JP2012141402A - Spatial light modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetooptical type spatial light modulator which is improved in selectivity with respect to pixels.SOLUTION: A spatial light modulator 10 is configured such that a plurality of pixels 4 arrayed on a substrate 7 each includes a magnetic thin line 1 formed by forming a magnetooptical material in a thin-line shape, and a magnetic transfer film 5 is provided on the substrate 7 while being in contact with an undersurface of the magnetic thin line 1; a magnetic wall DW between two magnetic domains D0, D1 moves in a thin-line direction with currents supplied by a pair of electrodes 2, 3 connected to both ends of the magnetic thin line 1, and one of the magnetic domains D0, D1 is selectively made to reach an incidence region 1r of light, thereby inverting a magnetization direction of the incidence region 1r. The magnetization direction of the magnetic thin line 1 is transferred to the magnetic transfer film 5, so the magnetic transfer film 5 right below the incidence region 1r is inverted in magnetization direction together with the magnetic thin line 1. Light which is transmitted through the substrate 7 to be made incident optically rotates large through Faraday effect when transmitted through the magnetic transfer film 5, is reflected by the magnetic thin line 1, and optically rotates to exit when transmitted through the magnetic transfer film 5 again.

Description

  The present invention relates to a spatial light modulator that emits incident light by spatially modulating the phase and amplitude of the light by a magneto-optic effect.

  A spatial light modulator uses an optical element (light modulation element) as a pixel and arranges it two-dimensionally in a matrix to spatially modulate the phase and amplitude of light. Display technology and recording technology Widely used in such fields. Liquid crystal is conventionally used as a spatial light modulator, but in recent years, a magneto-optical spatial light modulator using a magneto-optical material, which is expected to be capable of high-speed processing and pixel miniaturization of 1 μm or less. Development is underway.

  In a magneto-optic spatial light modulator (hereinafter referred to as a spatial light modulator), when light incident on a magnetic material is transmitted or reflected, the direction of polarization is changed (rotation) and emitted (in the case of reflection) Uses the Kerr effect) and uses a magneto-optic material that is particularly effective among magnetic materials. That is, assuming that the magnetization direction of the light modulation element in the selected pixel (selected pixel) is different from the magnetization direction of the light modulation element in the other pixel (non-selected pixel), the light emitted from the selected pixel and the non-selected pixel The emitted light causes a difference in the rotation angle (rotation angle) of the polarized light. As a method of changing the magnetization direction of such a light modulation element, in addition to a magnetic field application method in which a magnetic field is applied to the light modulation element, in recent years, a spin injection method in which spin is injected by supplying a current to the light modulation element ( For example, there is Patent Document 1). However, a light modulation element (spin injection light modulation element) that changes the magnetization direction by spin injection enables further pixel miniaturization, while a layer (magnetization free layer) in which the magnetization direction in the spin injection light modulation element changes. ) Has a film thickness of about several to several tens of nanometers. With such a thin magnetic material, it is difficult to rotate light greatly, that is, to increase the degree of light modulation.

  Accordingly, the inventors of the present invention have made it easy to form two or more magnetic domains in a thin wire direction in a magnetic material (magnetic thin wire) processed into fine wires, and the domain walls that delimit these magnetic domains supply current to the magnetic wires. The spatial light modulator which uses a magnetic wire as a light modulation element is developed using the magnetic domain wall movement in the magnetic wire which moves by doing (patent document 2). Specifically, as shown in FIG. 11, when a current is supplied in the direction of the thin line by a pair of electrodes 102 and 103 connected to both ends of the magnetic thin line 1, the domain wall DW moves in the direction opposite to the direction of the current, The magnetization direction in the incident region 1r is reversed. Since the magnetic fine wire only needs to have a sufficiently long length in the fine wire direction with respect to the width and thickness, the light can be rotated greatly by the Faraday effect with a sufficient thickness to transmit light.

JP 2008-83686 A JP 2010-20114 A

  When a spatial light modulator having a magnetic wire as a light modulation element as in Patent Document 2 is a reflective spatial light modulator, the optical rotation angle is a Kerr rotation angle due to the Kerr effect of the magnetic wire, and the magnetic material is Dependent. For example, even a Co / Pd multilayer film capable of obtaining a relatively large Kerr rotation angle is about 0.25 °, and there is room for further improvement in order to obtain a sufficient degree of light modulation.

  The present invention has been made in view of the above problems, and an object thereof is to provide a reflective spatial light modulator having a further improved degree of light modulation.

  In order to solve the above-mentioned problems, the present inventors have conceived that light is greatly rotated by superimposing a magnetic transfer film having a large Faraday effect on a magnetic wire and transmitting light therethrough.

  A spatial light modulator according to the present invention includes a substrate that transmits light, a plurality of pixels arranged in a matrix on the substrate, a pixel selection unit that selects one or more pixels from the plurality of pixels, Current supply means for supplying a predetermined current to the pixel selected by the pixel selection means, and changes the polarization direction of the light incident on the pixel selected by the pixel selection means through the substrate. The light is reflected and emitted. The pixel includes a magnetic thin line formed of a magneto-optical material in a thin line shape and two or more magnetic domains formed continuously in the thin line direction, and a pair of electrodes connected in the vicinity of both ends of the magnetic thin line. The magnetic thin wire is provided with an incident region, which is a region partitioned in the thin wire direction for allowing the light to enter, at a predetermined position, and the current is supplied in the thin wire direction through the pair of electrodes. As a result, the domain wall generated between the two adjacent magnetic domains moves in the direction of the thin line, and one of the two magnetic domains reaches the incident region. The spatial light modulator further includes a magnetic transfer film between the substrate and the plurality of pixels in contact with the surface of the magnetic wire on the substrate side.

  With this configuration, the spatial light modulator is provided with a magnetic transfer film having a large Faraday effect in contact with the light incident side of the magnetic wire, so that the light reflected by the magnetic wire passes through the magnetic transfer film and is incident. The emitted light is greatly rotated and emitted.

  Furthermore, in the spatial light modulator according to the present invention, it is preferable that the magnetic wire is formed in a shape that is locally confined outside the incident region. Or it is preferable that the said magnetic fine wire is formed in the fine wire shape bent outside the said incident area | region.

  With such a configuration, when the current supply is stopped, the magnetic domain wall reaches the constricted or bent portion of the magnetic thin wire and stops, so that there is no magnetic domain wall in the light incident area, so that one magnetic domain occupies the entire area. Thus, the light emitted from one pixel can be stably rotated at the same angle.

  Furthermore, in the spatial light modulator according to the present invention, the pair of electrodes are connected on the magnetic wire, and one of the pair of electrodes of the pixels arranged in the same row is one wiring in the plurality of pixels. The other of the pair of electrodes of the pixels arranged in the same column is preferably connected to one wiring disposed on the wiring via an insulating layer.

  With this configuration, a current can be supplied to each of a plurality of pixels that are two-dimensionally arranged in a matrix form using a grid-like wiring. In addition, since all the electrodes and wirings are arranged on the opposite side of the light incident / exit surface, the light is not blocked by these wirings, etc., so that the area ratio (aperture ratio) of the incident region in the pixel is increased. be able to.

  The spatial light modulator according to the present invention can be a reflective spatial light modulator having a large degree of light modulation.

It is a bottom view showing typically the composition of the spatial light modulator concerning a 1st embodiment. It is a schematic diagram explaining the structure of the display apparatus using the spatial light modulator which concerns on 1st Embodiment, and the state of pixel selection, and is a figure corresponding to AA sectional drawing of FIG. It is a top view which illustrates typically the movement of the domain wall in the magnetic fine wire of the spatial light modulator which concerns on 1st Embodiment. It is a schematic diagram explaining the manufacturing method of the pixel array of the spatial light modulator which concerns on this invention, (a) is sectional drawing in a magnetic wire formation process, (b) And (c) is a top view in a X contact hole formation process, The BB sectional drawing, (d) and (e) are the top views in the X electrode formation process, and the BB sectional drawing. It is a schematic diagram explaining the manufacturing method of the pixel array of the spatial light modulator which concerns on this invention, (a) is sectional drawing in a Y contact hole formation process, (b), (c) and (d) are Y electrode formation processes. FIG. 3 is a plan view, a BB cross-sectional view, and a bottom view thereof. It is a schematic diagram explaining the structure of a display apparatus using the spatial light modulator which concerns on the modification of 1st Embodiment, and the state of pixel selection, and is a figure corresponding to the AA sectional drawing of FIG. It is a bottom face schematic diagram of a pixel array of a spatial light modulator concerning a 2nd embodiment. It is a bottom face schematic diagram of a pixel array of a spatial light modulator concerning a 3rd embodiment, (a) is a 3rd embodiment and (b) is a modification of a 3rd embodiment. It is a top view which illustrates typically the movement of the magnetic wall in the magnetic fine wire of the spatial light modulator which concerns on 3rd Embodiment. It is a graph which shows the Kerr rotation angle characteristic with respect to the external magnetic field of the sample of a spatial light modulator, (a) is an Example which concerns on this invention, (b) is a comparative example. It is a cross-sectional schematic diagram of the spatial light modulator which applied the conventional magnetic fine wire to the pixel.

  Hereinafter, embodiments for realizing a spatial light modulator according to the present invention will be described with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the spatial light modulator 10 includes a pixel array 40 including a plurality of pixels 4 arranged in a matrix, and a current control unit 90 that selects and drives one or more pixels 4 from the pixel array 40. And comprising. The pixel in this specification refers to a means for presenting information (bright / dark) in the minimum unit of display by the spatial light modulator. The bottom surface (lower surface) in this specification is a light incident surface of the spatial light modulator, and the spatial light modulator 10 reflects light incident on the pixel 4 (pixel array 40) from below and reflects the light. It is a reflective spatial light modulator that modulates and emits downward.

  As shown in FIG. 2, the pixel array 40 is formed by laminating the magnetic transfer film 5 on the entire surface of the substrate 7 and further arranging the pixels 4 thereon. Since the substrate 7 and the magnetic transfer film 5 are the entire surface of the pixel array 40 shown in FIG. 1, the illustration is omitted in FIG. Here, a pixel array of a general spatial light modulator is about 300,000 pixels of 640 × 480 in a VGA (Video Graphics Array) which is one kind of screen display standard, for example, but is simplified in this specification. For the sake of explanation, as shown in FIG. 1, the pixel array 40 is shown as a configuration including 16 pixels 4 of 4 rows × 4 columns. The pixel array 40 has four striped X electrodes 2 extending in the column (vertical) direction in plan view, and is also striped on the X electrodes 2 and orthogonal to the X electrodes 2 in plan view. Thus, four Y electrodes 3 extending in the row (lateral) direction are provided, and one pixel 4 is provided for each intersection of the X electrode 2 and the Y electrode 3.

  In such a pixel array 40, four pixels 4 arranged in the column direction share one X electrode 2, and four pixels 4 arranged in the row direction share one Y electrode 3. It becomes a shared structure. The pixel 4 is provided with a thin line-shaped magnetic body (hereinafter referred to as a magnetic thin line) 1 along one diagonal line of the pixel array 40 in contact with the magnetic transfer film 5, and the magnetic thin line 1 has both ends connected to the pixel. The X electrode 2 and the Y electrode 3 of different combinations for every four are connected. The X electrode 2 and the Y electrode 3 are collectively referred to as electrodes 2 and 3 as appropriate. The wiring pitch, that is, the pixel size (pixel pitch) of the X electrode 2 and the Y electrode 3 depends on the wavelength of incident light (laser light in FIG. 2), but is preferably about 0.25 μm or more. In the pixel array 40, the region (gap) where the magnetic thin wire 1 and the electrodes 2 and 3 are not present, that is, the blank portion (from the top surface of the magnetic transfer film 5 to the top of the Y electrode 3) in FIG. (See FIG. 5 (c)).

  As shown in FIG. 1, the current control unit 90 controls the X electrode selection unit 92 that selects the X electrode 2, the Y electrode selection unit 93 that selects the Y electrode 3, and the electrode selection units 92 and 93. A pixel selection unit (pixel selection unit) 94 and a power source (current supply unit) 91 that supplies current to the electrodes 2 and 3 are provided. As these, known ones can be applied, and appropriate voltage / current is supplied to the magnetic wire 1.

The X electrode selection unit 92 selects one or more of the X electrodes 2, and the Y electrode selection unit 93 selects one or more of the Y electrodes 3, and each supplies a predetermined current from the power source 91. The pixel selection unit 94 selects, for example, one or more specific pixels 4 of the pixel array 40 based on an external signal (not shown), and connects the electrodes 2 and 3 connected to the selected pixel 4 (magnetic thin line 1). The selection units 92 and 93 are selected. The power supply 91 supplies a current to the magnetic thin wire 1 in the selected pixel 4 from the X electrode 2 to the Y electrode 3 and in either direction. The current supplied to the magnetic wire 1 is preferably a DC pulse current having a pulse width of 10 ns to 10 μs and a current density of 10 ⁵ to 10 ¹³ A / m ² . According to the supply of the pulse current, it is easy to control the moving distance of the domain wall described later. Moreover, since the magnetic thin wire 1 generates heat when supplied with a continuous current, it is desirable to apply a pulse current. With such a configuration, a specific pixel 4 is selected, and a current is supplied to the magnetic thin wire 1 of the pixel 4 to perform the operation described later.

(Magnetic wire)
The magnetic thin wire 1 has a magnetization direction in a predetermined region divided in the thin wire direction as either one direction or the opposite direction, so that when the light incident on this region is reflected, the polarization direction is binarized. The light modulation element of the spatial light modulator 10 is changed (rotates at a binary angle). An area where light is incident on the magnetic thin line 1 and is divided in the direction of the thin line is referred to as an incident area 1r (see FIGS. 3A and 3C). The incident region 1r is a region at a position designated in advance in the magnetic thin wire 1, and is a region for extracting light that has been incident on the pixel 4 and rotated at a binary angle. As shown in FIG. 2, the magnetic wire 1 has two magnetic domains D1 and D0 showing magnetization in opposite directions, which are continuously formed in the thin wire direction, and a domain wall DW is generated so as to separate these magnetic domains D1 and D0. ing. As will be described later, the domain wall DW moves in the thin wire direction by supplying current to the magnetic thin wire 1 in the thin wire direction and reaches either one of the outer sides of the incident region 1r, so that the magnetization direction in the incident region 1r is changed. Change (invert).

  A known ferromagnetic material can be applied to the magnetic wire 1, preferably a material having a high light reflectance, and more preferably a material having a large magneto-optic effect (Kerr effect). Specifically, as an in-plane magnetic anisotropic material, a transition metal selected from Ni, Fe, Co, a transition metal alloy such as Ni—Fe, Ni—Fe—Mo, Co—Cr, or Co—Pt, etc. And alloys with Pd, Pt, and Cu. Perpendicular magnetic anisotropic materials include multilayer films in which transition metals such as Co / Pd multilayer films and Pd, Pt, Cu are repeatedly laminated, and rare earth metals such as Tb-Fe-Co, Gd-Fe, and transition metals. Alloy (RE-TM alloy). The magnetic wire 1 may further include a protective layer (not shown) made of Ru or the like on the uppermost layer or the lowermost layer. These materials are formed into a film by a known method such as a sputtering method, and are formed into the following fine wire shape by photolithography and etching or lift-off to form the magnetic wire 1.

  The shape of the magnetic wire 1 is a thin wire that is sufficiently long with respect to the thickness and width. In the present embodiment, in the pixel 4, in order to increase the length of the magnetic thin line 1 in the thin line direction, the thin line direction is inclined 45 ° in a direction parallel to the diagonal line of the pixel array 40, that is, in plan (bottom) view. However, it is not limited to this. As for the size of the magnetic thin wire 1, a thickness (film thickness) of 70 nm or less and a width of 300 nm or less are preferable because the magnetic domains can be easily divided only in the thin wire direction during formation (manufacturing). In the present embodiment (see FIGS. 2 and 3), since the magnetic wire 1 is made of an in-plane magnetic anisotropic material, it becomes a magnetic domain of magnetization in one direction along the direction of the thin wire and in the opposite direction. As shown in FIG. 6, the magnetic wire 1A made of a perpendicular magnetic anisotropic material becomes a magnetic domain in the magnetization direction (upward and downward) along the thickness direction. In addition, magnetic thin wires having a thickness and width larger than the above may be formed by dividing a magnetic domain in the width direction or the like, but by applying an external magnetic field, the magnetic domain is divided only in the thin line direction. Can be in a state. Further, as the thickness and width (cross-sectional area) of the magnetic wire 1 are smaller, the pixel can be operated with a smaller current (see below). On the other hand, when the thickness of the magnetic wire 1 is less than 30 nm, incident light is transmitted and the amount of reflected light (emitted light) is reduced. The width of the magnetic wire 1 depends on the wavelength of the incident light (laser light shown in FIG. 2), but is preferably about 100 nm or more, and if it is too narrow with respect to the size of the pixel 4 (pixel pitch). Of the light incident on the pixel 4, less light is reflected by the magnetic wire 1 and rotated. Similarly, the length of the magnetic wire 1 in the thin wire direction is preferably sufficiently long. In particular, the incident region 1r is preferably about 100 nm or more depending on the wavelength. Note that the ratio of the area of the region where the light rotated at any one of the two selected angles is emitted with respect to the area of the pixel 4 is defined as the aperture ratio of the pixel 4. In principle, the region where the light rotated at any one of the angles is emitted is the lower surface (reflecting surface) of the incident region 1r of the magnetic wire 1. Therefore, in order to increase the aperture ratio in the pixel 4, the magnetic fine wire 1 is preferably provided with a large incident region 1r, that is, a long length in the fine wire direction.

  Further, as shown in FIG. 3, the magnetic fine wire 1 is preferably formed in a shape constricted on both sides outside the incident region 1r. In these constricted portions (constricted portions) 1c1 and 1c2, a domain wall DW is easily generated as described later, and is easily fixed (trapped) when the supply of current is stopped. Therefore, the domain wall DW is formed in the incident region 1r. As a result, the magnetic field occupies the entire incident region 1r when the current is stopped. As described above, since the magnetic thin wire 1 preferably has a wide incident region 1r, the entire region sandwiched between the constricted portion 1c1 and the constricted portion 1c2 is preferably used as the incident region 1r. In other words, the constricted portions 1c1, It is preferable to provide the incident region 1r so as to be separated in the thin line direction by 1c2.

  The fact that the magnetic wire 1 is formed in a constricted shape means that the cross-sectional area (cross-section perpendicular to the thin wire direction) is locally small. In the present embodiment, the magnetic fine wire 1 is formed by denting the side surfaces at the constricted portions 1c1 and 1c2 so as to be narrow in a plan view. What is necessary is just to become a shape with the constriction (4 dents) of a location. In the present embodiment, the constricted portions 1c1 and 1c2 are recessed on both side surfaces, but only one side surface may be recessed. Further, in the modified example shown in FIG. 6 described later, the constricted portions 1c1 and 1c2 are shown in a concave shape on the upper surface of the magnetic wire 1A for easy understanding of the position in the sectional view, but the magnetic wire 1A (1) is actually used. May be formed locally thin, for example, after the magnetic fine wires 1 and 1A are formed into a thin wire shape (a long and narrow rectangle in a plan view), the surface thereof may be locally shaved. It is preferable that the narrow portions 1c1 and 1c2 have a width or thickness that is narrower or thinner in a range of 20 to 98% in cross-sectional area than other portions. Further, the positions of the constricted portions 1c1 and 1c2 are 5 to 40% of the total length (length in the fine line direction) of the magnetic thin wire 1 from the respective ends of the magnetic thin wire 1, and the length between the constricted portions 1c1 and 1c2 is 30 of the same total length. It is preferable to set it to -90%. The distances from the respective ends of the magnetic fine wires 1 of the two constricted portions 1c1 and 1c2 may not be equal, and only one constricted portion may be formed only on one end side of the magnetic fine wire 1.

(electrode)
The X electrode 2 and the Y electrode 3 are connected to the magnetic wire 1 in order to supply a current in the direction of the wire to the magnetic wire 1 as a pair of electrodes. For this reason, the connection positions of the magnetic thin wires 1 in the thin wire direction are not defined, but the electrodes 2 and 3 may be connected in the vicinity of both ends. Since the supplied current flows between the connecting portions of the magnetic thin wires 1 between the electrodes 2 and 3 and the domain wall is movable as will be described later, the effective thin wires of the magnetic thin wires 1 are connected between the connecting portions of the electrodes 2 and 3. It can be said to be the direction length. Further, the connection surface of the electrodes 2 and 3 in the magnetic wire 1 is not limited, but the upper surface of the magnetic wire 1 is preferable as shown in FIG. By connecting both the electrodes 2 and 3 to the upper surface of the magnetic wire 1, the magnetic wire 1 is formed directly on the magnetic transfer film 5 formed on the entire surface of the substrate 7, and the entire lower surface of the magnetic wire 1 is formed. The magnetic transfer film 5 can be contacted. Therefore, the electrodes 2 and 3 are connected to the upper surface of the magnetic thin wire 1 downward from the stripe-like wiring of the pixel array 40 shown in FIG. 1 via the interlayer regions 62 and 61 as shown in FIG. In the present specification, the X electrode 2 and the Y electrode 3 are connected to the magnetic wire 1 for each pixel 4 (terminals of the magnetic wire 1) and stripes extending vertically and horizontally in the pixel array 40. Part (referred to as a wiring part as appropriate). The electrodes 2 and 3 are made of a general metal material for electrodes such as metals such as Cu, Al, Ta, Cr, W, Ag, Au, and Pt, and alloys thereof, and are formed by sputtering or the like, photolithography, etc. Is formed into a stripe shape. The thicknesses and widths of the electrodes 2 and 3 are set by the pixel pitch, material, supplied voltage / current, and the like.

(Magnetic transfer film)
The magnetic transfer film 5 is easily magnetized with external magnetism, and is particularly strongly influenced by the magnetism of the magnetic material in contact therewith. Therefore, as shown in FIG. 2, the magnetic transfer film 5 shows the same magnetization direction in the region immediately below the magnetic domains D0 and D1 of the magnetic wire 1 in the region where the magnetic wire 1 is in contact with the upper surface. Magnetic domains are formed, and domain walls that delimit the magnetic domains are generated. Therefore, if the magnetic domain D0, D1 expands or contracts in accordance with the movement of the domain wall DW in the magnetic wire 1 and the magnetization direction in a region where the magnetic wire 1 is changed, the magnetic transfer film 5 immediately below the region correspondingly changes. The magnetization direction of swiftly changes. The magnetic transfer film 5 may be formed on the entire surface of the pixel array 40 (substrate 7) because the magnetization direction changes only in the region immediately below where the magnetic thin wires 1 are arranged. Alternatively, it may be processed into the same plan view shape when the magnetic wire 1 is formed. With respect to the light incident on the pixel 4, the optical rotation angle of the reflected light is as small as less than 1 ° only at the Kerr rotation angle reflected from the magnetic wire 1. By doing so, the difference in the direction of polarization of the outgoing light due to the difference in the magnetization direction is expanded to improve the magnetic detection accuracy.

The magnetic transfer film 5 is made of an insulating magnetic material having a low coercive force and a large magneto-optical effect (a large Faraday rotation angle), and a material having a high transmittance is preferable. Specific examples of such a material include a magnetic garnet film such as yttrium iron garnet (Y ₃ Fe ₅ O ₁₂ : YIG), and in particular, a bismuth-substituted magnetic garnet (Y _{3 -X} Bi _x Fe ₅ O ₁₂ : Bi-YIG) is preferable because the Faraday rotation angle is as large as about 5 ° / μm (wavelength: 532 nm). A magnetic garnet film can be manufactured, for example, by forming a film on a Gd ₃ Ga ₅ O ₁₂ (gadolinium gallium garnet: GGG) single crystal substrate by a liquid phase epitaxy (LPE) method. The pixel 4 can be formed on the substrate 7 with the magnetic transfer film 5 formed thereon. Alternatively, the magnetic transfer film 5 is applied to a glass substrate or the like by a metal organic decomposition (MOD) method or a metal organic chemical vapor deposition (MOCVD) method which is a kind of spin coat sintering method. Can also be formed. The magnetic transfer film 5 has an easy axis along the magnetization direction of the magnetic wire 1, that is, in the present embodiment, the direction of the magnetic wire 1 (refer to the manufacturing method described later). The film thickness of the magnetic transfer film 5 is not particularly limited, and the Faraday rotation angle can be proportionally increased as the thickness is increased. On the other hand, the light is absorbed and the emitted light is attenuated. About 1 to 2 μm is preferable.

(Insulating material)
The insulating member 6 is formed between the magnetic thin wires 1 and 1, between the X electrodes 2 and 2 and between the Y electrodes 3 and 3, between the magnetic thin wire 1 and the X electrode 2 (interlayer region 61), and between the X electrodes 2 And the Y electrode 3 (interlayer region 62), and the upper surface of the Y electrode 3 may be covered. The insulating member 6 is made of a known insulating material such as SiO ₂ or Al ₂ O ₃ , and the same material may not be applied to the entire pixel array 40.

(substrate)
The substrate 7 is made of a transparent material so as to transmit light incident on the pixel 4 and further transmit light emitted from the pixel 4. For example, a known transparent substrate such as SiO ₂ , magnesium oxide (MgO), or glass is used. Materials. Further, when the GGG substrate is applied as described above, the magnetic transfer film 5 can be formed by the LPE method.

(Light absorption film)
As shown in FIG. 2, the lower surface (back surface) of the substrate 7 may be covered with a light absorbing film 8 (not shown in FIG. 1). The light absorption film 8 shields the light incident on the spatial light modulator 10 so that the light does not enter other than the incident region 1 r of each magnetic wire 1 of the pixel 4. Specifically, the light reflected by the region other than the incident region 1r of the magnetic wire 1 and the light transmitted through the region other than the region immediately below the incident region 1r (hereinafter referred to as the incident region 5r) of the magnetic transfer film 5 are the pixel array 40. Do not exit from Therefore, the light absorption film 8 is formed with a hole having a predetermined shape (opening region 8r, see FIG. 5D) for each pixel 4. The opening region 8r of the light absorbing film 8 is designed in shape and position in the pixel 4 according to the optical path of light (incident light and light reflected by the magnetic wire 1) transmitted through the incident region 5r of the magnetic transfer film 5. . Examples of such a light absorbing film 8 include known black films such as carbon, bismuth, manganese, and ferrite. Films are formed by a known method such as a coating method, and incident light and outgoing light are obtained by lithography and etching. An opening region 8r through which the light passes is formed. Further, since it is sufficient that incident light and outgoing light are not transmitted through the lower surface of the substrate 7, a light reflecting film (not shown) may be used instead of the light absorbing film 8, and Al, Au, Ag, Pt, etc. are applied. can do.

(Pixel array manufacturing method)
An example of a method for manufacturing a pixel array of a spatial light modulator according to the present invention will be described with reference to FIGS. In this description, vertical and horizontal indicate directions in the plan views of FIGS.

  First, the magnetic transfer film 5 is formed on the entire surface of the substrate 7. As described above, a GGG substrate is applied as the substrate 7, and a magnetic garnet film is formed on the entire surface by the LPE method (not shown). Here, in the magnetic garnet film formed on the GGG substrate by the LPE method, the easy axis of magnetization tends to be in the direction perpendicular to the film surface. Therefore, annealing is performed while applying a sufficiently large magnetic field along the direction of the fine magnetic wire 1 to be formed later, so that the magnetic transfer film 5 with the easy magnetization axis lying in the in-plane direction is obtained.

  Next, as shown in FIG. 4A, a ferromagnetic material is formed and formed on the surface of the magnetic transfer film 5 on the substrate 7 by a known method, and two constricted portions 1c1, 1c2 (FIG. 3 (a)) is formed, and a thin magnetic wire 1 (see FIG. 4 (b)) is formed. Next, an insulating material is deposited as the insulating member 6 between the magnetic wires 1 and 1 and on the magnetic wire 1 (interlayer region 61). 4B and 4C, contact holes V1 and V1 are formed on the insulating member 6 in the vicinity of both ends of the magnetic wire 1 so that the magnetic wire 1 is exposed.

  Next, a metal electrode material is deposited on the insulating member 6, and as shown in FIGS. 4D and 4E, the contact hole V1 at one end of the magnetic wire 1 is filled, and the magnetic wire 1 is formed in the vertical direction. , 1 is formed, and an X electrode 2 having a wiring portion for connecting the two is formed. At the same time, a contact hole V1 at the other end of the magnetic wire 1 is filled, and a metal layer 31 for connecting to the Y electrode 3 described later is formed. Next, an insulating material is deposited as the insulating member 6 between the X electrodes (wiring portions) 2 and 2 and on the X electrode 2 (interlayer region 62). Then, as shown in FIG. 5A, a contact hole V2 is formed on the metal layer 31 of the insulating member 6 so that the metal layer 31 is exposed.

  Next, a metal electrode material is formed on the insulating member 6, and as shown in FIGS. 5B and 5C, the contact hole V2 is filled and the metal layers 31, 31 are connected in the lateral direction. A Y layer 3 is formed by forming a metal layer 32 having a wiring portion. Then, as shown in FIG. 5C, the space between the Y electrodes (wiring portions) 3 and 3 is filled with an insulating material, and further an insulating material is deposited so as to cover the Y electrode 3. To do. Finally, as shown in FIGS. 5C and 5D, the lower surface of the substrate 7 is covered with the light absorption film 8 except for the opening region 8r for each pixel 4 (for each magnetic wire 1), and the pixel array 40 is formed. It becomes.

  Here, the inside of the magnetic material is divided into a plurality of magnetic domains so that the magnetic energy is stable. If the magnetic wire 1 is sufficiently thin (thickness and width), In (manufacturing), the magnetic domains in all the magnetic thin wires 1 of the pixel array 40 are likely to be divided only in the direction of the thin wires. Further, as shown in FIG. 3A, when two constricted portions 1c1 and 1c2 are formed on the magnetic thin wire 1, any of the constricted portions 1c1 and 1c2 is provided in each of the magnetic thin wires 1 of the pixel array 40. A domain wall is generated on one or both of them, and two or three magnetic domains are generated in the direction of the thin line (not shown). Therefore, as initialization work (reset), a magnetic field of about several tens of G to 5 kG (up to 0.5 T) is applied to all the magnetic thin wires 1 (pixel array 40) from the outside, and the desired one of the constricted portions 1c1 and 1c2 is applied. Only one domain wall DW is generated and fixed. The shape of the magnetic wire 1 including the constricted portions 1c1 and 1c2 is designed so that one magnetic wall 1 is provided for one magnetic wire 1 by this initialization operation.

(Movement of domain wall in magnetic wire)
Next, the movement of the domain wall in the magnetic wire, which is the pixel selection operation of the spatial light modulator according to the present invention, will be described with reference to FIG. In the first embodiment, the magnetic thin line 1 provided in the pixel 4 has two magnetic domains, a magnetic domain D1 in the right direction magnetization and a magnetic domain D0 in the left direction magnetization, in the thin line direction across the domain wall DW (see FIG. 3 side by side). In the magnetic thin wire 1 shown in FIG. 3, the magnetic domain D0 is hatched in order to make it easy to distinguish the magnetic domains D0 and D1. Inside the domain wall, the magnetization gradually changes, that is, rotates from the magnetization direction of one of the two magnetic domains sandwiching it to the magnetization direction of the other magnetic domain. In general, the length (thickness) of the domain wall depends on the shape and size (width, thickness, thin wire length) of the magnetic wire, but is about 5 to 100 nm with respect to the length of the magnetic domain. Although extremely short (narrow), the domain wall is schematically enlarged in FIG. FIG. 3A shows a state in which the current supply to the magnetic wire 1 is stopped. Since the domain wall DW is stationary at the left constricted portion 1c1, the magnetic domain D0 exists in the incident region 1r, so that the magnetization in the left direction Indicates.

In the magnetic thin wire 1 shown in FIG. 3A, the X electrode 2 is represented as “−”, the Y electrode 3 is represented as “+”, and the current I is written to the left in the thin wire direction (“+ I” in FIG. ). Then, as shown in FIG. 3B, the domain wall DW moves to the right under the influence of the spin torque of the electron e ⁻ flowing in the right direction. Due to the movement of the domain wall DW, the magnetic domain D1 expands in the thin line direction and the magnetic domain D0 contracts. When a constant current is supplied to a magnetic wire having a constant thickness and width, the domain wall moves at a constant speed, and the speed increases as the current density per cross-sectional area of the magnetic wire increases. In addition, although the magnetic narrow wire 1 has locally narrow portions (constricted portions 1c1 and 1c2), the domain wall moving speed is constant in regions other than the constricted portions 1c1 and 1c2. Then, as shown in FIG. 3C, when the supply of the current I is stopped when the domain wall DW reaches the right constricted portion 1c2, the domain wall DW is stopped, and the magnetic domain D1 exists in the incident region 1r. Therefore, it shows magnetization in the right direction. Therefore, when limited to the incident region 1r of the magnetic wire 1, it can be said that the magnetization is reversed from the left direction to the right direction by the current supply.

On the other hand, the magnetic thin wire 1 shown in FIG. 3C has a current I (referred to as “−I” in FIG. 3D) in the right direction with the X electrode 2 being “+” and the Y electrode 3 being “−”. 3), the domain wall DW moves to the left due to the electrons e ⁻ flowing in the left direction as shown in FIG. Due to the movement of the domain wall DW, the magnetic domain D1 contracts and the magnetic domain D0 expands. When the supply of the current I is stopped when the domain wall DW reaches the left constricted portion 1c1, the domain wall DW is stopped, and as shown in FIG. 3A, the magnetization in the left direction is again performed in the incident region 1r. Show. Thus, by changing the direction of the magnetic wire 1 and supplying a current, the magnetization can be reversed in the left direction or the right direction in the incident region 1r.

  As described above, since the moving speed of the domain wall DW is constant if the magnitude of the current supplied to the magnetic wire 1 is constant, the magnetization reversal of the incident region 1r is between the left and right outer sides of the domain wall Dr. What is necessary is just to supply the electric current I only for the time which moves a distance. However, when the stationary position of the domain wall DW is slightly shifted due to errors such as the magnitude of the current and the supply time, and this minute shift is accumulated, the domain wall DW is stationary in the incident region 1r when the current is stopped, and is moved to the incident region 1r. There is a possibility that the two magnetic domains D1 and D0 have reached, or the domain wall DW reaches the end of the magnetic wire 1 and disappears. In order to prevent such a position shift of the domain wall DW, it is preferable that the narrow portions 1c1 and 1c2 are formed on the magnetic thin wire 1 on both outer sides of the incident region 1r. A magnetic wall is easily formed in a locally thin portion of the magnetic wire 1, and when the magnetic wall DW moves due to current supply and reaches the vicinity of the constricted portion 1 c 1 (1 c 2) when the current is stopped, the constricted portion spontaneously occurs. It moves to 1c1 (1c2) and then stops. Therefore, if the current I is supplied to the magnetic wire 1 only for the time during which the domain wall DW moves the distance between the constricted portions 1c1 and 1c2, the domain wall DW is constricted when the current is stopped even if there is a slight error in the supply time. Locked to one of the portions 1c1 and 1c2, only one magnetization direction in the left direction or the right direction is shown in the entire incident region 1r.

  Here, as described above, the current supplied from the power source 91 to the magnetic wire 1 is preferably a pulse current. When a pulse current is supplied to the magnetic wire 1, the domain wall DW moves intermittently in synchronization with the pulse. Since the movement distance of one time (one pulse) depends on the pulse width and current density, the pulse current is supplied as many times as to move the distance between the constricted portions 1c1 and 1c2 in the total supply time (pulse width × number of times). do it.

  In the magnetic wire 1, after the domain wall DW is fixed by this operation, and after the domain wall DW is generated by the initialization, the two magnetic domains D 0 and D 1 sandwiching the domain wall DW are caused by the coercive force of the magnetic wire 1. Since the magnetization is maintained, the domain wall DW does not move or disappear until a new current is supplied to the magnetic wire 1 or a magnetic field is applied.

(Operation of spatial light modulator)
The light modulation operation of the spatial light modulator according to the present invention will be described with reference to FIG. 2 using a display device using this spatial light modulator. The display device has substantially the same configuration as that using the conventional reflective spatial light modulator 100 shown in FIG. 11, but the spatial light modulator 100 uses the upper surface of the pixel array as the light incident surface. On the other hand, the spatial light modulator 10 according to the present invention has the lower surface, that is, the substrate 7 side as the light incident surface. Therefore, in the display device using the spatial light modulator 10, an optical system OPS provided with a light source or the like that irradiates light (laser light) toward the pixel array 40 below the pixel array 40, and irradiation from the optical system OPS. Light having a specific polarization component from the light Pref that is reflected by the pixel array 40 and emitted from the pixel array 40 before being incident on the pixel array 40. A polarizer PFo that shields light and a detector PD that detects light transmitted through the polarizer PFo are arranged.

  The optical system OPS includes, for example, a laser light source, a beam expander that is optically connected to the laser light source and expands the laser light onto the entire surface of the pixel array 40, and a lens that converts the expanded laser light into parallel light. (Not shown). Since the light (laser light) emitted from the optical system OPS includes various polarization components, this light is transmitted through the polarizer PFi in front of the pixel array 40 to be light of one polarization component. Hereinafter, light of one polarization component is referred to as polarization. The polarizers PFi and Pfo are polarizing plates, respectively, and the detector PD is an image display means such as a screen.

  The optical system OPS irradiates the parallel laser beam so as to enter the lower surface of the pixel array 40 at a predetermined incident angle. The laser light passes through the polarizer PFi to become polarized light (incident polarized light), and enters the pixels 4 from below the pixel array 40. Incident polarized light passes through the substrate 7, further passes through the magnetic transfer film 5, reaches the magnetic thin wire 1 of each pixel 4, reflects off the lower surface thereof, and passes through the magnetic transfer film 5 and the substrate 7 again. The light is emitted from the pixel array 40 as outgoing polarized light. All outgoing polarized light reflected by each pixel 4 reaches the polarizer PFo. The polarizer PFo shields specific polarized light, and light transmitted through the polarizer PFo enters the detector PD.

  In the spatial light modulator 10 shown in FIG. 2, the magnetic thin line 1 of the pixel 4 on the left side has the domain wall DW reaching the left side of the incident region 1r (constricted portion 1c1, see FIG. 3A). In FIG. 5, there is a magnetic domain D0 of magnetization in the left direction. On the other hand, the magnetic thin line 1 of the right pixel 4 has a domain wall DW that reaches the right side of the incident region 1r (constricted portion 1c2, see FIG. 3C). D1 exists. In the magnetic transfer film 5 in the region (incident region 5r) immediately below the incident region 1r of the magnetic thin wire 1 of each pixel 4, the magnetization direction of the magnetic thin wire 1 is transferred to the same magnetization direction.

When the light incident on the pixel 4 passes through the magnetic transfer film 5 before entering the pixel 4, the light is rotated in a different rotation direction depending on the magnetization direction of the magnetic transfer film 5, and further reflected on the lower surface of the magnetic wire 1. At this time, the light rotates in different rotation directions depending on the magnetization direction of the magnetic wire 1, and is also rotated and emitted when passing through the magnetic transfer film 5 again. Therefore, the outgoing polarized light reflected by the incident region 1r of the magnetic wire 1 and reciprocatingly transmitted through the magnetic transfer film 5 in the incident region 5r immediately below it is the same as the incident polarized light depending on the magnetization direction in the incident region 1r. Polarized light that is optically rotated in opposite directions at an angle, that is, a binary angle −θ _K , + θ _K optically rotated.

Here, in the magnetic thin wire 1, a magnetic domain having a magnetization direction different from the magnetic domain in the incident region 1r is formed outside the incident region 1r. If light reflected by such a magnetic domain outside the incident region 1r or light transmitted through the magnetic transfer film 5 in the region where the same magnetization as this magnetic domain is transferred is emitted, correct information will not be displayed. Therefore, it is preferable to provide a light absorption film 8 having an opening region 8r for each pixel 4 on the lower surface of the substrate 7 so that light reflected from other than the incident region 1r of the magnetic wire 1 is not emitted. Due to the light absorbing film 8, only the polarized light rotated at any one of the binary angles −θ _K and + θ _K is emitted from the pixel array 40 for each pixel 4.

The polarizer PFo shields the polarized light having an angle + θ _K rotation with respect to the incident polarized light. Therefore, all the polarized light emitted from the pixel 4 on the right side shown in FIG. 2 is shielded by the polarizer PFo and does not enter the detector PD at all, so that the pixel 4 is displayed dark (black) on the detector PD. On the other hand, the outgoing polarized light from the left pixel 4 passes through the polarizer PFo and enters the detector PD, and this pixel 4 is displayed brightly (white) on the detector PD. As described above, the spatial light modulator 10 is divided into light / dark (white / black) for each pixel 4 and, as described above, the magnetic light according to the direction of the current supplied from the electrodes 2 and 3. Since the magnetization can be reversed in the reproduction region 1r of the thin wire 1, the light / dark can be switched. The polarized light passing through the polarizer PFo increases as the difference between the angle of the polarized light component and the polarized light obtained by rotating the angle + θ _{K with} respect to the incident polarized light increases, and the transmittance becomes 100% at 90 °. Therefore, the spatial light modulator 10 according to the present invention uses the polarization of the polarized light component emitted from the pixel 4 to be displayed brightly, that is, the polarized light that has been rotated by the angle −θ _K with respect to the incident polarized light at the magnetic transfer film 5. By increasing the difference 2 | θ _K |, a large amount of light is transmitted through the polarizer PFo, and the pixel selectivity becomes excellent.

In order to increase the optical rotation angle −θ _K , + θ _K (| θ _K |), that is, to increase the magneto-optical effect (the Kerr effect of the magnetic wire 1 and the Faraday effect of the magnetic transfer film 5), It is preferable that the light is incident along a direction closer to parallel with the magnetization direction in the incident regions 1r and 5r. In the spatial light modulator 10 according to the present embodiment, the magnetization direction in the incident regions 1 r and 5 r of the magnetic thin wire 1 and the magnetic transfer film 5 is the thin wire direction of the magnetic thin wire 1 and the diagonal direction of the pixel array 40. However, if the incident direction is too close to the magnetization direction, it becomes difficult for light to enter each pixel 4, so that the incident angle is within about 80 ° with respect to the thin wire direction of the magnetic thin wire 1. It is preferable that the direction is an angle of about 10 ° to 60 °. Therefore, in the spatial light modulator 10 according to the present embodiment, since the incident direction of the incident polarized light is tilted so that the incident angle is in the range of about 30 ° to 80 °, as shown in FIG. An optical system OPS, polarizers PFi, PFo, and the like are arranged in accordance with each optical path of polarized light.

(Modification)
A spatial light modulator according to a modification of the first embodiment will be described with reference to FIGS. 1 and 6. The spatial light modulator 10A according to the modification of the first embodiment applies a magnetic wire 1A made of a perpendicular magnetic anisotropic material, and the magnetization easy axis of the magnetic transfer film 5A is perpendicular to the film surface. The configuration is the same as that of the spatial light modulator 10 (see FIGS. 1 and 2), and the same elements are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 6, the magnetization direction of the magnetic wire 1A is upward or downward, and the magnetization direction of the magnetic transfer film 5A is transferred to the magnetization direction of the magnetic wire 1A immediately above. Therefore, since the fine wire shape of the magnetic fine wire 1A does not affect the magnetization direction, it may be a straight line parallel to the diagonal direction of the pixel array 40A as in the first embodiment (see FIG. 1). It may be formed in a curved shape such as a sufficiently gentle arc. Further, the magnetic wire 1A may be arranged in a different direction for each pixel 4A. However, the position of the incident region 1r in the pixel 4A is made uniform in all the pixels 4A. Also in such a magnetic wire 1A, the movement of the domain wall DW due to the current supply and the expansion and contraction of the magnetic domains D1, D0 accompanying therewith are the same as those of the magnetic wire 1 made of the in-plane magnetic anisotropic material (see FIG. 3). ), The magnetization direction in the incident region 1r can be reversed to a desired direction, either downward or upward.

  In the spatial light modulator 10A, light (incident polarization) is incident in parallel to the magnetization direction of the magnetic thin wire 1A and the magnetic transfer film 5A, that is, perpendicular to the pixel array 40A (in-plane direction of the pixel array 40A). The optical rotation angle of the outgoing polarized light is maximized. Therefore, in the display device using the spatial light modulator 10A, as shown in FIG. 6, the optical system OPS (see FIG. 2) and the polarizer PFi are arranged immediately below the pixel array 40A, and the incident polarized light is converted into pixels. It is preferable to enter the array 40A at an incident angle of 0 °. In the display device having such a configuration, the light reflected by the pixel array 40A and emitted (emitted polarized light) has the same optical path as the incident polarized light. Therefore, the pixel array 40A is interposed between the polarizer PFi and the pixel array 40A. A half mirror HM inclined by 45 ° is further arranged. In FIG. 6, the half mirror HM is divided into two parts, but in actuality, the single half mirror HM has a shape in which all the outgoing polarized light from the pixel array 40 </ b> A is incident. The half mirror HM transmits incident polarized light irradiated from below and reflects outgoing polarized light irradiated from above laterally. Therefore, the polarizer PFo and the detector PD are arranged on the side of the half mirror HM.

  Light vertically enters and exits the pixel array 40A. Therefore, the opening region 8r formed in the light absorption film 8 for shielding light reflected by the region other than the incident region 1r of the magnetic wire 1A and light transmitted through the region other than the incident region 5r of the magnetic transfer film 5A (FIG. 5 ( (d) makes the shape and position coincide with the incident region 1r of the magnetic wire 1A in plan view.

  In the display device using the spatial light modulator 10A, similarly to the spatial light modulator 10, the incident polarized light is tilted and incident on the pixel array 40A (incident angle> 0 °) so that the output polarized light does not overlap the optical path. The half mirror HM may not be disposed (see FIG. 2). However, as described above, the closer the incident direction is to be parallel to the magnetization direction, the better. Therefore, the incident angle is preferably within about 30 °.

  As described above, according to the spatial light modulator according to the first embodiment and the modification thereof, the difference in the optical rotation angle between the selected pixel and the non-selected pixel is larger than that of the conventional spatial light modulator. / A reflective spatial light modulator with excellent selectivity for dark separation and switching.

[Second Embodiment]
In the spatial light modulator according to the first embodiment and the modification thereof, one pixel is provided with one magnetic thin wire, but the configuration is not limited thereto. As shown in FIG. 7, the pixel array 40B of the spatial light modulator according to the second embodiment of the present invention has two magnetic thin wires 1B and 1B arranged in parallel in one pixel 4B in plan (bottom) view. Prepare. In the pixel 4B, the magnetic thin wires 1B and 1B are connected in parallel to the X electrode 2B and Y electrode 3B of the same combination at both ends. One magnetic wire 1B is the same as the magnetic wires 1 and 1A of the first embodiment and its modification in size and material, except that two constricted portions are formed on only one side. Yes, both in-plane magnetic anisotropic materials and perpendicular magnetic anisotropic materials can be applied. Since the electrodes 2B and 3B are connected to both ends of the magnetic thin wires 1B and 1B of the respective pixels 4B, the electrodes 2B and 3B are formed in a band shape bent in plan view, but the materials and the like are the same as those of the electrodes 2 and 3 in the first embodiment. . In addition, the pixel 4B is arranged on the magnetic transfer film 5 (5A) laminated on the entire surface of the substrate 7 to form a pixel array 40B, and the light absorption film 8 is further provided on the back surface of the substrate 7. CC sectional view of the array 40B has the same configuration as FIG. 2 or FIG. However, the magnetic thin wires 1B and 1B of the pixels 4B and 4B adjacent to each other in the thin wire direction of the magnetic thin wire 1B (diagonal direction of the pixel array 40B) face each other on the side to which the Y electrode 3B is connected, so It becomes symmetrical arrangement connected to. Therefore, the pixel array 40B includes five Y electrodes 3B, one more than the pixels 4B arranged in four columns. Further, the X electrode 2B and the Y electrode 3B are connected to the current control unit 90 (see FIG. 1) similarly to the electrodes 2 and 3 of the pixel array 40 of the spatial light modulator 10 according to the first embodiment. Illustration and description are omitted.

  As described above, it is preferable that the magnetic wire is thinner (smaller in width and thickness) so that the domain wall can be moved with a smaller current and the moving speed per current is increased. When the pixel size is large to some extent, if the width of the magnetic thin wire 1 (1A) is reduced, the area ratio (aperture ratio) of the incident region 1r in the pixel 4 (4A) is reduced, and the light extraction efficiency as a spatial light modulator is reduced. Will be inferior. As in the present embodiment, a plurality of magnetic thin wires 1B are arranged close to each incident region 1r (see FIGS. 2 and 6), so that an opening region 8r (see FIG. 7 shows only one pixel 4B).

  As described above, according to the spatial light modulator according to the second embodiment, like the spatial light modulator according to the first embodiment and its modification, the reflective spatial light is excellent in selectivity and has a high aperture ratio. It becomes a modulator.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIGS. The same elements as those in the first embodiment (see FIGS. 1, 2, and 3) are denoted by the same reference numerals, and description thereof is omitted. As shown in FIG. 8 (a), the magnetic thin wire 1C of the spatial light modulator in the third embodiment has a substantially U-shaped thin wire shape. And connected to the Y electrode 3. Further, the X electrode 2 and the Y electrode 3 are connected to the current control unit 90 (see FIG. 1), similarly to the electrodes 2 and 3 of the pixel array 40 of the spatial light modulator 10 according to the first embodiment. Illustration and description are omitted. Further, the pixel 4C is arranged on the magnetic transfer film 5 (5A) laminated on the entire surface of the substrate 7 to form the pixel array 40C, and the light absorption film 8 is provided on the back surface of the substrate 7, so that the pixel array The cross-sectional structure of 40C is the same structure as the pixel array 40 and the like in the first embodiment.

  As shown in FIG. 9A, the magnetic thin wire 1C has no constricted portion, has a constant thickness and width, has two bent portions 1f1 and 1f2 bent at 90 ° in plan view, and has a thin wire shape. It is substantially U-shaped and its full length is sufficiently long with respect to thickness and width. Regarding the other materials, thickness, and width, the magnetic wire 1C is the same as the magnetic wires 1 and 1A of the first embodiment and its modifications, and the in-plane magnetic anisotropy material and the perpendicular magnetic anisotropy material are the same. Either can be applied. The bent portions 1f1 and 1f2 in the magnetic wire 1C are for locking the domain wall when the current is stopped, similarly to the constricted portions 1c1 and 1c2 in the magnetic wire 1 of the first embodiment. In this embodiment, the angle of bending is 90 °, but is not limited to this, and it is preferably in the range of 15 ° to 135 ° in order to suitably lock the domain wall. Further, the bending directions of the bent portions 1f1 and 1f2 do not have to be the same, and may be a crank-type magnetic wire in plan view. Therefore, the magnetic thin wire 1C is provided with the incident region 1r in the substantially straight central portion of the U-shape, in other words, the bent portions 1f1 and 1f2 are formed on both sides outside the incident region 1r. The positions of the bent portions 1f1 and 1f2 in the magnetic thin wire 1C and the length between the bent portions 1f1 and 1f2 are the same as those of the constricted portions 1c1 and 1c2 in the magnetic thin wire 1, and one bent portion may be provided. Further, as shown in FIG. 8B, the magnetic thin wire 1C may be disposed at an inclination of, for example, 45 ° in a plan (bottom) view in the pixel 4D. With this arrangement, the distance between the bent portions 1f1 and 1f2 can be increased with respect to the pixel size. The pixel array 40D of the spatial light modulator according to the modification of the present embodiment has the same configuration as the pixel array 40C except for the shape (arrangement) of the magnetic thin wire 1C.

  Similarly to the magnetic wire 1 of the first embodiment, the magnetic wire 1C is divided in the direction of the magnetic wire 1C by the shape thereof or by applying an external magnetic field having an appropriate strength. Here, the fine line direction refers to the fine line direction in a region where the magnetic domain exists. When the magnetic thin wire 1C is made of an in-plane magnetic anisotropy material, the magnetization direction is along the thin wire direction. Therefore, in the plan view shown in FIG. 9, the straight line between the bent portions 1f1 and 1f2 has a magnetization in the right or left direction. Are formed, and magnetic domains indicating upward or downward magnetization are formed on the linear portions on both sides thereof. Then, similarly to the linear magnetic wire 1, the magnetic wire 1 </ b> C is divided into a plurality of magnetic domains different by 180 ° along the direction of the wire so that the magnetic energy is in a stable state. Therefore, as shown in FIG. 9, in the magnetic thin wire 1C, there are a magnetic domain D1 whose magnetization is clockwise (clockwise) and a magnetic domain D0 whose magnetization is counterclockwise in plan view. The boundary area of the section becomes the domain wall DW. In the magnetic wire 1C shown in FIG. 9, the magnetic domain D0 is hatched in the same manner as in the first embodiment (see FIG. 3) in order to make the distinction between the magnetic domains D0 and D1 easier to understand.

  In a thin wire-like magnetic body, a domain wall is easily generated and fixed at a bent portion, like a constricted portion having a small cross-sectional area, in the absence of an external magnetic field. Therefore, in the magnetic wire 1C according to the present embodiment, a domain wall is generated in one or both of the bent portions 1f1 and 1f2. However, as in the first embodiment, all the magnetic wires An external magnetic field is applied to the thin wire 1C (pixel array 40C) so that one domain wall DW is generated and fixed only at a desired one of the bent portions 1f1 and 1f2. The shape of the magnetic wire 1C including the bent portions 1f1 and 1f2 is designed so that one magnetic wall is formed in one magnetic wire 1C by this initialization operation. Here, for example, in the magnetic wire 1C shown in FIG. 9A, the magnetization direction is rotated by 90 ° in the two linear regions sandwiching the bent portion 1f2, but is aligned in the counterclockwise direction (magnetic domain). D0). In this case, no domain wall is generated in the bent portion 1f2, or even if it is generated, the domain wall has a relatively narrow region. In this embodiment, when the magnetization directions are aligned clockwise and counterclockwise as described above, a region in which the magnetization direction is rotated by 90 ° with the bent portion 1f1 or the bent portion 1f2 interposed therebetween is also defined as one magnetic domain. To do.

(Movement of domain wall in magnetic wire)
Next, the movement of the domain wall in the magnetic wire, which is the pixel selection operation of the spatial light modulator according to the present invention, will be described with reference to FIG. The magnetic wire 1C of the present embodiment is similar to the linear magnetic wire 1 of the first embodiment shown in FIG. 3 by supplying current in the direction of the thin line, so that the domain wall DW is opposite to the direction of current in the direction of the thin line. The magnetic domains D1 and D0 on both sides of the domain wall DW expand or contract accordingly. FIG. 9 (a) shows a state in which the current supply to the magnetic wire 1C is initialized and the magnetic domain wall DW is stationary at the left bent portion 1f1, so that the magnetic domain D0 exists in the incident region 1r. Therefore, it shows magnetization in the left direction. Hereinafter, the direction of magnetization, current supply, and the like of the magnetic wire 1C is appropriately indicated by the direction (right or left) at the straight line portion (incident region 1r) between the bent portions 1f1 and 1f2.

The magnetic thin wire 1C shown in FIG. 9A has the X electrode 2 as “−” and the Y electrode 3 as “+”, and represents the current I counterclockwise in the thin wire direction (“+ I” in FIG. 9B). Is supplied), as shown in FIG. 9B, the domain wall DW moves to the right due to electrons e ⁻ flowing in the right direction. Then, as shown in FIG. 9 (c), when the supply of the current I is stopped when the domain wall DW reaches the right bent portion 1f2, the domain wall DW stops, and the magnetic domain D1 exists in the incident region 1r. Therefore, it shows magnetization in the right direction. Conversely, when the current I is supplied clockwise to the magnetic wire 1 shown in FIG. 9C with the X electrode 2 being “+” and the Y electrode 3 being “−”, the domain wall DW moves to the left (not shown). ) When the supply of the current I is stopped at the time when the domain wall DW reaches the left bent portion 1f1, the domain wall DW stops, and as shown in FIG. 9A, the magnetization in the left direction is again performed in the incident region 1r. Show.

  Thus, also in the magnetic thin wire 1C, as in the first embodiment, by changing the direction at the electrodes 2 and 3 and supplying a current, the magnetization direction in the incident region 1r is either left or right. Alternatively, the magnetization can be reversed in a desired direction. Furthermore, since the magnetic wire 1C has a shape bent at two locations, the domain wall DW is locked to one of the bent portions 1f1 and 1f2, so that the magnetization direction in the incident region 1r between the bent portions 1f1 and 1f2 is stabilized. Can be controlled. Therefore, the spatial light modulator according to the third embodiment including the magnetic thin wire 1C in the pixel 4C can perform the pixel selection operation similarly to the spatial light modulator 10 according to the first embodiment, and has excellent selectivity. Type spatial light modulator.

  As mentioned above, although the form for implementing this invention was described, this invention is not limited to these embodiment, A various change is possible in the range shown to the claim.

(Sample preparation)
In order to confirm the effect of the present invention, a sample simulating the spatial light modulator 10A (see FIG. 6) according to the modification of the first embodiment of the present invention was produced, and the magneto-optical effect was evaluated. The Co—Pt alloy applied as the material of the magnetic wire 1A is an in-plane magnetic anisotropic material, and its magnetization direction was made vertical by applying a magnetic field perpendicularly from the outside. A bismuth-substituted magnetic garnet (Bi-YIG) film having a film thickness of 0.5 μm is formed on the GGG substrate (substrate 7) by the LPE method to form a magnetic transfer film 5A, and a Co—Pt alloy film having a film thickness of 40 nm thereon. Was formed by ion beam sputtering. This Co—Pt alloy film was processed by electron beam lithography into a thin wire having a width of 700 nm and a length of 20 μm to form a magnetic wire 1A, which was used as a sample. Further, as a sample of a comparative example (conventional example), the same magnetic wire 1A as that of the above example was formed on a Si substrate whose surface was thermally oxidized.

  As an initialization, an external magnetic field was applied vertically to the prepared sample, and the magnetizations of all the magnetic wires 1A and the magnetic transfer film 5A were made vertically uniform. Then, a laser beam having a wavelength of 408 nm was incident from directly above the sample, the reflected light from the sample (magnetic thin wire 1A) was taken out with a half mirror, and the angle of polarization was measured with a vertical magnetic field Kerr effect measuring device. Next, while continuing to measure the polarization of the reflected light, a magnetic field in the direction opposite to the applied magnetic field was applied while gradually increasing the magnitude, thereby reversing the magnetization of the magnetic wire 1A downward. FIG. 10 shows a graph (Kerr loop) of Kerr rotation angle (θk) characteristics with respect to the external magnetic field (H). As shown in FIG. 10A, the provision of the magnetic transfer film 5A significantly increases the Kerr rotation angle as compared with the comparative example in which the magnetic transfer film 5A shown in FIG. The effect was improved.

10, 10A Spatial light modulator 1, 1A, 1B, 1C Magnetic thin wire 1r Incident area 1c1, 1c2 Constricted part 1f1, 1f2 Bent part 2, 2B X electrode (electrode)
3,3B Y electrode (electrode)
40, 40A, 40B, 40C, 40D Pixel array 4, 4A, 4B, 4C, 4D Pixel 5, 5A Magnetic transfer film 7 Substrate 90 Current controller 91 Power supply (current supply means)
94 Pixel selection section (pixel selection means)
D0, D1 Domain DW Domain wall

Claims (4)

A substrate that transmits light, a plurality of pixels arranged in a matrix on the substrate, a pixel selection unit that selects one or more pixels from the plurality of pixels, and a pixel selected by the pixel selection unit Current supply means for supplying current, and is a spatial light that reflects and emits light incident on the pixel selected by the pixel selection means through the substrate while changing the direction of polarization in a specific direction. A modulator,
The pixel includes a magnetic thin wire in which a magneto-optical material is formed in a thin line shape and two or more magnetic domains are continuously formed in the thin line direction, and a pair of electrodes connected in the vicinity of both ends of the magnetic thin line,
The magnetic thin wire is provided with an incident region, which is a region partitioned in the thin wire direction for allowing the light to enter, at a predetermined position, and the current is supplied in the thin wire direction via the pair of electrodes. Thus, the domain wall generated between two adjacent magnetic domains moves in the direction of the thin line, and any one of the two magnetic domains reaches the incident region,
A spatial light modulator, further comprising a magnetic transfer film in contact with the surface of the magnetic thin wire on the substrate side between the substrate and the plurality of pixels.   The spatial light modulator according to claim 1, wherein the magnetic wire is formed in a locally confined shape outside the incident region.   The spatial light modulator according to claim 1, wherein the magnetic thin wire is formed in a thin wire shape bent outside the incident region. The pair of electrodes are connected on the magnetic wire,
In the plurality of pixels, one of the pair of electrodes of the pixels arranged in the same row is connected to one wiring, and the other of the pair of electrodes of the pixels arranged in the same column has an insulating layer on the wiring. The spatial light modulator according to any one of claims 1 to 3, wherein the spatial light modulator is connected to one wiring line disposed through the space light modulator.

Images