Spatial phase modulation element, spatial phase modulator, and light modulator

Abstract

In a spatial phase modulation element (50) in which the phase of light passing through an optical member (110) can be changed by generating a potential difference between a second electrode (130) and a first electrode (120) to change the refractive index of the optical member (110), a plurality of second electrodes (130) are arranged side by side in an arrangement direction perpendicular to the extension direction of a second side surface (114), and a potential difference can be individually generated between the plurality of second electrodes (130) and the first electrode (120).

Description

Spatial phase modulation element, spatial phase modulator, and optical modulator

[0001] The present invention relates to a spatial phase modulating element, a spatial phase modulator, and an optical modulator.

[0002] Known spatial phase modulation elements include those using piston-type micromirrors (see, for example, Patent Document 1), those using ferroelectric liquid crystals, etc. Such spatial phase modulation elements are required to change the phase of light at high speed with high precision.

[0003] U.S. Patent No. 6,965,119

[0004] The spatial phase modulation element of the present invention comprises an optical element formed using a translucent ferroelectric material, a first electrode provided on a first side surface extending in a predetermined direction connecting the light incident surface and light exit surface of the optical element, and a second electrode provided on a second side surface of the optical element opposite the first side surface, and is capable of changing the phase of light passing through the optical element by generating a potential difference between the second electrode and the first electrode to change the refractive index of the optical element, and the second electrodes are arranged in a row in an arrangement direction perpendicular to the predetermined direction, and it is possible to generate a potential difference individually between the plurality of second electrodes and the first electrode.

[0005] The spatial phase modulator according to the present invention includes a plurality of the spatial phase modulation elements described above, and the plurality of spatial phase modulation elements are arranged side by side along a direction from the first side surface to the second side surface.

[0006] 1 is a plan view of a spatial phase modulator. FIG. 2 is a side view of a spatial phase modulator. FIG. 3 is an exploded perspective view of a spatial phase modulator. FIG. 4 is a plan view of a spatial phase modulator according to a first embodiment. FIG. 5 is a cross-sectional view of the spatial phase modulator according to the first embodiment. FIG. 6 is a graph showing a comparison of the phase distribution of incident light, the phase distribution of emitted light, and the refractive index distribution of an optical element in the spatial phase modulator according to the first embodiment. FIG. 7 is a graph showing a comparison of the light intensity distribution of emitted light, and the phase distribution of emitted light in the spatial phase modulator according to the first embodiment. FIG. 8 is a plan view of a spatial phase modulator according to a second embodiment. FIG. 9 is a cross-sectional view of a spatial phase modulator according to the second embodiment. FIG. 10 is a graph showing a comparison of the phase distribution of incident light, the phase distribution of emitted light, and the refractive index distribution of an optical element in the spatial phase modulator according to the second embodiment. FIG. 11 is a plan view of a spatial phase modulator according to a third embodiment. FIG. 12 is a cross-sectional view of a spatial phase modulator according to the third embodiment. FIG. 13 is a graph showing a comparison of the phase distribution of incident light, the phase distribution of emitted light, and the refractive index distribution of an optical element in the spatial phase modulator according to the third embodiment. FIG. 14 is a plan view of a spatial phase modulator according to a fourth embodiment. FIG. 15 is a cross-sectional view of a spatial phase modulator according to the fourth embodiment. 10 is a graph showing a comparison between the phase distribution of incident light, the phase distribution of emitted light, and the refractive index distribution of an optical element in a spatial phase modulation element according to a fourth embodiment. FIG. 11 is a graph showing a comparison between the light intensity distribution of emitted light and the phase distribution of emitted light in a spatial phase modulation element according to a fourth embodiment. FIG. 12 is a plan view of a spatial phase modulation element according to a fifth embodiment. FIG. 13 is a cross-sectional view of a spatial phase modulation element according to a fifth embodiment. FIG. 14 is a graph showing a comparison between the phase distribution of incident light, the phase distribution of emitted light, and the refractive index distribution of an optical element in a spatial phase modulation element according to a fifth embodiment. FIG. 15 is a graph showing a comparison between the light intensity distribution of emitted light and the phase distribution of emitted light in a spatial phase modulation element according to a fifth embodiment.

[0007] Preferred embodiments will be described below. First, a spatial phase modulator equipped with a spatial phase modulation element according to each embodiment will be described with reference to Figures 1 and 2. In describing the spatial phase modulator, the directions indicated by the arrows in Figures 1 and 2 may be referred to as the X direction, Y direction, and Z direction, respectively. The X direction, Y direction, and Z direction are directions that are orthogonal to one another.

[0008] 1 and 2, the spatial phase modulator 1 includes a first cylindrical lens array 10, a plurality of spatial phase modulation elements 50, and a second cylindrical lens array 20. As shown in FIG. 2, the first cylindrical lens array 10 has a plurality of first cylindrical lenses 11 extending in the X direction. The first cylindrical lenses 11 are aligned in the Z direction and positioned in alignment with the plurality of spatial phase modulation elements 50. Eight first cylindrical lenses 11 may be aligned in the Z direction. The plurality of first cylindrical lenses 11 divide and focus light that travels in the +Y direction and enters the first cylindrical lens array 10 in the Z direction.

[0009] A plurality of incident light beams LA that have passed through a plurality of first cylindrical lenses 11 are incident on the plurality of spatial phase modulators 50. Hereinafter, the light beams that enter the plurality of spatial phase modulators 50 via the first cylindrical lens array 10 will be referred to as incident light beams LA. The cross-sectional shape of the incident light beams LA that enter the spatial phase modulator 50 is an ellipse whose width in the Z direction is smaller than its width in the X direction (see, for example, FIG. 5 ). Note that the incident light beams LA that enter the spatial phase modulator 50 and have an elliptical cross-sectional shape may also be referred to as slit-shaped incident light beams LA. The spatial phase modulators 50 are arranged side by side in the Z direction while held by the holding member 55, aligned with the plurality of first cylindrical lenses 11. When eight first cylindrical lenses 11 are arranged side by side in the Z direction, eight spatial phase modulators 50 may also be arranged side by side in the Z direction.

[0010] The spatial phase modulation element 50 may be disposed at the rear focal position of the first cylindrical lens 11. The spatial phase modulation element 50 modulates the phase of light (incident light LA) incident on the spatial phase modulation element 50 in accordance with voltages applied to the electrodes of the spatial phase modulation element 50, and emits the modulated light toward the second cylindrical lens array 20. Details of the spatial phase modulation element 50 will be described later. Hereinafter, the light emitted from the spatial phase modulation element 50 will be referred to as emitted light LB.

[0011] The second cylindrical lens array 20 has a plurality of second cylindrical lenses 21 extending in the X direction. The second cylindrical lenses 21 are aligned in the Z direction and aligned with the plurality of spatial phase modulators 50. When eight first cylindrical lenses 11 (and eight spatial phase modulators 50) are aligned in the Z direction, eight second cylindrical lenses 21 may also be aligned in the Z direction. A plurality of output light beams LB emitted from the plurality of spatial phase modulators 50 are incident on the plurality of second cylindrical lenses 21. The plurality of second cylindrical lenses 21 collimate the plurality of output light beams LB emitted from the plurality of spatial phase modulators 50.

[0012] The spatial phase modulator 1 configured as described above is used, for example, in a microscope (not shown) or an optical processing device (not shown). The spatial phase modulator 1 used in a microscope, for example, modulates the phase of light (incident light LA) from a sample received through an objective lens, thereby correcting a phase shift of the light from the sample. The spatial phase modulator 1 used in an optical processing device, for example, modulates the phase of light (incident light LA) from a light source irradiated onto a workpiece, thereby correcting a phase shift of the light from the light source.

[0013] In the spatial phase modulator 1, light transmitted through the first cylindrical lens array 10 is split into multiple incident light beams LA by multiple first cylindrical lenses 11 and then enters multiple spatial phase modulation elements 50. The spatial phase modulation element 50 modulates the phase of the light incident on the spatial phase modulation element 50 (incident light beam LA) in accordance with a voltage applied to each electrode of the spatial phase modulation element 50, and emits the modulated light toward the second cylindrical lens array 20. The multiple emitted light beams LB emitted from the multiple spatial phase modulation elements 50 are transmitted through multiple second cylindrical lenses 21 in the second cylindrical lens array 20 and become parallel light beams. According to this spatial phase modulator 1, the multiple spatial phase modulation elements 50 are arranged side by side in the Z direction (the direction from the first side surface to the second side surface of the optical member described below), thereby allowing the phase of the light to be modulated in two dimensions (X and Z directions). Furthermore, by including the spatial phase modulator 1 with the spatial phase modulation element 50 described below, the phase of the light (incident light LA) incident on the spatial phase modulator 1 can be changed quickly and with high precision.

[0014] [First Embodiment] Next, a spatial phase modulation element 50 according to the first embodiment will be described. As shown in Fig. 3, the spatial phase modulation element 50 according to the first embodiment includes a wiring substrate 60, a holding substrate 70, and a modulation element body 101. In the first embodiment, the directions indicated by the arrows in Fig. 3 may be referred to as the X direction, the Y direction, and the Z direction, respectively. The X direction, the Y direction, and the Z direction are directions that are orthogonal to one another.

[0015] The wiring substrate 60 is formed in a plate shape extending in the X and Y directions to match the outer peripheral shapes of the modulation element body 101 and the holding substrate 70. The modulation element body 101 and the holding substrate 70 are arranged on the wiring substrate 60, stacked in this order. A plurality of first probes 61, a plurality of second probes 62, and a connector portion 65 are provided on the surface of the wiring substrate 60 facing the modulation element body 101. The first probes 61 are arranged to sandwich the second probes 62. The first probes 61 are joined to and electrically connected to a joining surface 71 formed on the holding substrate 70. The first probes 61 are grounded via a cable (not shown) connected to the connector portion 65. The surface of the wiring substrate 60 and the underside of the modulation element body 101 are aligned and face each other. Most of the components of each of the plurality of first probes 61 may be embedded in the wiring substrate 60. Furthermore, the entire components of each of the plurality of second probes 62 may be embedded in the wiring substrate 60.

[0016] The second probes 62 are disposed opposite the modulation element body 101. The second probes 62 are joined to and electrically connected with the plurality of second electrodes 130 (see FIGS. 4 and 5 ) of the modulation element body 101. The second probes 62 are electrically connected to a drive circuit (not shown) via a cable (not shown) connected to the connector portion 65. The voltages applied to the plurality of second electrodes 130 of the modulation element body 101 are individually controlled by the voltage supplied from the drive circuit via the wiring board 60 (second probes 62).

[0017] The connector portion 65 is disposed on the end side of the wiring substrate 60 that does not face the modulation element body 101 and the holding substrate 70. The connector portion 65 is electrically connected to the first probe 61 and the second probe 62. The connector portion 65 is mated with and connected to the connector of a cable (not shown) that is electrically connected to the control substrate described above.

[0018] The holding substrate 70 is formed in a plate shape extending in the X and Y directions to match the outer periphery of the modulation element body 101. A bonding surface 71, on which a conductive metal film is vapor-deposited, is formed on the surface of the holding substrate 70 facing the modulation element body 101. The bonding surface 71 of the holding substrate 70 is bonded to the first electrode 120 of the modulation element body 101 (see also FIG. 5 ) via the metal film. The holding substrate 70 is also formed to be wider than the modulation element body 101 and overlap in the ±X directions. The portion of the bonding surface 71 of the holding substrate 70 that overlaps the modulation element body 101 is bonded to the first probe 61 of the wiring substrate 60 via the metal film. As a result, the first electrode 120 of the modulation element body 101 is grounded via the first probe 61 of the wiring substrate 60.

[0019] 4 and 5, the modulation element body 101 includes an optical member 110, a first electrode 120, and a plurality of second electrodes 130. The modulation element body 101 modulates the phase of slit-shaped incident light LA ​​whose cross section is shaped into a flattened ellipse, and emits the modulated light.

[0020] The optical element 110 is formed in a flat rectangular parallelepiped shape using a light-transmitting ferroelectric material. A ferroelectric is a type of dielectric, an optical crystal in which electric dipoles are aligned even in the absence of an external electric field, and the dipole direction can be changed by an electric field. Examples of light-transmitting ferroelectric materials include lithium niobate (lithium niobate), lithium tantalate (lithium tantalate), MgO:LN (MgO-doped lithium niobate), and MgO:SLT (MgO-doped stoichiometric lithium tantalate). An incident surface 111 is formed at one end (in the -Y direction) of the optical element 110. A slit-shaped (elliptical cross-sectional shape) incident light LA ​​traveling in the +Y direction is incident on the incident surface 111 as incident light. An exit surface 112 is formed at the end (in the +Y direction) of the optical element 110 opposite the incident surface 111. Light that enters the optical member 110 through the incident surface 111 exits from the exit surface 112 .

[0021] A first electrode 120 is provided on a first side surface 113 of the optical element 110, which extends from the incident surface 111 toward the exit surface 112. The first electrode 120 is formed using a metal material containing, for example, gold (Au). The first electrode 120 is formed to extend over the entire first side surface 113. A first insulating layer 115 is formed between the first side surface 113 and the first electrode 120. The first insulating layer 115 is formed using, for example, silicon dioxide (SiO2). The thickness of the first insulating layer 115 is set to be thicker than the amount of seepage of evanescent waves generated when light is totally reflected at the first side surface 113. This makes it possible to prevent the first electrode 120 from absorbing a portion of the light passing through the optical element 110.

[0022] A second electrode 130 is provided on a second side surface 114 of the optical element 110 opposite the first side surface 113 (the +Z direction side). The second electrode 130 is formed using, for example, a metal material containing gold (Au). A plurality of second electrodes 130 are arranged side by side in an arrangement direction (X direction) perpendicular to the extension direction of the second side surface 114. The extension direction of the first side surface 113 connecting the incident surface 111 and the exit surface 112 may be referred to as a predetermined direction. A plurality of second electrodes 130 may be arranged side by side in the arrangement direction (X direction) perpendicular to the predetermined direction. The plurality of second electrodes 130 are formed extending parallel to the Y direction from one end side to the other end side of the second side surface 114. A second insulating layer 116 is formed between the second side surface 114 and the plurality of second electrodes 130. The second insulating layer 116 is formed using, for example, silicon dioxide (SiO2). The thickness of the second insulating layer 116 is set to be thicker than the amount of seepage of evanescent waves that occurs when light is totally reflected at the second side surface 114. This makes it possible to prevent a portion of the light that passes through the inside of the optical member 110 from being absorbed by the second electrode 130.

[0023] The second electrodes 130 are electrically connected to the second probes 62 of the wiring substrate 60, which are grouped to correspond to each second electrode 130. As described above, the second probes 62 are electrically connected to a drive circuit (not shown). The second probes 62, which are grouped to correspond to each second electrode 130, individually apply a voltage supplied from the drive circuit to the second electrodes 130. By applying a voltage to the second electrodes 130 via the second probes 62, a potential difference can be created between the second electrodes 130 and the first electrode 120, which are arranged on either side of the optical member 110.

[0024] In the modulation element body 101 of the spatial phase modulation element 50 configured as described above, slit-shaped (elliptical in cross section) incident light LA ​​is incident on the incident surface 111 of the optical element 110, as shown in Figures 4 and 5. When a positive voltage is applied to the second electrode 130, a potential difference is generated between the second electrode 130 and the first electrode 120, which are arranged on either side of the optical element 110, and an electric field is generated inside the optical element 110, directed from the second electrode 130 to the first electrode 120.

[0025] As described above, the optical element 110 is formed using a light-transmitting ferroelectric material. In Figure 5, the polarization direction (orientation of the crystal axis) in the optical element 110 is schematically indicated by a thick arrow. The polarization direction in the optical element 110 is oriented in the direction from the first side surface 113 to the second side surface 114 (the +Z direction). As a result, as the electric field flows from the second electrode 130 to the first electrode 120, the refractive index inside the optical element 110 changes in a direction that increases due to the electro-optic effect.

[0026] By generating an electric field inside the optical element 110 and changing the refractive index inside the optical element 110, the phase of light (incident light LA) passing through the optical element 110 can be changed. The modulator body 101 of the spatial phase modulator 50 modulates the phase of light (incident light LA) incident on the incident surface 111 of the optical element 110 by the potential difference between the second electrode 130 and the first electrode 120, and emits emitted light LB from the exit surface 112. In the first embodiment, the potential difference between the multiple second electrodes 130 and the first electrode 120 can be individually changed. Since the potential difference between the multiple second electrodes 130 and the first electrode 120 occurs in the thickness direction of the optical element 110, the voltage (driving voltage) applied to the second electrode 130 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 110 can be changed quickly and with high precision without placing a burden on a driving circuit (not shown).

[0027] Furthermore, by providing gaps between the multiple second electrodes 130, the electric field from the second electrodes 130 is less likely to reach the portions of the optical element 110 located in the gaps between the multiple second electrodes 130, resulting in less change in the refractive index. As a result, the refractive index of the portions of the optical element 110 located in the gaps between the multiple second electrodes 130 is relatively lower than the refractive index of the portions of the optical element 110 where the second electrodes 130 are disposed. Therefore, light incident on the portions of the optical element 110 located in the gaps between the multiple second electrodes 130 can be made to enter the portions of the optical element 110 where the second electrodes 130 are disposed. Therefore, it is possible to utilize 100% of the incident light LA, thereby increasing the utilization efficiency of the incident light LA.

[0028] By changing the refractive index inside the optical element 110 using the electro-optic effect, it is possible to rapidly change the phase of light (incident light LA) passing through the optical element 110. Specifically, it is possible to change the refractive index inside the optical element 110 with a low voltage of several volts to several tens of volts. For example, if a voltage of approximately 10 V is applied to the second electrode 130, the frequency at which the refractive index inside the optical element 110 is changed can be approximately several tens of megahertz. Furthermore, if a voltage of approximately 35 V is applied to the second electrode 130, the frequency at which the refractive index inside the optical element 110 is changed can be approximately several megahertz.

[0029] The phase difference φe generated by the application of a voltage can be calculated as follows: The electro-optic crystal (ferroelectric material) constituting the optical element 110 has a crystal axis oriented so that a voltage can be applied in the Z direction. The distance between the electrodes is g, the length (in the Y direction) of the crystal (interaction distance with light) is L, and the wavelength of the light is λ. The phase difference φe generated by the application of a voltage is expressed by the following equation (1):

[0030]

[0031] In formula (1), Δn ｅ is the change in refractive index caused by the application of a voltage. The voltage applied to the electrodes is V ｅ The electro-optic coefficient (Pockels constant) of the electro-optic crystal is r ３３ The refractive index of the electro-optic crystal is n ｅ The change in refractive index caused by the application of voltage is Δn ｅ is expressed by the following equation (2).

[0032]

[0033] For example, in lithium niobate (LiNbO3) crystal, which is a typical electro-optic crystal, r ３３ = 30.8 pm / V (where λ = 633 nm). ｅ = 2.19, r ３３ = 30.8 pm / V, V ｅ = -35V, g = 200 μm, L = 20 mm. The voltage V applied to the electrodesｅ When a voltage is applied to the electro-optic crystal in the opposite direction (-Z direction), the sign is set to minus (-). ｅ = 1.21E-05, and φe ≒ 138°.

[0034] The graph shown in Fig. 5 shows the distribution of the refractive index of the optical element 110. The horizontal axis of the graph shown in Fig. 5 indicates the position in the X direction in the optical element 110. The vertical axis of the graph shown in Fig. 5 indicates the refractive index n(X) of the optical element 110 with respect to the position in the X direction. n ｅ indicates the refractive index of the optical element 110 (electro-optic crystal) when no voltage is applied to the electrodes. The region of the optical element 110 where the second electrode 130 is disposed on the −X direction side is referred to as the first region 119A of the optical element 110. The region of the optical element 110 where the second electrode 130 is disposed on the central side is referred to as the second region 119B of the optical element 110. The region of the optical element 110 where the second electrode 130 is disposed on the +X direction side is referred to as the third region 119C of the optical element 110.

[0035] FIG. 6 is a graph showing a comparison of the phase distribution of incident light LA, the phase distribution of emitted light LB, and the refractive index distribution of the optical element 110. The horizontal axis of the graph showing the phase distribution of incident light LA ​​indicates the X-direction position of the incident light LA. The vertical axis of the graph showing the phase distribution of incident light LA ​​indicates the phase φA(X) of the incident light LA ​​with respect to the X-direction position. For ease of explanation, it is assumed that the wavefront of the incident light LA ​​is planar and the phase distribution of the incident light LA ​​is constant. The horizontal axis of the graph showing the phase distribution of emitted light LB indicates the X-direction position of the emitted light LB. The vertical axis of the graph showing the phase distribution of emitted light LB indicates the phase φB(X) of the emitted light LB with respect to the X-direction position. The graph showing the refractive index distribution of the optical element 110 is the same as the graph shown in FIG. 5.

[0036] As described above, it is possible to individually change the potential difference between the plurality of second electrodes 130 and the first electrode 120. As can be seen from the graphs of FIGS. 5 and 6 showing the refractive index distribution of the optical element 110, the refractive index of the first region 119A, the refractive index of the second region 119B, and the refractive index of the third region 119C in the optical element 110 individually change depending on the potential difference between the plurality of second electrodes 130 and the first electrode 120. For example, in the first region 119A, as the electric field flows from the second electrode 130 to the first electrode 120, the refractive index of the first region 119A increases due to the electro-optic effect. In the second region 119B, as the electric field flows from the second electrode 130 to the first electrode 120, the refractive index of the second region 119B increases due to the electro-optic effect. In the third region 119C, as the electric field moves from the second electrode 130 to the first electrode 120, the refractive index of the third region 119C changes in an increasing direction due to the electro-optic effect.

[0037] Furthermore, in the portions of the optical element 110 located in the gaps between the second electrodes 130, the electric field from the second electrodes 130 is less likely to reach the portions, and the change in the refractive index is reduced. In other words, the refractive index n ｅ As a result, the refractive index of the portions of the optical member 110 located in the gaps between the plurality of second electrodes 130 becomes relatively lower than the refractive index of the portions of the optical member 110 where the second electrodes 130 are arranged.

[0038] 6 , the phase of light LA1 incident on the first region 119A changes depending on the refractive index of the first region 119A. The phase of light LA2 incident on the second region 119B changes depending on the refractive index of the second region 119B. The phase of light LA3 incident on the third region 119C changes depending on the refractive index of the third region 119C. This allows the phase of light incident on the optical element 110 (incident light LA) to be changed quickly and with high precision.

[0039] Furthermore, for example, light LA6 incident on the gap portion adjacent to the first region 119A on the −X direction side can be made to enter the first region 119A (or the region opposite the first region 119A). Light LA7 incident on the gap portion between the first region 119A and the second region 119B can be made to enter the first region 119A or the second region 119B. Light LA8 incident on the gap portion between the second region 119B and the third region 119C can be made to enter the second region 119B or the third region 119C. Light LA9 incident on the gap portion adjacent to the third region 119C on the +X direction side can be made to enter the third region 119C (or the region opposite the third region 119C). This can increase the utilization efficiency of the incident light LA.

[0040] FIG. 7 is a graph comparing the light intensity distribution of the emitted light LB with the phase distribution of the emitted light LB. The graph in FIG. 7 shows a specific example in which the optical element 110 is formed using lithium niobate (LiNbO3). The horizontal axis of the graph showing the light intensity distribution of the emitted light LB indicates the X-direction position of the emitted light LB. The vertical axis of the graph showing the light intensity distribution of the emitted light LB indicates the light intensity I(X) (arbitrary units) of the emitted light LB relative to the X-direction position. The horizontal axis of the graph showing the phase distribution of the emitted light LB indicates the X-direction position of the emitted light LB (units are mm). The vertical axis of the graph showing the phase distribution of the emitted light LB indicates the phase φB(X) (units are degrees (°)) of the emitted light LB relative to the X-direction position.

[0041] The thickness (crystal thickness) of the optical element 110 is 0.2 mm. The length (interaction distance) of the optical element 110 in the Y direction is 20 mm. The pitch between the multiple second electrodes 130 is 1 mm. The width of the second electrodes 130 is 0.9 mm. The direction of voltage application is the Z direction. The voltage applied to the second electrodes 130 in the first region 119A is 9 V, the voltage applied to the second electrodes 130 in the second region 119B is 15 V, and the voltage applied to the second electrodes 130 in the third region 119C is 4.5 V. The wavelength of the incident light is 633 nm. The incident light is incident to a thickness of 100 μm (1 / e 2 ) Gaussian slit beam.

[0042] 7 indicates the center position in the X direction of the gaps between the multiple second electrodes 130. From FIG. 7, it can be seen that there is little fluctuation in light intensity among the first to third regions 119A to 119C, and that the continuity of the phase change is good.

[0043] [Characteristic Configuration of First Embodiment] The spatial phase modulation element 50 according to the first embodiment includes a first electrode 120 provided on a first side surface 113 of the optical element 110 and a plurality of second electrodes 130 provided on a second side surface 114 of the optical element 110 opposite the first side surface 113. Potential differences can be individually generated between the plurality of second electrodes 130 and the first electrode 120. Because the potential differences between the plurality of second electrodes 130 and the first electrode 120 are generated in the thickness direction of the optical element 110, the voltage (driving voltage) applied to the second electrode 130 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 110 can be changed quickly and with high precision without imposing a burden on a driving circuit (not shown).

[0044] Furthermore, gaps are provided between the plurality of second electrodes 130. As a result, as described above, the refractive index of the portions of the optical element 110 located in the gaps between the plurality of second electrodes 130 is relatively lower than the refractive index of the portions of the optical element 110 where the second electrodes 130 are disposed. Therefore, light incident on the portions of the optical element 110 located in the gaps between the plurality of second electrodes 130 can be made to enter the portions of the optical element 110 where the second electrodes 130 are disposed. Therefore, it becomes possible to utilize 100% of the incident light LA, thereby increasing the utilization efficiency of the incident light LA.

[0045] In the first embodiment described above, the optical member 110 may include a slab waveguide that is provided so that light incident from the incident surface 111 (incident light LA) passes through the optical member 110 .

[0046] In the first embodiment described above, the first electrodes 120 are formed to extend over the entire first side surface 113, but this is not limiting. For example, a plurality of first electrodes may be arranged side by side in the same arrangement direction (X direction) as the second electrodes 130 on a portion of the first side surface 113 located opposite the second electrodes 130.

[0047] Second Embodiment Next, a spatial phase modulation element according to the second embodiment will be described. The spatial phase modulation element according to the second embodiment has the same configuration as the spatial phase modulation element 50 according to the first embodiment, except for the modulation element body. Therefore, in the second embodiment, only the modulation element body of the spatial phase modulation element will be described. As shown in FIGS. 8 and 9 , the modulation element body 201 of the spatial phase modulation element 200 according to the second embodiment includes an optical element 210, a first electrode 220, a plurality of second electrodes 230, and a plurality of third electrodes 235 to which a voltage can be applied individually. The modulation element body 201 modulates the phase of slit-shaped incident light LA ​​whose cross section is shaped into a flattened ellipse, and then emits the modulated light.

[0048] 8 and 9 may be referred to as the X direction, the Y direction, and the Z direction, respectively. The X direction, the Y direction, and the Z direction are perpendicular to each other.

[0049] The optical element 210 is formed in the same manner as the optical element 110 according to the first embodiment. An incident surface 211 is formed at one end (in the −Y direction) of the optical element 210. Slit-shaped (elliptical in cross section) incident light LA ​​traveling in the +Y direction is incident on the incident surface 211 as incident light. An exit surface 212 is formed at the end (in the +Y direction) of the optical element 210 opposite the incident surface 211. The light that enters the optical element 210 from the incident surface 211 is exited from the exit surface 212.

[0050] A first electrode 220 is provided on a first side surface 213 extending from the incident surface 211 toward the exit surface 212 of the optical member 210. The first electrode 220 is formed in the same manner as the first electrode 120 according to the first embodiment. A first insulating layer 215 is formed between the first side surface 213 and the first electrode 220. The first insulating layer 215 is formed in the same manner as the first insulating layer 115 according to the first embodiment.

[0051] A second electrode 230 is provided on a second side surface 214 of the optical member 210 on the opposite side (+Z direction side) to the first side surface 213. The second electrode 230 is formed in the same manner as the second electrode 130 according to the first embodiment. A plurality of second electrodes 230 are arranged side by side in an arrangement direction (X direction) perpendicular to the extension direction of the second side surface 214. The extension direction of the first side surface 213 connecting the incident surface 211 and the exit surface 212 may be referred to as a predetermined direction. A plurality of second electrodes 230 may be arranged side by side in the arrangement direction (X direction) perpendicular to the predetermined direction.

[0052] A third electrode 235 is provided in each gap between the multiple second electrodes 230 on the second side surface 214. The third electrodes 235 are formed using a metal material containing, for example, gold (Au), and have a width narrower than that of the second electrodes 230. The third electrodes 235 are formed to extend parallel to the second electrodes 230 in the Y direction from one end side to the other end side of the second side surface 214.

[0053] A second insulating layer 216 is formed between the second side surface 214 and the plurality of second electrodes 230 and the plurality of third electrodes 235. The second insulating layer 216 is formed in the same manner as the second insulating layer 116 according to the first embodiment.

[0054] The second electrodes 230 and the third electrodes 235 are electrically connected to the second probes 62 of the wiring substrate 60, which are grouped to correspond to the second electrodes 230 and the third electrodes 235. As described above, the second probes 62 are electrically connected to a drive circuit (not shown). The second probes 62, which are grouped to correspond to the second electrodes 230 and the third electrodes 235, individually apply voltages supplied from the drive circuit to the second electrodes 230 and the third electrodes 235. By applying a voltage to the second electrodes 230 via the second probes 62, a potential difference can be created between the second electrodes 230 and the first electrodes 220, which are disposed on either side of the optical member 210. Furthermore, by applying a voltage to the third electrode 235 via the second probes 62, a potential difference can be created between the third electrodes 235 and the first electrodes 220, which are disposed on either side of the optical member 210.

[0055] In the modulation element body 201 of the spatial phase modulation element 200 configured as described above, slit-shaped (elliptical in cross section) incident light LA ​​is incident on the incident surface 211 of the optical element 210 as shown in Figures 8 and 9. When a positive voltage is applied to the second electrode 230, a potential difference is generated between the second electrode 230 and the first electrode 220, which are arranged on either side of the optical element 210, and an electric field is generated inside the optical element 210 from the second electrode 230 to the first electrode 220. On the other hand, when a negative voltage is applied to the second electrode 230, a potential difference is generated between the second electrode 230 and the first electrode 220, which are arranged on either side of the optical element 210, and an electric field is generated inside the optical element 210 from the first electrode 220 to the second electrode 230.

[0056] Furthermore, when a positive voltage is applied to the third electrode 235, a potential difference is generated between the third electrode 235 and the first electrode 220, which are disposed on either side of the optical element 210, and an electric field is generated inside the optical element 210 from the third electrode 235 to the first electrode 220. On the other hand, when a negative voltage is applied to the third electrode 235, a potential difference is generated between the third electrode 235 and the first electrode 220, which are disposed on either side of the optical element 210, and an electric field is generated inside the optical element 210 from the first electrode 220 to the third electrode 235.

[0057] As described above, the optical element 210 is formed using a light-transmitting ferroelectric material. In FIG. 9 , the polarization direction (orientation of the crystal axis) in the optical element 210 is schematically indicated by a thick arrow. The polarization direction in the optical element 210 is oriented in the direction from the first side surface 213 to the second side surface 214 (the +Z direction). As a result, as the electric field flows from the second electrode 230 to the first electrode 220, the refractive index of the portion of the optical element 210 where the second electrode 230 is disposed increases due to the electro-optic effect. On the other hand, as the electric field flows from the first electrode 220 to the second electrode 230, the refractive index of the portion of the optical element 210 where the second electrode 230 is disposed decreases due to the electro-optic effect.

[0058] Furthermore, as the electric field moves from the third electrode 235 to the first electrode 220, the refractive index of the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230 changes in an increasing direction due to the electro-optical effect. On the other hand, as the electric field moves from the first electrode 220 to the third electrode 235, the refractive index of the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230 changes in a decreasing direction due to the electro-optical effect.

[0059] By generating an electric field inside the optical element 210 and changing the refractive index inside the optical element 210, the phase of light (incident light LA) passing through the optical element 210 can be changed. The modulator body 201 of the spatial phase modulator 200 modulates the phase of light (incident light LA) incident on the incident surface 211 of the optical element 210 by the potential difference between the second electrode 230 and the first electrode 220 (and the potential difference between the third electrode 235 and the first electrode 220), and emits emitted light LB from the exit surface 212. In the second embodiment, the potential differences between the multiple second electrodes 230 and the first electrodes 220 can be individually changed. Because the potential differences between the multiple second electrodes 230 and the first electrode 220 occur in the thickness direction of the optical element 210, the voltage (driving voltage) applied to the second electrode 230 can be reduced. Therefore, the phase of the light (incident light LA) incident on the optical member 210 can be changed at high speed with high precision without placing a burden on a drive circuit (not shown).

[0060] Furthermore, a third electrode 235 is provided in the gaps between the plurality of second electrodes 230 on the second side surface 214, and the potential difference between the third electrode 235 and the first electrode 220 can be individually changed. By generating an electric field from the first electrode 220 toward the third electrode 235 and lowering the refractive index of the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230, light incident on the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230 can be made to enter the portions of the optical element 210 where the second electrodes 230 are located. This allows 100% utilization of the incident light LA, thereby increasing the utilization efficiency of the incident light LA. Furthermore, by lowering the refractive index of the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230, the refractive index of the portions of the optical element 210 where the second electrodes 230 are located can be lowered, thereby increasing the utilization efficiency of the incident light LA ​​and widening the range in which the phase of light (incident light LA) incident on the optical element 210 can be changed.

[0061] The graph shown in Fig. 9 shows the distribution of the refractive index of the optical element 210. The horizontal and vertical axes of the graph shown in Fig. 9 are the same as the horizontal and vertical axes of the graph shown in Fig. 5. Furthermore, the region of the optical element 210 on the -X direction side where the second electrode 230 is arranged is referred to as a first region 219A of the optical element 210. The region of the optical element 210 on the central side where the second electrode 230 is arranged is referred to as a second region 219B of the optical element 210. The region of the optical element 210 on the +X direction side where the second electrode 230 is arranged is referred to as a third region 219C of the optical element 210.

[0062] 10 is a graph showing a comparison of the phase distribution of incident light LA, the phase distribution of emitted light LB, and the refractive index distribution of optical element 210. The horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​are the same as the horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​in FIG. 6. For ease of explanation, it is assumed that the wavefront of incident light LA ​​is planar and the phase distribution of incident light LA ​​is constant. The horizontal and vertical axes of the graph showing the phase distribution of emitted light LB are the same as the horizontal and vertical axes of the graph showing the phase distribution of emitted light LB in FIG. 6. The graph showing the refractive index distribution of optical element 210 is the same as the graph shown in FIG.

[0063] As described above, it is possible to individually change the potential difference between the plurality of second electrodes 230 and the first electrode 220. As can be seen from the graphs of FIGS. 9 and 10 showing the refractive index distribution of the optical element 210, the refractive index of the first region 219A, the refractive index of the second region 219B, and the refractive index of the third region 219C in the optical element 210 individually change depending on the potential difference between the plurality of second electrodes 230 and the first electrode 220. For example, in the first region 219A, as the electric field flows from the second electrode 230 to the first electrode 220, the refractive index of the first region 219A increases due to the electro-optic effect. In the second region 219B, as the electric field flows from the second electrode 230 to the first electrode 220, the refractive index of the second region 219B increases due to the electro-optic effect. In the third region 219C, as the electric field moves from the first electrode 220 to the second electrode 230, the refractive index of the third region 219C changes in a decreasing direction due to the electro-optic effect.

[0064] Furthermore, it is possible to individually change the potential difference between the third electrode 235 and the first electrode 220. For example, in the gap between the first region 219A and the second region 219B, as the electric field flows from the third electrode 235 to the first electrode 220, the refractive index of the gap between the first region 219A and the second region 219B increases due to the electro-optic effect, to an extent that the refractive index does not exceed the refractive index of the first region 219A and the second region 219B. In the gap between the second region 219B and the third region 219C, as the electric field flows from the first electrode 220 to the third electrode 235, the refractive index of the gap between the second region 219B and the third region 219C decreases due to the electro-optic effect, to become lower than the refractive index of the second region 219B and the third region 219C.

[0065] 10 , the phase of light LA1 incident on the first region 219A changes depending on the refractive index of the first region 219A. The phase of light LA2 incident on the second region 219B changes depending on the refractive index of the second region 219B. The phase of light LA3 incident on the third region 219C changes depending on the refractive index of the third region 219C. This allows the phase of light incident on the optical element 210 (incident light LA) to be changed quickly and with high precision.

[0066] Furthermore, for example, light LA6 incident on the gap adjacent to the first region 219A on the −X direction side can be made to enter the first region 219A (or the region opposite the first region 219A). Light LA7 incident on the gap between the first region 219A and the second region 219B can be made to enter the first region 219A or the second region 219B. Light LA8 incident on the gap between the second region 219B and the third region 219C can be made to enter the second region 219B or the third region 219C. Light LA9 incident on the gap adjacent to the third region 219C on the +X direction side can be made to enter the third region 219C (or the region opposite the third region 219C). This can increase the utilization efficiency of the incident light LA.

[0067] [Characteristic Configuration of Second Embodiment] The spatial phase modulation element 200 according to the second embodiment includes a first electrode 220 provided on a first side surface 213 of the optical element 210 and a plurality of second electrodes 230 provided on a second side surface 214 of the optical element 210 opposite the first side surface 213. Potential differences can be individually generated between the plurality of second electrodes 230 and the first electrode 220. Because the potential differences between the plurality of second electrodes 230 and the first electrode 220 occur in the thickness direction of the optical element 210, the voltage (driving voltage) applied to the second electrode 230 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 210 can be changed quickly and with high precision without imposing a burden on a driving circuit (not shown).

[0068] Furthermore, a third electrode 235 is provided in the gaps between the plurality of second electrodes 230 on the second side surface 214, and the potential difference between the third electrode 235 and the first electrode 220 can be individually changed. This reduces the refractive index of the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230, allowing light incident on the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230 to be incident on the portions of the optical element 210 where the second electrodes 230 are located. This allows 100% utilization of the incident light LA, thereby increasing the utilization efficiency of the incident light LA. Furthermore, reducing the refractive index of the portions of the optical element 210 located in the gaps between the plurality of second electrodes 230 reduces the refractive index of the portions of the optical element 210 where the second electrodes 230 are located. This increases the utilization efficiency of the incident light LA ​​while widening the range in which the phase of the light (incident light LA) incident on the optical element 210 can be changed.

[0069] In the second embodiment described above, the optical member 210 may include a slab waveguide that is provided so that light incident from the incident surface 211 (incident light LA) passes through the optical member 210 .

[0070] In the second embodiment described above, the first electrode 220 is formed to extend over the entire first side surface 213, but this is not limiting. For example, a plurality of first electrodes may be arranged in a line in the same arrangement direction (X direction) as the second electrode 230 (or the third electrode 235) on a portion of the first side surface 213 located opposite the second electrode 230 and on a portion of the first side surface 213 located opposite the third electrode 235.

[0071] [Third Embodiment] Next, a spatial phase modulation element according to a third embodiment will be described. The spatial phase modulation element according to the third embodiment has the same configuration as the spatial phase modulation element 50 according to the first embodiment, except for the modulation element body. Therefore, in the third embodiment, only the modulation element body of the spatial phase modulation element will be described. As shown in FIGS. 11 and 12 , the modulation element body 301 of the spatial phase modulation element 300 according to the third embodiment includes an optical member 310, a first electrode 320, and a plurality of second electrodes 330. The modulation element body 301 modulates the phase of slit-shaped incident light LA ​​whose cross section is shaped into a flattened ellipse, and then emits the modulated light.

[0072] 11 and 12 may be referred to as the X direction, the Y direction, and the Z direction, respectively. The X direction, the Y direction, and the Z direction are perpendicular to each other.

[0073] The optical element 310 is formed in a flat rectangular parallelepiped shape using a light-transmitting ferroelectric material. An incident surface 311 is formed at one end (in the -Y direction) of the optical element 310. Slit-shaped (elliptical in cross section) incident light LA ​​traveling in the +Y direction is incident on the incident surface 311 as incident light. An exit surface 312 is formed at the end (in the +Y direction) of the optical element 310 opposite the incident surface 311. The light that enters the optical element 310 from the incident surface 311 is exited from the exit surface 312.

[0074] A first electrode 320 is provided on a first side surface 313 extending from the incident surface 311 toward the exit surface 312 of the optical member 310. The first electrode 320 is formed in the same manner as the first electrode 120 according to the first embodiment.

[0075] A second electrode 330 is provided on a second side surface 314 of the optical member 310 opposite the first side surface 313 (the +Z direction side). The second electrode 330 is formed in the same manner as the second electrode 130 according to the first embodiment. A plurality of second electrodes 330 are arranged side by side in an arrangement direction (X direction) perpendicular to the extension direction of the second side surface 314. The extension direction of the first side surface 313 connecting the incident surface 311 and the exit surface 312 may also be referred to as a predetermined direction. A plurality of second electrodes 330 may also be arranged side by side in the arrangement direction (X direction) perpendicular to the predetermined direction. An insulating layer 316 is formed between the second side surface 314 and the plurality of second electrodes 330. The insulating layer 316 is formed in the same manner as the second insulating layer 116 according to the first embodiment.

[0076] An optical waveguide 317 extending from the incident surface 311 to the exit surface 312 is provided in each portion between the second electrode 330 and the first electrode 320 inside the optical element 310. The optical waveguide 317 may be formed by a proton exchange method. Alternatively, the optical waveguide 317 may be formed by a metal diffusion method using a metal such as titanium (Ti) or copper (Cu). The optical waveguide 317 may be referred to as a channel-type optical waveguide. Adjacent optical waveguides 317 are formed at a distance equal to or greater than the amount of seepage of evanescent waves generated when light is totally reflected in each optical waveguide 317. Alternatively, adjacent optical waveguides 317 may be formed at a distance equal to the length of the gap between the second electrodes 330. The refractive index of the optical waveguide 317 is higher than the refractive index of the portions of the optical element 310 located at the gaps between the second electrodes 330.

[0077] The second electrodes 330 are electrically connected to the second probes 62 of the wiring substrate 60, which are grouped to correspond to each second electrode 330. As described above, the second probes 62 are electrically connected to a drive circuit (not shown). The second probes 62, which are grouped to correspond to each second electrode 330, individually apply a voltage supplied from the drive circuit to the second electrodes 330. By applying a voltage to the second electrodes 330 via the second probes 62, a potential difference can be created between the second electrodes 330 and the first electrode 320, which are arranged on either side of the optical member 310.

[0078] In the modulation element body 301 of the spatial phase modulation element 300 configured as described above, slit-shaped (elliptical in cross section) incident light LA ​​is incident on the incident surface 311 of the optical element 310, as shown in Figures 11 and 12. When a positive voltage is applied to the second electrode 330, a potential difference is generated between the second electrode 330 and the first electrode 320, which are arranged on either side of the optical element 310, and an electric field is generated inside the optical element 310 from the second electrode 330 to the first electrode 320. On the other hand, when a negative voltage is applied to the second electrode 330, a potential difference is generated between the second electrode 330 and the first electrode 320, which are arranged on either side of the optical element 310, and an electric field is generated inside the optical element 310 from the first electrode 320 to the second electrode 330.

[0079] As described above, the optical element 310 is formed using a light-transmitting ferroelectric material. In FIG. 12 , the polarization direction (orientation of the crystal axis) in the optical element 310 is schematically indicated by a thick arrow. The polarization direction in the optical element 310 is oriented in the direction from the first side surface 313 to the second side surface 314 (the +Z direction). As a result, as the electric field flows from the second electrode 330 to the first electrode 320, the refractive index of the portion of the optical element 310 where the second electrode 330 is located, i.e., the optical waveguide 317, increases due to the electro-optic effect. Meanwhile, as the electric field flows from the first electrode 320 to the second electrode 330, the refractive index of the optical waveguide 317 in the optical element 310 decreases due to the electro-optic effect.

[0080] By generating an electric field inside the optical element 310 and changing the refractive index inside the optical element 310, the phase of light (incident light LA) passing through the optical element 310 can be changed. The modulator body 301 of the spatial phase modulator 300 modulates the phase of light (incident light LA) incident on the incident surface 311 of the optical element 310 by the potential difference between the second electrode 330 and the first electrode 320, and emits emitted light LB from the exit surface 312. In the third embodiment, the potential difference between the multiple second electrodes 330 and the first electrode 320 can be individually changed. Since the potential difference between the multiple second electrodes 330 and the first electrode 320 occurs in the thickness direction of the optical element 310, the voltage (driving voltage) applied to the second electrode 330 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 310 can be changed quickly and with high precision without placing a burden on a driving circuit (not shown).

[0081] Furthermore, the refractive index of the optical waveguide 317 in the optical element 310 is higher than the refractive index of the portions of the optical element 310 located in the gaps between the plurality of second electrodes 330. This allows light incident on the portions of the optical element 310 located in the gaps between the plurality of second electrodes 330 to be incident on the portions of the optical element 310 where the second electrodes 330 are disposed, i.e., the optical waveguide 317. This makes it possible to utilize 100% of the incident light LA, thereby increasing the utilization efficiency of the incident light LA. Furthermore, because the refractive index of the optical waveguide 317 in the optical element 310 is higher than the refractive index of the portions of the optical element 310 located in the gaps between the plurality of second electrodes 330, the range in which the phase of light incident on the optical element 310 (the incident light LA) can be changed can be expanded while increasing the utilization efficiency of the incident light LA.

[0082] The graph shown in Fig. 12 shows the distribution of the refractive index of the optical element 310. The horizontal and vertical axes of the graph shown in Fig. 12 are the same as the horizontal and vertical axes of the graph shown in Fig. 5. Furthermore, the region of the optical element 310 on the -X direction side where the second electrode 330 is arranged is referred to as a first region 319A of the optical element 310. The region of the optical element 310 on the central side where the second electrode 330 is arranged is referred to as a second region 319B of the optical element 310. The region of the optical element 310 on the +X direction side where the second electrode 330 is arranged is referred to as a third region 319C of the optical element 310.

[0083] 13 is a graph showing a comparison between the phase distribution of incident light LA, the phase distribution of emitted light LB, and the refractive index distribution of optical element 310. The horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​are the same as the horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​in FIG. 6. For ease of explanation, it is assumed that the wavefront of incident light LA ​​is planar and the phase distribution of incident light LA ​​is constant. The horizontal and vertical axes of the graph showing the phase distribution of emitted light LB are the same as the horizontal and vertical axes of the graph showing the phase distribution of emitted light LB in FIG. 6. The graph showing the refractive index distribution of optical element 310 is the same as the graph shown in FIG. 12.

[0084] As described above, it is possible to individually change the potential difference between the plurality of second electrodes 330 and the first electrode 320. As can be seen from the graphs of FIGS. 12 and 13 showing the refractive index distribution of the optical element 310, the refractive index of the first region 319A, the refractive index of the second region 319B, and the refractive index of the third region 319C in the optical element 310 individually change depending on the potential difference between the plurality of second electrodes 330 and the first electrode 320. For example, in the first region 319A, as the electric field flows from the second electrode 330 to the first electrode 320, the refractive index of the first region 319A increases due to the electro-optic effect. In the second region 319B, as the electric field flows from the second electrode 330 to the first electrode 320, the refractive index of the second region 319B increases due to the electro-optic effect. In the third region 319C, as the electric field moves from the first electrode 320 to the second electrode 330, the refractive index of the third region 319C changes in a decreasing direction due to the electro-optic effect.

[0085] Furthermore, the refractive index of the optical waveguide 317 in the optical member 310 is higher than the refractive index of the portions of the optical member 310 located in the gaps between the plurality of second electrodes 330. This allows light incident on the portions of the optical member 310 located in the gaps between the plurality of second electrodes 330 to be incident on the portions of the optical member 310 where the second electrodes 330 are arranged, i.e., the optical waveguide 317.

[0086] 13 , the phase of light LA1 incident on the first region 319A changes depending on the refractive index of the first region 319A. The phase of light LA2 incident on the second region 319B changes depending on the refractive index of the second region 319B. The phase of light LA3 incident on the third region 319C changes depending on the refractive index of the third region 319C. This allows the phase of light incident on the optical element 310 (incident light LA) to be changed quickly and with high precision.

[0087] Furthermore, for example, light LA6 incident on the gap adjacent to the first region 319A on the −X direction side can be made to enter the first region 319A (or the region opposite the first region 319A). Light LA7 incident on the gap between the first region 319A and the second region 319B can be made to enter the first region 319A or the second region 319B. Light LA8 incident on the gap between the second region 319B and the third region 319C can be made to enter the second region 319B or the third region 319C. Light LA9 incident on the gap adjacent to the third region 319C on the +X direction side can be made to enter the third region 319C (or the region opposite the third region 319C). This can increase the utilization efficiency of the incident light LA.

[0088] [Characteristic Configuration of Third Embodiment] The spatial phase modulation element 300 according to the third embodiment includes a first electrode 320 provided on a first side surface 313 of the optical element 310 and a plurality of second electrodes 330 provided on a second side surface 314 of the optical element 310 opposite the first side surface 313. It is possible to individually generate a potential difference between the plurality of second electrodes 330 and the first electrode 320. Because the potential difference between the plurality of second electrodes 330 and the first electrode 320 occurs in the thickness direction of the optical element 310, it is possible to reduce the voltage (driving voltage) applied to the second electrode 330. Therefore, it is possible to quickly and accurately change the phase of light (incident light LA) incident on the optical element 310 without imposing a burden on a driving circuit (not shown).

[0089] Furthermore, the refractive index of the optical waveguide 317 in the optical element 310 is higher than the refractive index of the portions of the optical element 310 located in the gaps between the plurality of second electrodes 330. This allows light incident on the portions of the optical element 310 located in the gaps between the plurality of second electrodes 330 to be incident on the portions of the optical element 310 where the second electrodes 330 are disposed, i.e., the optical waveguide 317. This makes it possible to utilize 100% of the incident light LA, thereby increasing the utilization efficiency of the incident light LA. Furthermore, because the refractive index of the optical waveguide 317 in the optical element 310 is higher than the refractive index of the portions of the optical element 310 located in the gaps between the plurality of second electrodes 330, the range in which the phase of light incident on the optical element 310 (the incident light LA) can be changed can be expanded while increasing the utilization efficiency of the incident light LA.

[0090] In the third embodiment described above, the first electrodes 320 are formed to extend over the entire first side surface 313, but this is not limiting. For example, a plurality of first electrodes may be arranged side by side in the same arrangement direction (X direction) as the second electrodes 330 on a portion of the first side surface 313 located opposite the second electrodes 330.

[0091] [Fourth Embodiment] Next, a spatial phase modulation element according to the fourth embodiment will be described. The spatial phase modulation element according to the fourth embodiment has the same configuration as the spatial phase modulation element 50 according to the first embodiment, except for the modulation element body. Therefore, in the fourth embodiment, only the modulation element body of the spatial phase modulation element will be described. As shown in FIGS. 14 and 15 , the modulation element body 401 of the spatial phase modulation element 400 according to the fourth embodiment includes an optical member 410, a first electrode 420, and a plurality of second electrodes 430. The modulation element body 401 modulates the phase of slit-shaped incident light LA ​​whose cross section is shaped into a flattened ellipse, and then emits the modulated light.

[0092] 14 and 15 may be referred to as the X direction, the Y direction, and the Z direction, respectively. The X direction, the Y direction, and the Z direction are perpendicular to each other.

[0093] The optical element 410 is formed in a flat rectangular parallelepiped shape using a light-transmitting ferroelectric material. An incident surface 411 is formed at one end (in the -Y direction) of the optical element 410. Slit-shaped (elliptical in cross section) incident light LA ​​traveling in the +Y direction is incident on the incident surface 411 as incident light. An exit surface 412 is formed at the end (in the +Y direction) of the optical element 410 opposite the incident surface 411. Light entering the optical element 410 from the incident surface 411 is exited from the exit surface 412.

[0094] A first electrode 420 is provided on a first side surface 413 extending from the incident surface 411 toward the exit surface 412 of the optical member 410. The first electrode 420 is formed in the same manner as the first electrode 120 according to the first embodiment. A first insulating layer 415 is formed between the first side surface 413 and the first electrode 420. The first insulating layer 415 is formed in the same manner as the first insulating layer 115 according to the first embodiment.

[0095] A second electrode 430 is provided on a second side surface 414 of the optical member 410 opposite the first side surface 413 (the +Z direction side). The second electrode 430 is formed in the same manner as the second electrode 130 according to the first embodiment. A plurality of second electrodes 430 are arranged side by side in an arrangement direction (X direction) perpendicular to the extension direction of the second side surface 414. The extension direction of the first side surface 413 connecting the incident surface 411 and the exit surface 412 may also be referred to as a predetermined direction. A plurality of second electrodes 430 may also be arranged side by side in the arrangement direction (X direction) perpendicular to the predetermined direction. A second insulating layer 416 is formed between the second side surface 414 and the plurality of second electrodes 430. The second insulating layer 416 is formed in the same manner as the second insulating layer 116 according to the first embodiment.

[0096] The optical element 410 has a polarization inversion structure. The optical element 410 includes first polarization portions 417 extending in the Y direction and second polarization portions 418 adjacent to the first polarization portions 417 and extending in the Y direction, arranged alternately along the X direction (the same arrangement direction as the second electrodes 430). The second polarization portions 418 are polarized in a different direction (specifically, the opposite direction) from the first polarization portions 417. To provide the polarization inversion structure in the optical element 410, the polarization direction of the portion corresponding to the second polarization portion 418 is inverted by 180° for a rectangular parallelepiped optical element having uniform polarization (dielectric polarization). For example, when using a known method known as the "electric field application method," an electrode is attached to the portion corresponding to the second polarization portion 418, and a voltage above a certain level (also referred to as a polarization inversion voltage or coercive field) is applied to invert the polarization direction of the second polarization portion 418. It should be noted that the direction of polarization of the first polarized portion 417 may be reversed, not just the second polarized portion 418 .

[0097] A first electrode 420 is provided across a portion of the first side surface 413 where the first polarized portion 417 is located and a portion of the second polarized portion 418 is located. A second electrode 430 is provided at each portion of the second side surface 414 where the first polarized portion 417 is located. In the portion of the second side surface 414 where the first polarized portion 417 is located, the second electrode 430 is formed to extend parallel to the Y direction from one end side to the other end side of the first polarized portion 417.

[0098] The second electrodes 430 are electrically connected to the second probes 62 of the wiring substrate 60, which are grouped to correspond to each second electrode 430. As described above, the second probes 62 are electrically connected to a drive circuit (not shown). The second probes 62, which are grouped to correspond to each second electrode 430, individually apply a voltage supplied from the drive circuit to the second electrodes 430. By applying a voltage to the second electrodes 430 via the second probes 62, a potential difference can be created between the second electrodes 430 and the first electrode 420, which are arranged on either side of the optical member 410.

[0099] In the modulation element body 401 of the spatial phase modulation element 400 configured as described above, slit-shaped (elliptical in cross section) incident light LA ​​is incident on the incident surface 411 of the optical element 410, as shown in Figures 14 and 15. When a positive voltage is applied to the second electrode 430, a potential difference is generated between the second electrode 430 and the first electrode 420, which are arranged on either side of the optical element 410, and an electric field is generated inside the optical element 410, directed from the second electrode 430 to the first electrode 420.

[0100] As described above, the optical element 410 has a polarization inversion structure. In Fig. 15, the polarization direction (orientation of the crystal axis) in the first polarization portion 417 of the optical element 410 is schematically indicated by a thick arrow. The polarization direction in the first polarization portion 417 is oriented in the direction from the first side surface 413 to the second side surface 414 (the +Z direction). As a result, as the electric field flows from the second electrode 430 to the first electrode 420, the refractive index of the first polarization portion 417 where the second electrode 430 is located changes in an increasing direction due to the electro-optic effect.

[0101] By generating an electric field inside the optical element 410 and changing the refractive index inside the optical element 410, the phase of light (incident light LA) passing through the optical element 410 can be changed. The modulator body 401 of the spatial phase modulator 400 modulates the phase of light (incident light LA) incident on the incident surface 411 of the optical element 410 by the potential difference between the second electrode 430 and the first electrode 420, and emits emitted light LB from the exit surface 412. In the fourth embodiment, the potential difference between the multiple second electrodes 430 and the first electrode 420 can be individually changed. Since the potential difference between the multiple second electrodes 430 and the first electrode 420 occurs in the thickness direction of the optical element 410, the voltage (driving voltage) applied to the second electrode 430 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 410 can be changed quickly and with high precision without placing a burden on a driving circuit (not shown).

[0102] Furthermore, by providing gaps between the multiple second electrodes 430, the electric field from the second electrodes 430 is less likely to reach the second polarization portions 418 located in the gaps between the multiple second electrodes 430 in the optical element 410, thereby reducing the change in refractive index. As described above, the second polarization portions 418 are polarized in the opposite direction to the first polarization portions 417. Therefore, even if the electric field from the second electrodes 430 reaches the second polarization portions 418, the refractive index of the second polarization portions 418 decreases due to the electro-optic effect. As a result, the refractive index of the second polarization portions 418 located in the gaps between the multiple second electrodes 430 is relatively lower than the refractive index of the first polarization portions 417 in which the second electrodes 430 are disposed. Therefore, light incident on the second polarization portions 418 located in the gaps between the multiple second electrodes 430 can be incident on the first polarization portions 417 in which the second electrodes 430 are disposed. Therefore, it becomes possible to utilize 100% of the incident light LA, and the utilization efficiency of the incident light LA ​​can be increased.

[0103] The graph shown in Fig. 15 shows the distribution of the refractive index of the optical element 410. The horizontal and vertical axes of the graph shown in Fig. 15 are the same as the horizontal and vertical axes of the graph shown in Fig. 5. Furthermore, the region of the first polarization portion 417 where the second electrode 430 on the -X direction side of the optical element 410 is arranged is referred to as the first region 419A of the optical element 410. The region of the first polarization portion 417 where the second electrode 430 on the central side of the optical element 410 is arranged is referred to as the second region 419B of the optical element 410. The region of the first polarization portion 417 where the second electrode 430 on the +X direction side of the optical element 410 is arranged is referred to as the third region 419C of the optical element 410.

[0104] 16 is a graph showing a comparison of the phase distribution of incident light LA, the phase distribution of emitted light LB, and the refractive index distribution of the optical element 410. The horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​are the same as the horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​in FIG. 6. For ease of explanation, it is assumed that the wavefront of incident light LA ​​is planar and the phase distribution of incident light LA ​​is constant. The horizontal and vertical axes of the graph showing the phase distribution of emitted light LB are the same as the horizontal and vertical axes of the graph showing the phase distribution of emitted light LB in FIG. 6. The graph showing the refractive index distribution of the optical element 410 is the same as the graph shown in FIG. 15.

[0105] As described above, it is possible to individually change the potential difference between the plurality of second electrodes 430 and the first electrode 420. As can be seen from the graphs of FIGS. 15 and 16 showing the refractive index distribution of the optical element 410, the refractive index of the first region 419A, the refractive index of the second region 419B, and the refractive index of the third region 419C in the optical element 410 individually change depending on the potential difference between the plurality of second electrodes 430 and the first electrode 420. For example, in the first region 419A, as the electric field flows from the second electrode 430 to the first electrode 420, the refractive index of the first region 419A increases due to the electro-optic effect. In the second region 419B, as the electric field flows from the second electrode 430 to the first electrode 420, the refractive index of the second region 419B increases due to the electro-optic effect. In the third region 419C, as the electric field moves from the second electrode 430 to the first electrode 420, the refractive index of the third region 419C changes in an increasing direction due to the electro-optic effect.

[0106] Furthermore, the second polarized portions 418 located in the gaps between the multiple second electrodes 430 are polarized in the opposite direction to the first polarized portions 417. For example, in the second polarized portion 418 located in the gap between the first region 419A and the second region 419B, the electric field from the second electrode 430 reaches the second polarized portion 418, and the refractive index of the second polarized portion 418 changes in a decreasing direction due to the electro-optic effect. In the second polarized portion 418 located in the gap between the second region 419B and the third region 419C, the electric field from the second electrode 430 reaches the second polarized portion 418, and the refractive index of the second polarized portion 418 changes in a decreasing direction due to the electro-optic effect.

[0107] 16 , for example, the phase of light LA1 incident on the first region 419A changes depending on the refractive index of the first region 419A. The phase of light LA2 incident on the second region 419B changes depending on the refractive index of the second region 419B. The phase of light LA3 incident on the third region 419C changes depending on the refractive index of the third region 419C. This allows the phase of light incident on the optical element 410 (incident light LA) to be changed quickly and with high precision.

[0108] Furthermore, for example, light LA6 incident on the gap portion (second polarized portion 418) adjacent to the first region 419A on the −X direction side can be made to enter the first region 419A (or the region opposite the first region 419A). Light LA7 incident on the gap portion (second polarized portion 418) between the first region 419A and the second region 419B can be made to enter the first region 419A or the second region 419B. Light LA8 incident on the gap portion (second polarized portion 418) between the second region 419B and the third region 419C can be made to enter the second region 419B or the third region 419C. Light LA9 incident on the gap portion (second polarized portion 418) adjacent to the third region 419C on the +X direction side can be made to enter the third region 419C (or the region opposite the third region 419C). This can increase the utilization efficiency of the incident light LA.

[0109] Fig. 17 is a graph showing a comparison between the light intensity distribution of the emitted light LB and the phase distribution of the emitted light LB. The graph shown in Fig. 17 shows a specific example in which the optical member 410 is formed using lithium niobate (LiNbO3). The horizontal and vertical axes of the graph showing the light intensity distribution of the emitted light LB are the same as the horizontal and vertical axes of the graph showing the light intensity distribution of the emitted light LB in Fig. 7. The horizontal and vertical axes of the graph showing the phase distribution of the emitted light LB are the same as the horizontal and vertical axes of the graph showing the phase distribution of the emitted light LB in Fig. 7.

[0110] The thickness (crystal thickness) of the optical element 410 is 0.2 mm. The length (interaction distance) of the optical element 410 in the Y direction is 20 mm. The pitch between the multiple second electrodes 430 is 1 mm. The width of the second electrode 430 is 0.9 mm. The voltage application direction is the Z direction. The voltage applied to the second electrode 430 in the first region 419A is 9 V, the voltage applied to the second electrode 430 in the second region 419B is 15 V, and the voltage applied to the second electrode 430 in the third region 419C is 4.5 V. The width of the second polarization portion 418 is 50 μm. The wavelength of the incident light is 633 nm. The incident light is incident to a thickness of 100 μm (1 / e 2 ) Gaussian slit beam.

[0111] 17 indicates the center position in the X direction of the gaps between the plurality of second electrodes 430. As can be seen from Fig. 17, because the optical member 410 has a polarization inversion structure, it is possible to separate the phase changes in the first to third regions 419A to 419C at clear boundaries, thereby realizing a phase distribution with high separability.

[0112] [Characteristic Configuration of Fourth Embodiment] The spatial phase modulation element 400 according to the fourth embodiment includes a first electrode 420 provided on a first side surface 413 of the optical element 410 and a plurality of second electrodes 430 provided on a second side surface 414 of the optical element 410 opposite the first side surface 413. Potential differences can be individually generated between the plurality of second electrodes 430 and the first electrode 420. Because the potential differences between the plurality of second electrodes 430 and the first electrode 420 occur in the thickness direction of the optical element 410, the voltage (driving voltage) applied to the second electrode 430 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 410 can be changed quickly and with high precision without imposing a burden on a driving circuit (not shown).

[0113] The optical element 410 also includes a first polarized portion 417 on which a second electrode 430 is provided and a second polarized portion 418 polarized in a different direction (specifically, the opposite direction) from the first polarized portion 417. Therefore, the electric field from the second electrode 430 reaches the second polarized portion 418, and the refractive index of the second polarized portion 418 decreases due to the electro-optic effect. As a result, the refractive index of the second polarized portion 418 located in the gaps between the plurality of second electrodes 430 is relatively lower than the refractive index of the first polarized portion 417 on which the second electrode 430 is located. Therefore, light incident on the second polarized portion 418 located in the gaps between the plurality of second electrodes 430 can be incident on the first polarized portion 417 on which the second electrode 430 is located. This allows 100% utilization of the incident light LA, thereby increasing the utilization efficiency of the incident light LA.

[0114] In the above-described fourth embodiment, the optical member 410 may include a slab waveguide provided so that light incident from the incident surface 411 (incident light LA) passes through the optical member 410 .

[0115] In the fourth embodiment described above, the first electrodes 420 are formed to extend over the entire first side surface 413, but this is not limiting. For example, a plurality of first electrodes may be arranged side by side in the same arrangement direction (X direction) as the second electrodes 430 on a portion of the first side surface 413 located opposite the second electrodes 430.

[0116] Fifth Embodiment Next, a spatial phase modulation element according to a fifth embodiment will be described. The spatial phase modulation element according to the fifth embodiment has the same configuration as the spatial phase modulation element 50 according to the first embodiment, except for the modulation element body. Therefore, in the fifth embodiment, only the modulation element body of the spatial phase modulation element will be described. As shown in FIGS. 18 and 19 , the modulation element body 501 of the spatial phase modulation element 500 according to the fifth embodiment includes an optical member 510, a first electrode 520, a plurality of second electrodes 530, and a plurality of third electrodes 535. The modulation element body 501 modulates the phase of slit-shaped incident light LA ​​whose cross section is shaped into a flattened ellipse, and then emits the modulated light.

[0117] 18 and 19 may be referred to as the X direction, the Y direction, and the Z direction, respectively. The X direction, the Y direction, and the Z direction are perpendicular to each other.

[0118] The optical member 510 is formed in the same manner as the optical member 410 according to the fourth embodiment. An incident surface 511 is formed at one end (in the −Y direction) of the optical member 510. Slit-shaped (elliptical in cross section) incident light LA ​​traveling in the +Y direction is incident on the incident surface 511 as incident light. An exit surface 512 is formed at the end (in the +Y direction) of the optical member 510 opposite the incident surface 511. Light entering the optical member 510 from the incident surface 511 is exited from the exit surface 512.

[0119] A first electrode 520 is provided on a first side surface 513 extending from the incident surface 511 toward the exit surface 512 of the optical member 510. The first electrode 520 is formed in the same manner as the first electrode 120 according to the first embodiment. A first insulating layer 515 is formed between the first side surface 513 and the first electrode 520. The first insulating layer 515 is formed in the same manner as the first insulating layer 115 according to the first embodiment.

[0120] A second electrode 530 is provided on a second side surface 514 of the optical member 510 on the opposite side (+Z direction side) to the first side surface 513. The second electrode 530 is formed in the same manner as the second electrode 130 according to the first embodiment. A plurality of second electrodes 530 are arranged side by side in an arrangement direction (X direction) perpendicular to the extension direction of the second side surface 514. The extension direction of the first side surface 513 connecting the incident surface 511 and the exit surface 512 may be referred to as a predetermined direction. A plurality of second electrodes 530 may be arranged side by side in the arrangement direction (X direction) perpendicular to the predetermined direction.

[0121] Third electrodes 535, to which a voltage can be applied individually, are provided in the gaps between the plurality of second electrodes 530 on the second side surface 514. The third electrodes 535 are formed using a metal material containing, for example, gold (Au), and have a width narrower than that of the second electrodes 530. The third electrodes 535 are formed to extend parallel to the second electrodes 530 in the Y direction from one end side to the other end side of the second side surface 514.

[0122] A second insulating layer 516 is formed between the second side surface 514 and the plurality of second electrodes 530 and the plurality of third electrodes 535. The second insulating layer 516 is formed in the same manner as the second insulating layer 116 according to the first embodiment.

[0123] The optical member 510 has a polarization inversion structure similar to the optical member 410 according to the fourth embodiment. The optical member 510 has first polarization portions 517 extending in the Y direction and second polarization portions 518 extending in the Y direction adjacent to the first polarization portions 517, which are alternately arranged along the X direction (the same arrangement direction as the second electrodes 530). The second polarization portions 518 are polarized in a different direction (specifically, the opposite direction) from the first polarization portions 517.

[0124] A first electrode 520 is provided across a portion of the first side surface 513 where the first polarized portion 517 is located and a portion of the second polarized portion 518 is located. A second electrode 530 is provided on each portion of the second side surface 514 where the first polarized portion 517 is located. The second electrode 530 is formed to extend parallel to the Y direction from one end to the other end of the first polarized portion 517 on each portion of the second side surface 514 where the first polarized portion 517 is located. A third electrode 535 is provided on each portion of the second side surface 514 where the second polarized portion 518 is located. The third electrode 535 is formed to extend parallel to the Y direction from one end to the other end of the second polarized portion 518 on each portion of the second side surface 514 where the second polarized portion 518 is located.

[0125] The second electrodes 530 and the third electrodes 535 are electrically connected to the second probes 62 of the wiring substrate 60, which are grouped to correspond to the second electrodes 530 and the third electrodes 535. As described above, the second probes 62 are electrically connected to a drive circuit (not shown). The second probes 62, which are grouped to correspond to the second electrodes 530 and the third electrodes 535, individually apply voltages supplied from the drive circuit to the second electrodes 530 and the third electrodes 535. By applying a voltage to the second electrodes 530 via the second probes 62, a potential difference can be created between the second electrodes 530 and the first electrodes 520, which are disposed on either side of the optical member 510. Furthermore, by applying a voltage to the third electrode 535 via the second probes 62, a potential difference can be created between the third electrodes 535 and the first electrodes 520, which are disposed on either side of the optical member 510.

[0126] In the modulation element body 501 of the spatial phase modulation element 500 configured as described above, slit-shaped (elliptical in cross section) incident light LA ​​is incident on the incident surface 511 of the optical element 510, as shown in Figures 18 and 19. When a positive voltage is applied to the second electrode 530, a potential difference is generated between the second electrode 530 and the first electrode 520, which are arranged on either side of the optical element 510, and an electric field is generated inside the optical element 510 from the second electrode 530 to the first electrode 520. On the other hand, when a negative voltage is applied to the second electrode 530, a potential difference is generated between the second electrode 530 and the first electrode 520, which are arranged on either side of the optical element 510, and an electric field is generated inside the optical element 510 from the first electrode 520 to the second electrode 530.

[0127] Furthermore, when a positive voltage is applied to the third electrode 535, a potential difference is generated between the third electrode 535 and the first electrode 520, which are disposed on either side of the optical member 510, and an electric field is generated inside the optical member 510 from the third electrode 535 to the first electrode 520. On the other hand, when a negative voltage is applied to the third electrode 535, a potential difference is generated between the third electrode 535 and the first electrode 520, which are disposed on either side of the optical member 510, and an electric field is generated inside the optical member 510 from the first electrode 520 to the third electrode 535.

[0128] As described above, the optical element 510 has a polarization inversion structure. In FIG. 19 , the polarization direction (orientation of the crystal axis) in the first polarization portion 517 of the optical element 510 is schematically indicated by a thick arrow. The polarization direction in the first polarization portion 517 is oriented in the direction from the first side surface 513 to the second side surface 514 (the +Z direction). As a result, as the electric field flows from the second electrode 530 to the first electrode 520, the refractive index of the first polarization portion 517 where the second electrode 530 is disposed changes in an increasing direction due to the electro-optic effect. On the other hand, as the electric field flows from the first electrode 520 to the second electrode 530, the refractive index of the first polarization portion 517 where the second electrode 530 is disposed changes in a decreasing direction due to the electro-optic effect.

[0129] Furthermore, the second polarized portion 518 is polarized in the opposite direction to the first polarized portion 517. As a result, as the electric field moves from the third electrode 535 to the first electrode 520, the refractive index of the second polarized portion 518 where the third electrode 535 is located changes in a decreasing direction due to the electro-optical effect. On the other hand, as the electric field moves from the first electrode 520 to the third electrode 535, the refractive index of the second polarized portion 518 where the third electrode 535 is located changes in a increasing direction due to the electro-optical effect.

[0130] By generating an electric field inside the optical element 510 and changing the refractive index inside the optical element 510, the phase of light (incident light LA) passing through the optical element 510 can be changed. The modulator body 501 of the spatial phase modulator 500 modulates the phase of light (incident light LA) incident on the incident surface 511 of the optical element 510 by the potential difference between the second electrode 530 and the first electrode 520 (and the potential difference between the third electrode 535 and the first electrode 520), and emits emitted light LB from the emission surface 512. In the fifth embodiment, the potential differences between the multiple second electrodes 530 and the first electrodes 520 can be individually changed. Because the potential differences between the multiple second electrodes 530 and the first electrode 520 occur in the thickness direction of the optical element 510, the voltage (driving voltage) applied to the second electrode 530 can be reduced. Therefore, the phase of the light (incident light LA) incident on the optical member 510 can be changed at high speed with high precision without placing a burden on a drive circuit (not shown).

[0131] Furthermore, a third electrode 535 is provided in the second polarized portion 518 located in the gap between the plurality of second electrodes 530 in the optical member 510, and it is possible to individually change the potential difference between the third electrode 535 and the first electrode 520. By generating an electric field from the third electrode 535 toward the first electrode 520 and lowering the refractive index of the second polarized portion 518 in which the third electrode 535 is disposed, it is possible to make light incident on the second polarized portion 518 in which the third electrode 535 is disposed incident on the first polarized portion 517 in which the second electrode 530 is disposed. Therefore, it is possible to utilize 100% of the incident light LA, and the utilization efficiency of the incident light LA ​​can be increased. Furthermore, by lowering the refractive index of the second polarized portion 518 where the third electrode 535 is arranged, the refractive index of the first polarized portion 517 where the second electrode 530 is arranged can be lowered, thereby increasing the utilization efficiency of the incident light LA ​​and widening the range in which the phase of the light (incident light LA) incident on the optical element 510 can be changed.

[0132] The graph shown in Figure 19 shows the distribution of the refractive index of the optical element 510. The horizontal and vertical axes of the graph shown in Figure 19 are the same as the horizontal and vertical axes of the graph shown in Figure 5. Furthermore, the region of the first polarization portion 517 where the second electrode 430 on the -X direction side of the optical element 510 is arranged is referred to as the first region 519A of the optical element 510. The region of the first polarization portion 517 where the second electrode 530 on the central side of the optical element 510 is arranged is referred to as the second region 519B of the optical element 510. The region of the first polarization portion 517 where the second electrode 530 on the +X direction side of the optical element 510 is arranged is referred to as the third region 519C of the optical element 510.

[0133] 20 is a graph showing a comparison of the phase distribution of incident light LA, the phase distribution of emitted light LB, and the distribution of the refractive index of the optical element 510. The horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​are the same as the horizontal and vertical axes of the graph showing the phase distribution of incident light LA ​​in FIG. 6. For ease of explanation, it is assumed that the wavefront of incident light LA ​​is planar and the phase distribution of incident light LA ​​is constant. The horizontal and vertical axes of the graph showing the phase distribution of emitted light LB are the same as the horizontal and vertical axes of the graph showing the phase distribution of emitted light LB in FIG. 6. The graph showing the distribution of the refractive index of the optical element 510 is the same as the graph shown in FIG. 19.

[0134] As described above, it is possible to individually change the potential difference between the plurality of second electrodes 530 and the first electrode 520. As can be seen from the graphs of FIGS. 19 and 20 showing the refractive index distribution of the optical element 510, the refractive index of the first region 519A, the refractive index of the second region 519B, and the refractive index of the third region 519C in the optical element 510 individually change depending on the potential difference between the plurality of second electrodes 530 and the first electrode 520. For example, in the first region 519A, as the electric field flows from the second electrode 530 to the first electrode 520, the refractive index of the first region 519A increases due to the electro-optic effect. In the second region 519B, as the electric field flows from the second electrode 530 to the first electrode 520, the refractive index of the second region 519B increases due to the electro-optic effect. In the third region 519C, as the electric field moves from the first electrode 520 to the second electrode 530, the refractive index of the third region 519C changes in a decreasing direction due to the electro-optic effect.

[0135] It is also possible to individually change the potential difference between the third electrode 535 and the first electrode 520. For example, in the second polarized portion 518 located in the gap between the first region 519A and the second region 519B, as the electric field flows from the first electrode 520 to the third electrode 535, the refractive index of the second polarized portion 518 increases due to the electro-optic effect, but does not exceed the refractive indexes of the first region 519A and the second region 519B. In the second polarized portion 518 located in the gap between the second region 519B and the third region 519C, as the electric field flows from the third electrode 535 to the first electrode 520, the refractive index of the second polarized portion 518 decreases due to the electro-optic effect, so that the refractive index becomes lower than the refractive indexes of the second region 519B and the third region 519C.

[0136] 20 , the phase of light LA1 incident on the first region 519A changes depending on the refractive index of the first region 519A. The phase of light LA2 incident on the second region 519B changes depending on the refractive index of the second region 519B. The phase of light LA3 incident on the third region 519C changes depending on the refractive index of the third region 519C. This allows the phase of light (incident light LA) incident on the optical element 510 to be changed quickly and with high precision.

[0137] Furthermore, for example, light LA6 incident on the gap portion (second polarized portion 518) adjacent to the first region 519A on the −X direction side can be made to enter the first region 519A (or the region opposite the first region 519A). Light LA7 incident on the gap portion (second polarized portion 518) between the first region 519A and the second region 519B can be made to enter the first region 519A or the second region 519B. Light LA8 incident on the gap portion (second polarized portion 518) between the second region 519B and the third region 519C can be made to enter the second region 519B or the third region 519C. Light LA9 incident on the gap portion (second polarized portion 518) adjacent to the third region 519C on the +X direction side can be made to enter the third region 519C (or the region opposite the third region 519C). This can increase the utilization efficiency of the incident light LA.

[0138] Fig. 21 is a graph showing a comparison between the light intensity distribution of the emitted light LB and the phase distribution of the emitted light LB. The graph shown in Fig. 21 shows a specific example in which the optical element 510 is formed using lithium niobate (LiNbO3). The horizontal and vertical axes of the graph showing the light intensity distribution of the emitted light LB are the same as the horizontal and vertical axes of the graph showing the light intensity distribution of the emitted light LB in Fig. 7. The horizontal and vertical axes of the graph showing the phase distribution of the emitted light LB are the same as the horizontal and vertical axes of the graph showing the phase distribution of the emitted light LB in Fig. 7.

[0139] The thickness (crystal thickness) of the optical element 510 is 0.2 mm. The length (interaction distance) of the optical element 510 in the Y direction is 20 mm. The pitch between the multiple second electrodes 530 is 1 mm. The width of the second electrode 530 is 0.9 mm. The voltage application direction is the Z direction. The voltage applied to the second electrode 530 in the first region 519A is 9 V, the voltage applied to the second electrode 530 in the second region 519B is 15 V, and the voltage applied to the second electrode 530 in the third region 519C is -9 V. The width of the second polarization portion 418 is 50 μm. The width of the third electrode 535 is 20 μm. The voltage applied to the third electrode 535 of the second polarization portion 518 adjacent to the first region 519A on the -X direction side is -13.5V, and the voltage applied to the second polarization portion 518 located in the gap between the first region 519A and the second region 519B is -31.5V. The voltage applied to the third electrode 535 of the second polarization portion 518 located in the gap between the second region 519B and the third region 519C is +13.5V, and the voltage applied to the third electrode 535 of the second polarization portion 518 adjacent to the third region 519C on the +X direction side is +13.5V. The wavelength of the incident light is 633 nm. The incident light is incident on a 100 μm thick (1 / e 2 ) Gaussian slit beam.

[0140] 21 indicates the center position in the X direction of the gaps between the multiple second electrodes 530. As can be seen from FIG. 21 , because the optical element 510 has a polarization inversion structure, it is possible to separate the phase changes in the first to third regions 519A to 519C at clear boundaries, thereby achieving a highly separable phase distribution. Furthermore, it can be seen that applying a voltage to the third electrode 535 of the second polarization portion 518 changes the refractive index of the second polarization portion 518, thereby reducing fluctuations in light intensity in the second polarization portion 518 (boundaries between the first to third regions 519A to 519C).

[0141] [Characteristic Configuration of Fifth Embodiment] The spatial phase modulation element 500 according to the fifth embodiment includes a first electrode 520 provided on a first side surface 513 of the optical element 510 and a plurality of second electrodes 530 provided on a second side surface 514 of the optical element 510 opposite the first side surface 513. Potential differences can be individually generated between the plurality of second electrodes 530 and the first electrode 520. Because the potential differences between the plurality of second electrodes 530 and the first electrode 520 occur in the thickness direction of the optical element 510, the voltage (driving voltage) applied to the second electrode 530 can be reduced. Therefore, the phase of light (incident light LA) incident on the optical element 510 can be changed quickly and with high precision without imposing a burden on a driving circuit (not shown).

[0142] The optical element 510 also includes a first polarized portion 517 on which the second electrode 530 is provided, and a second polarized portion 518 polarized in a different direction (specifically, the opposite direction) from the first polarized portion 517. Furthermore, a third electrode 535 is provided on the second polarized portion 518, and the potential difference between the third electrode 535 and the first electrode 520 can be individually changed. By generating an electric field from the third electrode 535 toward the first electrode 520 and lowering the refractive index of the second polarized portion 518 on which the third electrode 535 is provided, light incident on the second polarized portion 518 on which the third electrode 535 is provided can be made to enter the first polarized portion 517 on which the second electrode 530 is provided. Therefore, 100% of the incident light LA ​​can be utilized, thereby increasing the utilization efficiency of the incident light LA. Furthermore, by lowering the refractive index of the second polarized portion 518 where the third electrode 535 is arranged, the refractive index of the first polarized portion 517 where the second electrode 530 is arranged can be lowered, thereby increasing the utilization efficiency of the incident light LA ​​and widening the range in which the phase of the light (incident light LA) incident on the optical element 510 can be changed.

[0143] In the above-described fifth embodiment, the optical member 510 may include a slab waveguide provided so that light incident from the incident surface 511 (incident light LA) passes through the optical member 510 .

[0144] In the fifth embodiment described above, the first electrode 520 is formed to extend over the entire first side surface 513, but this is not limiting. For example, a plurality of first electrodes may be arranged side by side in the same arrangement direction (X direction) as the second electrode 530 (or the third electrode 535) on a portion of the first side surface 513 located opposite the second electrode 530 and on a portion of the first side surface 513 located opposite the third electrode 535.

[0145] 1 Spatial phase modulator 50 Spatial phase modulation element (first embodiment) 101 Modulation element body 110 Optical member 111 Incident surface 112 Emission surface 113 First side surface 114 Second side surface 120 First electrode 130 Second electrode 200 Spatial phase modulation element (second embodiment) 201 Modulation element body 210 Optical member 211 Incident surface 212 Emission surface 213 First side surface 214 Second side surface 220 First electrode 230 Second electrode 235 Third electrode 300 Spatial phase modulation element (third embodiment) 301 Modulation element body 310 Optical member 311 Incident surface 312 Emission surface 313 First side surface 314 Second side surface 317 Optical waveguide 320 First electrode 330 Second electrode 400 Spatial phase modulation element (fourth embodiment) 401 Modulation element body 410 Optical member 411 Incident surface 412 Emitting surface 413 First side surface 414 Second side surface 417 First polarized portion 418 Second polarized portion 420 First electrode 430 Second electrode 500 Spatial phase modulation element (fifth embodiment) 501 Modulation element body 510 Optical member 511 Incident surface 512 Emitting surface 513 First side surface 514 Second side surface 517 First polarized portion 518 Second polarized portion 520 First electrode 530 Second electrode 535 Third electrode

Claims

1. A spatial phase modulation element comprising: an optical element formed using a light-transmitting ferroelectric material; a first electrode provided on a first side extending in a predetermined direction connecting the light entrance surface and exit surface of the optical element; and a second electrode provided on a second side of the optical element opposite the first side, wherein a potential difference is generated between the second electrode and the first electrode to change the refractive index of the optical element, thereby changing the phase of light passing through the optical element, wherein the second electrodes are arranged in a row in an arrangement direction perpendicular to the predetermined direction, and wherein a potential difference can be generated individually between the second electrodes and the first electrode.

2. A spatial phase modulation element as claimed in claim 1, wherein gaps are provided between the second electrodes.

3. A spatial phase modulation element as described in claim 2, further comprising a third electrode provided in the gap between the plurality of second electrodes on the second side surface, and capable of generating a potential difference between the third electrode and the first electrode.

4. The optical member has a first polarization portion extending from the incident surface toward the exit surface, and a second polarization portion extending from the incident surface toward the exit surface with a width in the arrangement direction smaller than that of the first polarization portion and polarized in a direction different from that of the first polarization portion, the first polarization portion and the second polarization portion being arranged adjacent to each other alternately in the arrangement direction in a plurality of first and second polarization portions, and the second electrode being arranged in a portion of the second side where the first polarization portion is located. A spatial phase modulation element as described in claim 1 or 2, characterized in that 5. A spatial phase modulation element as described in claim 4, further comprising a third electrode provided in a portion of the second side surface where the second polarization portion is located, and capable of generating a potential difference between the third electrode and the first electrode.

6. The spatial phase modulation element of claim 2, wherein an optical waveguide is provided in a portion between the second electrode and the first electrode inside the optical member, extending from the entrance surface to the exit surface, and the refractive index of the optical waveguide is higher than the refractive index of portions of the optical member located in the gaps between the plurality of second electrodes.

7. A spatial phase modulator comprising a plurality of spatial phase modulation elements according to any one of claims 1 to 6, the plurality of spatial phase modulation elements being arranged side by side in a direction from the first side surface to the second side surface.

8. An optical modulator which modulates and emits incident light based on a signal from a drive circuit, comprising: a substrate of a ferroelectric optical crystal onto which the incident light traveling along a first axis is incident; and electrodes arranged on two opposing surfaces of the substrate along a second axis intersecting the first axis, wherein the substrate of the ferroelectric optical crystal has a periodic polarization inversion structure in which polarization alternates along the second axis, and the electrodes arranged on one of the two surfaces include a plurality of pixel electrodes arranged along the second axis and a plurality of control electrodes arranged between each of the plurality of pixel electrodes, wherein the pixel electrodes change the refractive index by applying a voltage between the pixel electrode and an electrode on the opposing surface due to an electric field generated in the ferroelectric optical crystal, and modulate the light by interaction with the light that has passed through the inside of the ferroelectric optical crystal, and the control electrodes are controlled independently of the control of the voltage of the pixel electrodes by the drive circuit.

9. An optical modulator as described in claim 8, wherein the periodic polarization inversion structure in the substrate of the ferroelectric optical crystal comprises a plurality of regions having polarization directions different from each other, and the plurality of pixel electrodes and the plurality of control electrodes are provided at positions different from the boundaries of the plurality of regions.

10. The optical modulator according to claim 9, wherein one of said plurality of pixel electrodes changes the refractive index in one of said plurality of regions of said periodically poled structure.

11. An optical modulator according to any one of claims 8 to 10, wherein the width of the control electrode in the direction along the second axis is narrower than the width of the pixel electrode in the direction along the second axis.

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