JP2001343619A - Spatial light modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a spatial light modulator(SLM) which is simple in structure and is high in operation speed. SOLUTION: The SLM 1 has magnetization setting layers 11 which consist of a magnetoptical material and are respectively set in the directions of magnetization and include plural pixels to impart rotation in the polarization directions meeting the directions of the magnetization to incident light by a magneto- optical effect, plural thin-film coils 12 which are disposed to correspond to each of the respective pixels of the magnetization setting layers 11 and generate magnetic fields for independently setting the directions of the magnetization in the respective pixels and reflection layers 13 which are disposed between the magnetization setting layers 11 and the thin-film coils 12 and reflect the light. The incident light which is made incident to the spacial light modulator 1 passes through the magnetizing setting layers 11, is reflected on the reflection layers 13, is again emitted through the magnetization setting layers 11. The rotation of the polarization directions meeting the directions of the magnetization in the respective pixels of the magnetization setting layers 11 is imparted to this light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spatial light modulator for spatially modulating incident light.

[0002]

2. Description of the Related Art Spatial light modulators for spatially modulating incident light are used in fields such as optical information processing and computer-generated holograms.

Conventional spatial light modulators include those using liquid crystal and those using micromirror devices.

[0004]

In the fields of the above-mentioned optical information processing and computer-generated holograms, it is necessary to process a large amount of information at a high speed. Is desired.

However, the spatial light modulator using liquid crystal has a problem that the operation speed is low. For example,
The response time of a spatial light modulator using a ferroelectric liquid crystal having a high operation speed among liquid crystals is on the order of microseconds.

A spatial light modulator using a micromirror device can operate at a relatively high speed. However, since the spatial light modulator is a micro-machine having a complicated structure manufactured by an advanced semiconductor manufacturing process, the manufacturing cost is high, and there is a problem in terms of reliability because of having a mechanical driving part. Remains.

By the way, for example, US Pat.
No. 4,237, No. 5,241,421, No. 5,25
5,119 and 5,386,313 disclose a spatial light modulator utilizing a magneto-optical effect. Hereinafter, such a spatial light modulator is referred to as a magneto-optical spatial light modulator. This magneto-optical spatial light modulator is made of a magneto-optical material, and has a plurality of pixels whose magnetization directions can be independently selected. In the magneto-optic spatial light modulator, the polarization directions of light passing through each pixel are rotated by a predetermined angle in directions opposite to each other according to the direction of magnetization in each pixel by the Faraday effect. Therefore, the magneto-optical spatial light modulator can generate spatially modulated light by arbitrarily selecting the direction of magnetization in each pixel.

In the magneto-optic spatial light modulator, since the reversal speed of the magnetization in each pixel is high, the operation speed can be made higher in pixel units than in the spatial light modulator using liquid crystal.

However, in the conventional magneto-optical spatial light modulator as described above, two types of conductors are provided in a lattice shape so as to intersect at the position of each pixel, and when reversing the magnetization in an arbitrary pixel, By applying a current to two conductors that intersect at the position where the pixel is arranged, a magnetic field for reversing the magnetization in the pixel is generated. Therefore, in the conventional magneto-optical spatial light modulator, the magnetization of all the pixels cannot be set at the same time, and the operating speed of the entire magneto-optical spatial light modulator is lower than the operating speed of each pixel. There is a problem.

Further, in the conventional magneto-optical spatial light modulator, a current is applied to two intersecting conductors to generate a magnetic field for reversing the magnetization in the pixel. There is a problem that a current is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a spatial light modulator having a simple structure and a high operation speed.

[0012]

The spatial light modulator of the present invention is made of a magneto-optical material, and the direction of magnetization is set independently of each other. A magnetization setting layer including a plurality of pixels for applying a rotation of the polarization direction, and a plurality of magnetization setting layers provided to correspond to each pixel of the magnetization setting layer and generating a magnetic field for independently setting the magnetization direction in each pixel. And a magnetic field generating element.

In the spatial light modulator according to the present invention, the direction of magnetization in each pixel of the magnetization setting layer is independently set by the magnetic field generating element, and the light incident on the magnetization setting layer is changed according to the direction of magnetization in each pixel. The rotation of the polarization direction is given, and the light incident on the magnetization setting layer is spatially modulated.

In the spatial light modulator according to the present invention, the magnetic field generating element may be a thin film coil.

Further, in the spatial light modulator of the present invention, the magnetic field generating element is arranged so as to be adjacent to a surface of the magnetization setting layer opposite to a surface on which light is incident, and the spatial light modulator further comprises: A reflection layer provided between the magnetization setting layer and the magnetic field generating element and reflecting light may be provided. In this case, the magnetic field generating element may generate a magnetic field by being energized through two conductive paths, and the reflective layer may have conductivity and also serve as one conductive path. Further, the spatial light modulator of the present invention is further provided so as to be adjacent to the light incident surface of the magnetization setting layer, and rotates the polarization direction of the passing light by a predetermined angle by a magneto-optical effect. An optical rotation layer may be provided. The optical rotation layer has a plurality of types of regions each corresponding to each pixel of the magnetization setting layer and having a different rotation angle of the polarization direction, and each type of region may be arranged according to a predetermined pattern.

Further, in the spatial light modulator of the present invention, the magnetization setting layer may further include a domain wall movement suppressing unit provided at a boundary position between adjacent pixels to suppress the movement of the domain wall.

Further, the spatial light modulator of the present invention is further formed of a soft magnetic material, is provided adjacent to a surface of the magnetization setting layer opposite to the magnetic field generating element, and is generated by the magnetic field generating element. A soft magnetic layer forming a part of a magnetic path corresponding to a magnetic field may be provided.

Further, the spatial light modulator of the present invention further comprises a soft magnetic material, and is disposed on a side of the magnetic field generating element opposite to the magnetization setting layer, and has a magnetic path corresponding to a magnetic field generated by the magnetic field generating element. May be provided.

In the spatial light modulator of the present invention, the magnetization setting layer may be formed of a magnetic garnet thin film or may be formed of a one-dimensional magnetic photonic crystal.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. [First Embodiment] First, a spatial light modulator according to a first embodiment of the present invention will be described. FIG. 1 is a sectional view showing a main part of the spatial light modulator according to the present embodiment, and FIG. 2 is an explanatory diagram showing the spatial light modulator according to the present embodiment and its peripheral circuits.

As shown in FIGS. 1 and 2, the spatial light modulator 1 according to the present embodiment is made of a magneto-optical material, the directions of magnetization are set independently of each other, and the light enters due to the magneto-optical effect. A magnetization setting layer 11 including a plurality of pixels for applying a rotation of a polarization direction to light in accordance with the direction of magnetization, and a magnetization setting layer 11 provided to correspond to each pixel of the magnetization setting layer 11;
Thin film coil 12 as a plurality of magnetic field generating elements for generating a magnetic field for independently setting the direction of magnetization in each pixel
And a reflection layer 13 provided between the magnetization setting layer 11 and the thin film coil 12 and reflecting light.

The magnetization setting layer 11 is provided with a domain wall movement suppressing portion 11b for suppressing the movement of the domain wall at a boundary position between adjacent pixels. The domain wall movement suppressing unit 11b is, for example, as shown in FIG.
The protrusion as shown in FIG.

[0023] In Figures 1 and 2, reference numeral 11a ₀ is magnetized downward pixel (hereinafter, also referred to as a pixel off.) Indicates, reference numeral 11a ₁ is magnetized upward pixel (hereinafter, also referred to as on-pixel. ).

FIG. 3 is a plan view of the thin-film coil 12.
In FIG. 3, reference numeral 11A represents an area of one pixel.

1 and 2, the magnetization setting layer 11
Is the surface on which light is incident. The magnetization setting layer 11 has a property of transmitting at least light to be used. The thin-film coil 12 is arranged via the reflective layer 13 so as to be adjacent to the surface of the magnetization setting layer 11 opposite to the surface on which light is incident.

The reflection layer 13 has conductivity. One end, for example, the inner end of each thin-film coil 12 is connected to the reflective layer 13. A terminal 14 is connected to the other end of each thin-film coil 12, for example, an outer end. The reflection layer 13 also serves as one of two conductive paths for supplying electricity to the thin-film coil 12. Terminal 14
Constitutes the other of the two conductive paths for energizing the thin-film coil 12.

The spatial light modulator 1 is further formed of a soft magnetic material, is disposed on the opposite side of the thin film coil 12 from the magnetization setting layer 11, and has a magnetic path 20 corresponding to a magnetic field generated by the thin film coil 12. And a magnetic path forming part 15 for forming the part. An insulating layer 16 is formed around the thin-film coil 12, the terminal 14, and the magnetic path forming portion 15.

The spatial light modulator 1 is further made of a soft magnetic material, provided so as to be adjacent to a surface of the magnetization setting layer 11 opposite to the thin film coil 12, and corresponding to a magnetic field generated by the thin film coil 12. And a soft magnetic layer 17 forming another part of the magnetic path 20. The soft magnetic layer 17 has a property of transmitting at least light to be used.

As shown in FIG. 2, each thin film coil 12
Are connected to the drive unit 2 for independently supplying current to each thin-film coil 12 by a terminal 14, a reflective layer 13 and a wiring connected thereto. The drive unit 2 supplies a positive or negative pulse-like current to the thin-film coil 12 at a cycle of, for example, nanoseconds. The drive unit 2 is controlled by the control unit 3.

FIG. 4 shows a magnetic hysteresis curve representing the relationship between the applied magnetic field and the magnetization in the magnetization setting layer 11. As shown in FIG. 4, the magnetization setting layer 11 has large coercive forces Hc and −Hc. Then, the magnetization setting layer 1
1 has an absolute value of Hc when magnetized in the positive direction.
When a negative magnetic field exceeding is applied, the direction of magnetization is reversed,
When magnetized in the negative direction, the direction of magnetization is reversed when a positive magnetic field whose absolute value exceeds Hc is applied. The thin film coil 12 generates a positive or negative magnetic field whose absolute value exceeds Hc.

FIG. 5 shows a magnetic hysteresis curve representing the relationship between the applied magnetic field and the magnetization in the soft magnetic layer 17.
As shown in FIG. 5, the coercive force of the soft magnetic layer 17 is extremely small, and the direction of magnetization is easily reversed by a small applied magnetic field. The characteristics of the magnetic path forming portion 15 are the same as those of the soft magnetic layer 17.

The material of the magnetization setting layer 11 may be a magneto-optical material having a magneto-optical effect, but it is particularly preferable to use a magnetic garnet thin film or a one-dimensional magnetic photonic crystal.

A typical example of the magnetic garnet thin film is a rare earth iron-based garnet thin film. As a method of producing a magnetic garnet thin film, for example, there is a method of forming a single crystal magnetic garnet thin film on a substrate such as gadolinium gallium garnet (GGG) by a liquid phase epitaxial growth method (LPE method) or a sputtering method.

FIG. 6 is an explanatory view showing the structure of a one-dimensional magnetic photonic crystal. The one-dimensional magnetic photonic crystal 30 has a structure in which a dielectric multilayer film is formed on both sides of a magnetic layer 31. As the material of the magnetic layer 31, rare earth iron garnet, bismuth-substituted rare earth iron garnet, or the like is used. The dielectric multilayer film is formed by alternately stacking, for example, SiO ₂ films 32 and Ta ₂ O ₅ films 33. The period of the layer structure in the one-dimensional magnetic photonic crystal 30 is on the order of the wavelength of light used. In the one-dimensional magnetic photonic crystal 30, a large Faraday rotation angle can be obtained.

Inoue, one of the inventors of the present invention, has been working since October 1998 on PRESTO Research 2 by the Japan Science and Technology Agency.
1. Individual research on "Structure and Function of Magneto-Photonic Crystal" in "Shape and Function Region". In this research, a strong optical localization state is developed in a one-dimensional magnetic photonic crystal in which an extremely thin magnetic garnet thin film is sandwiched by a dielectric multilayer film, and as a result, the transmittance and the Faraday effect of the medium are significantly increased. That was found theoretically. Based on this theory, Inoue actually produced a one-dimensional magnetic photonic crystal, and obtained a 90% optical localized wavelength.
And a Faraday rotation angle of 5 ° or more was successfully formed despite the use of an extremely thin magnetic garnet thin film of about 150 nm. This Faraday rotation angle is extremely large, reaching about 100 times that of the bulk magnetic garnet thin film.

The spatial light modulator 1 according to the present embodiment
May be manufactured by forming all the components in a monolithic manner, or may be manufactured by dividing into a plurality of parts and then combining a plurality of parts. When the spatial light modulator 1 is formed in a plurality of parts, for example, the soft magnetic layer 1
The portion from 7 to the reflective layer 13 may be divided into other portions. Further, all components of spatial light modulator 1 according to the present embodiment can be manufactured using a semiconductor manufacturing process.

Next, the spatial light modulator 1 according to the present embodiment
The operation of will be described. In the spatial light modulator 1 according to the present embodiment, the thin film coil 1 is selectively provided according to the modulation information.
2 is supplied with a positive or negative pulse current. As a result, a magnetic field is independently applied to each pixel of the magnetization setting layer 11 by the thin film coil 12. According to a simple calculation, by supplying a pulse current having a peak value of about 40 mA to the thin-film coil 12, a pulse-like magnetic field of about 100 Oe can be generated at the center of the thin-film coil 12, and this magnetic field causes The magnetization in the pixel can be reversed.

When a magnetic field in the direction opposite to the direction of the magnetization is applied to each pixel, a magnetic domain of the same direction as the applied magnetic field is generated, and the magnetic domain expands. The expansion of the magnetic domain stops when the domain wall reaches the domain wall movement suppressing unit 11b.
As a result, the entirety of one pixel is magnetized in the same direction as the applied magnetic field. In this way, by applying a magnetic field to each pixel of the magnetization setting layer 11 independently by the thin film coil 12, the direction of magnetization in each pixel of the magnetization setting layer 11 is set independently.

The light incident on the spatial light modulator 1 from the soft magnetic layer 17 side passes through the soft magnetic layer 17 and then enters the magnetization setting layer 11.
Pass through. Due to the Faraday effect, the light passing through the magnetization setting layer 11 is given a rotation in the polarization direction according to the direction of magnetization in each pixel of the magnetization setting layer 11, that is, Faraday rotation. For example, if the polarization direction of the light magnetization passes through the pixel 11a ₁ upward on is rotated by + theta _F, the polarization direction of the light magnetization passes through the pixel 11a ₀ downward off rotated by - [theta] _F Is done.

The light passing through the magnetization setting layer 11 is reflected by the reflection layer 1
3, passes through the magnetization setting layer 11 and the soft magnetic layer 17 again, and is emitted from the spatial light modulator 1. Light that passes through the magnetization setting layer 11 after being reflected by the reflection layer 13 has the same Faraday effect as the light passing through the magnetization setting layer 11 before reaching the reflection layer 13. A rotation of the polarization direction according to the direction of the magnetization is provided. Therefore, as described above, the polarization direction of light passing through the pixels 11a ₁ ON is rotated by + theta _F, pixel OFF 1
Assuming that the polarization direction of light passing through 1a ₀ is rotated by −θ _F , the polarization direction of light emitted from spatial light modulator 1 after passing back and forth through ON pixel 11a ₁ twice is + 2θ _F. is rotated, the polarization direction of the light emitted from the spatial light modulator 1 through 2 times the pixel 11a ₀ off round-trip is rotated by -2θ _F.

As described above, according to the spatial light modulator 1 of the present embodiment, the rotation of the polarization direction according to the direction of the magnetization in each pixel of the magnetization setting layer 11 is given to the incident light. The incident light is spatially modulated.

Next, an example of a method of using the spatial light modulator 1 according to the present embodiment and an example of an operation thereof will be described with reference to FIG. In this example, the magnetization setting layer 11 of the spatial light modulator 1, the rotation angle + 2 [Theta] _F in the polarization direction of light passing through two pixels 11a ₁ ON round trip and 90 °, with a reciprocating pixel 11a ₀ Off The rotation angle -2 [theta] _F of the polarization direction of the light that has passed twice is -90 [deg.].

In the example shown in FIG. 7, a polarization beam splitter 21 is disposed on the light incident side of the spatial light modulator 1. The polarization beam splitter 21 has a polarization beam splitter surface 21a that makes an angle of 45 ° with the plane on the incident side of the spatial light modulator 1. The polarization beam splitter surface 21a transmits P-polarized light and reflects S-polarized light. P-polarized light is linearly polarized light whose polarization direction is parallel to the incident surface (the paper surface in FIG. 7), and S-polarized light is linearly polarized light whose polarization direction is perpendicular to the incident surface.

In the example shown in FIG. 7, P-polarized light is incident on the polarization beam splitter 21 in a direction perpendicular to the plane on the incident side of the spatial light modulator 1. This light passes through the polarization beam splitter surface 21a, enters the spatial light modulator 1, passes through the magnetization setting layer 11, is reflected by the reflection layer 13, passes through the magnetization setting layer 11 again, and is polarized. The beam returns to the beam splitter 21. In this example, the light that has passed through the ON pixel 11a ₁ twice in a reciprocating manner has a polarization direction of 90 °.
Is rotated to become S-polarized light, the light which has passed through twice the pixel 11a ₀ off in round trip, become S-polarized light the polarization direction is rotated -90 °. Therefore, all the return light from the spatial light modulator 1 is reflected by the polarization beam splitter surface 21a and is emitted from the polarization beam splitter 21. 7 illustrates a path of light passing through the pixels 11a ₁ on (represented by reference numeral ON.) In code to D. Also shows the paths of light passing through the pixel 11a ₀ off (represented by reference numeral OFF.) In code a'-d '.

In the example shown in FIG. 7, the return light from the spatial light modulator 1 is all S-polarized light, but the ON pixels 11a ₁
In the light passing through the pixel 11a ₀ of light and OFF that has passed through the phase are different 180 °. Therefore, the spatial light modulator 1 in this example is a phase spatial light modulator that spatially modulates the phase of light.

As described above, in the spatial light modulator 1 according to the present embodiment, the direction of magnetization in each pixel of the magnetization setting layer 11 is independently set by the thin film coil 12 so that the magnetization setting layer 11 The incident light is rotated in the direction of polarization according to the direction of magnetization in each pixel to spatially modulate the light incident on the magnetization setting layer 11.
Switching of the magnetization direction in each pixel of the magnetization setting layer 11 can be performed in about several nanoseconds. Moreover, in the present embodiment, the thin film coil 12 is provided for each pixel so that the direction of magnetization in each pixel can be set independently, so that the direction of magnetization in all pixels can be set simultaneously. It is. Therefore, in the spatial light modulator 1 according to the present embodiment, the overall response time of the spatial light
As in the case of the response time in pixel units, it can be set to about several nanoseconds, and an extremely high operation speed can be obtained.

The spatial light modulator 1 according to the present embodiment
Has a simple structure without mechanical driving parts,
High reliability because it does not contain liquids such as liquid crystal. Further, the spatial light modulator 1 according to the present embodiment has a simple structure and can be mass-produced by using a semiconductor manufacturing process, so that the manufacturing cost can be reduced.

The spatial light modulator 1 according to the present embodiment
In this case, since the reflection layer 13 also serves as one of the two conductive paths for supplying electricity to the thin-film coil 12, the structure can be simplified.

In the spatial light modulator using liquid crystal, a part of the pixel is used by a transistor or the like for switching the state of the liquid crystal in the entire spatial light modulator or in the pixel, or by switching the state of the pixel. There is a problem that the emitted light becomes non-uniform due to factors other than modulation information.

On the other hand, in the spatial light modulator 1 according to the present embodiment, the material state and the magnetization state in the pixels of the magnetization setting layer 11 can be made uniform. In the spatial light modulator 1, a thin-film coil 1 for switching the state of a pixel is provided.
2 is arranged so as to be adjacent to the surface of the magnetization setting layer 11 opposite to the surface on which light is incident via the reflection layer 13, so that the thin-film coil 12 affects the light to be modulated. Nothing. For these reasons, according to the spatial light modulator 1 according to the present embodiment, it is possible to prevent the emitted light from becoming non-uniform due to factors other than the modulation information.

Further, in a spatial light modulator using liquid crystal, since a transparent electrode is arranged in a light path, the characteristics are deteriorated by scattering of light by the transparent electrode, particularly when a pixel is miniaturized. On the other hand, in the spatial light modulator 1 according to the present embodiment, since the transparent electrode is not disposed in the light path, there is no deterioration in characteristics due to light scattering, which is particularly advantageous for miniaturization of pixels. is there.

The spatial light modulator 1 according to the present embodiment
According to the method, the thin-film coil 12 generates a magnetic field for setting the direction of magnetization in each pixel of the magnetization setting layer 11, so that the magnetization in the pixel is smaller than that in the conventional magneto-optical spatial light modulator. The current for inversion can be reduced.

The spatial light modulator 1 according to the present embodiment
Since the soft magnetic layer 17 and the magnetic path forming portion 15 which form a part of the magnetic path 20 corresponding to the magnetic field generated by the thin film coil 12 are provided, the magnetic flux can be effectively reduced. As a result, in the spatial light modulator 1, the magnetomotive force generated by the thin film coil 12 can be effectively used for setting the magnetization in the pixel.

The spatial light modulator 1 according to the present embodiment
If the thin film coil 12 is not driven, the magnetization setting layer 1
Since the state of magnetization in each of the pixels 1 is held, modulation information can be held by the spatial light modulator 1.

The spatial light modulator 1 according to the present embodiment
Are highly resistant to ultraviolet rays and cosmic rays, so that the spatial light modulator 1 can be used in a wide range of fields such as use in outer space.

[Second Embodiment] Next, a second embodiment of the present invention will be described.
The spatial light modulator according to the embodiment will be described. FIG. 8 is a cross-sectional view illustrating a main part of the spatial light modulator according to the present embodiment, and FIG. 9 is an explanatory diagram schematically illustrating a configuration of the spatial light modulator according to the present embodiment.

The spatial light modulator 41 according to the present embodiment
In addition to the components of the spatial light modulator 1 according to the first embodiment, a substrate 42 provided so as to be adjacent to the surface of the soft magnetic layer 17 on the light incident side, and a light incident side of the substrate 42 Optical rotation layer 43 provided so as to be adjacent to the surface. The substrate 42 serves as a base for forming another layer in the spatial light modulator 41, for example. For the substrate 42, for example, gadolinium gallium garnet (GGG) is used. The optical rotation layer 43 includes the magnetization setting layer 1
The magnetization in the optical rotation layer 43 is set in the same direction, for example, upward in FIGS. 8 and 9. The optical rotation layer 43 rotates the polarization direction of the passing light by a predetermined angle due to the magneto-optical effect (Faraday effect).

Other configurations of the spatial light modulator 41 according to the present embodiment are the same as those of the spatial light modulator 1 according to the first embodiment.

The spatial light modulator 4 according to the present embodiment
As shown in FIG. 9, 1 may be manufactured by forming all the components in a monolithic manner, or may be formed by dividing into a plurality of parts and then combining a plurality of parts. When the spatial light modulator 1 is formed in a plurality of parts, for example, as shown in FIG.
, A portion including the magnetization setting layer 11 and the reflective layer 13, a portion including the soft magnetic layer 17 and the substrate 42, and a portion including the optical rotation layer 43. In this case, FIG.
As shown in FIG. 0, the magnetization setting layer 11 and the reflection layer 13 are sequentially formed on one surface of a substrate 51 made of gadolinium gallium garnet (GGG), and the other surface of the substrate 51 is joined to the soft magnetic layer 17. You may. Further, an optical rotation layer 43 is formed on one surface of a substrate 52 made of, for example, gadolinium gallium garnet (GGG).
May be bonded to the substrate 42.

Next, an example of a method of using the spatial light modulator 41 according to the present embodiment and an example of an operation thereof will be described with reference to FIG. In this example, the magnetization setting layer 11 of the spatial light modulator 41, the rotation angle + 2 [Theta] _F in the polarization direction of light passing through two pixels 11a ₁ ON round trip and 45 °, in a reciprocating pixel 11a ₀ Off The rotation angle -2 [theta] _F of the polarization direction of the light that has passed twice is -45 [deg.]. In this example, the optical rotation layer 43 rotates the polarization direction of the passing light by 22.5 ° per pass and 45 ° by the reciprocating pass.

In the example shown in FIG. 11, the spatial light modulator 41
The polarization beam splitter 21 is disposed on the light incident side of the light source. The polarization beam splitter 21 has a polarization beam splitter surface 21a that makes an angle of 45 ° with the plane on the incident side of the spatial light modulator 1. The polarization beam splitter surface 21a transmits P-polarized light and reflects S-polarized light.

In the example shown in FIG. 11, P-polarized light is made to enter the polarization beam splitter 21 from a direction perpendicular to the plane on the incident side of the spatial light modulator 41. This light passes through the polarization beam splitter surface 21a and enters the spatial light modulator 41, where the optical rotation layer 43 and the magnetization setting layer 11
, Are reflected by the reflection layer 13, pass through the magnetization setting layer 11 and the optical rotation layer 43, and return to the polarization beam splitter 21.

In this example, the light passing through the ON pixel 11 a ₁ passes through the optical rotation layer 43 twice in a reciprocating manner, whereby the polarization direction is rotated by 45 °, and passes through the magnetization setting layer 11 twice in a reciprocating manner. , The polarization direction is rotated by 45 °, and the polarization direction is rotated by 90 ° in total, and becomes S-polarized light. Therefore, the light that has passed through the ON pixel 11 a ₁ is reflected by the polarization beam splitter surface 21 a and emitted from the polarization beam splitter 21.

On the other hand, the light passing through the off pixel 11a ₀ is rotated 45 ° by passing through the optical rotation layer 43 twice in a reciprocating manner, and is polarized by passing through the magnetization setting layer 11 twice in a reciprocating manner. The direction is rotated -45 °, resulting in a return to P-polarized light. Therefore, light passing through the pixel 11a ₀ off, it passes through the polarization beam splitter surface 21a, and is emitted from the polarizing beam splitter 21.

[0065] In FIG 11, illustrates a path of light passing through the pixels 11a ₁ on (represented by reference numeral ON.) In code to F. Also, the light passing through the pixel 11a ₀ off (sign OF
Expressed as F. ) Are indicated by reference signs A ′ to F ′.

In the example shown in FIG. 11, the spatial light modulator 41
Is returned by the polarizing beam splitter 21.
It is separated into a light passing through the pixel 11a ₀ of light and OFF that has passed through the pixel 11a ₁ on. Polarizing beam splitter 21
The two lights that are further separated and emitted are lights whose light intensities are spatially modulated. The spatial light modulator 41 in the example shown in FIG. 11 can theoretically obtain an extinction ratio of 60 dB or more.

Since the spatial light modulator 41 according to the present embodiment includes the optical rotation layer 43 that rotates the polarization direction of the passing light by a predetermined angle, the polarization direction of the light emitted from the spatial light modulator 41 Can be set in a desired direction. This makes it possible to easily separate two types of light having different polarization directions with a large extinction ratio as in the example shown in FIG.

The spatial light modulator 4 according to the present embodiment
In (1), the rotation angle of the polarization direction in the optical rotation layer 43 can be adjusted by adjusting the thickness of the optical rotation layer 43. Thus, for example, the optical rotation layer 43 is formed to have a predetermined thickness, and the optical rotation layer 43 is polished and the predetermined thickness of the optical rotation layer 43 is adjusted, so that the extinction ratio can be adjusted to be maximum. Will be possible.

Here, FIG. 12 and FIG.
3 shows two examples of the relationship between the amount of polishing and the extinction ratio. 12 and 13, reference numeral 61, in the example shown in FIG. 11, it passes through the pixel 11a ₁ on, the light emitted is reflected by the polarization beam splitter surface 21a of the polarization beam splitter 21 (hereinafter, ON The reference numeral 62 indicates the intensity of light passing through the pixel 11a ₀ that is off in the example shown in FIG. 11, and is reflected by the polarization beam splitter surface 21a of the polarization beam splitter 21 and emitted. It shows the intensity of light (hereinafter, referred to as off output light). The ratio between the intensity of the ON output light and the intensity of the OFF output light is the extinction ratio.

In the example shown in FIG. 12, when the polishing amount is a predetermined value, the intensity of the ON output light is maximized and the intensity of the OFF output light is minimized. Will be the largest. Therefore, the polishing amount of the optical rotation layer 43 may be adjusted so as to be in this state.

In the example shown in FIG. 13, the polishing amount when the intensity of the ON output light is maximum is different from the polishing amount when the intensity of the OFF output light is minimum. In such a case, the polishing amount at which the extinction ratio becomes the maximum (the polishing amount when the intensity of the off-state output light becomes the minimum in the example shown in FIG. 13) is searched, and the optical rotation is set so as to be the polishing amount. The layer 43 may be polished.

In the present embodiment, the optical rotation layer 43 has a plurality of types of regions corresponding to the respective pixels of the magnetization setting layer 11 and having different rotation angles of the polarization direction, and each type of region is determined in advance. May be arranged according to a given pattern.

FIG. 14 shows an example of the configuration of the spatial light modulator 41 in the case where the optical rotation layer 43 has a plurality of types of regions having different rotation angles of the polarization direction. In this example,
The optical rotation layer 43 has a plurality of regions corresponding to each pixel of the magnetization setting layer 11. These regions include two types of regions: a region where the direction of magnetization is upward and a region where the direction of magnetization is downward. In the region where the direction of magnetization is upward, the polarization direction of the passing light is rotated by 22.5 ° per pass and 45 ° by reciprocating pass. On the other hand, in the region where the direction of magnetization is downward, the polarization direction of the passing light is rotated by -22.5 ° per pass and -45 ° by reciprocating pass.
The two types of regions are arranged according to a predetermined pattern such as a mosaic shape. The information on the arrangement pattern of the two types of regions is stored in, for example, the driving unit 2 or the control unit 3 in FIG.

Further, in the example shown in FIG. 14, when the direction of magnetization is upward, each pixel of the magnetization setting layer 11 rotates the polarization direction of the passing light by 45 ° by reciprocating passage, and Is downward, the polarization direction of the passing light is
It rotates -45 ° in the reciprocating passage.

Here, the spatial light modulator 41 shown in FIG.
The operation of the spatial light modulator 41 will be described assuming that P-polarized light is incident on. In the spatial light modulator 41 shown in FIG. 14, the polarization direction of the light that has passed through the region where the direction of magnetization in the optical rotation layer 43 is upward and the pixel in which the direction of magnetization in the magnetization setting layer 11 is upward is rotated by 90 °. To be S-polarized light. Hereinafter referred to the light and the light ON ₁ of the first one. Further, in the spatial light modulator 41 shown in FIG. 14, the light passing through the region where the magnetization direction in the optical rotation layer 43 is downward and the pixel in the magnetization setting layer 11 where the magnetization direction is downward have a polarization direction of −90. Is rotated by an angle of .degree. To become S-polarized light. Hereinafter referred to the light and the light ON ₂ of the second one. Also, the first ON light ON ₁ and the second ON light
The ON light ON ₂ is referred to as ON light. The first ON light ON ₁ and the second ON light ON ₂ are both S-polarized light, but have a phase difference of 180 °. Further, in the spatial light modulator 41 shown in FIG. 14, the light passing through the region where the direction of magnetization in the optical rotation layer 43 is downward and the pixel in the magnetization setting layer 11 where the direction of magnetization is upward,
The light that has passed through the region in which the magnetization direction is upward and the pixel in the magnetization setting layer 11 whose magnetization direction is downward are both P-polarized light. These lights are referred to as off light OFF.

Therefore, the spatial light modulator 41 shown in FIG.
In, among magnetization setting layer 11, when the light direction of magnetization of the optical rotation layer 43 passes through the pixels corresponding to the upward region and light ON ₁ of the first on is upward direction of magnetization of the pixel When the light is turned off, the direction of magnetization in the pixel may be directed downward. Also, of the magnetization setting layer 11, when the light direction of magnetization of the optical rotation layer 43 passes through the pixels corresponding to the downward region and light ON ₂ of the second ON the downward direction of magnetization of the pixel When the light is turned off, the direction of magnetization in the pixel may be directed upward.

Since the arrangement patterns of the two types of regions in the optical rotation layer 43 are known in advance, by setting the direction of magnetization in each pixel of the magnetization setting layer 11 according to the type of the region in the optical rotation layer 43, space The light emitted from the light modulator 41 can be switched between ON light and OFF light for each pixel.

As described above, the first ON light ON ₁ and the second ON light ON ₂ do not interfere with each other because they have a phase difference of 180 °. Therefore, the spatial light modulator 4 shown in FIG.
According to 1, it is possible to reduce speckle noise generated in ON light.

Other functions and effects of the present embodiment are the same as those of the first embodiment.

The present invention is not limited to the above embodiments, and various changes can be made. For example, the thin film coil 12 may be composed of a plurality of layers.

[0081]

As described above, claims 1 to 1
According to the spatial light modulator of any one of the first to third aspects, the direction of magnetization in each pixel of the magnetization setting layer is independently set by the magnetic field generating element, and the direction of magnetization in each pixel with respect to light incident on the magnetization setting layer is set. Give rotation of the polarization direction according to the direction,
Since the light incident on the magnetization setting layer is spatially modulated, there is an effect that a spatial light modulator having a simple structure and a high operation speed can be realized.

According to the spatial light modulator of the third aspect, the magnetic field generating element is disposed adjacent to the surface of the magnetization setting layer opposite to the surface on which light is incident, and the spatial light modulator is provided. Further has a reflection layer provided between the magnetization setting layer and the magnetic field generating element and reflecting light, so that the magnetic field generating element does not affect the modulated light.

According to the spatial light modulator of the fourth aspect, the magnetic field generating element generates a magnetic field when energized through the two conductive paths, and the reflection layer has conductivity. , The structure of the spatial light modulator can be simplified.

According to the spatial light modulator of the fifth or sixth aspect, furthermore, the spatial light modulator is provided so as to be adjacent to the light incident surface of the magnetization setting layer, and the polarization direction of the light passing therethrough due to the magneto-optical effect. Is provided with an optical rotation layer that rotates by a predetermined angle, so that it is possible to set the polarization direction of the light emitted from the spatial light modulator to a desired direction.
There is an effect that two types of light having different polarization directions can be easily separated at a large extinction ratio.

According to the spatial light modulator of the sixth aspect, the optical rotation layer has a plurality of types of regions corresponding to the respective pixels of the magnetization setting layer and having different rotation angles of the polarization direction. Are arranged according to a predetermined pattern, so that it is possible to reduce the speckle noise generated in the emitted light.

According to the spatial light modulator of the eighth aspect, the spatial light modulator is further provided so as to be adjacent to a surface of the magnetization setting layer opposite to the magnetic field generating element,
Since a soft magnetic layer that forms a part of a magnetic path corresponding to the magnetic field generated by the magnetic field generating element is provided, the magnetomotive force generated by the magnetic field generating element is effectively used for setting the magnetization in the pixel. It has the effect of being able to do so.

According to the spatial light modulator of the ninth aspect, furthermore, the spatial light modulator is made of a soft magnetic material, is disposed on the side opposite to the magnetization setting layer in the magnetic field generating element, and is provided with a magnetic field generated by the magnetic field generating element. Since the magnetic path forming part that forms a part of the corresponding magnetic path is provided, an effect is obtained that the magnetomotive force generated by the magnetic field generating element can be effectively used for setting the magnetization in the pixel.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a spatial light modulator according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a spatial light modulator and its peripheral circuits according to the first embodiment of the present invention.

FIG. 3 is a plan view of the thin-film coil according to the first embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a magnetic hysteresis curve representing a relationship between an applied magnetic field and magnetization in the magnetization setting layer shown in FIG.

FIG. 5 is a characteristic diagram showing a magnetic hysteresis curve representing a relationship between an applied magnetic field and magnetization in the soft magnetic layer shown in FIG.

FIG. 6 is an explanatory diagram showing a structure of a one-dimensional magnetic photonic crystal.

FIG. 7 is an explanatory diagram for explaining an example of a usage method and an operation of the spatial light modulator according to the first embodiment of the present invention.

FIG. 8 is a sectional view showing a main part of a spatial light modulator according to a second embodiment of the present invention.

FIG. 9 is an explanatory view schematically showing a configuration of a spatial light modulator according to a second embodiment of the present invention.

FIG. 10 is an explanatory diagram illustrating an example of a method for manufacturing a spatial light modulator according to the second embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating an example of a method of using a spatial light modulator and an operation of the spatial light modulator according to the second embodiment of the present invention.

12 is a characteristic diagram showing an example of the relationship between the amount of polishing of the optical rotation layer and the extinction ratio in FIG.

13 is a characteristic diagram showing another example of the relationship between the amount of polishing of the optical rotation layer and the extinction ratio in FIG.

FIG. 14 is an explanatory diagram showing an example of a configuration of a spatial light modulator in a case where the optical rotation layer has a plurality of types of regions in the second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Spatial light modulator, 2 ... drive part, 3 ... control part, 11 ... magnetization setting layer, 12 ... thin film coil, 13 ... reflection layer, 14 ... terminal, 15 ... magnetic path formation part, 16 ... insulating layer, 17 ... Soft magnetic layer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H079 AA03 BA01 CA02 DA12 DA22 EB18 GA03 HA15 KA06 KA14

Claims (11)

[Claims] 1. A magnetization comprising a plurality of pixels, each of which is made of a magneto-optical material, has a direction of magnetization independently set, and gives a rotation of a polarization direction to incident light according to a direction of magnetization by a magneto-optical effect. A setting layer, provided to correspond to each pixel of the magnetization setting layer,
A spatial light modulator comprising: a plurality of magnetic field generating elements for generating a magnetic field for independently setting the direction of magnetization in each pixel. 2. The spatial light modulator according to claim 1, wherein said magnetic field generating element is a thin film coil. 3. The magnetic field generating element is disposed so as to be adjacent to a surface of the magnetization setting layer opposite to a surface on which light is incident, and a spatial light modulator further includes: The spatial light modulator according to claim 1, further comprising a reflection layer provided between the generation element and the light reflection element. 4. The magnetic field generating element generates a magnetic field by being energized through two conductive paths, and the reflection layer
4. The spatial light modulator according to claim 3, which has conductivity and also serves as one of the conductive paths. 5. An optical rotation layer provided so as to be adjacent to a surface of the magnetization setting layer on which light is incident and which rotates a polarization direction of light passing therethrough by a predetermined angle due to a magneto-optical effect. 5. The spatial light modulator according to claim 3, wherein: 6. The optical rotation layer has a plurality of types of regions corresponding to respective pixels of the magnetization setting layer and having different rotation angles of polarization directions, and the types of regions are arranged according to a predetermined pattern. The spatial light modulator according to claim 5, wherein: 7. The magnetic field setting layer according to claim 1, wherein the magnetization setting layer further includes a domain wall movement suppressing unit provided at a boundary position between adjacent pixels to suppress movement of the domain wall. Spatial light modulator. 8. A magnetic path made of a soft magnetic material, provided adjacent to a surface of the magnetization setting layer opposite to the magnetic field generating element, and corresponding to a magnetic field generated by the magnetic field generating element. 8. The spatial light modulator according to claim 1, further comprising a soft magnetic layer forming a part of the spatial light modulator. 9. The magnetic field generating element further comprises a soft magnetic material, and is disposed on a side opposite to the magnetization setting layer in the magnetic field generating element.
9. The spatial light modulator according to claim 1, further comprising: a magnetic path forming unit that forms a part of a magnetic path corresponding to a magnetic field generated by the magnetic field generating element. 10. The spatial light modulator according to claim 1, wherein the magnetization setting layer is formed of a magnetic garnet thin film. 11. The spatial light modulator according to claim 1, wherein the magnetization setting layer is formed of a one-dimensional magnetic photonic crystal.