Optical modulation element, spatial light modulator, and display device

Abstract

The present invention provides an optical modulation element exhibiting a Kerr rotation angle of 0.5° or greater, a spatial light modulator equipped with the optical modulation element, and a display device equipped with the spatial light modulator. [Solution] The optical modulation element comprises a second electrode facing the incident surface into which light is incident, a ferromagnetic ferroelectric layer disposed on the incident surface side of the second electrode, and a ferromagnetic layer disposed on the incident surface side of the ferromagnetic ferroelectric layer, wherein the thickness of the ferromagnetic ferroelectric layer is in the range of 20 to 100 nm, and the thickness of the ferromagnetic layer is in the range of 3 to 20 nm. When a voltage is applied to the ferromagnetic ferroelectric layer by the second electrode, electric polarization is induced in the ferromagnetic ferroelectric layer, and the magnetization of the ferromagnetic ferroelectric layer and the ferromagnetic layer is controlled according to this electric polarization. The spatial light modulator comprises this optical modulation element. The display device comprises this spatial light modulator.

Description

[Technical Field]

[0001] The present invention relates to an optical modulation element, a spatial light modulator, and a display device. [Background technology]

[0002] A spatial light modulator is a device in which optical elements (light modulators) acting as pixels are arranged in a two-dimensional matrix to spatially modulate the phase, amplitude, and other properties of light. Spatial light modulators are widely used in fields such as exposure equipment (including holography devices), display technology, and recording technology. Furthermore, because spatial light modulators can process optical information in parallel in two dimensions, their application to optical information processing technology is being researched.

[0003] As an example of a spatial light modulator, display devices that utilize the polarization of liquid crystals are widely known. On the other hand, spatial light modulators have problems with insufficient response speed and pixel resolution for holography or optical information processing. Therefore, in recent years, development of magneto-optical spatial light modulators using magneto-optical materials, which are expected to enable high-speed processing and miniaturization of pixels, has been progressing.

[0004] A magneto-optical spatial light modulator (hereinafter referred to as a spatial light modulator) utilizes the effect that the direction of polarization changes (optical rotation) when light incident on a magneto-optical material, i.e., a magnetic material, is transmitted or reflected. This effect is called the Faraday effect when light is transmitted through a magnetic material, and the Kerr effect when light is reflected by a magnetic material.

[0005] Patent Document 1 discloses an optical modulation element comprising a transparent first electrode positioned on the incident surface side to which light is incident, a second electrode facing the first electrode, a single layer of ferromagnetic ferroelectric layer sandwiched between the first electrode and the second electrode, and a magnetic transfer layer connected to one or both sides of the ferromagnetic ferroelectric layer, wherein an electric polarization is induced in the ferromagnetic ferroelectric layer by applying a voltage to the ferromagnetic ferroelectric layer using the first electrode and the second electrode, and the magnetization of the ferromagnetic ferroelectric layer and the magnetization of the magnetic transfer layer magnetically coupled thereto are controlled according to the electric polarization.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The single-layer ferromagnetic ferroelectric layer has only the function of applying an electric field to the magnetic transfer layer, and the magnetic transfer layer has only the function of deriving the Kerr effect. As a result, the optical modulation element can control the Kerr effect with an electric field, but the Kerr effect is a value determined by the physical properties of the magnetic transfer layer alone, and the Kerr rotation angle shown by the magnetic transfer layer is as small as about 0.1°. In recent years, there has been a demand for an optical modulation element that shows a Kerr rotation angle of 0.5° or more, which can display a stereoscopic image with higher brightness and a wider viewing angle range for three-dimensional viewing.

[0008] Therefore, the problem to be solved by the present invention is to provide an optical modulation element that shows a Kerr rotation angle of 0.5° or more, a spatial light modulator including the optical modulation element, and a display device including the spatial light modulator.

Means for Solving the Problems

[0009] In view of the above problems, the present inventors have repeatedly studied and found that an optical modulation element in which the thicknesses of the ferromagnetic ferroelectric layer and the ferromagnetic layer included in the optical modulation element are each limited to a specific range shows a Kerr rotation angle of 0.5° or more. The present invention has been completed based on these findings.

[0010] The present invention relates to an optical modulation element including a second electrode facing an incident surface on which light is incident, a ferromagnetic ferroelectric layer disposed on the incident surface side of the second electrode, and a ferromagnetic layer disposed on the incident surface side of the ferromagnetic ferroelectric layer, wherein the thickness of the ferromagnetic ferroelectric layer is in the range of 20 to 100 nm, the thickness of the ferromagnetic layer is in the range of 3 to 20 nm, and when a voltage is applied to the ferromagnetic ferroelectric layer by the second electrode, an electric polarization is induced in the ferromagnetic ferroelectric layer, and the magnetization of the ferromagnetic ferroelectric layer and the ferromagnetic layer is controlled according to the electric polarization. Preferably, the optical modulation element exhibits a magnetic Kerr rotation angle in the range of 0.5 degrees or more across the entire visible light range. A transparent first electrode may be further disposed on the incident surface side of the ferromagnetic layer.

[0011] The present invention relates to a spatial light modulator including the optical modulation element, pixel selection means connected to the optical modulation element for controlling the direction of magnetization of the ferromagnetic ferroelectric layer for each predetermined pixel, and a first polarization unit for polarizing light incident on the optical modulation element. Preferably, the ferromagnetic ferroelectric layer is not separated for each predetermined pixel. Furthermore, the present invention relates to a display device including the spatial light modulator.

Effects of the Invention

[0012] The optical modulation element of the present invention provides an optical modulation element that exhibits a Kerr rotation angle of 0.5° or more, has a sufficiently bright luminance, and can display a stereoscopic image with a sufficiently wide angular range for three-dimensional viewing. The spatial light modulator of the present invention provides a spatial light modulator including the optical modulation element. The display device of the present invention provides a display device including the spatial light modulator.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic cross-sectional view of a spatial light modulator according to a first embodiment of the present invention. [Figure 2] It is a diagram schematically showing a circuit configuration of a spatial light modulator according to a first embodiment of the present invention. [Figure 3]This is a schematic diagram illustrating the operation of a spatial light modulator according to the first embodiment of the present invention. [Figure 4] This is a schematic cross-sectional view of a spatial light modulator according to a second embodiment of the present invention. [Figure 5] This figure schematically shows the circuit configuration of a spatial light modulator according to a second embodiment of the present invention. [Figure 6] This is a schematic diagram illustrating the operation of a spatial light modulator according to a second embodiment of the present invention. [Figure 7] This is a schematic cross-sectional view of a spatial light modulator according to a third embodiment of the present invention. [Figure 8] This is a schematic diagram illustrating the operation of a spatial light modulator according to a third embodiment of the present invention. [Figure 9] This is a schematic diagram illustrating multiple reflections. [Figure 10] This is a simulation result of the Kerr rotation angle shown in one embodiment of the optical modulation element of the present invention. [Modes for carrying out the invention]

[0014] The present invention will be described in further detail with reference to the figures as appropriate. Unless otherwise specified, the numerical range "X~Y" represents the range from X or greater to Y or less, including both values ​​at either end. Furthermore, when a numerical range is indicated, the upper and lower limits may be combined as appropriate, and the resulting numerical range will also be disclosed. Furthermore, in the drawings, identical elements are given the same reference numerals, and redundant explanations are omitted. Also, the dimensional ratios in the drawings are exaggerated for explanatory purposes and may differ from the actual ratios.

[0015] [Optical Modulator] Figure 1 is a schematic cross-sectional view of a spatial light modulator according to one embodiment of the present invention. The spatial light modulator 100 according to the embodiment includes an optical modulation element 10, a pixel selection means 2, and a first polarization means 30 (see Figure 3). The optical modulation element 10 is driven by an external power supply 40 connected to the outside.

[0016] The optical modulation element 10 is an element that utilizes the magneto-optical effect. The optical modulation element 10 shown in Figure 1 comprises a second electrode 2 facing the incident surface into which light is incident, a ferromagnetic ferroelectric layer 3 disposed on the incident surface side of the second electrode 2, and a ferromagnetic layer 4 disposed on the incident surface side of the ferromagnetic ferroelectric layer 3.

[0017] The optical modulation element of the present invention may have a transparent first electrode on the incident surface side of the ferromagnetic layer 4. The optical modulation element 10 shown in Figure 1 includes the transparent first electrode 1. The transparent first electrode 1 is a transparent electrode that is transparent enough for incident light to reach the ferromagnetic ferroelectric layer 3.

[0018] <1st electrode> Examples of transparent electrode materials used in the first electrode 1 include indium zinc oxide (IZO), indium tin oxide (ITO), tin oxide (SnO2), antimond-doped tin oxide (ATO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), indium oxide (In2O3), indium gallium zinc oxide (IGZO), graphene, and carbon nanotubes. Furthermore, if the incident light reaches the ferromagnetic ferroelectric layer 3, a thin metal layer or the like can be used as the transparent electrode material.

[0019] <Second electrode> Multiple second electrodes 2 are provided facing the first electrode 1. By applying a voltage to the second electrodes 2, the direction of magnetization of the ferromagnetic ferroelectric layer 3 changes. In Figure 1, the voltage is applied between the first electrode 1 and the second electrodes 2. Each region affected by the electric field of one of the second electrodes 2 becomes a single pixel.

[0020] The material of the second electrode 2 is not particularly limited as long as it is electrically conductive. For example, in addition to the material used for the first electrode 1, copper, aluminum, silver, etc., can be used as materials for the second electrode 2.

[0021] The ferromagnetic ferroelectric layer 3 extends uniformly in the plane. That is, it is not separated for each pixel of the spatial light modulator 100. Depending on the application, as a modification, the ferromagnetic ferroelectric layer 3 may be separated for each pixel.

[0022] <Ferromagnetic ferroelectric layer> The ferromagnetic ferroelectric layer 3 contains a multiferroic material. The multiferroic material is a material in which "magnetic order" and "ferroelectric order" coexist. That is, it is a material that has both ferromagnetism and ferroelectricity. By including the multiferroic material in the ferromagnetic ferroelectric layer 3, it is possible to control the direction of magnetization by an electric field and the direction of electric polarization by a magnetic field.

[0023] As the multiferroic material, a substance represented by the following general formula (1) may be used. (A w B x C 1-w-x ) s (L y M z N1 -yーz ) t Ou···(1) In the general formula (1), A, B, and C are each one of the elements Bi, La, Tb, Pb, Y, Cr, Co, Ba, Lu, Yb, or Eu. In the general formula (1), L, M, and N are each one of the elements Fe, Mn, Ni, Ti, Cr, Co, or V. In the general formula (1), w, x, y, and z are real numbers from 0 to 1, and w + x and y + z do not exceed 1. In the general formula (1), s is an integer from 1 to 3, t is an integer from 1 to 3, and n is an integer from 3 to 6.

[0024] Specific examples satisfying the general formula (1) include, for example, BiMnO3, TbMnO3, TbMn2O5, YMnO3, EuTiO3, CoCr2O4, Cr2O3, BiMn 0.5 Ni 0.5 O3, BiFe0.5 Cr 0.5 O3, La 0.1 Bo 0.9 MnO3, La 1-x Bi x Ni 0.5 Mn 0.5 O3, Bi 1-x Ba x FeO, (Bi w Ba x La 1-w-x )s(Fe y Mn 1-y ) t O u , (Bi w Ba x La 1-w-x ) s (Fe y Mn z Ti 1-yーz ) t O u These are some examples.

[0025] The thickness of the ferromagnetic ferroelectric layer is in the range of 20 to 100 nm to enable multiple reflection across the entire visible light region. When the thickness is less than 20 nm, it is suitable for multiple reflection of ultraviolet light. When the thickness exceeds 100 nm, it is suitable for multiple reflection of far-infrared light.

[0026] <Ferromagnetic layer> The ferromagnetic layer 4 is positioned on the incident surface side of the ferromagnetic ferroelectric layer 3. In the spatial light modulator 100 shown in Figure 1, the ferromagnetic layer 4 is positioned on the surface of the ferromagnetic ferroelectric layer 3 that is on the side of the first electrode 1.

[0027] The ferromagnetic layer 4 includes a ferromagnetic material. The constituent material of the ferromagnetic layer 4 may be any of the following materials, including a ferromagnetic material and having the function of a half-mirror that transmits half of visible light and reflects the other half: a metal, a semiconductor, or an insulator, or a combination of these materials may be used.

[0028] To efficiently apply an electric field to the ferromagnetic ferroelectric layer 3, the ferromagnetic layer 4 may be made of a metal and brought to the same potential as the first electrode 1. The ferromagnetic layer 4 may be made of an optically transparent material. Preferably, an insulator with a wide range of material types is used as the transparent material.

[0029] The thickness of the ferromagnetic layer 4 is in the range of 3 to 20 nm. If the thickness is less than 3 nm, the ferromagnetic layer 4 becomes almost transparent, does not reflect visible light, and the Kerr effect does not occur. If the thickness exceeds 20 nm, the ferromagnetic layer 4 becomes silvery and does not transmit visible light like a mirror, so visible light does not reach the ferromagnetic ferroelectric layer 3, and the multiple reflection effect does not occur.

[0030] As the ferromagnetic layer 4, for example, transition metal-based materials, multilayer films of transition metals and noble metals, alloys of transition metals and noble metals, alloys of rare earth metals and transition metals, etc., can be used. In addition, nitride magnetic materials such as MnN and FeN, MnBi alloys, Mn / Bi multilayer films, PtMnSb alloys, Pt / MnSb multilayer films, etc., can be used.

[0031] Examples of transition metal materials include CoFeB, CoFe, Co, Fe, CoFeSi, and CoFeGe. Examples of multilayer films of transition metals and noble metals include Co / Pt multilayer films, Co / Pd multilayer films, Fe / Pd multilayer films, CoFe / Pd multilayer films, and Fe / Pt multilayer films. Examples of alloys of transition metals and noble metals include CoPt alloys, CoPd alloys, FePd alloys, and FePt alloys. Examples of alloys of rare earth metals and transition metals include GdFe alloys, GdCoFe alloys, GdCo alloys, TbFe alloys, and TbFeCo alloys.

[0032] As the ferromagnetic layer 4 containing the insulator ferromagnetic material, for example, yttrium iron garnet (Y3Fe5O 12 ), Bi, which replaces some of the yttrium in yttrium iron garnet with Bi. x Y 3-x Fe5O 12 These are used.

[0033] The ferromagnetic layer 4 is strongly magnetically coupled to the ferromagnetic ferroelectric layer 3 at its interface. That is, when the magnetization direction of the ferromagnetic ferroelectric layer 3 changes, the magnetization direction of the ferromagnetic layer 4 also changes. The magnetization directions of the ferromagnetic ferroelectric layer 3 and the ferromagnetic layer 4 do not necessarily have to be in the same direction. In order to efficiently obtain the magneto-optical effect, it is preferable that the magnetization directions of the ferromagnetic ferroelectric layer 3 and the ferromagnetic layer 4 are the same.

[0034] The ferromagnetic ferroelectric layer 3 has a multiple reflection function of light and a magnetic transfer function of electric field application to the ferromagnetic layer 4. The ferromagnetic layer 4 has a half-mirror function and a Kerr effect derivation function. As a result, a large Kerr rotation angle across the entire visible light range, specifically a Kerr rotation angle of 0.5 degrees or more across the entire visible light range, can be controlled by the electric field. Therefore, the optical modulation element of the present invention can drive a spatial light modulator having a small and numerous dot array with high brightness and low power consumption.

[0035] Here, we will explain multiple reflections using Figure 9. A portion of the incident visible light is reflected by the surface of the ferromagnetic layer 4, and a portion is transmitted through the ferromagnetic layer 4. The transmitted visible light undergoes multiple reflections inside the transparent ferromagnetic ferroelectric layer 3, and each time it is reflected by the lower surface of the ferromagnetic layer 4, the Kerr rotation angle due to the Kerr effect changes in a certain direction repeatedly, and when the visible light finally passes through the ferromagnetic layer 4, it exits the ferromagnetic layer 4 with a huge Kerr rotation angle.

[0036] [Spatial light modulator] The pixel selection means 20 shown in Figure 1 is a MOS-FET. The pixel selection means 20 includes a semiconductor substrate 21, a gate electrode 23, a source electrode 24, a drain electrode 27, and insulators 25 and 26.

[0037] For example, silicon can be used for the semiconductor substrate 21. The pixel selection means 20 shown in Figure 1 has a source region 22a and a drain region 22b in which an n-type dopant is doped in a part of the semiconductor substrate 21 to which a p-type dopant has been added.

[0038] The gate electrode 23 is arranged via the semiconductor substrate 21 and the insulator 25. A voltage is applied to the gate electrode 23, and a channel is formed between the source region 22a and the drain region 22b.

[0039] The source electrode 24 connects the external power supply 40 to the source region 22a. The drain electrode 27 connects the drain region 22b to the second electrode 2.

[0040] The insulators 25 and 26 are positioned between the second electrode 2, the semiconductor substrate 21, the gate electrode 23, and the source electrode 24, insulating them from each other. Although they overlap in Figure 1, the drain electrode 27 is also insulated from the gate electrode 23 and the source electrode 24.

[0041] The first polarizing unit 30 is disposed between the light source and the light modulation element 10. The first polarizing unit 30 can be a known object, such as a polarizing plate.

[0042] A known power supply may be used as the external power supply 40. The external power supply 40 is connected to the optical modulation element 10 and the pixel selection means 20 via the selection element 41.

[0043] The spatial light modulator 100 may be manufactured by known methods. For example, film deposition methods such as sputtering or photolithography may be used.

[0044] Next, the electrical operation of the spatial light modulator 100 will be described using Figures 1 and 2. Figure 2 is a schematic diagram showing the circuit configuration of the spatial light modulator according to the first embodiment of the present invention.

[0045] When the optical modulation element of the present invention includes the first electrode 1, the ferromagnetic ferroelectric layer 3 sandwiched between the first electrode 1 and the second electrode 2 forms a plurality of pixels R. In Figure 2, the plurality of pixels R are arranged in a two-dimensional manner. Each pixel is provided with one pixel selection means 20A. A collection of multiple pixel selection means 20A corresponds to the pixel selection means 20 in Figure 1.

[0046] The source electrode 24 of the one pixel selection means 20A is connected to the source line SL, and the gate electrode 23 is connected to the gate line GL. Also, as described above, the drain electrode 27 is connected to the second electrode 2.

[0047] The current flowing through the source line SL is controlled by the selection element 41. The current flowing through the gate line GL is controlled by the second selection element 42.

[0048] We will explain this in detail using the example of applying a voltage to an arbitrary pixel R. First, the source line SL to which a voltage is applied is selected by the selection element 41. A voltage is then applied from the external power supply 40 to each of the source electrodes 24 connected to the selected source line SL.

[0049] Next, the gate line GL to which a voltage is applied is selected by the second selection element 42. A voltage is applied to the gate electrode 23 connected to the selected gate line GL, and a channel is formed in the semiconductor 21 facing the gate electrode 23. Once the channel is formed, the source region 22a and the drain region 22b are connected.

[0050] In other words, in the pixel selection means 20A located at the intersection of the selected source line SL and the gate line GL, a voltage applied from the external power supply 40 is applied to the second electrode 2 via the channel. As a result, a potential difference is generated between the first electrode 1 and the second electrode 2, and a voltage is applied to the ferromagnetic ferroelectric layer 3 in the selected pixel R.

[0051] Next, the operation of a spatial light modulator, in which a voltage is applied to a selected pixel R and spatial light modulation occurs, will be described. Figure 3 is a schematic diagram illustrating the operation of a spatial light modulator according to the first embodiment of the present invention.

[0052] As described above, a voltage is applied to the selected pixel R. When a voltage is applied, polarization P1 is induced in the ferromagnetic ferroelectric layer 3. The magnetization is then affected by the polarization P1, and the direction of the magnetization changes. As a result, in the selected pixel R1, magnetization M1 that is strongly coupled to the polarization P1 is preferentially distributed.

[0053] When magnetization M1 occurs in the ferromagnetic ferroelectric layer 3, the magnetic moment near magnetization M1 in the ferromagnetic layer 4 located nearby magnetically couples with the magnetic moment of magnetization M1, and magnetization M3 is preferentially distributed in the region of the selected pixel R1 in the ferromagnetic layer 4.

[0054] In contrast, a voltage opposite to that applied to the selected pixel R1 is applied to the non-selected pixels R2, excluding the selected pixel R1. When a voltage in the opposite direction is applied, polarization P2 is induced opposite to polarization P1. The magnetization is then affected by polarization P2, and the direction of magnetization changes. As a result, in the non-selected pixels R2, magnetization M2 with a magnetization direction opposite to that of magnetization M1, which is strongly coupled to polarization P2, is preferentially distributed.

[0055] When magnetization M2 occurs in the non-selected pixel R2 of the ferromagnetic ferroelectric layer 3, the magnetic moment near the magnetization M2 in the ferromagnetic layer 4 located nearby magnetically couples with the magnetic moment of magnetization M2, and magnetization M4, which is in the opposite direction to the magnetization direction of magnetization M3 occurring in the selected pixel R1, is preferentially distributed in the region of the non-selected pixel R2 in the ferromagnetic layer 4.

[0056] Light is shone onto an optical modulation element 10 having multiple pixels whose magnetization direction has been determined. Light L1 emitted from the light irradiation means 31 is polarized light L2 by the first polarizing means 30 in a specific direction. The polarized light L2 passes through the first electrode 1 of the light modulation element 10 and is reflected or diffracted by the ferromagnetic ferroelectric layer 3. When reflected or diffracted, the polarized light L2 rotates due to the magneto-optical Kerr effect depending on the direction of magnetization of the pixel.

[0057] As a result, the polarized light L2 reflected or diffracted by the selected pixel R1 becomes optically rotated light L3 with a Kerr rotation angle of -θk, and the polarized light L2 reflected or diffracted by the non-selected pixel R2 becomes optically rotated light L4 with a Kerr rotation angle of θk.

[0058] For example, if a second polarization means is provided on the output side of optical rotation light L3 and optical rotation light L4, with a polarization setting of 90° for either optical rotation light L3 or optical rotation light L4, the light after passing through the second polarization means is separated into a bright state and a dark state. That is, an image is obtained in which the incident light is modulated into two values ​​of bright and dark by the spatial light modulator 100. Furthermore, by interfering optical rotation light L3 and optical rotation light L4, a holographic image or the like can also be obtained. Such a modulated image or holographic image is used, and the spatial light modulator is used as a display device.

[0059] As described above, the spatial light modulator 100 according to the first embodiment is used, and the magnetization direction of the ferromagnetic ferroelectric layer 3 is controlled by voltage drive. Therefore, lower power consumption is achieved compared to a current-driven spatial light modulator.

[0060] The magnetization direction of the ferromagnetic ferroelectric layer 3 does not change even after the voltage application from the external power supply 40 is stopped, unless another external force is applied. In other words, it has a memory function that records the magnetization. Therefore, there is no need to apply voltage from the external power supply 40 except when driving, which enables further reduction in power consumption.

[0061] The ferromagnetic ferroelectric layer 3 is not separated for each pixel R. Therefore, the size of the pixel R can be freely controlled by the applied voltage intensity. In other words, a more seamless display image can be obtained. Furthermore, a black matrix or the like is not required to separate the pixel R, and a high aperture ratio can be achieved.

[0062] The spatial light modulator 100 according to the first embodiment has a ferromagnetic layer 4. Therefore, a large magnetization intensity can be obtained by combining the ferromagnetic ferroelectric layer 3 and the ferromagnetic layer 4, and large magneto-optical properties can be obtained.

[0063] The present invention is not necessarily limited to the configuration of the spatial light modulator 100 shown as the first embodiment, and various modifications can be made without departing from the spirit of the invention.

[0064] (Second Embodiment) Next, a spatial light modulator according to the second embodiment will be described. Figure 4 is a schematic cross-sectional view of a spatial light modulator according to a second embodiment of the present invention.

[0065] The spatial light modulator 103 according to the second embodiment shown in Figure 4 differs from the spatial light modulator according to the first embodiment in that it is a transmissive type rather than a reflective type. It also differs in that the pixel selection means 20 is a simple matrix rather than an active matrix.

[0066] Since the pixel selection means 20 is a simple matrix, a transistor structure such as a MOS-FET is not required, and the second electrode 2 is arranged on the transparent substrate 60. Both the second electrode 2 and the transparent substrate 60 are transparent. The second electrode can be the same as the first electrode in the first embodiment. The transparent substrate 60 can be an SiO2 substrate, an MgO substrate, a sapphire substrate, or the like.

[0067] First, the configuration of the pixel selection means will be described. As shown in Figures 4 and 5, the spatial light modulator 103 according to the second embodiment selects pixels using a selection element 41 and a third selection element 43. That is, the selection element 41 and the third selection element 43 together constitute the pixel selection means.

[0068] As shown in Figure 5, in the spatial light modulator 103, the first electrode 1 has a plurality of first electrode rows extending in a first direction. The second electrode 2 has a plurality of second electrode rows extending in a second direction intersecting the first direction.

[0069] The selection element 41 selects the second electrode row, and the third selection element 43 selects the first electrode row. When a voltage is applied from the external power supply 40, the voltage is applied to the pixels at the intersection of the selected second electrode row and the selected first electrode row.

[0070] Next, the operation of a transmissive spatial light modulator, which generates spatial light modulation by applying a voltage to a selected pixel R, will be described. Figure 6 is a schematic diagram illustrating the operation of a spatial light modulator according to the second embodiment of the present invention.

[0071] When a voltage is applied to the selected pixel R, polarizations P1 and P2 are generated in the ferromagnetic ferroelectric layer 3, and magnetizations M1 and M2, which are strongly coupled to polarizations P1 and P2 respectively, are preferentially distributed to each pixel. As a result, magnetizations M3 and M4 are preferentially distributed to each pixel in the ferromagnetic layer 4. This is the same as in the spatial light modulator 100 according to the first embodiment.

[0072] Light is shone onto an optical modulation element 10 having multiple pixels whose magnetization directions are determined by magnetizations M1 and M3 and M2 and M4, respectively. Light L1 emitted from the light irradiation means 31 is polarized light L2 by the first polarizing means 30 in a specific direction. The polarized light L2 passes through the first electrode 1 of the light modulation element 10 and is transmitted or diffracted by the ferromagnetic ferroelectric layer 3. When transmitted or diffracted, the polarized light L2 rotates due to the Faraday effect depending on the direction of magnetization of the pixels.

[0073] As a result, polarized light L2 transmitted or diffracted through the selected pixel R1 becomes optically rotated light L5 with a rotation angle of -θk, and polarized light L2 transmitted or diffracted through the non-selected pixel R2 becomes optically rotated light L6 with a rotation angle of θk.

[0074] For example, if a second polarization means is provided on the output side of optical rotation light L5 and optical rotation light L6, with a polarization setting of 90° for either optical rotation light L5 or optical rotation light L6, the light after passing through the second polarization means is separated into a bright state and a dark state. That is, an image is obtained in which the incident light is modulated into two values, bright and dark, by the spatial light modulator 103. Furthermore, by interfering optical rotation light L5 and optical rotation light L6, a holographic image or the like can also be obtained. The spatial light modulator can also be used as a display device using such modulated images or holographic images.

[0075] As described above, the spatial light modulator 103 according to the second embodiment enables spatial light modulation even in a transmissive type. Furthermore, since the pixel selection means is a simple matrix, the spatial light modulator is easy to manufacture.

[0076] (Third embodiment) Next, a spatial light modulator according to the third embodiment will be described. Figure 7 is a schematic cross-sectional view of a spatial light modulator according to a third embodiment of the present invention.

[0077] The spatial light modulator 104 according to the third embodiment shown in Figure 7 differs from the spatial light modulator 103 according to the second embodiment in that it is of the reflective type. Furthermore, it differs from the spatial light modulator 100 according to the first embodiment in that the pixel selection means 20 is a simple matrix rather than an active matrix.

[0078] The spatial light modulator 104 according to the third embodiment is of the reflective type. Therefore, unlike the spatial light modulator 103 according to the second embodiment, any second electrode 2 and substrate 61 can be used.

[0079] Figure 8 is a schematic diagram illustrating the operation of a spatial light modulator according to a third embodiment of the present invention. The method of selecting pixels, controlling the orientation of polarizations P1, P2 and magnetizations M1, M2 generated in the ferromagnetic ferroelectric layer 3 within the pixels, and controlling the orientation of magnetizations M3, M4 generated in the ferromagnetic layer 4 within the pixels is the same as in the spatial light modulator 103 according to the second embodiment. The method of optical modulation is the same as in the spatial light modulator 100 according to the first embodiment.

[0080] As described above, using the spatial light modulator 104 according to the third embodiment, the magnetization direction of the ferromagnetic ferroelectric layer 3 can be controlled by voltage drive. Therefore, lower power consumption can be achieved compared to a current-driven spatial light modulator. In addition, since the pixel selection means is a simple matrix, the spatial light modulator can be easily manufactured. [Examples]

[0081] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0082] The second electrode 2 uses Pt as the material, and La as the multiferroic material. 1-x Bi x Fe 0.75 Co 0.25 When visible light is shone on an optical modulation element comprising a ferromagnetic ferroelectric layer 3 containing O3 and having a thickness of 30 nm, and a ferromagnetic layer 4 made of a CoPt alloy film and having a thickness of 10 nm, half of the visible light passes through the CoPt alloy film, and the passed visible light is converted into La with a visible light transmittance of 80%. 1-x Bi x Fe 0.75 Co 0.25 The calculation was performed under conditions of multiple reflections within the O3 layer. The results are shown in Figure 10.

[0083] Although the device structure of the optical modulation element is very simple, the optical modulation element exhibits a large Kerr rotation angle of 0.5 degrees or more across the entire visible light region. [Explanation of symbols]

[0084] 1...First electrode, 2...Second electrode, 3...Ferromagnetic ferroelectric layer, 4...Ferromagnetic layer 10...Optical modulation element, 20...Pixel selection means, 20A...Pixel selection element, 21...Semiconductor substrate, 22a...Source region, 22b...Drain region, 23...Gate electrode, 24...Source electrode, 25, 26...insulator, 27...drain electrode, 30...first polarization means, 31...light irradiation means, 40...External power supply, 41...Selection element, 42...Second selection element, 43...Third selection element, 50...Additional capacitor, 51...Third electrode, 60...Transparent substrate, 61...Substrate, 100, 103, 104...Spatial light modulator, SL...Source line, GL...Gate line, R...Pixel, R1...Selected pixel, R2...Deselected pixel, L1...Light, L2...Polarized light, L3, L4, L5, L6...Optical rotation light, M1, M2, M3, M4...Magnetization, P1, P2... Polarization.

Claims

1. The second electrode facing the incident surface into which light enters, A ferromagnetic ferroelectric layer is disposed on the incident surface side of the second electrode, and The ferromagnetic layer comprises a ferromagnetic layer positioned on the incident surface side of the ferromagnetic ferroelectric layer, The thickness of the ferromagnetic ferroelectric layer is in the range of 20 to 100 nm, and the thickness of the ferromagnetic layer is in the range of 3 to 20 nm. An optical modulation element in which, when a voltage is applied to the ferromagnetic ferroelectric layer by the second electrode, electric polarization is induced in the ferromagnetic ferroelectric layer, and the magnetization of the ferromagnetic ferroelectric layer and the magnetic layer is controlled in accordance with the electric polarization.

2. An optical modulation element according to claim 1, wherein the optical modulation element exhibits a magnetic Kerr rotation angle of 0.5 degrees or more in the entire visible light range.

3. An optical modulation element according to claim 1, wherein a transparent first electrode is further disposed on the incident surface side of the magnetic layer.

4. An optical modulation element according to any one of claims 1 to 3, A pixel selection means connected to the optical modulation element for controlling the magnetization direction of the ferromagnetic ferroelectric layer for each predetermined pixel, and A spatial light modulator comprising a first polarization unit for polarizing light incident on the aforementioned optical modulation element.

5. A spatial light modulator according to claim 4, wherein the ferromagnetic ferroelectric layer is not separated for each predetermined pixel.

6. A display device comprising a spatial light modulator as described in claim 4.

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