JP2010282103A - Magneto-optical element, optical modulator, magneto-optical control element, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a robust magneto-optical element capable of performing high-speed optical modulation and exhibiting a favorable S/N ratio, and a magneto-optical type optical modulator using the magneto-optical element. <P>SOLUTION: The magneto-optical element is composed of a microstructure 2 including a magnetic material layer 11 formed on a substrate 8 and a precious metal material layer 12 layered on the magnetic material layer 11 with its circumference covered with an insulating material layer 14 except a contact part with the magnetic material layer 11. When the rotating direction of linearly polarized light incident by the change of a magnetic field applied to the microstructure 2 is varied, a magneto-optical effect by the magnetic material layer 11 is increased by an electric field enhancement effect of the plasmon in the precious metal material layer 12, and the linearly polarized light is rotated with high definition at high speed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention uses a magnetic material and plasmon, and is capable of high-speed optical modulation and good S / N, a magneto-optic optical modulator using the same, an optical switch, a sensor, etc. The present invention relates to a magneto-optical control element and an image display device.

  In products that involve optical information processing such as cameras and projectors, spatial light modulators (SLMs) that control the phase and amplitude of propagating light are used as key devices for displaying images. As the spatial light modulator, there is a growing demand for a spatial light modulator that has a response speed superior to that of a liquid crystal type or a MEMS (Micro Electro Mechanical System) type that is currently in practical use. However, in the liquid crystal type that controls the molecular orientation and the MEMS type that changes the angle of the mirror, the response speed remains at the microsecond level, and in order to achieve a spatial light modulator with a further response speed, in principle these It is necessary to develop a spatial light modulator different from the above.

  In principle, there is a magneto-optical method as a method having a response speed from nanoseconds to sub-nanoseconds. In this magneto-optical method, the effect of rotating the polarization plane of linearly polarized light when a magnetic field is applied to a substance is based on the magneto-optical effect. When the transmitted light is affected, the Faraday effect and reflected light are affected. The effect is called the magnetic Kerr effect. In the magneto-optical system, high-speed switching is possible using the fact that the magnetization reversal speed of the magnetic moment of the magnetic thin film is from nanoseconds to subnanoseconds. Spatial light modulators using this magneto-optical method are disclosed in Non-Patent Document 1, Patent Document 1, and the like.

  The spatial light modulator disclosed in Patent Document 2 includes a layer having a magneto-optic effect and a magnetic field generation layer, and a plurality of magnetic domains are defined in the layer having a magneto-optic effect. Each having at least one wiring layer (vertical wiring layer) provided with vertical wiring for applying a magnetic field and horizontal wiring layer (horizontal wiring layer) provided with horizontal wiring, and each of the wirings in the forward direction or the reverse direction. The light intensity is continuously modulated by the magneto-optic effect of the layer having the magneto-optic effect by supplying or stopping the current.

  The spatial light modulator disclosed in Patent Document 3 uses a CPP (Current Perpendicular to the Plane) -GMR (Giant Magneto-Resistance) element or a TMR (Tunneling Magneto-resistance) element as a magneto-optical element, and has a pixel size. The light is modulated with high-speed response. However, there is a problem that the yield is poor because the element structure becomes complicated and requires many processing processes.

  Patent Document 4 describes a display device, a holography device, and a hologram recording device using an optical modulator. In this optical modulator, magnetization reaction elements are arranged in a plurality of pixels arranged in an array, and a nonmagnetic insulator is formed between the magnetization reaction elements. This magnetization reaction element has a columnar laminated structure of a magnetization direction fixed layer whose magnetization direction is fixed, a separation layer made of a nonmagnetic material, and a magnetization direction variable layer whose magnetization direction is reversed by applying a voltage. The electrodes arranged in an array are connected to each other so that a desired pixel can be selected, and the magnetization direction of the magnetization direction variable layer of the magnetization reaction element of the selected pixel is reversed to change the polarization direction of incident light. It is detected with a polarizing plate.

  Although it is not a spatial light modulator, for example, as shown in Patent Document 5 and Patent Document 6, research and development of a light control device and an information reproducing device using a magneto-optic effect have been made so far. These all use a magnetic thin film and do not use a microstructure.

In recent years, attempts have been made to improve magneto-optical characteristics by a novel optical phenomenon. Examples using plasmon resonance and photonic crystals are given below.
Research on nanometer to micrometer-scale structures (hereinafter referred to as microstructures) is progressing in many fields such as nanophotonics, high-density recording media, optical elements, and biochips. Localized surface plasmon resonance is one of the optical phenomena peculiar to microstructures. Localized surface plasmon resonance is a resonance phenomenon that is peculiar to noble metals such as Au, Ag, Cu, and Al, and shows an effect of enhancing the electric field of light. For example, in the surface enhanced Raman scattering (SERS) method, the Raman scattering intensity of a certain molecule adsorbed on the surface of a metal nanoparticle such as gold or silver is higher than when the molecule exists in a liquid. ^Is also known as an analysis method utilizing the fact that it is remarkably enhanced (about 10 ³ to ⁶ ). In the magnetic material, it is expected that the magneto-optic effect is increased by adopting a laminated structure with a noble metal thin film and a composite material structure with noble metal nanoparticles.

  The magneto-optical body disclosed in Patent Document 7 increases the magneto-optical effect by combining metal nanoparticles with a transmissive magnetic thin film made of Bi: YIG. Further, the magneto-optical element disclosed in Patent Document 8 has a fine particle arrangement layer containing metal magnetic fine particles regularly arranged on a nonmagnetic support, and applies a magnetic field to the metal magnetic fine particles from the outside. In addition, linearly polarized light is incident, and a magneto-optical effect is generated by the interaction between the incident light on the metal magnetic fine particles and the metal surface plasmon vibration, thereby improving the contrast when applied as a display element.

  A photonic crystal is an artificial crystal whose dielectric constant is periodically modulated. As a magneto-optic element that increases the magneto-optic effect in a photonic crystal, the magneto-optic body disclosed in Patent Document 9 and an optical isolator using this magneto-optic body are a first set of one-dimensional elements having a magneto-optic thin film. A low refractive index dielectric having an optical length of λ / 4 + mλ / 2 (λ is the wavelength of light, m is 0 or a positive integer) of a second set of one-dimensional magnetophotonic crystals having a magnetophotonic crystal and a magneto-optic thin film By stacking through a thin film, the Faraday rotation angle is increased.

  In addition, the refractive index control method, the periodic structure, and the optical element disclosed in Patent Document 10 apply a magnetic field to a periodic structure in which an optical medium is periodically arranged on an optical substrate, and thereby the refractive index of the periodic structure. Is controlling. However, there is a problem that the light transmittance is greatly reduced in the case of fine particles having a size of several hundred nm. The manufacturing method of the refractive index periodic structure having the photonic structure shown in Patent Document 11 and the optical functional element using the same are the same. When a magnetic material is used as the optical functional material, the light transmittance is It is difficult to obtain a desired effect such as an increase in the Faraday effect.

  Patent Document 12 proposes a magneto-optical element using a dielectric multilayer film. The optical element disclosed in Patent Document 13 includes incident light having a predetermined wavelength in a structure in which a second optical medium and a third optical medium are periodically arranged in the first optical medium at intervals of the wavelength order of incident light. The photonic band wavelength is controlled by adding an external field condition that modulates. The optical switch disclosed in Patent Document 14 is an optical switch composed of a magnetic head layer, a layer having a magneto-optic effect, and a polarizer layer. It consists of a periodic structure of magnetic material.

  Non-patent document 2 reports that the Co / Au structure increases the sensitivity three times compared to a normal biosensor. Non-patent document 3 discloses a microstructure of Au / Co / Au. It shows that the magneto-optic effect can be increased by localized surface plasmon resonance in the body. However, there has been no proposal as an optical device that can withstand practical use.

  The present invention uses a microstructure, can perform high-speed light modulation, has a good S / N, and is a robust magneto-optical element, a magneto-optical light modulator using the same, An object of the present invention is to provide magneto-optical control elements such as switches and sensors and an image display device.

  The magneto-optical element of the present invention is formed to be smaller than half of the wavelength of light, and is at least a magnetic material layer provided on a substrate and laminated on the magnetic material layer, and has a periphery other than a contact portion with the magnetic material layer. It comprises a microstructure having a noble metal material layer covered with an insulating material, and the rotation direction of linearly polarized light that is incident is varied by changing the magnetic field applied to the microstructure.

  An insulating layer and a noble metal material layer are laminated from the substrate side between the substrate and the magnetic material layer.

  The microstructure may have a square, rectangular, or asymmetric shape in cross section parallel to the surface of the substrate.

  The noble metal material layer of the microstructure is formed of any one of Au, Ag, Cu, Al, or an alloy material thereof.

In addition, the magnetic material layer of the microstructure includes at least one of Co, Fe, and Ni. In addition, the magnetic material layer includes a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between crystal grains containing at least Co and grown in a columnar shape, Fe / Pt, Co / Pt, Co / Pd. A multilayer structure with perpendicular magnetic anisotropy selected from any of the above, or a garnet-type ferrite that is yttrium-iron-garnet (YIG, Y ₃ Fe ₃ O ₁₂ ) or a part thereof is replaced. It may be formed of a material or half metal.

  A first optical modulator according to the present invention includes any one of the magneto-optical elements, a polarizer, a magnetic field control unit, and an analyzer, and the polarizer converts incident light into linearly polarized light. The magnetic field control means changes the magnetic field applied to the magneto-optical element, and the magneto-optical element changes the rotation direction of the incident linearly polarized light by the change of the magnetic field applied by the magnetic field control means. The analyzer transmits a polarization component rotated in a certain direction of transmitted light from the magneto-optical element.

  A second optical modulator according to the present invention includes any one of the magneto-optical elements, a polarizer, a magnetic field control unit, and an analyzer, and the polarizer converts incident light into linearly polarized light. The magnetic field control means changes the magnetic field applied to the magneto-optical element, and the magneto-optical element changes the rotation direction of the incident linearly polarized light by the change of the magnetic field applied by the magnetic field control means. The analyzer transmits a polarization component rotated in a direction of reflected light from the magneto-optical element.

  According to a third optical modulator of the present invention, in the first and second magneto-optic modulators, the magneto-optical elements are two-dimensionally arranged on the surface of the substrate, and the phase and amplitude of light are two-dimensionally arranged. It is characterized by spatial modulation.

  The magneto-optical control element according to the present invention includes the optical modulator, and performs on / off control of light by changing a magnetic field applied to the magneto-optical element by the magnetic field control means.

  The image display apparatus according to the present invention includes the third light modulator, and performs a two-dimensional spatial light modulation by changing a magnetic field applied to the magneto-optical element by the magnetic field control means. .

  The magneto-optical element according to the present invention includes a magnetic material layer provided on a substrate and a noble metal material layer laminated on the magnetic material layer and covered with an insulating material except for a contact portion with the magnetic material layer. Because it consists of a structure and the direction of rotation of incident linearly polarized light can be changed by changing the magnetic field applied to the microstructure, the magneto-optic effect of the magnetic material layer can be reduced by the plasmon electric field enhancement effect of the noble metal material layer. The linearly polarized light can be rotated with high definition and high speed.

As the magnetic material layer of this microstructure, a granular material containing at least one of Co, Fe, Ni, or containing at least Co, and forming a grain boundary portion made of a nonmagnetic substance between crystal grains grown in a columnar shape. Or a multilayer structure with perpendicular magnetic anisotropy selected from Fe / Pt, Co / Pt, Co / Pd, or yttrium-iron-garnet (YIG, Y ₃ Fe _A magneto-optical element having a high signal intensity can be obtained by forming the garnet-type ferrite that is ₃ O ₁₂ ), or a material or a half metal in which a part thereof is substituted.

  The optical modulator having the magneto-optical element according to the present invention causes the linearly polarized light from the polarizer to enter the magneto-optical element and changes the magnetic field applied to the magneto-optical element to rotate the linearly-polarized light incident on the magneto-optical element By changing the direction and transmitting the polarized component rotated in a certain direction of the transmitted light or reflected light from the magneto-optical element with the analyzer, it is possible to perform light modulation at high definition and high speed, and the signal strength is strong and robust. An optical modulator can be provided.

  In addition, the magneto-optical control element of the present invention has an optical modulator capable of optical modulation at high definition and high speed, and performs on / off control of light by changing a magnetic field applied to the magneto-optical element. , You can know the ultrafast optical switching possible.

  Furthermore, an image display device that includes a magneto-optic control element and performs two-dimensional spatial light modulation can increase the signal intensity and respond at high speed.

It is a cross-sectional schematic diagram which shows the structure of the light transmission type | mold spatial light modulator of this invention. It is an upper surface schematic diagram which shows the electrode part of a light transmissive spatial light modulator. It is a schematic diagram which shows the operation | movement principle of a light transmission type | mold spatial light modulator. It is an arrangement view showing the shape of a microstructure constituting a light transmission type spatial light modulator. It is a magneto-optical characteristic view of a microstructure. It is a cross-sectional schematic diagram which shows the structure of the light reflection type spatial light modulator of this invention. It is a perspective view which shows the electrode part of a light reflection type spatial light modulator. It is a schematic diagram which shows the principle of operation of a light reflection type spatial light modulator. It is a cross-sectional schematic diagram which shows the other structure of a light reflection type spatial light modulator. It is an arrangement view showing the shape of a microstructure constituting a light reflection type spatial light modulator. It is a cross-sectional schematic diagram which shows the structure of a 2nd light reflection type spatial light modulator. It is a perspective view which shows the electrode part of the 2nd light reflection type spatial light modulator.

First, the light transmission type spatial light modulator of the present invention will be described.
1 and 2 show the configuration of a light-transmitting spatial light modulator according to the magneto-optical method of the present invention, and FIG. 1 is a schematic cross-sectional view of the light-transmitting spatial light modulator cut along a vertical plane (XZ plane). FIG. 2 is a schematic top view showing only the electrode part of the light transmission type spatial light modulator so that it can be understood well. 1A shows the X1-X1 cross section of FIG. 2, and FIG. 1B shows the X2-X2 cross section of FIG.

As shown in FIG. 1, the light transmission type spatial light modulator 1 includes a plurality of microstructures 2, an X-direction line electrode 3, a Y-direction line electrode 4, a polarizer 5, an analyzer 6, and a first glass. A substrate 7, a second glass substrate 8, and a third glass substrate 9 are provided. The plurality of microstructures 2 are formed by laminating a first noble metal material layer 10, a magnetic material layer (magneto-optic signal layer) 11, a second noble metal material layer 12, and an insulating layer 13, for example, a substantially rectangular parallelepiped having a width of about 200 nm. It is formed into a shape. The first noble metal material layer 10 is made of, for example, Au having a thickness of about 20 nm, and the magnetic material layer (magneto-optic signal layer) 11 is made of, for example, CoCrPt—SiO ₂ having a thickness of about 5 nm. The noble metal material layer 12 is made of, for example, Au having a thickness of 10 nm, and the insulating layer 13 is made of, for example, SiN having a thickness of 2 nm. The microstructure 2 is formed on the surface of the second glass substrate 8 with the insulating layer 13 facing the second glass substrate 8 at an interval of about 200 nm, and one signal (one pixel) is formed by one. N × n modulators are formed in the XY plane. The periphery of the microstructure 2 is covered with an insulating material layer 14 made of silicon dioxide (SiO ₂ ).

  On the surface of the second glass substrate 8 having the microstructure 2, a line-shaped X-direction electrode 3 is formed between the microstructures 2 in the X direction. In addition, in the insulating material layer 14 covering the microstructure 2, the Y-direction line electrode 4 that is linear in the Y direction orthogonal to the X-direction line electrode 4 is disposed between the microstructure 2 and the X-direction line electrode 3. It is formed not to come into contact with. The X-direction line electrode 3 and the Y-direction line electrode 4 are made of indium tin oxide (ITO) and have a width of about 80 nm.

  The polarizer 5 is bonded to the first glass substrate 7 with a photo-curing resin 15, and the insulating material layer 14 having the microstructure 2 and the Y-direction line electrode 4 is opposite to the second glass substrate 8. Bonded to the surface. The analyzer 6 is bonded to the third glass substrate 9 with a photocurable resin 16 and bonded to the surface of the second glass substrate 8 opposite to the surface having the microstructure 2. The polarizer 5 and the analyzer 6 are optical elements that produce linearly polarized light in a certain direction. Iodine or dichroic dye is mixed in polyvinyl alcohol, which is an organic polymer material, and a film is formed, and then stretched. It is produced by processing.

CoCrPt—SiO ₂ forming the magnetic material layer (magneto-optic signal layer) 11 has a granular structure and has perpendicular magnetic anisotropy. Granular means “granular” and refers to a material having a structure in which nanometer-scale particles are dispersed in a matrix of another material. Co in the magnetic material layer 11 forms a crystal having a hexagonal close-packed crystal lattice structure, and Cr and SiO ₂ are segregated to form a grain boundary. By using CoCrPt—SiO ₂ for the magnetic material layer (magneto-optic signal layer) 11 in this way, SiO ₂ is segregated around ferromagnetic Co, so that it is easy to form physically independent fine Co particles. There is a feature.

The operation principle of the light transmission type spatial light modulator 1 will be described with reference to the schematic diagram of FIG. The spatial light modulator 1 converts incident light into a linearly polarized light with a polarizer 5 and enters the microstructure 2. When linearly polarized light is incident on the microstructure 2, the current flowing through the X-direction line electrode 3 and the Y-direction line electrode 4 is variably controlled to change the magnetic field applied to the microstructure 2. Due to the change of the magnetic field, the direction of the magnetic moment of the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2 changes. Due to the change in the direction of the magnetic moment of the magnetic material layer (magneto-optic signal layer) 11, the linearly polarized reflected light or transmitted light that has entered the microstructure 2 is rotated. The analyzer 6 transmits the polarization component rotated in a certain direction of the transmitted light from the microstructure 2 and blocks the polarization component rotated in the opposite direction. In this way, on / off of light can be controlled by changing the magnetic field applied to the microstructure 2. For example, when a positive direction magnetic field is applied, + θ _F Faraday rotation occurs, and when a negative direction magnetic field is applied, −θ _F Faraday rotation occurs, and the polarization transmission surface of the analyzer 6 becomes + θ _F. When set, is transmitted through the light Faraday rotation of + theta _F (oN state), - theta light rotation _F places the analyzer 6 to prevent transmission (oFF state). Therefore, on / off of light can be controlled by controlling the direction of the magnetic field, and the light-transmissive spatial light modulator 1 can be used as a magneto-optical element such as an optical switch or a sensor. In FIG. 3, Faraday rotation by a quartz substrate is not considered, but when a material having a relatively large Faraday rotation, such as quartz, is actually used as the glass substrates 7 to 9, it is necessary to consider the rotation angle. is there.

  Conventionally, as a problem of the prior art, there has been a problem that the rotation angle is small, as a result, the S / N is bad, and the signal intensity is small when the pixel is miniaturized. However, in the light transmission type spatial light modulator 1 of the present invention, the magnetic material layer (magneto-optic signal layer) 11 is made of Au of the first noble metal material layer 10 and the second noble metal material layer 12 that excite plasmons from above and below. The point which shows the structure using the micro structure 2 of the structure inserted | pinched differs greatly from a prior art example. Such a configuration is characterized in that the rotation angle is larger than in the case of using only a magnetic material. This is due to the electric field enhancement effect by the localized surface plasmon in the microstructure 2. In particular, the plasmon excitation effect is large in the Au layer of the first noble metal material layer 10. Although an Au layer is used as the plasmon excitation layer, since the plasmon is generated by the vibration of electrons, the periphery needs to be an insulating material. It is presumed that the vibration of electrons generated in the Au layer of the first noble metal material layer 10 of the microstructure 2 affects the magnetic material layer (magneto-optic signal layer) 11 and strengthens the magneto-optic effect. In addition, when a He—Ne laser having a wavelength of 633 nm was used as the incident light 20, the Faraday rotation angle was a relatively large value of about 0.2 degrees, and switching was possible with a large contrast ratio.

  The direction of the magnetic moment of the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2 is controlled by controlling the current flowing through the X-direction line electrode 3 and the Y-direction line electrode 4 shown in FIG. Magnetization in the horizontal direction is obtained by simulation so as to control the magnetic field generated around the direction line electrode 3 and the Y direction line electrode 4 so as to be synchronized with one microstructure 2 in the XY direction. Control inversion.

  FIG. 4 is a schematic top view of various shapes of the microstructure 2. The microstructure 2 has a square cross section as shown in FIG. 4 (a), a circular cross section as shown in FIG. 4 (b), or a cono-shaped cross section as shown in FIG. 4 (c). It is good to make it. If the microstructure 2 has a square or circular cross section, it can be easily processed. Further, if the microstructure 2 is asymmetrically shaped with a conical cross section, the optical rotation can be utilized and an enhanced magneto-optical signal can be obtained. Furthermore, S / N can be improved by making the microstructure 2 have rectangular shapes with different side lengths.

Next, a manufacturing method of the light transmission type spatial light modulator 1 having the microstructure 2 will be described. First, a second glass substrate 8 made of quartz subjected to surface polishing was prepared. This indicates the role of the microstructure 2 as a support. A thin film structure was formed on the glass substrate 8 by using an ultra-high vacuum sputtering apparatus to form the ITO and the microstructure 2 serving as the X-direction line-shaped electrode 3. Thereafter, a pattern was produced using a focused ion beam apparatus. In the focused ion beam, the sample can be cut by repelling atoms on the sample surface with the Ga ion beam. Thereafter, the space between the microstructures 2 was filled with SiO ₂ , and processing and film formation were repeated again to produce a Y-direction line electrode 4. Thereafter, the polarizer 5 and the analyzer 6 were fixed using a photocurable resin. Although an example using a focused ion beam apparatus is shown here, a method of forming a resist pattern by electron beam drawing and performing ion milling on the magnetic thin film based on the pattern may be used.

  As a feature of the light transmissive spatial light modulator 1, the magnetization reversal speed is several nanoseconds, and when a liquid crystal film is used for a similar spatial light modulator, switching takes several microseconds. The light transmissive spatial light modulator 1 using the microstructure 2 can perform ultrafast optical switching.

  In other words, a significant feature is that an increase in magneto-optical effect by localized surface plasmon resonance in the microstructure 2 is utilized. The magneto-optic effect increases at an incident wavelength that substantially corresponds to the plasmon resonance wavelength. In the optical path, it is known that the larger the volume of the magnetic material, the greater the magneto-optic effect. However, when plasmon resonance is used when compared at the same volume, the magneto-optic effect is caused by the resonance effect of light. Be enhanced. In addition, the microstructure 2 has an asymmetrical shape with a cross-section of a cono section, and Au is used among the noble metals, so that the plasmon resonance wavelength exists in the visible light region, which is an excellent resonance effect. This is because it is a chemically stable element. Further, by providing an insulating layer 13 and a second noble metal material layer 12 from the lower side below the magnetic material layer (magneto-optic signal layer) 11, the magneto-optic signal is further strengthened, and the role of adjusting the signal intensity is also provided. Can fulfill.

  In the above description, the magnetic field generated around the X-direction line electrode 3 and the Y-direction line electrode 4 is used as the magnetic field application method. However, a method using a magnetic head (TMR or GMR) used for a hard disk, There are also a method using a micro magnetic head made of a magnetic core and a method of bringing a permanent magnet close to each other. In particular, when a transparent magnetic head is used, perpendicular incidence is easy.

  In the above description, the structure in which the microstructures 2 are periodically arranged in a two-dimensional manner is shown, and a case in which one of the microstructures 2 is used as one pixel is shown. A plurality of light modulation functions can be exhibited, such as forming one signal (one pixel) with one microstructure 2. By forming one pixel with a plurality of microstructures 2 in this manner, when one of the microstructures 2 is a pixel, the pixel is higher in definition and the light intensity can be improved. That is, the size of one microstructure 2 is about several tens to several hundreds of nanometers and is not more than half the wavelength of the light to be used, which is suitable for use requiring high definition. Such a magneto-optical device having a function of spatially modulating light has a wide application range, and can be used as a sensor such as a biosensor or a gas sensor in addition to an optical switch. In addition to using the micro structure 2 as a single application, it can be used in a two-dimensional space. When the microstructure 2 is used as one piece, the main purpose is to scan the laser beam at high speed. On the other hand, in the case of two-dimensional spatial use using a plurality of microstructures 2, it is used for applications that require parallel processing.

  In addition, the shape of the microstructure 2 is a rectangular parallelepiped shape that can be easily processed and the localized surface plasmon mode can be selected. For example, the processing accuracy is slightly worse, but the horizontal cross-sectional shape is a saddle shape or a cono shape It is known as a structure that provides optical rotation, and the optical optical function can be further enhanced by superimposing the optical rotation function.

The insulating layer 13 of the microstructure 2 is provided so that the vibrational movement of electrons during plasmon excitation sufficiently affects the magnetic material layer (magneto-optic signal layer) 11, and plasmon excitation is actually performed. And has the effect of enhancing the magneto-optical effect. Furthermore, although the case where Co is included as the magnetic material layer (magneto-optic signal layer) 11 is shown, it is preferable that at least one of Co, Fe, and Ni is included. This is because Co, Fe, and Ni are basic elements advantageous for generating a magneto-optical signal. Further, by using a granular structure made of CoCrPt—SiO ₂ as the magnetic material layer (magneto-optic signal layer) 11, a strong and stable magneto-optic signal can be obtained.

What is important as the material of the magnetic material layer (magneto-optic signal layer) 11 is a combination of a ferromagnetic metal / alloy and a nonmagnetic insulator. Examples of ferromagnetic materials include Fe, Co, and FeCo alloys, and examples of insulators include oxides such as SiO ₂ and MgO, and fluorides such as MGF ₂ , and these materials are sputtered at the same time. Separation forms a nanometer scale structure.

Moreover, ITO was used as the X-direction line-shaped electrode 3 and the Y-direction line-shaped electrode 4, but ITO is preferable for optical device applications because it is almost transparent in the visible light region. Indium zinc oxide (IZO), tin oxide (SnO ₂ ), and the like are also optically transparent. It is also possible to use a metal electrode such as Cu that is not transparent.

  A Co / Pt multilayer film may be used as the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2 constituting the light transmissive spatial light modulator 1. This Co / Pt multilayer film has an artificial lattice structure composed of five layers of Co; 1 nm / (Co; 0.5 nm / Pt; 1 nm), and has perpendicular magnetic anisotropy. The light transmissive spatial light modulator 1 using a Co / Pt multilayer film as the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2 was also confirmed to have a light modulation function. Here, the number of layers (Co; 0.5 nm / Pt; 1 nm) is not limited. From the relationship of light reflectance and saturation magnetization, about 5 or 7 layers are preferable. A multilayer film such as Fe / Pt or Co / Pd can also be used.

FIG. 5 shows an example of magneto-optical characteristics (Faraday rotation angle, Faraday ellipticity). The measurement samples are the following two.
Sample 1; Glass substrate / Ti2nm / Au 20nm / [(Co 0.5 nm / Pt 1nm) 7 layers] / Au 20nm
Sample 2; glass substrate / Ti 2 nm / Pt 1 nm / [(Co 0.5 nm / Pt 1 nm) 7 layers] / Pt 3 nm
The shape of the sample is a circular dot shape, and the dot period is 250 nm for all. The periphery of the dot is protected by applying an organic resist material. Comparing with the same dot diameter, it can be seen that the rotation angle of sample 1 is about twice or more larger than that of sample 2. The measured wavelength of light is 630 nm, the plasmon resonance wavelength is about 630 nm when the dot diameter is 50 nm, and light in the vicinity of 630 nm causes plasmon resonance. Also, the plasmon resonance wavelength shifts to the longer wavelength side as the dot diameter increases. The reason why the rotation angle of the sample 1 is larger than that of the sample 2 is due to plasmon resonance. Such characteristics include, for example, changing Au to other noble metal materials such as Ag, Cu, and Al, changing the Co / Pt multilayer film showing magnetic characteristics to other materials, changing the dot period, the film thickness of each material, etc. Since the magneto-optical characteristics change by changing, it can be adjusted according to the application.

Further, as a magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2 constituting the light transmission type spatial light modulator 1, a garnet type ferrite which is yttrium-iron-garnet (YIG, Y ₃ Fe ₃ O ₁₂ ). Bi: YIG may be used in which a part of is substituted with bismuth (Bi). Bi; YIG has the advantage that it has a relatively high transmittance as a material that emits a magneto-optical signal, and as a result, the light intensity increases.

  As a method for forming Bi: YIG, a sputtering method is used, but there is also a method using a solution (MOD (Metal Organic Decomposition) coating material) in which an organic compound of Bi: YIG is dissolved in an organic solvent. In this method, for example, a solution is applied to a substrate and dried five times, and then a heat treatment step of 100 ° C. for 30 minutes, 500 ° C. for 15 minutes, and 700 ° C. for 180 minutes is added, and Bi: YIG is fired. Thus, the crystallinity can be improved.

  Bi: YIG was used as the magnetic material layer (magneto-optic signal layer) 11, which is a rare earth iron garnet, and in addition to Y as a rare earth metal, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. may be used. Further, although it is a Bi substitution type, it may be Ce, Pb, Ca, or Pt. Furthermore, a part of Fe may be Al, Ga, Cr, Mn, Sc, In, Ru, Rh, Co, Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, or the like.

Next, the light reflection type spatial light modulator of the present invention will be described.
6 and 7 show the configuration of the light reflection type spatial light modulator 21 of the present invention, FIG. 6 is a schematic sectional view of the light reflection type spatial light modulator 21, and FIG. 7 shows the light reflection type spatial light modulator 21. It is the perspective view which showed typically the electrode part. As shown in the figure, the light reflection type spatial light modulator 21 includes a plurality of microstructures 2a, an X-direction line electrode 3, a Y-direction line electrode 4, a first glass substrate 7, a second glass substrate 8, and It has a polarizer 5 and an analyzer 6. An X-direction line-shaped electrode 3 is formed on a second glass substrate 8 made of quartz whose surface is polished, and a substantially rectangular parallelepiped microstructure having a width of, for example, about 250 nm is formed on the X-direction line-shaped electrode 3. 2a is formed. The microstructure 2a includes an insulating layer 13 made of, for example, SiN having a thickness of about 2 nm from the second glass substrate 8 side, a second noble metal material layer 12 having a thickness of, for example, 5 nm, and a thickness of, for example, Is a magnetic material layer (magneto-optic signal layer) 11 made of NiFe having a thickness of about 30 nm, a first noble metal material layer 10 made of Au having a thickness of about 30 nm, and SiN having a thickness of about 2 nm. The insulating layers 22 are stacked in this order. NiFe forming the magnetic material layer (magneto-optic signal layer) 11 has in-plane magnetic anisotropy. A Y-direction line-shaped electrode 4 formed on the first glass substrate 7 is disposed on the microstructure 2a, and the periphery of the microstructure 2a and the Y-direction line-shaped electrode 4 are fixed by a photocurable resin 15. ing. The X-direction line-shaped electrode 3 and the Y-direction line-shaped electrode 4 are formed with a width of about 250 nm, which is the same as that of the microstructure 2a. The X-direction line electrode 3 is made of Al, and the Y-direction line electrode 4 is made of ITO. In this case, Al in the X-direction line-shaped electrode 3 also functions as a reflection film. ITO in the Y-direction line-shaped electrode 4 transmits almost visible light, whereas Al substantially reflects visible light. The polarizer 5 and the analyzer 6 are Glan-Thompson prisms and are disposed above the first glass substrate 7. One microstructure 2a is a modulator that forms one signal (one pixel), and n × n are formed in the XY plane. The X-direction line electrode 3 is made of Al, and the Y-direction line electrode 4 is made of ITO.

The operation principle of the light reflection type spatial light modulator 21 will be described with reference to the schematic diagram of FIG.
The linearly polarized light transmitted through the polarizer 5 is reflected after entering the microstructure 2a. At this time, the Kerr rotation directions of the incident linearly polarized light and the reflected linearly polarized light are opposite to each other depending on the direction of the NiFe magnetic moment of the magnetic material layer (magneto-optic signal layer) 11 forming the microstructure 2a. As shown in FIG. 8A, the analyzer 6 transmits light subjected to Kerr rotation of + θk and does not transmit light subjected to Kerr rotation of −θk as illustrated in FIG. 8B. That is, it is arranged so as to transmit one linearly polarized light. Therefore, by changing the direction of the magnetic field applied to the magnetic material layer (magneto-optic signal layer) 11, the magnetic moment of NiFe forming the magnetic material layer (magneto-optic signal layer) 11 is changed and transmitted through the polarizer 5. Thus, the optical signal reflected by the microstructure 2a can be turned on / off.

  A magnetic field application method for turning on / off the optical signal is based on a pulse current flowing through the X-direction line electrode 3 and the Y-direction line electrode 4. The magnetic field generated in the XY directions can be controlled by setting the pulse currents flowing through the X-direction line electrodes 3 and the Y-direction line electrodes 4 to optimum pulse currents obtained by simulation. Here, NiFe forming the magnetic material layer (magneto-optic signal layer) 11 is an in-plane magnetization film, and other examples of the in-plane magnetization film include CoFeB.

  Further, PtMnSb may be used as the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2a constituting the light reflection type spatial light modulator 21. By adjusting the composition ratio of platinum (Pt), manganese (Mn), and antimony (Sb), PtMnSb can form a state having spin in only one direction (theoretical spin polarization is 100%).

  FIGS. 9 and 10 show the configuration of a light reflection type spatial light modulator 21 that uses PtMnSb as the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2a. FIG. 9 is a schematic cross-sectional view of the light-reflective spatial light modulator 21, and FIG. 10 is a schematic top view showing the shape of the microstructure 2a of the light-reflective spatial light modulator 21. The microstructure 2a has a width in the X direction of 250 nm and a width in the Y direction of 50 nm, and may have a rectangular shape in cross section as shown in FIG. 9A or as shown in FIG. Alternatively, the cross section may be elliptical. A micro magnetic head was used as a magnetic field application method.

Further, a half metal material may be used as the magnetic material layer (magneto-optic signal layer) 11 of the microstructure 2a. This half-metal material is formed of a Heusler alloy or a half-metal ferromagnetic film (for example, a Co ₂ MnSi film) in which all electrons are spin-polarized in a predetermined direction when an external magnetic field is applied. Is preferred. Also, other ferromagnetic films similar to Heusler alloys and half-metal ferromagnetic films may be used. For the half metal, conductive ferromagnetic oxide such as (La, Sr) MnO ₃ , Fe ₃ O ₄ , CrO ₂ , half-Heusler alloy such as NiMnSb, Co ₂ MnSi, Co ₂ MnAl, Co ₂ MnGe, Co ₂ CrGa Full Heusler alloys and zinc blende type CrAs are known.

  Further, Ag was used as the material of the first noble metal material layer 10 and the second noble metal material layer 12 of the microstructure 2a. Ag has a drawback that it is slightly unstable chemically, but it has a greater enhancement effect than Au as an element causing plasmon resonance.

  The microstructure 2a constituting the light reflection type spatial light modulator 21 has a plasmon resonance wavelength that is selectively utilized by changing a length in one direction and a length in a direction perpendicular thereto by selectively using a plasmon resonance mode. There is an advantage that it can be controlled.

Next, another light reflection type spatial light modulator of the present invention will be described.
11 and 12 show the configuration of the light-reflective spatial light modulator 21a, FIG. 11 is a schematic cross-sectional view of the light-reflective spatial light modulator 21a, and FIG. 12 shows the electrode part of the light-reflective spatial light modulator 21a. It is the perspective view which showed typically. The arrangement of the X-direction line-shaped electrode 3 and the Y-direction line-shaped electrode 4 with respect to the microstructure 2b of the light reflection type spatial light modulator 21a is the same as the configuration shown in FIGS. As shown in the figure, the light-reflecting spatial light modulator 21 a has an X-direction line-shaped electrode 3 formed on a second glass substrate 8 made of quartz whose surface is polished. A substantially rectangular parallelepiped microstructure 2b is formed. A Y-direction line-shaped electrode 4 formed on the first glass substrate 7 is disposed on the microstructure 2b.

The microstructure 2b is formed of, for example, a magnetization fixed layer 31 made of Tb ₁₁ (Co ₉₀ Fe ₁₀ ) ₈₉ having a thickness of about 30 nm and CoFeB having a thickness of about 2 nm from the second glass substrate 8 side. Interface layer 32, intermediate layer (tunnel insulating layer) 33 made of MgO having a thickness of about 1 nm, interface layer 34 made of CoFeB having a thickness of about 1 nm, and Tb having a thickness of about 3 nm. _The magnetic free layer (magneto-optic signal layer) 35 formed of ₁₅ (Co ₉₀ Fe ₁₀ ) ₈₅ and the localized surface plasmon excitation layer 36 formed of Ag having a thickness of about 20 nm. Further, the localized surface plasmon excitation layer 36 also serves to flow a current flowing from the Y-direction line electrode 4 made of ITO. The periphery of the microstructure 2b is fixed by silicon dioxide (SiO ₂ ). The width of the microstructure 2b, the X-direction line electrode 3 and the Y-direction line electrode 4 is approximately 200 nm, and one microstructure (one pixel) is formed by one microstructure. Such n × n pixels are formed in the XY plane. The polarizer 5 and the analyzer 6 are Glan-Thompson prisms.

  The principle of turning on / off the light of the light reflection type spatial light modulator 21a is a change in the magnetic moment of the magnetization free layer 45 in the spin valve multilayer film. The spin injection method is a method in which magnetization is reversed by the action of electron spin in a current. In a configuration in which an insulating film is sandwiched between magnetic materials, a current having the same electron spin direction is passed to reverse the magnetization. The direction of the magnetic moment of the magnetization fixed layer 31 is always unidirectional, but the direction of the magnetic moment of the magnetization free layer 35 changes depending on the current. The perpendicular magnetization method used in the microstructure 2b is a method that uses the magnetization in the perpendicular direction of the magnetic layer, and has lower energy at the time of magnetization reversal than the conventional in-plane magnetization method, and can be magnetized with a small current. Can be reversed.

  Further, as described above, Ag of the localized surface plasmon excitation layer 36 also serves as the plasmon excitation and the electrode. The vibration of electrons generated in Ag strengthens the magneto-optical signal generated from the magnetization free layer 35. In this way, there is no example in which a configuration in which a noble metal material layer having a minute size is in contact with the magnetization free layer is focused on the plasmon effect, and is a new configuration.

  As described above, the present invention can produce a spatial light modulator based on the Faraday effect using transmitted light and the magnetic Kerr effect using reflected light.

  In the step of forming the magneto-optic signal layer of the microstructures 2, 2a, 2b, a method using a magnetic material / polymer composite material, a method using a sol-gel method, or a method using a MOD (Metal Organic Decomposition) material In addition, there are a film forming method using sputtering, a method using a molecular magnetic material such as vanadium chromium hexacyano complex, a method using nanosheet lamination, and an aerosol deposition method (ADM) using a room temperature impact solidification phenomenon. The sol-gel material is a material in which a colloidal material obtained by hydrolyzing and polymerizing an alkoxide or the like is dispersed in a solution, and has excellent low-temperature film-forming properties. The MOD coating type material is a solution in which a metal organic compound is dissolved in an organic solvent, and the oxide thin film can be easily formed by coating the solution on a substrate and applying heat treatment after drying. Material. Further, a ferromagnetic semiconductor material such as (Ga, Mn) As or GeFe may be used.

  The light-transmitting spatial light modulator 1 and the light-reflecting spatial light modulators 31 and 31a of the present invention can be used for, for example, an optical switch that performs optical scanning composed of a single micro structure, and two-dimensionally spatially modulates light. The optical signal can be turned on / off at a very high speed.

DESCRIPTION OF SYMBOLS 1; Light transmission type spatial light modulator, 2; Micro structure, 3; X direction line-shaped electrode,
4; Y direction linear electrode, 5; Polarizer, 6; Analyzer, 7; Glass substrate,
8; glass substrate, 9; glass substrate, 10; noble metal material layer,
11; magnetic material layer (magneto-optic signal layer), 12; noble metal material layer, 13; insulating layer,
14; insulating material layer, 15; photocurable resin, 16; photocurable resin,
21; light-reflective spatial light modulator, 22; insulating layer, 31; magnetization fixed layer,
32; interface layer, 33; intermediate layer (tunnel insulating layer), 34; interface layer,
35; magnetization free layer (magneto-optic signal layer), 36; localized surface plasmon excitation layer.

JP 2007-310177 A JP 2004-354441 A JP 2008-145748 A JP 2008-83686 A JP-A 63-149623 JP 2000-173071 A JP 2008-268862 A JP 2007-214304 A JP 2002-90525 A Japanese Patent Laid-Open No. 2003-177201 JP 2001-296442 A JP 2002-303840 A Japanese Patent No. 3763709 JP 2004-309700 A

J. Appl. Phys., Vol. 76, p1910-1919 (1994), J-k. Cho et al., "Design, fabrication, switching, and optical characteristics of new magneto-optic spatial light modulator" Opt. Lett., Vol. 31, No. 8, p1085-1087 (2006), B. Sepulveda et al., `` Higyly sensitive detection of biomolecules with the magneto-optic surface-plasmon-resonance sensor '' small, Vol. 4, No. 2, p202-205 (2008), Juan B. Gonzalez-Diaz et al., `` Plasmonic Au / Co / Au nanosandwiches with enhanced magneto-optical activity '', `` Higyly sensitive detection of biomolecules with the magneto- optic surface-plasmon-resonance sensor "

Claims (16)

A substrate and a microstructure,
The microstructure is formed to be smaller than half of the wavelength of light, and is laminated on at least the magnetic material layer provided on the substrate, and the surroundings other than the contact portion with the magnetic material layer are insulated. A magneto-optical element having a noble metal material layer covered with a material, and changing a rotation direction of incident linearly polarized light according to a change in a magnetic field applied to the microstructure.   2. The magneto-optical element according to claim 1, wherein an insulating layer and a noble metal material layer are laminated between the substrate and the magnetic material layer from the substrate side.   The magneto-optical element according to claim 1, wherein the microstructure has a square cross-sectional shape parallel to the surface of the substrate.   The magneto-optical element according to claim 1, wherein the microstructure has a rectangular cross-sectional shape parallel to the surface of the substrate.   The magneto-optical element according to claim 1, wherein the microstructure has an asymmetrical cross-sectional shape parallel to the surface of the substrate.   6. The magneto-optical element according to claim 1, wherein the noble metal material layer of the microstructure is formed of any one of Au, Ag, Cu, Al, or an alloy material thereof.   The magneto-optical element according to claim 1, wherein the magnetic material layer of the microstructure includes at least one of Co, Fe, and Ni.   The magnetic material layer of the microstructure has a granular structure in which a grain boundary portion made of a nonmagnetic substance is formed between crystal grains containing at least Co and growing in a columnar shape. The magneto-optical element according to any one of 6.   2. The magnetic material layer of the microstructure is a multilayer structure having perpendicular magnetic anisotropy selected from any one of Fe / Pt, Co / Pt, and Co / Pd. The magneto-optical element according to any one of items 1 to 6. The magnetic material layer of the microstructure is formed of a garnet-type ferrite that is yttrium-iron-garnet (YIG, Y ₃ Fe ₃ O ₁₂ ), or a material in which a part thereof is substituted. Item 7. The magneto-optical element according to any one of Items 1 to 6.   The magneto-optical element according to claim 1, wherein the magnetic material layer of the microstructure is formed of a half metal. A magneto-optical element according to any one of claims 1 to 11, a polarizer, a magnetic field control means, and an analyzer,
The polarizer makes the incident light linearly polarized and enters the magneto-optical element,
The magnetic field control means changes a magnetic field applied to the magneto-optical element,
The magneto-optical element varies the rotation direction of incident linearly polarized light by changing the magnetic field applied by the magnetic field control means,
The optical modulator transmits a polarization component rotated in a certain direction of transmitted light from the magneto-optical element. A magneto-optical element according to any one of claims 1 to 11, a polarizer, a magnetic field control means, and an analyzer,
The polarizer makes the incident light linearly polarized and enters the magneto-optical element,
The magnetic field control means changes a magnetic field applied to the magneto-optical element,
The magneto-optical element varies the rotation direction of incident linearly polarized light by changing the magnetic field applied by the magnetic field control means,
The optical modulator transmits a polarization component rotated in a certain direction of reflected light from the magneto-optical element.   The optical modulator according to claim 12 or 13, wherein the magneto-optical elements are two-dimensionally arranged on the surface of the substrate, and the phase and amplitude of light are two-dimensionally spatially modulated.   15. A magneto-optical device comprising the optical modulator according to claim 12, wherein the magnetic field control means changes a magnetic field applied to the magneto-optical element to control light on / off. Control element.   15. An image display device comprising: the optical modulator according to claim 14; wherein the magnetic field control means changes a magnetic field applied to the magneto-optical element to perform two-dimensional spatial light modulation.

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