JP2012078580A - Light modulation element and spatial light modulator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light modulation element having no need to use a transparent electrode for a drive electrode, and capable of increasing an aperture ratio and efficiently modulating polarization besides accurately sensing a magnetization reversal action, and a spatial light modulator using the light modulation element.SOLUTION: A light modulation element 1 is formed on a substrate 7 transmitting light and comprises a spin injection magnetization reversal element structure in which a magnetization free layer 3, intermediate layers 21, 22 and magnetization fixation layers 11, 12 are laminated in this order. The light modulation element 1 further comprises a transparent electrode layer 8 between the substrate 7 and the magnetization free layer 3. In the light modulation element 1, the magnetization fixation layers 11, 12 are made up of two magnetization fixation layers 11 and 12 separated on one same plane and the two magnetization fixation layers 11 and 12 are fixed in magnetization intensity antiparallel to each other, and respectively a magnetic body having a larger coercive force than the magnetization free layer 3.

Description

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

  A spatial light modulator uses an optical element (light modulation element) as a pixel and arranges it in a two-dimensional array to spatially modulate the phase and amplitude of light. Widely used in fields such as equipment, display technology, and recording technology. In addition, since optical information can be processed in two dimensions in parallel, its application to optical information processing technology is also being studied. As a spatial light modulator, liquid crystal has been conventionally used and widely used as a display device, but for holography and optical information processing, since response speed and high definition of pixels are insufficient, in recent years, Development of a magneto-optic spatial light modulator using a magneto-optic material that is expected to be capable of high-speed processing and pixel miniaturization is in progress.

  In a magneto-optical spatial light modulator (hereinafter referred to as a spatial light modulator), when light incident on a magneto-optical material, that is, a magnetic material is transmitted or diffracted, the direction of polarization is changed (rotation) and emitted. The effect (Kerr effect in the case of diffraction) is used. 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, Patent Document 1) and a domain wall drive system for driving a domain wall (for example, see Patent Document 2) are available.

As shown in FIG. 13, a spin injection spatial light modulator 100 using a spin injection method includes a pair of drive electrodes (an upper electrode 102 and a lower electrode 103) above and below a light modulation element 101 provided on a substrate 107. ) To supply a current perpendicular to the film surface, the magnetization direction of a part of the magnetic film (magnetization free layer) laminated by spin injection is changed (reversed). The polarization state of the outgoing light (outgoing polarized light) can be modulated into two values of θ _k and −θ _k according to the direction of magnetization of the magnetization free layer by the magnetic Kerr effect. In such a spatial light modulator 100, polarizers PFi and Pfo are provided on the incident polarization side and the output polarization side, respectively, and the polarization planes of these polarizers PFi and Pfo are set to a crossed Nicols arrangement with a predetermined angle. When the plane of polarization is rotated by the angle −θ _k by the light modulation element 101, the outgoing polarized light cannot pass through the polarizer PFo and becomes dark, and when rotated by the angle θ _k , the outgoing polarized light passes through the polarizer PFo. It becomes bright.

As shown in FIG. 14, the domain wall drive type spatial light modulator 200 using the domain wall drive system has a magnetization at a central portion at one end of a magnetic wire (magnetization free layer) 201 provided on a substrate 207. The magnetic domain wall 201a generated between one end and the center of the magnetic wire 201 is supplied by supplying a current to the drive electrode 202 provided at the end of the magnetic wire 201. It is driven (moved) to the other end side to change (reverse) the magnetization direction at the center of the magnetic wire 201. The polarization state of outgoing light (outgoing polarized light) can be modulated into two values of θ _k and −θ _k according to the magnetization direction of the magnetic wire 201 by the magnetic Kerr effect. In such a spatial light modulator 200, polarizers PFi and Pfo are provided on the incident polarization side and the output polarization side, respectively, and the polarization planes of these polarizers PFi and Pfo are set to a crossed Nicol arrangement in which the polarization planes are set at a predetermined angle. Then, when the plane of polarization is rotated by the angle −θ _k by the magnetic wire 201, the outgoing polarized light cannot pass through the polarizer PFo and becomes dark, and when rotated by the angle θ _k , the outgoing polarized light passes through the polarizer PFo. It becomes bright.

JP 2008-83686 A JP 2010-20114 A

However, the conventional techniques have the following problems.
Since the spin injection magnetization reversal element is provided with drive electrodes for supplying current vertically, the light modulation element of the diffractive spatial light modulator can be used to make light incident on the spin injection magnetization reversal element. Alternatively, a transparent electrode that transmits light must be applied to one of the lower and upper and lower sides of the light modulation element of a transmissive spatial light modulator. The transparent electrode has a problem that it is difficult to supply a uniform current to a plurality of pixels because the transparent electrode is significantly inferior to the metal electrode. In particular, the higher the spatial light modulator having a larger number of light modulation elements arranged in a two-dimensional array, the more the operation may be delayed at the center. In order to prevent this, it is necessary to increase the thickness of the drive electrode or supply a large current to operate the spatial light modulator, and there is room for improvement in terms of power saving.

  Further, in order to increase the area ratio (aperture ratio) of the effective region to be light-modulated, it is necessary to increase the element size (area). On the other hand, the spin-injection magnetization reversal element suitably reverses the magnetization. In addition, it is necessary to make the element size as small as 300 nm or less on one side. Therefore, it is desired to develop a spatial light modulator capable of increasing the aperture ratio by increasing the element size and performing efficient magnetization reversal.

  In the spatial light modulator described in Patent Document 2, a metal electrode such as Cu can be used as the drive electrode, and a transparent electrode (specific resistance) such as IZO or ITO having a high specific resistance used in Patent Document 1 is used. Can be supplied with a uniform current to a plurality of pixels, but has the following problems.

  Since antiparallel magnetization always exists at the end of the magnetic wire, the aperture ratio of the magnetic wire (light modulation element) decreases. In general, the domain wall generation depends strongly on the shape and material of the magnetic wire, and it is difficult to stably form the desired antiparallel magnetization at the end of the magnetic wire. It is difficult to do. Furthermore, since there are only two electrodes, the only way to know the magnetization reversal operation of the magnetic wire (light modulation element) is to measure the domain wall resistance between the electrodes arranged at both ends of the magnetic wire. The domain wall resistance has a small rate of change, and it is difficult to accurately know the magnetization reversal operation of the light modulation element.

  The present invention was devised in view of the above problems, and there is no need to apply a transparent electrode to the drive electrode, the aperture ratio can be increased, and efficient polarization modulation can be performed. It is an object of the present invention to provide a light modulation element that can accurately know the magnetization reversal operation and a spatial light modulator using the light modulation element when used in a spatial light modulator.

  In order to solve the above-mentioned problems, the inventors changed the arrangement of the layers of the light modulation element (see JP 2010-60748 A) to which the spin-injection magnetization reversal element having the dual pin structure already invented was applied, By laminating the magnetization fixed layers arranged above and below the magnetization free layer on the magnetization free layer, a current path is formed in a U shape with the magnetization free layer as the bottom, and It came to the structure which does not require a drive electrode below. In addition, this configuration makes it possible to increase the aperture ratio and perform efficient magnetization reversal. Further, by providing a transparent electrode layer between the substrate and the magnetization free layer, the magnetization reversal operation in the magnetization free layer can be accurately known.

  That is, the light modulation element according to the present invention has a spin-injection magnetization reversal element structure that is formed on a substrate that transmits light and in which a magnetization free layer, an intermediate layer, and a magnetization fixed layer are stacked in this order. Then, a current is supplied between a pair of drive electrodes connected on the magnetization fixed layer, and the polarization direction of light incident through the substrate is changed by changing the magnetization direction of the magnetization free layer. A light modulation element that diffracts and emits, wherein the light modulation element further includes a transparent electrode layer between the substrate and the magnetization free layer, and the magnetization fixed layer is separated on the same plane 2 The two magnetization fixed layers are magnetic bodies which are fixed to antiparallel magnetization and have a coercive force larger than that of the magnetization free layer.

  According to such a configuration, since the two magnetization fixed layers separated on the same plane are provided, both of the pair of drive electrodes can be provided on the upper side of the light modulation element, so that the light is incident on the light modulation element from the substrate side. The light reaches the magnetization free layer without going through the drive electrode and is diffracted. Therefore, the drive electrode constituting the pixel does not need to transmit light, and a metal electrode having excellent conductivity can be applied to the drive electrode. In addition, since two magnetization fixed layers are provided and these are fixed to magnetizations antiparallel to each other, a kind of double spin injection method is obtained, and the spin torque is doubled. Therefore, the efficiency of spin injection is improved. Further, since the magnetization reversal of the magnetization free layer occurs efficiently even if the area of the light incident surface (light exit surface) is increased, the aperture ratio of the pixel can be increased. Furthermore, by providing the transparent electrode layer between the substrate and the magnetization free layer, it becomes easy to electrically measure the magnetization reversal operation of the magnetization free layer. Further, the Kerr rotation angle in the magnetization free layer can be increased by utilizing the effect of multiple diffraction in the transparent electrode layer.

Furthermore, in the light modulation element according to the present invention, it is preferable that one of the two magnetization fixed layers has a multilayer structure including a magnetic exchange coupling film.
According to such a configuration, the two magnetization fixed layers can be easily fixed to magnetizations antiparallel to each other.

Furthermore, the light modulation element according to the present invention preferably includes a metal thin film layer having a thickness of 1 to 3 nm between the substrate and the transparent electrode layer.
According to this configuration, the effect of multiple diffraction is increased by the metal thin film layer, and the magneto-optical effect of the magnetization free layer is improved. In addition, the adhesion between the substrate and the transparent electrode layer is improved.

  A spatial light modulator according to the present invention is a spatial light modulator using the above-described light modulation element, and includes a substrate that transmits light, a plurality of pixels that are two-dimensionally arranged on the substrate, and a plurality of the plurality of pixels. Pixel selection means for selecting one or more pixels from the pixel, and current supply means for supplying a predetermined current to the pixel selected by the pixel selection means, wherein the pixel includes the light modulation element, the two A pair of drive electrodes connected to each of the magnetization fixed layers and supplying a current to the light modulation element; and one drive electrode of the pair in the selected pixel; and the light A measuring unit that measures a voltage value between the transparent electrode layer of the modulation element; and the pixel selecting unit is configured to calculate an electric resistance value from the voltage value measured by the measuring unit; In the pre-set magnetization direction in the pixel A storage unit for storing a standard electric resistance value setting range determined in the same time, and determining that the magnetization reversal is good when the calculated electric resistance value is a value within the standard electric resistance value setting range, A determination unit that determines that the magnetization reversal is defective when it is out of the set range; and a command unit that commands resupply of the current to the drive electrode when the magnetization reversal is determined to be defective. And

  According to this configuration, the use of the light modulation element eliminates the need to apply a transparent electrode to the pair of drive electrodes as a diffractive spatial light modulator that diffracts light incident from the substrate side. In addition, by using the above light modulation element, the efficiency of polarization modulation is improved by efficient spin injection magnetization reversal, the aperture ratio of the pixels is increased, and the magnetization reversal operation of the entire array of pixels is electrically performed. Measurement can be easily performed and the magnetization state can be controlled.

  In the spatial light modulator according to the present invention, in the two pixels adjacent to each other in the arranged direction in which the two magnetization fixed layers are arranged on the same plane, two of the light modulation elements are arranged as one The magnetization fixed layers of the two light modulation elements connected to the same drive electrode are integrated into one integrated element.

  According to such a configuration, the sizes of the two magnetization fixed layers in the light modulation element can be made different, and different coercive forces can be obtained. Therefore, an integrated element in which the magnetizations of the two magnetization fixed layers are easily fixed in an antiparallel state can be obtained.

Furthermore, the spatial light modulator according to the present invention may be configured such that each of the plurality of pixels includes a plurality of light modulation elements.
According to this configuration, the magnetization direction of the magnetization free layer can be made different in each of the plurality of light modulation elements of one pixel. Thereby, multi-stage display of pixels is possible.

  According to the light modulation element of the present invention, when used in a spatial light modulator, it is not necessary to apply a transparent electrode to the pair of drive electrodes, so that it is possible to save power in the spatial light modulator. In addition, by providing two magnetization fixed layers, the efficiency of spin injection is improved, and efficient spin injection magnetization reversal can be performed, thereby enabling efficient polarization modulation. In addition, since the area of the light incident surface (outgoing surface) can be more than twice that of a normal spin injection magnetization reversal element, a pixel with an increased aperture ratio can be obtained. Furthermore, by forming the transparent electrode layer, the magnetization reversal operation in the magnetization free layer can be accurately known.

  According to the spatial light modulator of the present invention, by using the light modulation element, a pair of drive electrodes can be formed by metal electrodes, and polarization modulation by efficient spin injection magnetization reversal is possible. The aperture ratio increases. Further, it is possible to accurately detect the magnetization reversal operation on the entire surface of the plurality of arranged pixels, and the magnetization state becomes a desired state.

It is sectional drawing which shows typically the structure of the light modulation element which concerns on this invention, (a) is 1st Embodiment, (b) is 2nd Embodiment. It is the bottom view seen from the substrate side which shows the composition of the spatial light modulator concerning a 1st embodiment of the present invention typically. It is a block diagram which shows typically the structure of a pixel selection part. It is a flowchart which shows the procedure of the drive operation of a spatial light modulator, and the detection operation of a magnetization reversal operation. It is sectional drawing which shows typically the structure of the spatial light modulator which concerns on 1st Embodiment of this invention. It is explanatory drawing for demonstrating operation | movement of the light modulation element which concerns on this invention. It is explanatory drawing for demonstrating the binary state of the magnetization direction in the light modulation element which concerns on this invention. It is the bottom view seen from the substrate side which shows the composition of the spatial light modulator concerning a 2nd embodiment of the present invention typically. It is sectional drawing which shows typically the structure of the spatial light modulator which concerns on 2nd Embodiment of this invention. It is a schematic diagram for demonstrating the manufacturing method of the light modulation element of the spatial light modulator which concerns on 2nd Embodiment of this invention. It is the bottom view seen from the substrate side which shows the composition of the spatial light modulator concerning a 3rd embodiment of the present invention typically. It is sectional drawing which shows typically the structure of the spatial light modulator which concerns on other embodiment of this invention. It is sectional drawing which shows the structure of the conventional spatial light modulator typically. It is sectional drawing which shows the structure of the conventional spatial light modulator typically.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
≪Light modulation element≫
[First Embodiment]
As shown in FIG. 1 (a), the light modulation element 1 of the present invention is formed on a substrate 7 that transmits light, and includes a magnetization free layer 3, a first intermediate layer 21, and a second intermediate layer 22 (hereinafter referred to as “the second intermediate layer 22”). Spin transfer magnetization reversal in which intermediate layers 21 and 22 are appropriately referred to, and first magnetization fixed layer 11 and second magnetization fixed layer 12 (hereinafter appropriately referred to as magnetization fixed layers 11 and 12) are stacked in this order. It has an element structure. Further, here, the light modulation element 1 includes a transparent electrode layer 8 between the substrate 7 and the magnetization free layer 3. An X electrode 51 is connected to the upper surface of the first magnetization fixed layer 11 and a Y electrode 52 is connected to the upper surface of the second magnetization fixed layer 12 as a drive electrode layer. In the light modulation element 1, a current is supplied between an X electrode 51 and a Y electrode 52 (hereinafter, appropriately referred to as drive electrodes 51 and 52) that are a pair of drive electrodes connected on the magnetization fixed layers 11 and 12. By changing the magnetization direction of the magnetization free layer 3, the light transmitted through the substrate 7 from below is diffracted by changing its polarization direction, and is modulated into different binary light (polarization component) Is emitted. Since reflected light can be expressed as zero-order diffracted light, diffraction includes reflection.

As the light modulation element 1, a so-called CPP-GMR (Current Perpendicular to the Plane Giant MagnetoResistance) type or TMR (Tunneling MagnetoResistance) type structure is used. .
In the present embodiment, the light modulation element 1 will be described in the case where the magnetization direction is the vertical direction (direction perpendicular to the layer surface).
Hereinafter, the configuration of the light modulation element 1 will be described.

(Magnetization free layer)
The magnetization free layer 3 changes its magnetization direction when a current is supplied between a pair of drive electrodes (X electrode 51 and Y electrode 52) through the drive electrode layers connected on the two magnetization fixed layers 11 and 12, respectively. To do. That is, according to the direction of the current supplied between the X electrode 51 and the Y electrode 52, the magnetization in the magnetization free layer 3 is caused by the interaction between the spin of injected electrons and the electron spin in the magnetization free layer 3. The direction of is reversed.

  The magnetization free layer 3 uses a material having perpendicular magnetic anisotropy together with the magnetization fixed layers 11 and 12. Specifically, transition metal materials such as CoFeB, CoFe, Co, Fe, CoFeSi, and CoFeGe can be mainly used. In addition, a material having a large magneto-optic effect such as a multilayer film in which a thin film layer made of transition metal and a thin film layer made of noble metal are alternately laminated, an alloy of transition metal and noble metal, an alloy of rare earth metal and transition metal, etc. Can be used.

  Examples of the multilayer film include a Co / Pt (laminated in order from the material described from the left side) multilayer film, a Co / Pd multilayer film, an Fe / Pd multilayer film, a CoFe / Pd multilayer film, and an Fe / Pt multilayer film. Examples of the alloy of the transition metal and the noble metal include a CoPt alloy, a CoPd alloy, an FePd alloy, and an FePt alloy. Examples of alloys of rare earth metals and transition metals include GdFe alloys, GdCoFe alloys, GdCo alloys, TbFeCo alloys, and the like. In addition, a material having a large magneto-optical effect such as a MnBi alloy, a Mn / Bi multilayer film, a PtMnSb alloy, or a Pt / MnSb multilayer film can be used.

  In addition, the magnetization free layer 3 is preferably a magnetic material that has a magneto-optic effect at the wavelength of incident light that is greater than that of the two magnetization fixed layers 11 and 12. With this configuration, the light modulation element 1 suppresses the variation in optical rotation angle due to the magnetizations antiparallel to each other when the incident light passes through the magnetization free layer 3 and reaches the two magnetization fixed layers 11 and 12. Can do.

  The thickness of the magnetization free layer 3 is not particularly limited. However, if the magnetization free layer 3 is too thin, the coercive force is reduced, whereas if it is too thick, the perpendicular magnetic anisotropy is deteriorated. Therefore, the thickness of the magnetization free layer 3 is preferably 1.5 to 15 nm.

(Magnetic pinned layer)
The magnetization fixed layers 11 and 12 include two magnetization fixed layers separated on the same plane, that is, the first magnetization fixed layer 11 and the second magnetization fixed layer 12, and each of the two magnetization fixed layers 11 and 12 is provided. It is laminated on one magnetization free layer 3 with intermediate layers 21 and 22 interposed therebetween. The magnetization pinned layers 11 and 12 are pinned in one direction of a predetermined direction, that is, a direction (perpendicular direction) parallel to the height direction, and the first magnetization pinned layer 11 and the second magnetization pinned layer. 12 are fixed to magnetizations antiparallel to each other. Further, the magnetization fixed layers 11 and 12 are made of a ferromagnetic material and are magnetic bodies having a coercive force larger than that of the magnetization free layer 3.

In order to make the magnetizations of the first magnetization fixed layer 11 and the second magnetization fixed layer 12 antiparallel to each other, a laminated film of CoFe / TbFeCo or the like is used for the magnetization fixed layers 11 and 12, and one of the film thicknesses is increased. By increasing the thickness or changing the shape of one of the magnetization fixed layers 11 (12), the first magnetization fixed layer 11 and the second magnetization fixed layer 12 have different coercive forces H _C1 and H _C2 , respectively. That's fine. Alternatively, different coercive forces H _C1 and H _C2 may be used by using different materials. However, the coercive force of the magnetization free layer 3 when the _{H Cf,} it is necessary to set _{H Cf <H C1 <H C2} . Then, after applying a magnetic field H _max larger than H _C2 , two magnetizations are applied by applying a negative magnetic field −H _mid (H _C1 <H _mid <H _C2 ) having an intermediate magnitude between H _C1 and H _C2. The magnetizations of the fixed layers 11 and 12 can be initialized to an antiparallel state. This magnetic field may be applied before or after the drive electrodes 51 and 52 are formed.

  As a material used for the magnetization fixed layers 11 and 12, a transition metal thin film is laminated on an alloy of a rare earth metal and a transition metal (for example, TbFeCo, TbFe, TbCo, DyCo, DyCoFe, GdFe, GdCo, GdFeCo, etc.) Transition metal / noble metal-based multilayer films (for example, Co / Pd multilayer films, Fe / Pt multilayer films, Co / Pt multilayer films, etc.) and alloys of transition metals and noble metals (for example, CoPt alloys, FePt alloys, etc.) Etc. In addition, there are a Co / Ni multilayer film, a CoNi alloy / Pt multilayer film, and the like. Examples of the transition metal include Fe, Co, and Ni, and examples of the noble metal include Au, Ag, Ru, Rh, Pd, Os, Ir, and Pt.

Further, it is preferable that one of the magnetization fixed layers 11 and 12 has a multilayer structure including a magnetic exchange coupling film such as Ru, for example, CoFe / Ru / CoFe / TbFeCo. With such a configuration, the magnetizations of the two magnetization fixed layers 11 and 12 can be initialized in an antiparallel state without applying a magnetic field such as H _max or H _mid .

  The thickness of the magnetization pinned layers 11 and 12 is not particularly limited. However, if the magnetization pinned layers 11 and 12 are too thin, the coercive force is reduced. On the other hand, if the magnetization pinned layers 11 and 12 are too thick, the perpendicular magnetic anisotropy is deteriorated. Therefore, the thickness of the magnetization fixed layers 11 and 12 is preferably 3 to 50 nm. Further, the distance between the first magnetization fixed layer 11 and the second magnetization fixed layer 12 is preferably 10 to 300 nm from the viewpoints of increase in aperture ratio and workability. Assuming that the film thickness of the magnetization free layer 3 is the same as that of a normal element (that is, a conventional light modulation element), the magnetization fixed layer that gives the spin torque of the spin injection magnetization reversal is Therefore, the size of the light modulation element 1 can be increased up to about twice the normal element (for example, 300 nm × 100 nm × 2 element) (for example, 300 nm × 400 nm × 1 element).

(Middle layer)
The first intermediate layer 21 and the second intermediate layer 22 are disposed between the magnetization free layer 3 and the first magnetization fixed layer 11 and between the magnetization free layer 3 and the second magnetization fixed layer 12, respectively. Is a layer. The intermediate layers 21 and 22 are necessary for separating the magnetization state of the magnetization free layer 3 and the magnetization states of the magnetization fixed layers 11 and 12, as will be described later in “Transition of the magnetic domain state of the light modulation element”. It functions as a path when exchanging spin-polarized electrons between the magnetization free layer 3 and the magnetization fixed layers 11 and 12. As described above, since the intermediate layers 21 and 22 function as a spin path, a material having a small spin orbit interaction and a long spin diffusion length (spin holding distance) is used for the intermediate layers 21 and 22. preferable.

When the light modulation element 1 is a CPP-GMR type magnetoresistive element, a nonmagnetic metal is used for the intermediate layers 21 and 22. In this case, the nonmagnetic metal material is preferably Cu, Al, Ag, Au or the like, and a semiconductor material such as ZnO may be used. The thickness is preferably 2 to 6 nm so that spin-polarized electrons flow while maintaining a sufficient spin state.
In the case of a TMR type magnetoresistive element, an insulating material such as magnesia (MgO), alumina (Al ₂ O ₃ ), MgF ₂ is used for the intermediate layers 21 and 22. By using the intermediate layers 21 and 22 as insulator layers, the magnetoresistive effect ratio (MR ratio) of the light modulation element 1 can be improved, and the magnetization reversal current inversely proportional to the MR ratio can be reduced. In the case of the TMR type, the thickness of the intermediate layers 21 and 22 is preferably about 0.6 to 2 nm.

(Transparent electrode layer)
The transparent electrode layer 8 is a layer provided between the substrate 7 and the magnetization free layer 3. As will be described later, the spatial light modulator 10 uses light that is transmitted through the substrate 7 and the transparent electrode layer 8 and is reflected after being incident on the light modulation element 1. Therefore, the transparent electrode layer 8 includes IZO, ITO. A transparent electrode material such as As will be described later, by providing the transparent electrode layer 8, the voltage value between the X electrode 51 and the transparent electrode layer 8 can be measured, and the electrical resistance value calculated from this voltage value is stored in advance. Compared with the standard electric resistance value, it becomes easy to electrically measure the magnetization reversal operation of the magnetization free layer 3. Further, the Kerr rotation angle in the magnetization free layer 3 can be increased by utilizing the effect of multiple diffraction in the transparent electrode layer 8.

  As mentioned above, although embodiment of the light modulation element 1 which concerns on this invention was described, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the meaning of this invention. For example, the following configuration may be used.

[Second Embodiment]
As shown in FIG. 1B, the light modulation element 1A according to the present invention is formed on a substrate 7 that transmits light, and includes a magnetization free layer 3, an intermediate layer 2A, a first magnetization fixed layer 11, and a first magnetization fixed layer 11. The dual magnetization fixed layer 12 and the protective layers 41 and 42 have a spin-injection magnetization reversal element structure in which the two magnetization fixed layers 12 and the protective layers 41 and 42 are stacked in this order. The light modulation element 1 </ b> A includes a transparent electrode layer 8 between the substrate 7 and the magnetization free layer 3. Since the configuration of the intermediate layer 2A and the layers other than the protective layers 41 and 42 are the same as those of the light modulation device 1 according to the first embodiment, the configuration of the intermediate layer 2A and the protective layers 41 and 42 will be described here.

(Form of intermediate layer)
As shown in FIG. 1B, when the TMR type element is used for the intermediate layer 2A, an insulating material is used for the intermediate layer 2A. Similarly, the intermediate layer 2A may be formed as one intermediate layer. With such a configuration, in the optical modulator manufacturing method described later, when the element film is dug down by etching, milling, or the like, the center of the element film may be removed up to the upper surface or midway of the intermediate layer 2A. Even if excessive etching or the like is performed, the magnetization free layer 3 can be prevented from being damaged.

(Protective layer)
The protective layers 41 and 42 are layers provided between the first magnetization fixed layer 11 and the X electrode 51 and between the second magnetization fixed layer 12 and the Y electrode 52, respectively, as necessary. The protective layers 41 and 42 are layers that play a role of preventing damage to the magnetization pinned layers 11 and 12 due to oxidation or alkaline chemicals during development, and in particular, magnetization pinning in the heat treatment when forming the light modulation element 1A. Prevent oxidation of layers 11 and 12. Further, the material constituting the protective layers 41 and 42 is required to have a property that does not react with the material constituting the magnetization fixed layers 11 and 12 during the heat treatment. Ta, Ru, or the like can be used as a material that satisfies such requirements. In particular, Ru is preferably used in the light modulation element 1A of the present invention because its resistivity does not increase even if it is oxidized itself. Here, the light modulation element 1A as one intermediate layer 2A is illustrated, but the light modulation element 1 of the first embodiment may also be configured to include the protective layers 41 and 42.

[Others]
A metal thin film layer 9 may be provided between the substrate 7 and the transparent electrode layer 8 (see FIG. 12). By providing the metal thin film layer 9 as an underlayer, the effect of multiple diffraction can be increased. Thereby, the magneto-optical effect of the magnetization free layer 3 can be improved. Furthermore, the adhesion between the substrate 7 and the transparent electrode layer 8 can be improved. Here, by setting the thickness of the metal thin film layer 9 to 1 nm or more, it is possible to increase the effects of multiple diffraction and adhesion. On the other hand, if it exceeds 3 nm, the light transmittance decreases, so that effect Also attenuates. Accordingly, the thickness of the metal thin film layer 9 is set to 1 to 3 nm. As will be described later, in the spatial light modulator 10C, since light that is diffracted after passing through the substrate 7 and the transparent electrode layer 8 and entering the light modulation element 1 is used, the space between the substrate 7 and the transparent electrode layer 8 is used. A metal material such as Ta, Pt, or Ru is used as the metal thin film layer 9 provided on the substrate.

  In addition, in each of the above embodiments, the case of perpendicular magnetization has been described. However, in-plane magnetization in which the magnetization direction is parallel to the layer surface may be used. In the case of in-plane magnetization, a material having in-plane magnetic anisotropy is used for the magnetization free layer 3 and the magnetization fixed layers 11 and 12. When one of the magnetization fixed layers 11 and 12 has a multilayer structure including a magnetic exchange coupling film, if it is in-plane magnetization, CoFe / Ru / CoFe / IrMn (in place of IrMn, FeMn, PtMn, etc. It is also possible to use an antiferromagnetic material.

≪Spatial light modulator≫
Next, the spatial light modulator of the present invention will be described here by taking as an example the case of using the light modulation element 1 of FIG.
[First Embodiment]
FIG. 2 is a schematic view of the configuration of the spatial light modulator 10 as viewed from the bottom.
As shown in FIG. 2, the spatial light modulator 10 uses the light modulation element 1 described above, and is arranged two-dimensionally on the substrate 7 (see FIG. 1) that transmits light and the substrate 7. A plurality of pixels 4, pixel selection means (pixel selection unit 94) for selecting one or more pixels 4 from the plurality of pixels 4, and current supply means for supplying a predetermined current to the pixels 4 selected by the pixel selection means (Power supply 93). Further, the spatial light modulator 10 includes a measuring unit 96 that measures a voltage value between the X electrode 51 and a transparent electrode layer (hereinafter, referred to as a transparent electrode as appropriate) 8 in the selected pixel 4. The driving (operation) of the pixel selection unit and the current supply unit is controlled by a current control unit 90 that is a current control unit. Then, the spatial light modulator 10 diffracts and emits light by changing the direction of polarization of the light that has passed through the substrate 7 and entered the pixel 4 selected by the pixel selection unit in a specific direction. Here, the substrate 7 and the transparent electrode layer 8 are seen through, but for the sake of convenience, the transparent electrode layer (transparent electrode) 8 is indicated by reference numeral 8. In FIG. 2, two X electrode selectors 91 that are two on the top and bottom of the page are essentially the same one X electrode selector 91, and two pixel selectors 94 that are two on the left and right of the page are originally Although the same pixel selection unit 94 is shown here, it is divided into two for convenience.
Each configuration will be described below.

(substrate)
The substrate 7 serves as a base for forming the light modulation element 1 and the drive electrodes 51 and 52. As will be described later, since the spatial light modulator 10 uses light that is diffracted after passing through the substrate 7 and the transparent electrode 8 and entering the light modulation element 1, the substrate 7 includes SiO ₂ , MgO, and sapphire. A transparent substrate having excellent permeability such as quartz glass is used.

(Pixel)
The pixels 4 are arranged in a two-dimensional array on the light incident surface of the spatial light modulator 10 to constitute a pixel array 40. That is, the pixel array 40 includes a plurality of X electrodes 51 in a plan view and a plurality of Y electrodes 52 orthogonal to the X electrode 51 in a plan view, one for each intersection of the X electrode 51 and the Y electrode 52. Pixel 4 is provided. In the present embodiment, the pixel array 40 is exemplified by a configuration including 16 pixels 4 of 4 rows × 4 columns.

  The pixel 4 includes the light modulation element 1 and a pair of drive electrodes 51 and 52 that are connected to the two magnetization fixed layers 11 and 12 and supply current to the light modulation element 1. Further, the groove of the light modulation element 1 (between the magnetization fixed layers 11 and 12 and between the intermediate layers 21 and 22), between the adjacent X electrodes 51 and 51, between the light modulation elements 1 and 1, and between the Y electrodes 52 and 52. In other words, the blank portion in FIG. 2 is filled with the insulating member 6.

<Light modulation element>
When the light modulation element 1 supplies a constant current between the X electrode 51 and the Y electrode 52, the light modulation element 1 diffracts by rotating the polarization plane of incident light incident on the light modulation element 1 by a Kerr effect by a certain angle. Take on. The size of the light modulation element 1 in a plan view is, for example, the width of the magnetization free layer 3 (the length in the lateral direction) (the width here means that the two magnetization fixed layers 11 and 12 are on the same plane) The alignment direction (hereinafter the same) is 400 nm and the length (length in the vertical direction) is 300 nm, or the width is 300 nm, the length is 400 nm, and the like. In addition, the width of the first magnetization fixed layer 11 and the second magnetization fixed layer 12 is 150 nm, and the distance between the first magnetization fixed layer 11 and the second magnetization fixed layer 12 is 100 nm. However, the size of the light modulation element 1 or the like is not limited to this.

  Further, in the spatial light modulator 10, the light modulation elements 1 are arranged in a two-dimensional matrix (a state in which the light modulation elements 1 are arranged two-dimensionally at regular intervals in the vertical and horizontal directions). It is a pixel. Here, the transparent electrode 8 is integrally formed with the light modulation elements 1 in the two pixels 4 adjacent to each other in the direction in which the two magnetization fixed layers 11 and 12 arranged in the same plane are arranged on the same plane. Yes. In addition, examples of the shape of the light modulation element 1 include a square and a rectangle (rectangle), but other shapes may be used. The pitch between the light modulation elements 1 depends on the precision of the drive electrodes 51 and 52 and the film formation technique of the light modulation element 1 (a semiconductor manufacturing process is preferably used), and is appropriately determined, for example, 1 μm or less. In this light modulation element 1, a first magnetization fixed layer 11 and a second magnetization fixed layer 12 are connected to a pair of drive electrodes, an X electrode 51 and a Y electrode 52, respectively, and current is supplied perpendicular to the layer surface. (See FIG. 1).

<X electrode and Y electrode>
The X electrode 51 is one of a pair of drive electrodes for supplying a current to the light modulation element 1, and the Y electrode 52 is the other electrode. As a material constituting the X electrode 51 and the Y electrode 52, copper (Cu) which is inexpensive and excellent in conductivity is preferably used, but is not limited to this, and gold (Au) or platinum (Pt) is not limited thereto. You may use noble metals, such as. As will be described later, since the incident polarized light enters the light modulation element 1 from the substrate 7 side and is diffracted by the magnetization free layer 3, the drive electrodes 51 and 52 do not need to transmit light. Therefore, the drive electrodes 51 and 52 need not be made of a transparent material. The widths of the drive electrodes 51 and 52 are appropriately determined according to the shape of the light modulation element 1 formed on the substrate 7. In the spatial light modulator 10, the light modulation elements 1 are two-dimensionally arranged at regular intervals in the vertical and horizontal directions. Therefore, the X electrode 51 has a belt-like shape and has the first magnetization fixed layer 11 at a constant width and a constant interval. It is provided above. The Y electrodes 52 are also arranged on the second magnetization fixed layer 12 so as to be arranged in parallel at regular intervals so that the longitudinal direction thereof is orthogonal to the longitudinal direction of the X electrodes 51.

<Insulating material>
The insulating member 6 is a member for insulating between the drive electrodes of the X electrode 51 and the Y electrode 52 and between the light modulation elements 1 and 1. As the insulating member 6, a conventionally known insulating material such as SiO ₂ or Al ₂ O ₃ may be used.

(Measurement part)
The measurement unit 96 measures the voltage value between the X electrode 51 which is one of the pair of drive electrodes 51 and 52 in the pixel 4 selected by the pixel selection unit 94 which will be described later, and the transparent electrode 8. Is. Here, the selection of the X electrode 51 and the transparent electrode 8 is performed by selection by the X electrode selection unit 91 and the transparent electrode selection unit 95. As will be described later, the voltage value measured by the measurement unit 96 is sent to the pixel selection unit 94, and the electrical resistance value is calculated.

(Power supply and pixel selector)
The driving operation of the power supply 93 and the pixel selection unit 94 is controlled by the current control unit 90.
<Current controller>
As shown in FIG. 2, the current control unit 90 controls the driving operation of the spatial light modulator 10 and the detection operation of the magnetization reversal operation of the spatial light modulator 10 (light modulation element 1). The current control unit 90 includes a pixel selection unit 94 (pixel selection unit) and a power source 93 (current supply unit) controlled by the pixel selection unit 94. As shown in FIG. 3, the pixel selection unit 94 selects the X electrode 51, the Y electrode 52, and the transparent electrode 8, and controls the driving of the power source 93, and the voltage measured by the measurement unit 96. A calculation unit 94b that calculates an electric resistance value from the value, a storage unit 94c that stores a setting range of a standard electric resistance value determined in accordance with a magnetization direction set in advance in the selected pixel 4, and a calculated electric value A determination unit 94d that determines that the magnetization reversal is good when the resistance value is within a set range of the standard electric resistance value, and determines that the magnetization reversal is defective when the resistance value is outside the setting range; A command unit 94e that commands resupply of current to the drive electrodes (X electrode 51 and Y electrode 52) when it is determined. Here, the standard electric resistance value means the electric resistance values R _H and R _{L in the} binary magnetization directions shown in FIGS. 7 (a) and 7 (b). R _H and R _L will be described later.

<Spatial light modulator drive and magnetization reversal detection operation>
Next, driving of the spatial light modulator 10 and detection operation of the magnetization reversal operation will be described with reference to FIGS.
As shown in FIGS. 3 and 4, first, an X electrode 51 that supplies current from a plurality of X electrodes 51 by an X electrode selection unit 91 that receives a command from an electrode selection unit 94 a provided in the pixel selection unit 94. Is selected, and the Y electrode 52 that supplies a current is selected from the plurality of Y electrodes 52 by the Y electrode selection unit 92 that has received a command from the electrode selection unit 94a. Further, the transparent electrode 8 that measures the voltage value with respect to the X electrode 51 is selected from the plurality of transparent electrodes 8 by the transparent electrode selection unit 95 that has received a command from the electrode selection unit 94a (S1). Thereby, a predetermined pixel 4 is selected. Here, the storage unit 94c provided in the pixel selection unit 94 stores a standard electric resistance value setting range determined according to a preset magnetization direction (S101). Then, along with the selection of the predetermined pixel 4, a standard electric resistance value range corresponding to the pixel 4 is selected. Next, current is supplied to the selected X electrode 51 and Y electrode 52 by the power supply 93 that has received a command from the pixel selection unit 94 (S2).

Next, the voltage value of the X electrode 51 and the transparent electrode 8 selected in S1 is measured by the measurement unit 96 (S3), and the voltage value measured by the measurement unit 96 is sent to the pixel selection unit 94. Next, the electrical resistance value is calculated from the voltage value by the calculation unit 94b provided in the pixel selection unit 94 (S4). The calculated electric resistance value is determined by the determination unit 94d as a set range of one value corresponding to the set magnetization inversion among the standard electric resistance values (R _H , R _L ) stored in the storage unit 94c in advance. Compared (S5). Here, the standard electric resistance value is a value within a predetermined range when the magnetization direction of the magnetization free layer 3 is downward (R _H ), and is downward when the magnetization direction is upward (R _L ). It is assumed that the value is within a predetermined range lower than (R _H ) (see FIGS. 7A and 7B). Then, it is determined whether or not the calculated electrical resistance value is within a desired range (S6). For example, when one value corresponding to the desired magnetization reversal is R _H , assuming that the calculated electrical resistance value is R ₂ , if R ₂ is within the R _H range, it is determined that the magnetization reversal is good. On the other hand, if “R ₂ is within the range of R _L , that is, out of the range of R _H ”, it is determined that the magnetization reversal is defective (see FIG. 7 for details: “Binary state of magnetization direction” described later) ”). That is, when it is within the desired range (S6: Yes), the magnetization reversal is considered good, and the process proceeds to the next step. On the other hand, when it is not within the desired range (S6: No), the magnetization reversal is determined to be defective, and the command unit 94e commands the resupply of the current to the drive electrodes 51 and 52, and the power source 93 to the drive electrodes 51 and 52. Current is supplied. Then, in all the pixels 4, it is determined whether or not the processing is finished. If the processing is finished (S7: Yes), the processing is finished. If not finished (S7: No), the next electrode is changed. select.
As a result, the spatial light modulator 10 is driven, and the magnetization direction of the spatial light modulator 10 (the magnetization free layer 3 of the light modulation element 1) is detected and reversed to a desired magnetization state.

  The X electrode selection unit 91 includes a plurality of switching elements provided corresponding to the plurality of X electrodes 51, respectively. Similarly, the Y electrode selection unit 92 includes a plurality of switching elements provided corresponding to the plurality of Y electrodes 52, respectively. A constant current is supplied from the power source 93 to each switching element, and is connected to the light modulation element 1 to be driven via the X electrode 51 and the Y electrode 52. When the switching element receives a command (operation signal) from the pixel selection unit 94 and performs a conduction operation, a current is supplied to the light modulation element 1.

  Similar to the X electrode selection unit 91 and the Y electrode selection unit 92, the transparent electrode selection unit 95 includes a plurality of switching elements provided corresponding to the transparent electrodes 8 of the plurality of light modulation elements 1, respectively. The switching element connected to the light modulation element 1 to be detected through the transparent electrode 8 performs a conduction operation in response to a command (operation signal) from the pixel selection unit 94, whereby the electric resistance of the light modulation element 1 Is measured, and the magnetization reversal operation of the light modulation element 1 is detected. Selection of the light modulation element 1 to be driven or detected, driving of the light modulation element 1, and operation control of the switching element for detecting the magnetization reversal operation are performed by the pixel selection unit 94. .

The power supply 93 has a current reversal function. That is, a positive current can be supplied to the X electrode 51 and a negative current can be supplied to the Y electrode 52. Conversely, a negative current can be supplied to the X electrode 51 and a positive current can be supplied to the Y electrode 52. You can also. The pixel selector 94 also controls the current reversal function of the power supply 93.
The pixel selection unit 94 is a so-called computer, and an X electrode selection unit 91, a Y electrode selection unit 92, a transparent electrode selection unit 95, and a power source 93 are executed by a central processing unit (not shown) executing a program stored in the ROM. The operation control is performed. Each selection by the X electrode selection unit 91, the Y electrode selection unit 92, and the transparent electrode selection unit 95 is performed by artificially setting a desired program in the pixel selection unit 94 and executing this program. .

<Operation of spatial light modulator>
Next, the operation of the spatial light modulator 10 will be described with reference to FIG.
First, laser light is emitted from an optical system OPS that is a light source. Since the laser light emitted from the optical system OPS includes various polarization components, the laser light is transmitted through the polarizer PFi below the substrate 7 to be light of one polarization component. Hereinafter, light of one polarization component is referred to as polarization. This polarized light (incident polarized light) is incident on all the pixels 4 of the pixel array 40 (see FIG. 2) at a predetermined incident angle. In each pixel 4, incident polarized light passes through the substrate 7 and the transparent electrode 8 and enters the light modulation element 1, and the polarization direction is rotated by a predetermined angle due to the Kerr effect by the magnetization free layer 3 of the light modulation element 1. The light is emitted from the light modulation element 1 as outgoing polarized light, passes through the transparent electrode 8 and the substrate 7 again, and is emitted from the pixel 4. All outgoing polarized light emitted from the respective pixels 4 reaches the polarizer PFo. The polarizer PFo transmits only specific polarized light, here, polarized light whose angle θ _k is rotated with respect to incident polarized light, and this transmitted outgoing polarized light is incident on the detector PD. On the other hand, the polarized light having the angle −θ _k rotation cannot pass through the polarizer PFo. The polarizers PFi and Pfo are polarizing plates or the like, and the detector PD is an image display means such as a screen, a camera, or the like.

As described above, the diffracted light (emitted polarized light) when the angle θ _k is rotated can pass through the polarizer PFo, but the diffracted light when the angle −θ _k is rotated cannot pass through the polarizer PFo. Can produce. Since the spatial light modulator 10 can selectively drive (current supply) the X electrode 51 and the Y electrode 52 as described above to flow a current to a desired light modulation element 1, Whether the magnetization direction of the magnetization free layer 3 is controlled by the direction and magnitude of the current for each modulation element 1 (for each pixel 4), and whether the diffracted light can pass through the polarizer PFo or not. Thus, the intensity (contrast) of the diffracted light can be controlled. In this control, the transparent electrode 8 of the light modulation element 1 is used to measure the electric resistance of the light modulation element 1, specifically, the electric resistance between the X electrode 51 and the transparent electrode 8, and the value is measured. Thus, it is detected whether or not the magnetization reversal operation of the light modulation element 1 (magnetization free layer 3) is satisfactorily performed. If the magnetization reversal operation is defective, the current is supplied again.

The contrast ratio of the diffracted light is determined by the magnitude of the Kerr effect (the Kerr rotation angle) by the magnetization free layer 3. As shown in FIG. 5, or transmitted through the angle theta _k rotatory to the diffracted light, or in the case of one of the states to shield angularly - [theta] _k optical rotation, the Kerr rotation angle (-θ _{k, θ k)} is constant When the angle is greater than the angle, high contrast can be obtained, but when the Kerr rotation angle is small, the contrast is low. As shown in FIG. 5, when the magnetization direction of the magnetization free layer 3 is downward, the output of the photodetector is “bright”, and conversely, when the magnetization direction of the magnetization free layer 3 is upward. “Dark state”.

<Transition of magnetic domain state of light modulation element>
Next, the transition of the magnetic domain state of the light modulation element 1 will be described with reference to FIG.
As shown in FIG. 6A, in the initial state, the magnetization direction is downward in the magnetization free layer 3, upward in the first magnetization fixed layer 11, and downward in the second magnetization fixed layer 12.

  From this state, as shown in FIG. 6B, when a pulse current is supplied with the X electrode 51 negative and the Y electrode 52 positive, the upward spin electron d1 is the first in the electrons injected from the X electrode 51. Although passing through the magnetization pinned layer 11, the downward spin electron d <b> 2 cannot pass through the first magnetization pinned layer 11. That is, electrons injected from the X electrode 51 are discriminated by the first magnetization fixed layer 11, and spins are aligned in the magnetization direction of the first magnetization fixed layer 11 inside the first magnetization fixed layer 11 (spin polarization). Spin-polarized electrons (upward-spin electrons d1) pass through the first intermediate layer 21 while maintaining spin, and are injected into the magnetization free layer 3. In the magnetization free layer 3, a force called local spin torque is generated by the interaction between the internal electrons that determine the magnetization direction of the magnetization free layer 3 and the injected spin-polarized electrons. It reverses the spin of internal electrons that determines the magnetization direction. For this reason, as a result, magnetization reversal occurs from the magnetization free layer 3 near the first magnetization fixed layer 11.

  At the same time, among the electrons in the magnetization free layer 3 near the second magnetization fixed layer 12, the downward spin electrons d 2 pass through the second magnetization fixed layer 12, while the upward spin electrons d 1 are transmitted in the second magnetization fixed layer 12. Can not pass. That is, the electrons in the magnetization free layer 3 are discriminated by the second magnetization fixed layer 12 as only the downward spin electrons d2 pass through the second magnetization fixed layer 12 while maintaining the spin. As a result, the upward spin electrons d1 remain in the magnetization free layer 3 near the second magnetization fixed layer 12 and from the magnetization free layer 3 near the second magnetization fixed layer 12 due to the torque due to the upward spin. Also causes magnetization reversal. At this time, a small amount of current also leaks to the transparent electrode layer 8 and a part of the upward spin electrons d1 leaks. Generally, however, the transparent electrode layer 8 such as IZO or ITO is a magnetization free layer. 3 is about 20 times larger than the specific resistance (˜20 μΩ · cm), so that the influence of the leakage current can be kept low. In this way, by supplying a pulse current having an appropriate width, the magnetization of the magnetization free layer 3 is reversed, and as a result, the state shifts from FIG. 6B to FIG. 6C.

  As shown in FIG. 6C, in this state, the magnetization direction of the magnetization free layer 3 is upward. In this state, as shown in FIG. 6D, when a pulse current is supplied with the X electrode 51 being positive and the Y electrode 52 being negative, the downward spin electron d2 discriminated by the second magnetization fixed layer 12 is free of magnetization. Magnetization reversal occurs from the magnetization free layer 3 near the second magnetization fixed layer 12 due to the torque caused by the downward spin that is injected into the layer 3. At the same time, due to the torque due to the downward spin electrons d2 discriminated by the first magnetization pinned layer 11, magnetization reversal also occurs from the magnetization free layer 3 immediately below the first magnetization pinned layer 11. At this time, the current slightly leaks to the transparent electrode layer 8 and part of the downward spin electrons d2 leaks. However, as described above, the influence of the leakage current can be kept low. In this way, by supplying a pulse current having an appropriate width, the magnetization direction of the magnetization free layer 3 is reversed, and as a result, the state shifts from FIG. 6D to FIG. 6A.

Thus, since the magnetization direction of the magnetization free layer 3 can be controlled by the direction in which the pulse current flows, it can be operated as the light modulation element 1 that controls the polarization plane of the light diffracted by the pulse current. Note that a direct current may be used instead of the pulse current. Moreover, although it demonstrated as what supplies an electric current here, you may apply a voltage. It should be noted that the direction of magnetization after the pulse supply is maintained as it is, and it is not necessary to separately pass a current. That is, the light modulation element 1 of the present invention has its own memory function.
By providing the two magnetization fixed layers 11 and 12, the efficiency of spin injection can be improved, and the magnetization reversal of the magnetization free layer 3 can be achieved even if the area of the light incident surface (emission surface) is increased. Since this occurs efficiently, the aperture ratio of the pixel 4 can be increased.

<About the binary state of the magnetization direction>
In the present invention, the magnetization reversal operation of the magnetization free layer 3 can be electrically measured. This will be described with reference to FIG. 7A shows a state in which the magnetization direction of the magnetization free layer 3 is downward, and FIG. 7B shows a state in which the magnetization direction of the magnetization free layer 3 is upward.
As shown in FIGS. 7A and 7B, for example, the first magnetization fixed layer 11 and the second magnetization fixed layer 12 are made of the same material, and the first intermediate layer 21 and the second intermediate layer 22 are the same. If the material and the film thickness are the same, the resistance between the magnetization fixed layers 11 and 12 and the magnetization free layer 3 is either R _H or R _L depending on the combination of the magnetization directions. Here, “H” indicates that the resistance value is high, and “L” indicates that the resistance value is low. Therefore, if the resistance between the X electrode 51 and the Y electrode 52 is R ₁ , both are “R ₁ = R _H + R _L ” in the states of FIGS. Cannot detect magnetization reversal. However, if the resistance between the X electrode 51 and the transparent electrode layer 8 is R ₂ , R ₂ is R ₂ = R _{H in} the state of FIG. 7A in which the magnetization direction of the magnetization free layer 3 is downward. In the state of FIG. 7B where the magnetization direction of the magnetization free layer 3 is upward, R ₂ = R _L , and the values are different (R _H or R _L ).

Then, as described above, the set range of the standard electric resistance value (for example, R _H ) determined and stored according to the magnetization direction set in advance in the selected pixel 4 is compared with the calculated electric resistance value R ₂ . to the magnetization reversal if the electric resistance value R ₂ is a value within the set range is good, it is possible to determine the magnetization reversal good or bad as a defective if a value outside the range. That is, by providing the transparent electrode layer 8, the magnetization reversal operation of the magnetization free layer 3 can be accurately known. As a result, when it is determined that the magnetization reversal operation of the magnetization free layer 3 is not performed accurately, the current may be supplied again to reverse the magnetization state to a desired state. In this way, for example, it can be used for error correction when an error that does not cause desired magnetization reversal occurs.

<Method for manufacturing optical modulator>
Next, an example of a method for manufacturing the spatial light modulator 10 will be described with reference to FIGS. Here, the case where the metal thin film layer 9 and the protective layers 41 and 42 are not provided will be described.

  First, each layer film for forming the transparent electrode layer 8, the magnetization free layer 3, the intermediate layers 21, 22 and the magnetization fixed layers 11 and 12 on the substrate 7 is formed in this order by sputtering (for example, magnetron sputtering, ion beam sputtering). ), Etc., to form a device film by consistently forming a film in a vacuum. Further, the element film formed on the substrate 7 is heat-treated as necessary. This heat treatment is performed in order to improve the characteristics of the light modulation element 1 and to suppress changes in the characteristics of the light modulation element 1 during a photolithography process performed later. As heat treatment conditions, for example, vacuum heat treatment is performed at 190 to 500 ° C. for 1 hour.

  Next, a pixel-size resist is formed on the element film layer to form a resist pattern. The resist is formed by an EB (electron beam) exposure method or the like so that a resist pattern of a predetermined size becomes a mesa pattern according to the size of the light modulation element 1. Then, the portion of the resist pattern where the resist is not formed is removed up to the upper surface of the transparent electrode layer 8 (until the surface is exposed) in the film thickness direction of the element film. The removal can be performed by etching or milling by an ion beam milling method using Ar ions or the like.

  Thereafter, without peeling off the resist, an insulating material (insulating member 6) such as alumina or silicon oxide is deposited on the entire surface, and the groove formed by milling or the like is filled with the insulating member 6. The insulating member 6 can be formed by a reactive sputtering method, a CVD method, a sol-gel method, or the like. The thickness of the insulating member 6 deposited in the groove is equal to or greater than the groove depth. In addition, since the insulating member 6 is deposited before the resist is removed, the insulating member 6 is also deposited on the resist.

  After the insulating member 6 is deposited, it is immersed in a resist stripping solution and lifted off (resist stripping). Alternatively, the resist may be removed by a CMP (Chemical Mechanical Polishing) method. When performing CMP processing or the like, it may be formed thicker by the polishing thickness so that the thickness of the magnetization fixed layers 11 and 12 formed at the uppermost portion has a predetermined value. Good.

  Next, a resist pattern having a hole that divides the central portion of the element film is formed, and the center of the element film is removed to the upper surface of the magnetization free layer 3 by milling or the like (see FIG. 1A). Alternatively, the intermediate layer 2A is removed to the upper surface or partway (see FIG. 1B). Thereafter, without peeling off the resist, an insulating material (insulating member 6) such as alumina or silicon oxide is deposited again on the entire surface, and the groove formed by milling or the like is filled with the insulating member 6 by the same method as described above. The thickness of the insulating member 6 deposited in the groove is equal to or greater than the groove depth. In addition, since the insulating member 6 is deposited before the resist is removed, the insulating member 6 is also deposited on the resist. After the insulating member 6 is deposited, it is immersed in a resist stripping solution and lifted off. Alternatively, the resist may be removed by a CMP method.

  After removing the resist, the X electrode 51 is formed on the first magnetization fixed layer 11 and the Y electrode 52 is formed on the second magnetization fixed layer 12 at predetermined intervals so as to be orthogonal to each other. This electrode can be formed in the same manner as the element film formation method. The insulating member 6 is filled between the X electrodes 51 and the Y electrodes 52.

  As mentioned above, although embodiment of the spatial light modulator 10 which concerns on this invention was described, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the meaning of this invention. For example, the following configuration may be used.

[Second Embodiment]
As illustrated in FIGS. 8 and 9, the spatial light modulator 10 </ b> A includes two light-emitting elements 4 arranged adjacent to each other in the direction in which the two magnetization fixed layers 11 and 12 are arranged on the same plane. The two are formed as one integrated element 15 by integrating the second magnetization fixed layers 12 of the two light modulation elements 1 connected to the same Y electrode 52. Specifically, as shown in FIG. 9, there is one second magnetization fixed layer 12 of one light modulation element 1 and one second magnetization fixed layer 12 of the light modulation element 1 adjacent to this light modulation element 1. It is configured as a magnetization fixed layer F. Other configurations are the same as those of the spatial light modulator 10 of the first embodiment.

  That is, the integrated element 15 is composed of three magnetization fixed layers 11, F, 11 separated on the same plane, and each of the three magnetization fixed layers 11, F, 11 is on the same plane. Is laminated on the two magnetization free layers 3 and 3 separated by the intermediate layers 22 and 22 therebetween. The magnetization pinned layer F located at the center of the three magnetization pinned layers 11, F and 11 is laminated so as to straddle the two magnetization free layers 3 and 3, and the other two magnetization pinned layers each have two magnetization free layers. It is laminated on either one of the layers 3 and 3. The three magnetization fixed layers 11, F, 11 have one magnetization fixed layer F located in the center fixed to an antiparallel magnetization to the other two magnetization fixed layers 11, 11, and two magnetization free layers It is a magnetic body having a larger coercive force than the layers 3 and 3.

  By setting it as such a structure, the magnitude | sizes of the 1st magnetization fixed layer 11 and the 2nd magnetization fixed layer 12 in the light modulation element 1 can be made different, and it can be set as a different coercive force, respectively. Therefore, the magnetizations of the first magnetization fixed layer 11 and the second magnetization fixed layer 12 can be easily fixed in an antiparallel state.

Next, a method for manufacturing the spatial light modulator 10A will be described with reference to FIG. In addition, about the matter similar to the manufacturing method of the above-mentioned spatial light modulator 10, description is abbreviate | omitted suitably.
First, an element film A in which a transparent electrode layer film 300, a magnetization free layer film 301, an intermediate layer film 302, a magnetization fixed layer film 303, and a first electrode layer film 304 are stacked on a substrate 7 is formed ( FIG. 10 (a)). Next, a resist pattern having a hole that divides the central portion of the element film A by the resist B is formed (FIG. 10B). Thereafter, the center of the element film A is removed to the upper surface of the transparent electrode layer film 300, and two element films Aa and Ab are formed with a groove interposed therebetween (FIG. 10C). Then, without peeling off the resist B, the insulating member 6 is deposited on the entire surface, the formed groove is filled with the insulating member 6 to the height of the upper surface of the intermediate layer film 302, and the magnetization fixed layer film 303 is further formed on the entire surface. Then, the groove formed is filled with the magnetization fixed layer film 303 up to the height of the upper surface of the magnetization fixed layer film 303 on the intermediate layer film 302 (FIG. 10D). As a result, the magnetization fixed layer film 303 is connected at the groove portion to form an integrated film 303a. In these cases, the insulating member 6 is also deposited on the resist B, and the magnetization fixed layer film 303 is also deposited on the insulating member 6 (FIG. 10D).

  Then, it is immersed in a resist stripping solution and lifted off (FIG. 10E). Next, a perforated resist pattern is formed so as to divide the central portions of the element films Aa and Ab (FIG. 10F), and the center of each of the element films Aa and Ab is formed in the magnetization free layer. The top surface of the working film 301 is removed (FIG. 10G). Next, the insulating member 6 is deposited again on the entire surface without peeling off the resist B, and the formed groove is filled with the insulating member 6, and then immersed in a resist stripping solution to lift off (FIG. 10 (h)). . Next, the second electrode layer film 305 is laminated on the first electrode layer film 304 on the integrated film 303a and in the groove portion on the integrated film 303a (FIG. 10I). The second electrode layer film 305 and the first electrode layer film 304 (the first electrode layer film 304 on the integral film 303a) in contact with the second electrode layer film 305 are integrated to form the Y electrode 52. Further, the first electrode layer films 304, 304 on both the left and right sides on the paper surface become the X electrode 51.

[Third Embodiment]
As shown in FIG. 11, in the spatial light modulator 10 </ b> B, one pixel 4 includes three light modulation elements 1, and these light modulation elements 1 include common drive electrodes 51 and 52. . Other configurations are the same as those of the spatial light modulator 10 of the first embodiment.

  With such a configuration, since the plurality of light modulation elements 1 are set as one pixel 4, multi-stage display of the pixel 4 can be performed. In other words, when one light modulation element 1 constitutes one pixel, one pixel can take only two states corresponding to the direction of the magnetization direction, and the light gradation of one pixel is, for example, “1”. There are two gradations, a state and a dark state indicated by “0”. However, when one pixel is constituted by the three light modulation elements 1, a state between the bright state and the dark state, that is, an intermediate state that is darker than the bright state and brighter than the dark state is created. be able to. Specifically, the magnetization directions of the three light modulation elements 1 are respectively (1) “up, up, up”, (2) “up, up, down”, “up, down, up”, or , “Bottom, top, top”, (3) “top, bottom, bottom”, “bottom, top, bottom” or “bottom, bottom, top”, (4) “bottom, bottom, bottom” Four states can be formed. According to these four states, the light / dark state can be changed in four stages. As described above, when one pixel includes three light modulation elements 1, each pixel 4 is changed from a bright state to a dark state (or from a dark state to a bright state) according to the direction and magnitude of a current flowing through the light modulation element 1. It is possible to create a plurality of different intermediate states by changing to stepwise. Therefore, for example, when displaying an image or an image using the spatial light modulator 10B, it is possible to express a precise gradation.

[Others]
In addition, in each of the embodiments described above, the case where one pixel 4 includes one or three light modulation elements 1 has been described. However, one pixel 4 includes two light modulation elements 1 or four. It may be the above. In the case of two, the above-described intermediate state is one. That is, each of the plurality of pixels 4 may have a plurality of light modulation elements 1. In the second embodiment, the second magnetization fixed layer 12 of the two light modulation elements 1 connected to the same Y electrode 52 is integrated into one integrated element 15. The first magnetization fixed layer 11 of each light modulation element 1 connected to each other is integrated into one integrated element, and the second magnetization fixed layer 12 of the light modulation element 1 connected to the Y electrode 52 is separated. May be. Note that if the first magnetization fixed layer 11 and the second magnetization fixed layer 12 are integrated together, an arbitrary pixel cannot be selected by the drive electrodes 51 and 52 arranged in a matrix. Don't do it. That is, in the two pixels 4 adjacent in the direction in which the two magnetization fixed layers 11 and 12 arranged in the same plane are aligned, two of the light modulation elements 1 are connected to one of the two drive electrodes 51 and 52. One magnetization fixed layer (first magnetization fixed layer 11 or second magnetization fixed layer 12) of two light modulation elements 1 connected to any one of the same drive electrodes (X electrode 51 or Y electrode 52) is integrated into one It is an integrated element. Further, only a part of the light modulation element may be an integrated element.

  Furthermore, the light modulation element 1 may be used as a magnetoresistive effect element in a magnetic random access memory (MRAM). In each of the above embodiments, the light modulation element 1 shown in FIG. 1A has been described as an example. However, a spatial light modulator is configured using the light modulation element 1A shown in FIG. Alternatively, a light modulation element that has been changed without departing from the gist of the present invention may be used. For example, as shown in FIG. 12, the spatial light modulator 10C uses a light modulation element 1B. That is, the metal thin film layer 9 is provided between the substrate 7 and the transparent electrode layer 8. Thereby, since the effect of multiple diffraction can be increased, the spatial light modulator 10C in which the magneto-optical effect of the magnetization free layer 3 is improved can be obtained.

  Further, the transparent electrode layer 8 is formed integrally with the light modulation elements 1 in the two pixels 4 adjacent in the direction in which the two magnetization fixed layers 11 and 12 arranged in the same plane are arranged in the same plane. You may divide and comprise for every light modulation element 1. FIG. When the metal thin film layer 9 is provided, the metal thin film layer 9 may also be divided and configured in accordance with the transparent electrode layer 8. Furthermore, although the transparent electrode layer 8 and the metal thin film layer 9 are constituent elements of the light modulation element 1, only the metal thin film layer 9 or the transparent electrode layer 8 and the metal thin film layer 9 are constituent elements of the spatial light modulator. It is good.

DESCRIPTION OF SYMBOLS 1,1A Light modulation element 2A Intermediate layer 3 Magnetization free layer 4 Pixel 6 Insulation member 7 Substrate 8 Transparent electrode layer (transparent electrode)
9 Metal thin film layer 10, 10A, 10B, 10C Spatial light modulator 11 First magnetization fixed layer 12 Second magnetization fixed layer 15 Integrated element 21 First intermediate layer 22 Second intermediate layer 40 Pixel array 41, 42 Protective layer 51 X electrode (drive electrode)
52 Y electrode (drive electrode)
90 Current control unit (current control means)
91 X electrode selector 92 Y electrode selector 93 Power supply (current supply means)
94 Pixel selection section (pixel selection means)
94a Electrode selection unit 94b Calculation unit 94c Storage unit 94d Judgment unit 94e Command unit 95 Transparent electrode selection unit 96 Measurement unit

Claims (6)

A pair of spin injection magnetization reversal element structures formed on a substrate that transmits light and having a magnetization free layer, an intermediate layer, and a magnetization fixed layer stacked in this order, and connected to the magnetization fixed layer A light modulation element that diffracts and emits light that is transmitted through the substrate and changes its polarization direction by changing a magnetization direction of the magnetization free layer by supplying a current between the drive electrodes of ,
The light modulation element further includes a transparent electrode layer between the substrate and the magnetization free layer,
The magnetization fixed layer is composed of two magnetization fixed layers separated on the same plane,
The light modulation element, wherein the two magnetization fixed layers are fixed to antiparallel magnetization and have a coercive force larger than that of the magnetization free layer.   The light modulation element according to claim 1, wherein one of the two magnetization fixed layers has a multilayer structure including a magnetic exchange coupling film.   The light modulation element according to claim 1, further comprising a metal thin film layer having a thickness of 1 to 3 nm between the substrate and the transparent electrode layer. A spatial light modulator using the light modulation element according to any one of claims 1 to 3,
A substrate that transmits light, a plurality of pixels that are two-dimensionally arranged on the substrate, a pixel selection unit that selects one or more pixels from the plurality of pixels, and a predetermined current in the pixel selected by the pixel selection unit Current supply means for supplying
The pixel includes the light modulation element and a pair of drive electrodes connected to the two magnetization fixed layers and supplying a current to the light modulation element,
And a measuring unit that measures a voltage value between one of the pair of drive electrodes in the selected pixel and the transparent electrode layer of the light modulation element,
The pixel selection means includes a calculation unit that calculates an electric resistance value from the voltage value measured by the measurement unit, and a standard electric resistance value that is determined according to a magnetization direction that is set in advance in the selected pixel. A storage unit for storing a range, and when the calculated electrical resistance value is a value within the set range of the standard electrical resistance value, it is determined that the magnetization reversal is good, and when it is outside the set range, the magnetization reversal is A spatial light modulator comprising: a determination unit that determines a defect; and a command unit that commands resupply of current to the drive electrode when the magnetization reversal is determined to be defective.   In the two pixels arranged adjacent to each other in the direction in which the two magnetization fixed layers are arranged on the same plane, two of the light modulation elements are connected to the same drive electrode. 5. The spatial light modulator according to claim 4, wherein the magnetization fixed layer of the element is integrated into one integrated element.   6. The spatial light modulator according to claim 4, wherein each of the plurality of pixels includes a plurality of light modulation elements.

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