion generated by the electric field application is 85.9 °. At this time, the incident angle of the incident light to the electro-optic crystal is 9.3 °.

  In order to reflect all the incident light having a diameter of 20 μm by the refractive index interface of the refractive index changing portion, the length of the electrode 106 needs to be 283 μm or more. At this time, the total interelectrode capacitance of the electrode portion is about 319 pF. On the other hand, when an electrode having the same shape and size as the electrode 106 is formed in the comparative structure having no void portion, it is about 419 pF. From this, it can be seen that according to this example, the interelectrode capacitance can be reduced to about 80% of the comparative structure.

  The mirror surface has a side of about 61 μm and is formed at the same height as the electrode toward the side from which transmitted light is emitted.

  Next, the case where lithium niobate (LN) is used for the electro-optic crystal will be described.

  The width of the incident light beam in the direction perpendicular to the electrode surface is 20 μm, and the width in the direction parallel to the electrode surface is 50 μm. The wavelength λ of incident light is 640 nm, and the refractive index n of lithium niobate (LN) in that case is 2.284.

  The electrode portion is composed of 14 electrodes 106 having a width w of 1 μm, and the distance between the electrodes 106 is 3 μm. The electrode is formed in a deep groove having a depth of 10 μm.

  The refractive index change amount Δn is −0.0070 when a voltage of 200 V is applied from the external power source 111 to the electrode portion. Under this condition, the critical angle θm when the incident light is totally reflected by the refractive index interface of the refractive index changing portion generated by the electric field application is 85.5 °. At this time, the incident angle of the incident light to the electro-optic crystal is 10.3 °.

  In order to reflect all the incident light having a diameter of 20 μm by the refractive index interface of the refractive index changing portion, the length of the electrode 106 needs to be 256 μm or more. The total interelectrode capacitance of the electrode part at this time is approximately 1.25 pF. On the other hand, when an electrode having the same shape and size as the electrode 106 is formed in the comparative structure having no void portion, it is approximately 1.59 pF. From this, it can be seen that according to this example, the interelectrode capacitance can be reduced to about 80% of the comparative structure.

  The mirror surface has a side of about 55 μm and is formed at the same height as the electrode toward the side from which transmitted light is emitted.

  In the optical switch of each embodiment described above, a film (for example, an insulating film) having a dielectric constant smaller than that of the electro-optic crystal may be provided between the side wall and the electrode. Such an insulating film is formed as follows, for example. First, after the steps (a) to (i) in FIG. 5 are performed, the entire surface on which the electrodes are formed is covered with an insulating film. Then, the surface covered with the insulating film is polished to expose the surface of the electrode. Thereby, a structure having an insulating film between the side wall and the electrode is obtained.

  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]
FIG. 21 is a schematic diagram showing an example of an image display device equipped with the optical switch of the present invention. The image display device 1401 includes laser light sources 1402 to 1404, collimator lenses 1405 to 1407, a reflection mirror 1408, dichroic mirrors 1409 and 1410, a horizontal scanning mirror 1411, a vertical scanning mirror 1412, and optical switches 1414 to 1416. The optical switches 1414 to 1416 are the optical switches of the present invention.

  A collimator lens 1407, an optical switch 1416, and a reflection mirror 1408 are sequentially arranged in the traveling direction of the laser light from the laser light source 1402. A parallel light beam from the collimator lens 1407 enters the optical switch 1416. The optical switch 1416 operates in accordance with a control signal supplied from a control unit (not shown). During a period when the control signal is on (voltage supply period), a voltage is applied to the electrode portion of the optical switch 1416 to form a refractive index change region, and thus incident light is reflected in the refractive index change region. This reflected light deviates from the optical path toward the reflecting mirror 1408. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 1416 and travels toward the reflection mirror 108.

  A collimator lens 1406, an optical switch 1415, and a dichroic mirror 1410 are sequentially arranged in the traveling direction of the laser light from the laser light source 1403. A parallel light beam from the collimator lens 1406 enters the optical switch 1415. In the optical switch 1415, the same operation as that of the optical switch 1416 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 1410. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 1415 and travels toward the dichroic mirror 1410.

  A collimator lens 1405, an optical switch 1414, and a dichroic mirror 1409 are sequentially arranged in the traveling direction of the laser light from the laser light source 1404. A parallel light beam from the collimator lens 1405 enters the optical switch 1414. In the optical switch 1414, the same operation as that of the optical switch 1416 is performed. During the period when the control signal is on (voltage supply period), the incident light is reflected in the refractive index change region, and the reflected light deviates from the optical path toward the dichroic mirror 1409. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 1414 and travels toward the dichroic mirror 1409.

  The dichroic mirror 1410 is provided at a position where the light beam from the optical switch 1415 and the light beam reflected by the reflection mirror 1408 intersect. The dichroic mirror 1410 has a wavelength selection characteristic that reflects light from the optical switch 1415 and transmits light from the reflection mirror 1408.

  The dichroic mirror 1409 is provided at a position where the light beam from the optical switch 1414 and the light beam from the dichroic mirror 1410 intersect. The dichroic mirror 1409 has a wavelength selection characteristic that reflects light from the optical switch 1414 and transmits light from the dichroic mirror 1410.

  The horizontal scanning mirror 1411 is arranged in the traveling direction of the light beam from the dichroic mirror 1409, and its operation is controlled by a horizontal scanning control signal from a control unit (not shown). The vertical scanning mirror 1412 is arranged in the traveling direction of the light beam from the horizontal scanning mirror 1411, and its operation is controlled by a vertical scanning control signal from a control unit (not shown).

  As the laser light sources 1402, 1403, and 1404, light sources that emit laser beams having colors corresponding to the three primary colors R, G, and B are used. A color image can be displayed on the screen 1413 by controlling on / off of the optical switches 1414, 1415, and 1416 and controlling the horizontal scanning mirror 1411 and the vertical scanning mirror 1412.

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

  FIG. 22 is a schematic diagram showing an example of an image forming apparatus equipped with the optical switch of the present invention. The image forming apparatus 1501 includes a laser light source 1502, a collimator lens 1503, a reflection mirror 1504, a scanning mirror 1505, an optical switch 1506, an fθ lens 1507, and a photoreceptor 1508. The optical switch 1506 is the optical switch of the present invention.

  A collimator lens 1503, an optical switch 1506, and a reflection mirror 1504 are sequentially arranged in the traveling direction of the laser light from the laser light source 1502. A parallel light beam from the collimator lens 1503 enters the optical switch 1506. The optical switch 1506 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 1506 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 1505. During a period when the control signal is off (voltage supply stop period), incident light passes through the optical switch 1506 and travels toward the reflection mirror 1505.

  The scanning mirror 1505 is arranged in the traveling direction of the light beam from the reflection mirror 1505, and its operation is controlled by a scanning control signal from a control unit (not shown). Light from the scanning mirror 1505 is applied to the photoreceptor 1508 via the fθ lens 1507.

  By controlling on / off of the optical switch 1506 and controlling the scanning mirror 1505, an image can be formed on the photoreceptor 1508.

  Further, it is also possible to use as a device for projecting a scanned image as it is on the photoreceptor 1508 without using the fθ lens 1507 inserted immediately before the photoreceptor 1508.

  The optical switch of the first to third embodiments described above and the system using the optical switch are examples of the present invention, and the configuration and the manufacturing procedure of the optical switch are appropriately set within the scope of the invention. Can be changed.

  According to one aspect of the present invention, an electro-optic crystal and an electrode portion composed of a plurality of electrodes arranged on the same plane, and a part of the electro-optic crystal is refracted by an electric field generated by the electrode portion. An optical switch that switches between transmission and reflection of incident light incident on the electro-optic crystal by changing a rate, wherein the electro-optic crystal is disposed between the electrodes constituting the electrode portion from the plane. A region having a side wall whose height is higher than that of the electrode and at least an electric field from the electrode portion of the electro-optic crystal is formed from an optically homogeneous material.

  In the above-described optical switch, the electrode section may be composed of a plurality of linear electrodes having a main cross section with the largest area arranged in the same plane, and the side wall may be formed between the linear electrodes.

  The plurality of linear electrodes may have the same film thickness and be arranged in parallel and at equal intervals.

  Further, the electro-optic crystal may have a plurality of grooves partitioned by the side wall, and electrodes constituting the electrode part may be formed in each groove.

Further, the critical angle, which is a condition for total reflection, at the refractive index interface between the region where the refractive index is changed by the electric field from the electrode portion in the electro-optic crystal and the region around the region is θm, When the beam diameter in the plane including the perpendicular direction of the plane of the incident light and the traveling direction of the beam is r, and the diameter of the electrode of the incident light in the horizontal direction is w, the length L of the electrodes constituting the electrode portion And the width W of the electrode part is L ≧ r / cos θm
W ≧ w
May be given in

  Furthermore, the electro-optic crystal has a void portion partitioned by the side wall, and an electrode constituting the electrode portion is formed for each void portion, and a part of the electrode is exposed in the void portion. May be.

  Further, the inside of the gap may be in a reduced pressure state or filled with air.

  Furthermore, the electrode constituting the electrode part may be in contact with a substance having a dielectric constant smaller than that of the electro-optic crystal.

  Furthermore, the thermal conductivity of the substance may be higher than that of the electro-optic crystal.

  Furthermore, a plurality of the electrode portions may be arranged on an optical path through which the incident light passes in the electro-optic crystal.

  Further, an incident surface is formed at one end of the electro-optic crystal, an exit surface is formed at the other end opposite to the one end, and the entrance surface and the exit surface are orthogonal to the plane. The length in the perpendicular direction of the plane of the region where the incident light on the incident surface is incident and the region where the light transmitted through the electrode portion of the emission surface is emitted are respectively perpendicular to the perpendicular direction of the incident light. It may be longer than

  Further, an incident surface is formed at one end of the electro-optic crystal, and an exit surface is formed at the other end opposite to the one end. The entrance surface and the exit surface are orthogonal to the plane. The length of the incident surface of the incident surface on which the incident light is incident is longer than half of the length of the incident light in the perpendicular direction to the plane, and the other end is the plane. A mirror surface may be formed in parallel with.

Further, the length from the end on the exit surface side of the incident light of the electro-optic crystal to the end on the exit surface side of the electrode portion is l, and the mirror surface is formed from the surface on which the electrode portion is formed. When the height to the surface is H and the critical angle at the refractive index interface is θm,
H ≧ l / tan θm
You may comprise so that these conditions may be satisfy | filled.

  In the method for manufacturing an optical switch which is one embodiment of the present invention, a plurality of grooves, a plurality of electrodes, and a mirror surface constituting the optical switch may be formed on the substrate in the same process.

It is a schematic diagram which shows the structure of the optical switch which is the 1st Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch shown to FIG. 1A from the output surface side. It is a schematic diagram for demonstrating the refractive index change in the optical switch shown to FIG. 1A. It is a figure for demonstrating the change of the refractive index with respect to the applied voltage, and optical power in the optical switch shown to FIG. 1A. It is a characteristic view which shows the relationship between the electrode space | interval and the electric field strength which generate | occur | produces between electrodes in the optical switch shown to FIG. 1A. It is a schematic diagram which shows the modification of the optical switch of the 1st Embodiment of this invention. It is a figure for demonstrating the electrode formation method of the optical switch of the 1st Embodiment of this invention, Comprising: (a)-(j) is sectional process drawing. It is a figure for demonstrating another electrode formation method of the optical switch of the 1st Embodiment of this invention, Comprising: (a) And (b) is sectional process drawing. It is a figure for demonstrating another electrode formation method of the optical switch of the 1st Embodiment of this invention, Comprising: (a)-(c) is sectional process drawing. It is a figure for demonstrating the other electrode formation method of the optical switch of the 1st Embodiment of this invention. It is a schematic diagram which shows the multi-electrode structure which is a modification of the optical switch of the 1st Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch shown to FIG. 9A from the output surface side. It is a schematic diagram for demonstrating the refractive index change in the optical switch shown to FIG. 9A. It is a schematic diagram which shows another multi-electrode structure which is a modification of the optical switch of the 1st Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch shown to FIG. 10A from the side surface. It is a figure for demonstrating the method to manufacture the multi-electrode structure which is a modification of the optical switch of the 1st Embodiment of this invention. It is a figure for demonstrating the method to manufacture the other multi-electrode structure which is a modification of the optical switch of the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the optical switch which is the 2nd Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch shown to FIG. 12A from the output surface side. It is a schematic diagram for demonstrating the refractive index change in the optical switch shown to FIG. 12A. It is a schematic diagram for demonstrating operation | movement of the optical switch shown to FIG. 12A. It is a schematic diagram for demonstrating operation | movement of the optical switch shown to FIG. 12A. It is a schematic diagram which shows the comparative example of the optical switch shown to FIG. 12A. It is a schematic diagram which shows the modification of the optical switch which is the 2nd Embodiment of this invention. It is a schematic diagram which shows the multi-electrode structure which is a modification of the optical switch of the 2nd Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch of the multi-electrode structure shown to FIG. 16A from the output surface side. It is a schematic diagram which shows the other multi-electrode structure which is a modification of the optical switch of the 2nd Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch of the multi-electrode structure shown to FIG. 17A from the output surface side. It is a figure for demonstrating the electrode formation method of the optical switch of the 2nd Embodiment of this invention, Comprising: (a)-(h) is sectional process drawing. It is a schematic diagram which shows the structure of the optical switch which is the 3rd Embodiment of this invention. It is sectional drawing at the time of seeing the optical switch shown to FIG. 19A from the output surface side. It is a schematic diagram for demonstrating the refractive index change in the optical switch shown to FIG. 19A. It is a schematic diagram for demonstrating operation | movement of the optical switch shown to FIG. 19A. It is a schematic diagram for demonstrating operation | movement of the optical switch shown to FIG. 19A. It is a schematic diagram which shows an example of the image display apparatus equipped with the optical switch of this invention. It is a schematic diagram showing an example of an image forming apparatus equipped with the optical switch of the present invention. 10 is a schematic diagram illustrating a configuration of an optical switch described in Patent Document 1. FIG. 10 is a schematic diagram illustrating a configuration of an optical switch described in Patent Document 2. FIG.

Explanation of symbols

101 Incident light 102 Transmitted light 103 Reflected light 104, 105 Electro-optic crystal 106 Electrode 107 Electrode part 108 Gap part 109 Light transmissive part 110 Side wall 111 External power supply

Claims (16)

An electro-optic crystal, and an electrode portion comprising a plurality of electrodes arranged on the same plane, and changing the refractive index of a part of the electro-optic crystal by an electric field generated by the electrode portion, An optical switch that switches between transmission and reflection of incident light incident on an optical crystal,
The electro-optic crystal has a side wall whose height from the plane is higher than that of the electrode between the electrodes constituting the electrode portion, and the electro-optic crystal is a region where at least an electric field from the electrode portion extends. Is formed from an optically homogeneous material ,
The plurality of electrodes includes first and second electrodes having different polarities, and the first and second electrodes are alternately arranged . The electro-optic crystal has a void portion partitioned by the side wall, and an electrode constituting the electrode portion is formed for each void portion, and a part of the electrode is exposed in the void portion. The optical switch according to claim 1 . The optical switch according to claim 2 , wherein the gap is in a state of being decompressed or filled with air. 4. The electrode part according to claim 1, wherein the electrode section includes a plurality of linear electrodes having a main cross section having a maximum area arranged in the same plane, and the side wall is formed between the linear electrodes . The optical switch according to item 1 . The optical switch according to claim 4 , wherein the plurality of linear electrodes have the same film thickness and are arranged in parallel and at equal intervals. The electro-optical crystal has a plurality of grooves which are partitioned by the side walls, the light according to any one of the electrodes constituting the electrode portion in each groove are formed respectively, claims 1 to 5, switch. In the electro-optic crystal, a critical angle which is a condition for total reflection at a refractive index interface between a region where the refractive index is changed by an electric field from the electrode portion and a region around the region is θm , and the incident light Traveling in the longitudinal direction of the electrode constituting the electrode portion and entering the refractive index interface at an angle less than the critical angle , the perpendicular direction of the plane of the incident light and the traveling direction of the incident light the diameter in a plane containing r, wherein when a w a diameter in a direction parallel to the plane containing the electrodes of the incident light, prior Symbol conductive length L and width W of the electrode portion of the electrode L ≧ r / cosθm
W ≧ w
Given in optical switch according to any one of claims 1 to 6. The optical switch according to any one of claims 1 to 7 , wherein an electrode constituting the electrode portion is in contact with a substance having a dielectric constant smaller than that of the electro-optic crystal.   The optical switch according to claim 8, wherein the thermal conductivity of the substance is higher than that of the electro-optic crystal.   10. The optical switch according to claim 1, wherein a plurality of the electrode portions are arranged on an optical path through which the incident light passes in the electro-optic crystal.   An entrance surface is formed at one end of the electro-optic crystal, an exit surface is formed at the other end facing the one end, and the entrance surface and the exit surface are each orthogonal to the plane, The length of the plane in the perpendicular direction of the plane of the region where the incident light is incident on the incident surface and the region where the light transmitted through the electrode portion of the output surface is emitted are the lengths in the perpendicular direction of the incident light, respectively. The optical switch according to any one of claims 1 to 10, wherein the optical switch is equal to or greater than one. An entrance surface is formed at one end of the electro-optic crystal, an exit surface is formed at the other end facing the one end, and the entrance surface and the exit surface are each orthogonal to the plane, The length in the direction perpendicular to the plane of the region where the light transmitted through the electrode portion of the emission surface is emitted is at least half the length in the direction perpendicular to the incident light, and the other end is The optical switch according to claim 1, wherein a mirror surface is formed in parallel to the plane. The length from the end on the exit surface side of the incident light of the electro-optic crystal to the end on the exit surface side of the electrode portion is l, and the surface on which the mirror surface is formed from the surface on which the electrode portion is formed When the height up to H is H and the critical angle at the refractive index interface is θm,
H ≧ l / tan θm
The optical switch according to claim 12, which satisfies the following condition. It is a manufacturing method of the optical switch according to claim 12 or 13,
A method of manufacturing an optical switch, wherein the plurality of grooves, the plurality of electrodes, and the mirror surface constituting the optical switch are formed on a substrate in the same process. A light source;
The optical switch according to any one of claims 1 to 13, which modulates light from the light source;
Scanning means for scanning on an external screen with a modulated light beam from the optical switch;
An image display apparatus comprising: a control unit that controls a modulation operation in the optical switch according to a control signal from the outside. A light source;
A photoreceptor,
The optical switch according to any one of claims 1 to 13, which modulates light from the light source;
Scanning means for scanning the photoreceptor with a modulated light beam from the optical switch;
An image forming apparatus comprising: a control unit that controls a modulation operation in the optical switch according to a control signal from the outside.

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