JP5339187B2 - Polarization control element and image display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarization control element which is a thin flat plate type optical element and has high polarization control efficiency. <P>SOLUTION: The polarization control element 1 is constituted, by cyclically arraying a first shape metallic structure 3 obtained by bonding metallic dot structure whose shape viewed from an upper surface is square, and a second shape metallic structure 4, obtained by arranging metallic dot structure, whose shape viewed from an upper surface is square to be spaced by a predetermined distance on a supporting substrate 2, and utilizes a resonance effect of plasmon excited by the first shape metallic structure 3 and the second shape metallic structure 4, thereby providing the high polarization control efficiency, and attains a polarization changing function with thin and flat plate type constitution, and contriving reduction in the number of optical elements and the miniaturization of the image display device. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a polarization control element that realizes high light utilization efficiency and a reduction in the number of optical elements, and an image display apparatus using the same.

  In image projection devices and image display devices that control the on / off of pixels using polarized light, such as liquid crystal projectors, it is necessary to introduce linearly polarized light inclined in a specific direction into a spatial modulation device (liquid crystal panel) is there. As a method for extracting linearly polarized light, conventionally, random polarized light obtained from a light source has been extracted only in one direction through linearly polarized light components through a polarizing plate (polarization selection element), so that 50% or more of light was not used. . On the other hand, in recent years, by using a polarization control element (polarization conversion element) and rotating the polarization plane of the remaining polarization component, which was an unnecessary component, by 90 degrees, it is introduced again into the spatial modulation device, thereby increasing the light intensity. Use efficiency is realized. Thereby, a high brightness liquid crystal projector or the like is realized.

  The polarization conversion element widely used in this liquid crystal projector or the like usually includes a polarization separation element that branches optical paths of two orthogonal polarization components, and a half-wave plate (phase shifter) that rotates one polarization plane by 90 degrees. ) Are attached and cut in an oblique direction to realize a polarization conversion function. Examples of polarization separation elements used for such polarization conversion elements include glass prisms and polarization beam splitters in which dielectric multilayer films having different refractive indexes are alternately laminated on a flat substrate surface. By setting the film structure and incident angle so that the Brewster angle is at the interface, the P polarization (polarization parallel to the incidence plane) goes straight, and the S polarization (polarization perpendicular to the incidence plane) ) Is reflected at right angles, and can separate polarized light. However, there is a drawback that the separation performance is low (ten dB) compared to the prism type polarizer using the birefringence of the crystal.

  In addition, phase shifters that use the anisotropy of the refractive index use optical crystal materials that exhibit birefringence. Usually, expensive anisotropic crystals such as rutile and calcite are precisely shaped into a wedge or prism type. It is realized by performing proper polishing. Such an element is extremely expensive, and is difficult to miniaturize and has a problem that a usable wavelength region is limited.

  Since the polarization conversion element is obtained by bonding the polarization separation element and the phase shifter to adjust the film thickness, that is, the optical path difference, and controlling the polarization state, the dependence on the optical crystal material is strong and the degree of freedom of polarization controllability is low. Furthermore, since it is the structure which laminates | stacks a some optical function element, price reduction and size reduction are difficult. In addition, in order to increase the light utilization efficiency, such a polarization conversion element uses a lens array to collect incident light on the polarization separation element and then emit light again through the lens array, so alignment accuracy is required. Thus, the manufacturing process becomes complicated.

  For such a problem, for example, Patent Document 1 and Patent Document 2 disclose a polarization control device (illumination device) that aims to improve light utilization efficiency and is miniaturized and simplified in manufacturing process and alignment. ing.

  As shown in FIG. 16, the polarization illumination device disclosed in Patent Document 1 includes a light source 51, an integrator 54 including a first lens array 52 and a second lens array 53, and a first optical element having a refractive index anisotropy. In the polarization illumination device in which the first diffractive optical element 55, the second diffractive optical element 56, and the polarizing unit 57 are arranged in order, the diffraction direction of the two diffractive optical elements 55 and 56 passes through the optical axis and is orthogonal to the line , The diffraction angle near the optical axis is increased and the periphery is reduced, and the wavelength dependency of the diffraction angle is compensated by the two diffractive optical elements 55 and 56, thereby adversely affecting the wavelength dependency of the diffraction angle. In addition, the light utilization efficiency is improved.

In the polarization light source unit disclosed in Patent Document 2, as shown in FIG. 17, the polarization control element 61 is formed on a substrate 62 in a stripe shape having a size and interval smaller than the wavelength of light emitted from the light source (LED chip) 63. The metal pattern 64 is two-dimensionally arranged in the smallest structural unit, the direction of the smallest structural unit is equal, the interval between the smallest structural units is larger than the wavelength emitted by the light source 63, and is two-dimensionally arranged at a constant cycle or randomly. Of the light emitted from the light source 63, only one linearly polarized light is transmitted from the reflective polarizer 65 to the LED panel 67 outside the unit, and the other straight line reflected by the reflective polarizer 65. The polarization control element 61 changes the polarization state of the other linearly polarized light while repeating multiple reflections between the reflecting means 66 and the reflective polarizer 65, and the other polarization It has a linear polarization to convert one of the linearly polarized light that can penetrate to the outside from the reflective polarizer 65.
JP 2000-356757 A JP 2008-122618 A

  The polarized light illumination device disclosed in Patent Document 1 can align the polarization direction in an alignment-free manner by utilizing the difference in diffraction angle depending on the polarization direction. However, since it includes components such as a lens array, two diffractive optical elements) and a half-wave plate in multiple stages, the manufacturing process is complicated and it is difficult to reduce the size of the apparatus. Further, as a diffractive optical element, an optical medium, that is, an organic material is used from a liquid crystal and a polymer, and there are problems in light resistance and heat resistance for use in a high brightness projector or the like.

  The polarization light source unit disclosed in Patent Document 2 realizes a polarization separation function and a phase shift function using a fine metal structure, and aligns polarized light through multiple reflection with a reflection structure on the light source surface. Therefore, it has only a function as a polarized light source, cannot be separated from the light source, and does not have a function as a polarization conversion element that aligns arbitrary polarized light in one direction. In addition, this configuration includes a scattering component in the oblique direction due to the fine metal structure and the light source structure, which reduces polarization conversion efficiency, and thus has a disadvantage that sufficient efficiency cannot be obtained.

  An object of the present invention is to provide a polarization control element which improves such disadvantages and has a high polarization control efficiency with a thin flat plate type optical element. It is another object of the present invention to provide a polarization control element capable of reducing the number of optical elements, reducing the size and cost of an optical apparatus, and an image display apparatus using the polarization control element.

  Furthermore, a specific metal structure shape and a specific arrangement method that expresses the function of the polarization control element of the present invention and a specific material of the metal structure can be specified, and the polarization can be designed with high polarization controllability. An object is to provide a control element.

In the polarization control element of the present invention, a plurality of metal structures having a maximum size smaller than the wavelength of the incident light are formed on the surface of the support made of a material transparent to the incident light or a plane in the support. having an arrangement with the structure, the said metal structure Ru contain at least two different shapes.

Further, at least one type of shape of the metal structure of the polarization control element has rotational symmetry in a plane perpendicular to the propagation direction of incident light, and the shape turned back with respect to a specific axis matches. Ri shape der having no line symmetry, other one kind of shape is characterized by shape der Rukoto having a linear symmetry as the shape folded back against the particular axis coincide.

Third polarization control element of the invention is the above polarization control element, in at least two different wavelengths following interval of the incident light in the plane of the metal structure perpendicular to the propagation direction of the incident light shapes It is characterized by being placed close to each other.

Fourth polarization control element of the present invention, the polarization control element Komata is a third polarization control element, metal and positioned proximate at least two different metal structures of shape in the same plane structure The body units are periodically arranged in a plane orthogonal to the propagation direction of incident light.

The fifth polarization control element of the present invention, the polarization control element Komata is a third polarization control element, in a plane perpendicular to the propagation direction of the incident light at least two different shapes of the metal structure It is characterized by random arrangement.

Sixth polarization control element of the present invention, the polarization control element Komata is a third polarization control element, the at least two different shapes of the metal structure, the metal structure of any shape periodically arranged in a plane perpendicular to the propagation direction of the incident light, characterized by being placed a metal structure having another shape at random position of the periodically arranged like.

Seventh polarization control element of this invention, the a polarization control element or the third polarization control element, the at least two different shapes of the metal structure, incidence of metal structures of any shape A second plane that is periodically arranged in a first plane orthogonal to the light propagation direction and has a shape different from the metal structure in the first plane is orthogonal to the incident light propagation direction. The first plane and the second plane are stacked at intervals smaller than the wavelength of incident light.

Eighth polarization control element of the present invention, the polarization control element Komata is a third polarization control element, the at least two different shapes of the metal structure, the metal structure of any shape A second plane that is randomly arranged in a first plane orthogonal to the propagation direction of incident light and has a shape different from that of the metal structure in the first plane is orthogonal to the propagation direction of incident light. The first plane and the second plane are stacked at an interval smaller than the wavelength of incident light.

Ninth polarization control element of the present invention, the polarization control element Komata is a third polarization control element, the at least two different shapes of the metal structure, the metal structure of any shape A metal structure that is periodically arranged in a first plane orthogonal to the propagation direction of incident light and has a shape different from that of the metal structure in the first plane is a second orthogonal to the propagation direction of incident light. The first and second planes are randomly arranged in a plane and are stacked at an interval smaller than the wavelength of incident light.

  In addition, the metal structure is constituted by a metal dot assembly in which a plurality of isolated metal dot structures are combined.

  Furthermore, the metal structure is composed of any one of Au, Ag, Pt, Al, Ni, Cr, Cu or a combination thereof, or an alloy material / mixed material containing these as a main component. And

  The image display device according to the present invention is characterized in that the polarization control element is laminated on a liquid crystal layer.

The polarization control element of the present invention has a configuration in which a plurality of metal structures having a maximum size smaller than the wavelength of incident light are arranged on the surface of the support or in the support. different shapes included, one type of shape has rotational symmetry in a plane perpendicular to the propagation direction of the incident light, and a line symmetry as folded shape is matched against the particular axis a shape with no other single type of shape by the shape der Rukoto having a linear symmetry as the shape folded back against the particular axis coincides, achieve high polarization control element polarization control efficiency it can. In addition, a thin flat element configuration is realized, so that the number of optical elements can be reduced, and the optical device can be reduced in size and price.

  In addition, by disposing at least two types of metal structures having different shapes constituting the polarization control element in a plane perpendicular to the propagation direction of the incident light at an interval equal to or smaller than the wavelength of the incident light, An influence can be avoided and a polarization control element with high polarization control efficiency can be realized.

  Further, metal structure units in which at least two different types of metal structures constituting the polarization control element are arranged close to each other in the same plane are periodically arranged in a plane perpendicular to the propagation direction of incident light. This facilitates the design of a polarization control element with high polarization control efficiency.

  Further, at least two types of metal structures having different shapes of the polarization control element are randomly arranged in a plane orthogonal to the propagation direction of incident light, or one of at least two types of metal structures having different shapes. Highly polarization control efficiency is achieved by periodically arranging the metal structures of the shape in a plane orthogonal to the propagation direction of incident light and arranging the metal structures of other shapes at random positions in the periodic array. A polarization control element can be easily produced.

  Further, among the at least two different types of metal structures of the polarization control element, the metal structures of any shape are periodically arranged in a first plane orthogonal to the propagation direction of incident light, and the first The metal structure having a shape different from the metal structure in the plane is periodically arranged in a second plane orthogonal to the propagation direction of the incident light, and the first plane and the second plane are Laminate at intervals smaller than the wavelength, or randomly arrange one of the metal structures of at least two different shapes in the first plane perpendicular to the propagation direction of the incident light. The metal structure having a shape different from the metal structure in the first plane is randomly arranged in the second plane orthogonal to the propagation direction of the incident light, and the first plane and the second plane are incident. Laminate at intervals smaller than the wavelength of light, or at least 2 Among metal structures of different shapes, the metal structures of any shape are periodically arranged in a first plane perpendicular to the propagation direction of incident light, and the metal structures in the first plane By randomly arranging metal structures having different shapes in a second plane perpendicular to the propagation direction of incident light, and laminating the first plane and the second plane at intervals smaller than the wavelength of the incident light. Therefore, it is possible to easily design and manufacture a polarization control element with high polarization control efficiency.

  In addition, by configuring the metal structure that constitutes the polarization control element with a metal dot assembly that combines a plurality of isolated metal dot structures, the polarization control function can be expressed in a simple shape. A polarization control element that can be easily manufactured can be provided.

  Furthermore, by constituting the metal structure with any one of Au, Ag, Pt, Al, Ni, Cr, Cu, a combination thereof, or an alloy material / mixed material containing these as a main component, polarization can be achieved. A polarization control element with high control efficiency can be provided.

  An image display apparatus using the polarization control element of the present invention for an image forming unit can stably display a high-quality image with a simple configuration.

  FIG. 1 is a plan view showing the configuration of the polarization control element of the present invention. As shown in the figure, the polarization control element 1 has a periodic arrangement of a plurality of metal structure units 5 composed of metal structures 3 and 4 having a maximum size smaller than the wavelength of incident light on the surface of a support substrate 2. Configured. As shown in the plan view of FIG. 2A and the AA cross-sectional view of FIG. 2B, each metal structure unit 5 is a first unit in which a plurality of metal dot structures having a square or rectangular shape as viewed from above are joined. As shown in the plan view of FIG. 2A and the BB cross-sectional view of FIG. 2C, a metal dot structure having a square or rectangular shape as viewed from above is arranged at a predetermined interval. It has the metal structure 4 of the 2nd shape. Here, for ease of design, a metal dot assembly having a configuration in which a plurality of metal dot structures having a rectangular shape when viewed from the upper surface are joined or arranged at predetermined intervals is illustrated as the metal structures 3 and 4. The metal dot structure is not necessarily required. Hereinafter, the metal dot aggregate is also collectively referred to as a metal structure. Further, in the AA sectional view of FIG. 2B and the BB sectional view of FIG. 2C, the first shape metal structure 3 and the second shape metal structure 4 are directly formed on the support substrate 2. In actuality, in order to improve the adhesion between the metal structures 3 and 4 and the support substrate 2 and to hold the metal structures 3 and 4 stably, the metal structures 3 and 4 are supported at the interface between the support substrate 2 and the substrate. An underlayer is provided. Details of the underlayer will be described later together with a method for manufacturing the polarization control element 1.

  2B includes only the first shape metal structure 3, and the portion illustrated in BB cross section of FIG. 2B includes the first shape metal structure 3 and the first shape. The metal structure 4 having the shape 2 is included. The metal structure 3 having the first shape has a rotational symmetry and a structure that does not have a line symmetry such that the folded shape with respect to a specific axis coincides with the second shape. This metal structure 4 has a structure having line symmetry in the vertical direction of the drawing. When linearly polarized light is incident on the metal structure 3 having the first shape, a part of any incident linearly polarized light is caused by the interaction between the metal structure 3 and light that resonates with electronic vibration (plasmon) inside the metal structure 3. Optical rotatory power that is converted into a polarized light component orthogonal to the direction of incident polarized light and emitted can be expressed. Further, when linearly polarized light is incident on the second-shaped metal structure 4, a phase difference is generated in the emitted light in the vertical direction and the horizontal direction on the paper surface. The light incident on the polarization control element 1 having the first-shaped metal structure 3 and the second-shaped metal structure 4 having different shapes interacts with the metal structures 3 and 4. Has different polarization anisotropy and interferes at distant observation positions. As a result, an asymmetry occurs between the polarized light component that is converted from the horizontal direction to the vertical direction and the polarized light component that is converted from the vertical direction to the horizontal direction, that is, a polarization conversion function is exhibited.

  FIG. 2 shows the case where the metal structure unit 5 has three metal structures 3 of the first shape, one metal structure 4 of the second shape, and four metal structures of two types. However, the number of metal structures in the metal structure unit 5 may be any number as long as it is two or more, and the shape of the metal structures may be two or more. Here, the interval between the metal structures 3 and 4 of the metal structure unit 5 is preferably smaller than the wavelength of the incident light. This is in order to avoid the influence of diffraction in the distance, but depending on the application, the metal structures 3 and 4 may be intentionally arranged at intervals greater than the wavelength, such as having an angle dependency or wavelength dependency. Absent.

  Next, individual components of the polarization control element 1 will be described. The material used as the support substrate 2 of the polarization control element 1 is preferably a transparent material having low absorption at a wavelength in the visible light region in order to obtain high efficiency, such as quartz glass, BK7, borosilicate glass such as Pyrex (registered trademark), An optical crystal material such as CaF2, ZnSe, or Al2O3 is used. Further, FIG. 1 is described on the assumption that the transmission type polarization control element 1 is used. However, the polarization control element may be of a reflection type. In this case, Al, Au, etc. are provided below the support substrate 2. A reflective film made of a metal material is formed. The thickness of the reflective film must be greater than the skin depth at which light penetrates into the metal, and is at least 30 nm. The same effect can be obtained by using a reflection structure with a total reflection coating of a dielectric multilayer film.

  1 and 2 show the case where two metal dot structures having a square shape when viewed from the upper surface are joined as the first-shaped metal structure 3, which has rotational symmetry and line symmetry. Any shape may be used as long as it has a structure having no optical property and optically exhibits optical rotation. For example, as shown in FIG. 3A, in addition to joining two metal dot structures having a square shape when viewed from the upper surface, a metal dot having a rectangular shape when viewed from the upper surface as shown in FIG. A shape in which two structures are joined, a shape in which the end of a rectangle is bent to the opposite side as shown in (c), an arc-like shape in an antisymmetric curvature as shown in (d), (e) As shown in FIG. 6, a structure in which a circular shape is overlapped with an end of a rectangle, or a combination of arbitrary shapes such as a shape in which two ellipses overlap as shown in FIG.

  The size of the first-shaped metal structure 3 and the second-shaped metal structure 4 needs to be equal to or smaller than the wavelength of the incident light. The size of the shaped metal structure 4 will be described with reference to the layout diagram of FIG. FIG. 4A shows the size of the first-shaped metal structure 3 in which two metal dot structures having a square shape when viewed from the top are joined. As shown in FIG. 4A, the longest diameter when an ellipsoid is drawn such that the longest linear distance of the first-shaped metal structure 3 is taken as the long axis, and the entire metal structure 3 fits within the ellipse. The size is defined by d1 and the minor axis d2. The first-shaped metal structure 3 is formed so that the major axis d1 is smaller than the wavelength of incident light. FIG. 4B shows the size of the second-shaped metal structure 4 having a metal dot structure with a predetermined interval when viewed from above. In this case, since there are two longest linear distances, the major axis d1 and the minor axis when the ellipsoid is drawn so as to pass through the four outer vertices with the straight line passing through the center as the major axis direction of the ellipsoid. The size is defined by d2. As shown in FIG. 4C, in the case of the metal structure 3 having a shape in which the end of the rectangle is bent to the opposite side, the longest linear distance is similarly taken as the major axis, and all of the metal structure 3 is within the ellipse. The size is defined by the major axis d1 and the minor axis d2 when an ellipsoid that fits in the circle is drawn. Further, regarding the height of the metal structures 3 and 4, assuming that the polarization direction of incident light is in a plane parallel to the paper surface, that is, assuming that light is incident perpendicular to the paper surface, the polarization anisotropy It does not need to be specified in particular. Further, the corners of the metal structure do not have to be sharp, and a dull structure obtained in the manufacturing process may be used.

  Moreover, the material which comprises the metal structures 3 and 4 should just be a material which can excite the plasmon which is a resonance collective motion of an electron in the metal structures 3 and 4, and a large polarization | polarized-light is excited by exciting a plasmon. Control characteristics can be realized. Plasmons are largely classified into surface plasmons that are excited on the metal surface in the interface region between metal and dielectric, and localized surface plasmons that are excited over the entire metal material when the metal structure becomes minute on the nanoscale. In the following, both surface plasmons and localized surface plasmons are expressed as plasmons. As a metal material capable of exciting plasmons, any of Au, Ag, Pt, Al, Ni, Cr, and Cu, a combination thereof, or an alloy material / mixed material containing these as a main component can be used.

  Further, when the metal structures 3 and 4 in the polarization control element 1 are formed on the support substrate 2, there is a problem that they are mechanically fragile and easily peeled off. In order to avoid this, a base layer or base structure for joining the support substrate 2 and the metal structures 3 and 4 may be provided. When the thickness of the underlying layer (underlying structure) is increased, the plasmon resonance effect is reduced. On the other hand, it is also possible to provide a function of controlling the polarization characteristics. As the support layer (underlying structure), a material having high adhesion between the support substrate material and the metal material is suitable, and Ti, Cr, Ta, V, Zr, Al, Mg, which form a solid solution at the interface with the substrate material. Metal materials such as Mo, Co, Cu, and Ni can be used.

  1 and 2 show the case where the metal structures 3 and 4 in the polarization control element 1 are exposed in the air, the metal structures 3 and 4 are shown in the cross-sectional view of FIG. A protective film 6 or a protective structure may be provided on the surface layer portion. By providing the protective film 6 and the protective structure in this way, it becomes possible to improve resistance to external damage and metal oxidation. The material used for the protective film 6 is the same as the support substrate 2, such as quartz glass, BK7, ZnS—SiO 2, borosilicate glass, CaF 2, Si, ZnSe, Materials such as Al2O3 and ZnO can be used.

  Next, a method for producing the metal structures 3 and 4 of the polarization control element 1 will be described with reference to the process diagram of FIG. To manufacture the first shape metal structure 3 and the second shape metal structure 4 having a size equal to or smaller than the wavelength of incident light, a technique having a processing accuracy equal to or lower than the diffraction limit of visible light is applied. Specific methods that can be used include a method using electron beam lithography, DUV / EUV lithography, nanoimprinting, and etching utilizing alteration of material properties.

  Although a method by electron beam lithography will be described below, the manufacturing method is not necessarily limited. As shown in step 1 of FIG. 6, optical glass such as SiO2 on a parallel plate is used as the support substrate 2, and a base layer 7 such as Ti and a metal film 8 such as Au are sequentially formed on the flat surface by sputtering or vacuum deposition. A photoresist film 9 is formed on the metal film 8 by deposition. Next, as shown in step 2, the photoresist film 9 is exposed by electron beam drawing so as to leave a metal array pattern, thereby forming an exposure pattern 10. Thereafter, as shown in Step 3, unnecessary metal portions are etched by reactive ion etching (RIE) or the like using the exposure pattern 10 as a mask. Thereafter, as shown in Step 4, the remaining exposure pattern of the photoresist film 9 is etched. 10 is removed. In this way, a two-dimensional array pattern can be formed by the metal structures 3 and 4 that are in close contact with the support substrate 2 via the underlayer 7. Further, instead of forming a two-dimensional array pattern of the metal structures 3 and 4 by etching, a metal material is deposited on the photoresist pattern, and then the lift-off method of removing the photoresist is used to form the metal structures 3 and 4. A method of forming a two-dimensional array pattern is also effective.

  Next, a numerical simulation performed for verifying the operation of the polarization control element 1 will be described with reference to FIGS. As the numerical simulation method, a finite difference time domain method (FDTD method) was used in which Maxwell's equations describing the time-space response of an electromagnetic field are differentiated into a time domain and a spatial domain. FIG. 7A is a plan view of a model of the polarization control element 1 used in the numerical simulation, and FIG. 7B is a cross-sectional view of the plan view of FIG. In this numerical simulation, in order to obtain the spectral characteristics of the transmitted light, a pulse light having a sufficiently short time width (the spectral width is sufficiently spread in the visible light region) as incident light is separated from the interface of the support substrate (SiO2) by 1000 nm. The polarization characteristics of the transmitted light were evaluated on a transmission surface that was incident from the surface and separated by 1000 nm. In addition, by adopting a square Au dot structure as the metal structures 3 and 4 and using a dielectric function in which the Drude model and the Lorentz model are superimposed in order to describe the response of electrons in Au to the photoelectric field, Introduced the wavelength dispersion characteristics of metal materials.

  The metal structures 3 and 4 used in this numerical simulation were composed of a combination of square dots having a side of 80 nm, and the height was set to 200 nm. The first-shaped metal structure 3 has a shape in which two rectangular dots are joined by shifting by 40 nm in the vertical direction, and the second-shaped metal structure 4 has a distance of 20 nm between two rectangular dots. The metal structure unit 5 is formed as a shape spaced apart from each other, the first shape metal structure 3 is arranged at three lattice points of a square lattice of 200 nm pitch, and the second shape metal structure 4 was arranged so that the center of gravity coincided with another point of a square lattice having a pitch of 200 nm.

  In the plan view of FIG. 7 (a), the incident polarization was set in the x and y directions with the horizontal direction of the paper as the x axis and the vertical direction as the y axis, and the polarization characteristics were evaluated by performing two numerical simulations. . In this numerical simulation, the periodic boundary condition is applied to the calculation region boundary in the x-axis direction and the y-axis direction, and the absorbing boundary condition is applied to the calculation region boundary in the z-axis direction. Accordingly, this corresponds to a model in which the metal structure units 5 in the polarization control element 1 are arranged in a square lattice at a pitch of 400 nm, and the metal structures 3 and 4 in the metal structure unit 5 are also at a pitch of 200 nm. The metal structures 3 and 4 are arranged in a square lattice with a pitch of 200 nm. Further, for the comparison of the numerical simulation results, detailed description of the model is omitted, but the calculation in the case where the entire metal structure unit 5 is configured by the first shape metal structure 3 was also performed. In this case, all other simulation parameters are the same.

  FIG. 8 is a diagram plotting the non-diagonal component of the transmittance obtained as a result of this numerical simulation. FIG. 8A shows the inside of the metal structure unit 5 in the first shape metal structure 3 and the second shape. When comprised by the metal structure 4, (b) shows the case where the inside of the metal structure unit 5 is comprised only by the metal structure 3 of the 1st shape for the comparison. The non-diagonal component of the transmittance means the transmittance Txy of the y component when the incident polarized light is in the x-axis direction, and the transmittance Tyx of the x component when the incident polarized light is the y polarized light. . In FIG. 8B, the transmittance Txy and the transmittance Tyx are equal and the polarization conversion function is not obtained. However, as shown in FIG. 8A, at least two types of metal structures 3 and 4 are shaped. In the polarization control element 1 having, the transmittance Txy and the transmittance Tyx greatly deviate in the vicinity of the resonance wavelength, and it can be seen that the polarization conversion function is exhibited. Although the model used for this numerical simulation is not the result of optimizing the polarization conversion efficiency, it has been confirmed by the numerical simulation that the polarization conversion function can be realized by the configuration of the polarization conversion element 1 of the present invention. In order to further improve the polarization conversion efficiency, the cross-sectional shape, height, and filling rate (period) of the first-shaped metal structure 3 and the second-shaped metal structure 4 may be optimized. In order to change the operating wavelength band, the metal material may be changed in addition to changing the shape of the metal structures 3 and 4. For example, when Ag is used as a material for the metal structures 3 and 4, the resonance wavelength is shifted to a shorter wavelength side than that of Au.

  Thus, the polarization control element 1 periodically arranges the metal structures 3 and 4 having two kinds of shapes on the support substrate 2 in the plane, and further, the resonance effect of plasmons excited in the metal structures 3 and 4. By using this, it becomes possible to have high polarization control efficiency. Further, the polarization conversion function is realized with a thin, flat plate-like structure, and the number of optical elements can be reduced and the optical device can be downsized.

  In the above description, a plurality of metal structure units 5 including a first shape metal structure 3 and a second shape metal structure 4 having a size equal to or smaller than the wavelength of incident light on the surface of the support substrate 2 are periodically arranged in a lattice pattern. As shown in the plan view of FIG. 9, the first shape metal structure 3 and the second shape metal structure 4 are attached to the support substrate 2 as shown in the plan view of FIG. 9. The second polarization control element 1a may be configured by being randomly arranged on the surface. Also in this case, it is preferable that the average distance between adjacent metal structures arranged at random is not more than the wavelength of incident light. This is to avoid spatial fluctuation of the intensity distribution due to diffraction in the distance.

  As the material used for the support substrate 2 and the metal structures 3 and 4 constituting the second polarization control element 1a, the same material as that of the polarization control element 1 may be used. The method of creating the metal structures 3 and 4 on the support substrate 2 of the second polarization control element 1 a is the same as that of the polarization control element 1. In addition, by providing the protective film 6 and the protective structure on the surface layer portions of the metal structures 3 and 4, resistance to external damage and metal oxidation can be improved.

  The characteristics of the second polarization control element 1a will be described. The second polarization control element 1a is characterized in that the arrangement of the metal structures 3 and 4 has no periodicity. As a parameter characterizing the function of the polarization control element 1a, the number density of the metal structures 3 and 4 (or It is sufficient to consider only the filling rate. Further, by adjusting the number density of the metal structures 3 and 4, the characteristics of the polarization control element 1a can be adjusted, and the design of the polarization control characteristics is facilitated. In addition, it is not necessary to consider the alignment accuracy and the influence of the connecting portion of the drawing region in electron beam drawing, and the manufacturing accuracy when manufacturing the polarization control element 1a can be relaxed.

  As described above, the second polarization control element 1 a is configured such that the metal structures 3 and 4 having two types of shapes are randomly arranged on the support substrate 2 in the same plane and further excited in the metal structures 3 and 4. By utilizing the plasmon resonance effect, it is possible to have high polarization control efficiency. In addition, the polarization conversion function is realized with a thin, flat plate-like structure, so that the number of optical elements can be reduced and the optical device can be miniaturized. Moreover, the arrangement of the metal structures 3 and 4 is configured as a random pattern and can be easily manufactured.

  In the above description, the case where the second polarization control element 1a is configured by randomly arranging the first-shaped metal structure 3 and the second-shaped metal structure 4 on the surface of the support substrate 2 has been described. As shown in the plan view of FIG. 10, the first shape metal structure 3 and the second shape metal structure 4 are arranged in a first shape periodically at random positions of the lattice points of the periodic array. The third polarization control element 1b may be configured by arranging the metal structure 3 and the second shape metal structure 4. The period of the arrangement of the first-shaped metal structure 3 and the second-shaped metal structure 4 may have anisotropy in the vertical direction and the horizontal direction in FIG. In addition, the period of the metal structures 3 and 4 is preferably equal to or less than the wavelength of the incident light in order to avoid the influence of far-field diffraction as in the polarization control element 1 and the second polarization control element 1a. The metal structures 3 and 4 may be intentionally arranged at intervals equal to or greater than the wavelength, depending on the application, such as having a property and wavelength dependency.

  The light incident on the metal structures 3 and 4 of the third polarization control element 1b has different polarization anisotropy by interacting with the metal structures 3 and 4, and interferes at a distant observation position. As a result, an asymmetry occurs between the polarization component that converts from the horizontal direction to the vertical direction and the polarization component that converts from the vertical direction to the horizontal direction, that is, a polarization conversion function is exhibited.

  The material used for the support substrate 2 and the metal structures 3 and 4 constituting the third polarization control element 1b may be the same material as the polarization control element 1 and the second polarization control element 1a. The method of creating the metal structures 3 and 4 on the support substrate 2 of the third polarization control element 1b is the same as in the case of the polarization control element 1 and the second polarization control element 1a. In addition, by providing the protective film 6 and the protective structure on the surface layer portions of the metal structures 3 and 4, resistance to external damage and metal oxidation can be improved.

  In the third polarization control element 1b, the arrangement period and the number density of the first-shaped metal structure 3 and the second-shaped metal structure 4 are design parameters, and the diffraction effect and the polarization conversion function are superimposed. Thus, it is possible to realize a polarization control characteristic with a high degree of freedom. In addition, the polarization conversion function is realized with a thin, flat plate-like structure, so that the number of optical elements can be reduced and the optical device can be miniaturized. In addition, it is possible to provide a polarization control element with a high degree of design freedom.

  The polarization control element 1, the second polarization control element 1 a, and the third polarization control element 1 b all have the first shape metal structure 3 and the second shape metal structure 4 on the same plane of the support substrate 2. Although the case where it is formed above has been described, the first-shaped metal structure 3 and the second-shaped metal structure 4 may be formed on different planes to form a laminated structure. FIG. 11 shows the configuration of a fourth polarization control element 1c having a laminated structure in which the first shape metal structure 3 and the second shape metal structure 4 are formed on different planes. FIG. 11A is a plan sectional view showing a two-dimensional array pattern of the second-shaped metal structures 4, and FIG. 11B is a plan sectional view showing a two-dimensional array pattern of the first-shaped metal structures 3. FIG. 11C is a side cross-sectional view obtained by cutting the plan cross-sectional views of FIGS.

  The first-shaped metal structures 3 of the fourth polarization control element 1c are periodically arranged on the surface of the support substrate 2 that is the first plane, and the second-shaped metal structures 4 are the first Are periodically arranged on the second plane which is the surface of the dielectric layer 11 provided in the surface layer portion of the metal structure 3 having the shape of A dielectric film 12 is formed on the surface layer of the second-shaped metal structure 4. The first-shaped metal structure 3 and the second-shaped metal structure 3 and the second-shaped metal structure 3 and the second-shaped metal structure 4 and the second-shaped metal structure 4 are separated from each other so that an interference effect due to multiple reflection does not appear. The metal structures 4 having the shape are arranged at intervals equal to or shorter than the wavelength of incident light. Thus, the number density of the two metal structures 3 and 4 can be increased by stacking and arranging the first shape metal structure 3 and the second shape metal structure 4.

  FIGS. 11A and 11B show an example in which the first shape metal structure 3 and the second shape metal structure 4 are stacked so as not to overlap. It may be a simple configuration. Further, the plane on which the first-shaped metal structure 3 and the second-shaped metal structure 4 are arranged may be composed of two or more layers. Furthermore, the period of the first-shaped metal structure 3 and the second-shaped metal structure 4 has anisotropy in the vertical and horizontal directions in FIG. 11 (a) and (b). However, in order to avoid the influence of diffraction in the distance, it is preferable to set the wavelength to be equal to or smaller than the wavelength of the incident light. The structures 3 and 4 may be arranged.

  As described above, the fourth polarization control element 1c has a rotationally symmetric and non-linearly symmetric structure, and converts a part of arbitrary incident linearly polarized light into a polarized light component orthogonal to the direction of incident polarized light. The first-shaped metal structure 3 and the second-shaped metal that has a line symmetry in the vertical direction on the paper surface and that causes a phase difference in the emitted light in the vertical and horizontal directions on the paper surface. Since the structure 4 is configured, the light incident on the fourth polarization control element 1c has different polarization anisotropy by interacting with the metal structures 3 and 4, and interferes at a distant observation position. As a result, asymmetry occurs between the polarization component that converts from the horizontal direction to the vertical direction and the polarization component that converts from the vertical direction to the horizontal direction, that is, a polarization conversion function can be exhibited.

  11A and 11B exemplify metal dot aggregates having a structure in which metal dot structures having a rectangular shape when viewed from the top are bonded or arranged at predetermined intervals as the metal structures 3 and 4. However, the metal dot structure is not necessarily required.

  The materials used for the support substrate 2 and the metal structures 3 and 4 constituting the fourth polarization control element 1c are the same as those of the polarization control element 1, the second polarization control element 1a, and the third polarization control element 1b. Use materials. Further, the method of creating the metal structures 3 and 4 on the support substrate 2 of the fourth polarization control element 1c is the same as in the case of the polarization control element 1 and the like. Further, by providing a protective film 6 made of a dielectric on the surface layer portion of the second-shaped metal structure 4 laminated on the upper part of the first-shaped metal structure 3, external damage, metal oxidation, etc. The resistance to can be improved. In the reflective configuration, a reflective film made of a metal material such as Al or Au thicker than the skin depth is formed below the support substrate 2, or a reflective structure by a total reflection coating with a dielectric multilayer film is provided. .

  Next, a method for producing the metal structures 3 and 4 of the fourth polarization control element 1c will be described. For the production of the first-shaped metal structure 3 and the second-shaped metal structure 4 having a size equal to or smaller than the wavelength of the incident light, a technique having a processing accuracy equal to or lower than the diffraction limit of visible light is applied. . Specific methods that can be used include a method using electron beam lithography, DUV / EUV lithography, nanoimprinting, and etching utilizing alteration of material properties. Although a method by electron beam lithography will be described below, the manufacturing method is not necessarily limited.

  The process of manufacturing the first-shaped metal structure 3 of the fourth polarization control element 1c on the support substrate 2 is the same as the process from process 1 to process 4 in FIG. Therefore, after the first shape metal structure 3 is formed on the support substrate 2 in steps 1 to 4 shown in the process diagram of FIG. 6, the second shape metal structure 4 is laminated as shown in FIG. This will be described with reference to the drawings.

  A dielectric layer 11 serving as a support structure for the second-shaped metal structure 4 is sputtered on the first-shaped metal structure 3 produced in the process 4 of FIG. 6 as shown in the process 5 of FIG. Then, the surface is planarized by a method such as polishing, and a base film 12 such as Ti and a metal film 13 such as Au are sequentially deposited, and a photoresist film 14 is formed on the metal film 13. Subsequently, as shown in Step 6, the photoresist film 14 is exposed so as to leave the arrangement pattern of the second-shaped metal structures 4 by electron beam drawing, thereby forming an exposure pattern 15. Thereafter, as shown in Step 7, unnecessary photoresist film and metal portions are removed by etching using RIE or the like using the exposure pattern 15 as a mask, and the remaining exposure pattern 15 is removed as shown in Step 8. Further, as shown in step 9, in order to match the resonance condition of the plasmon excited in the second-shaped metal structure 4, a protective film of a dielectric film is formed on the surface layer of the second-shaped metal structure 4. A fourth polarization control element 1c in which 6 is coated by a sputtering method, the surface is flattened by polishing, and a two-dimensional pattern of the first-shaped metal structure 3 and the second-shaped metal structure 4 is laminated. Make it.

  The features of the fourth polarization control element 1c will be described. In the fourth polarization control element 1c, the two-dimensional array pattern of the first-shaped metal structure 3 and the second-shaped metal structure 4 is laminated at intervals equal to or less than the wavelength of incident light, and unit deposition is performed. The number density of the surrounding metal structures 3 and 4 can be improved. In addition, the number density can be reduced by changing the period of the metal structures 3 and 4 between the plane on which the first-shaped metal structure 3 is formed and the plane on which the second-shaped metal structure 4 is formed. The polarization control characteristic can be easily controlled.

  As described above, the fourth polarization control element 1c is configured such that the metal structures 3 and 4 having different shapes are periodically arranged in different planes, and plasmons are excited in the metal structures 3 and 4. By utilizing the resonance effect, it is possible to provide a polarization control element having high polarization control efficiency. Further, it is easy to adjust the number density per unit deposition, and a polarization control element with a high degree of design freedom can be provided.

  In the fourth polarization control element 1c, the case where the first-shaped metal structure 3 and the second-shaped metal structure 4 are periodically arranged is shown. As shown in a plan cross-sectional view showing a two-dimensional array pattern of the metal structures 4 having the shape of FIG. 1B and a plan cross-sectional view showing a two-dimensional array pattern of the metal structures 3 having the first shape shown in FIG. The fifth polarization control element 1d may be configured by randomly arranging the metal structures 3 and the second-shaped metal structures 4 respectively.

  Also in the fifth polarization control element 1d, the first-shaped metal structure 3 and the second-shaped metal structure 4 are arranged randomly, but recently, in order to avoid the influence of diffraction in the distance, The average distance between the metal structures in contact with each other is preferably equal to or less than the wavelength of incident light. In the fifth polarization control element 1d, the first-shaped metal structure 3 has a rotational symmetry and no linear symmetry, and a part of any incident linearly polarized light is converted into the direction of the incident polarized light. The second-shaped metal structure 4 has a line symmetry in the vertical direction of the paper surface, and has a configuration that causes a phase difference in the emitted light in the vertical direction and the horizontal direction of the paper surface. ing. Therefore, the light incident on the fifth polarization control element 1d has different polarization anisotropy by interacting with the first-shaped metal structure 3 and the second-shaped metal structure 4, and is observed at a distance. As a result, there is an asymmetry between the polarization component that converts from the horizontal direction to the vertical direction and the polarization component that converts from the vertical direction to the horizontal direction, that is, the polarization conversion function appears. it can. In addition, in FIG. 13, metal dot assemblies having a configuration in which a plurality of metal dot structures having a rectangular shape when viewed from the top as metal structures 3 and 4 are arranged or arranged at predetermined intervals are illustrated. The metal dot structure is not necessarily required.

  The material used for the support substrate 2 and the metal structures 3 and 4 constituting the fifth polarization control element 1d may be the same material as that of the polarization control element 1 and the fourth polarization control element 1c. Further, the fifth polarization control element 1d is manufactured in the same manner as the fourth polarization control element 1c.

  As described above, the fifth polarization control element 1d in which the first-shaped metal structure 3 and the second-shaped metal structure 4 are randomly arranged and stacked is formed by the two-dimensional random structure of the metal structures 3 and 4. The patterns are stacked at intervals equal to or smaller than the wavelength of incident light, and the number density of the metal structures 3 and 4 per unit volume can be improved. Further, since the arrangement of the first shape metal structure 3 and the second shape metal structure 4 has no periodicity, the number of metal structures 3 and 4 is a parameter that characterizes the function of the polarization control element 1d. Only the density needs to be considered, and the design of the polarization control characteristic is easy. In addition, it is not necessary to consider the alignment accuracy or the influence of the connecting portion of the drawing region in electron beam drawing, and the manufacturing accuracy of the polarization control element 1d can be relaxed. Further, the fifth polarization control element 1d randomly arranges the metal structures 3 and 4 having different shapes in different planes, and further utilizes the resonance effect of plasmons excited in the metal structures 3 and 4. Thus, a polarization control element having high polarization control efficiency can be provided. In addition, it is easy to adjust the number density per unit volume, and it is possible to provide a polarization control element with a high degree of design freedom. In addition, since the arrangement of the metal structures is configured as a random pattern, it is possible to provide a polarization control element that can be easily manufactured.

  The fourth polarization control element 1c includes a first shape metal structure 3 and a second shape metal structure 4 which are periodically arranged and stacked, and a fifth polarization control element 1d is a first polarization control element 1d. Although the case where the metal structure 3 having the shape and the metal structure 4 having the second shape are formed by randomly arranging and laminating each of them is shown, the metal structure 4 having the second shape shown in FIG. As shown in the plan sectional view showing the two-dimensional array pattern and the plan sectional view showing the two-dimensional array pattern of the first-shaped metal structure 3 in (b), the second-shaped metal structure 4 is randomly selected. The sixth polarization control element 1e may be configured by arranging and periodically laminating and stacking the first shape metal structures 3. Alternatively, the sixth polarization control element 1e may be configured by periodically arranging the second-shaped metal structures 4 and randomly stacking the first-shaped metal structures 3 arranged at random. In this case, the number of the first shape metal structures 3 and the number of the second shape metal structures 4 may be different. Also in the sixth polarization control element 1e, in order to avoid the influence of far-field diffraction, on the plane on which the metal structures 3 and 4 are periodically arranged, the period is set to be equal to or less than the wavelength of incident light, and the metal is arranged randomly. It is preferable that the average distance between the structures 4 or the metal structures 3 be equal to or less than the wavelength of incident light.

  The sixth polarization control element 1e also has a structure in which the first-shaped metal structure 3 has rotational symmetry and no line symmetry, and a part of any incident linearly polarized light is converted into incident polarized light. The second-shaped metal structure 4 is converted into a polarized light component orthogonal to the direction, and has a line symmetry in the vertical direction of the paper, and a configuration that causes a phase difference in the emitted light in the vertical and horizontal directions of the paper. It has become. Therefore, the light incident on the sixth polarization control element 1e has different polarization anisotropy by interacting with the metal structure and interferes at a distant observation position. As a result, the light is converted from the horizontal direction to the vertical direction. Asymmetry occurs between the polarization component to be converted and the polarization component to be converted from the vertical direction to the horizontal direction in the drawing, that is, a polarization conversion function can be exhibited.

  The sixth polarization control element 1e may be configured by randomly arranging the second-shaped metal structures 4 and periodically arranging and stacking the first-shaped metal structures 3 or the second polarization-control elements 1e. Since the metal structures 4 having a shape are periodically arranged and the metal structures 3 having the first shape are randomly arranged and stacked, the number density of the metal structures per unit volume is improved. Can do. Moreover, since it has the two-dimensional arrangement pattern of the metal structures 3 and 4, it becomes possible to control angle dependence and wavelength dependence. In addition, a polarization control element having high polarization control efficiency can be provided by utilizing the resonance effect of plasmons excited in the first shape metal structure 3 and the second shape metal structure 4. it can. In addition, it is easy to adjust the number density per unit volume, and a polarization control element with a high degree of design freedom can be provided.

  Next, an image display apparatus using any one of the polarization control elements 1 to 1e formed as described above will be described.

  FIG. 15 shows a schematic configuration of a liquid crystal projector 30 using, for example, the polarization control element 1. As shown in the figure, the liquid crystal projector 30 includes three color image forming units 31 R, 31 G, and 31 B of R, G, and B, a light combining prism 32, a projection lens 33, and a screen 34. The image forming units 31R, 31G, and 31B are formed by laminating a light source 35, a polarization control element 1, a liquid crystal panel 36, and a polarizing plate 37, respectively.

  When an image is projected onto the screen 34 by the liquid crystal projector 30, the light emitted from the light source 35 of each image forming unit 31 R, 31 G, 31 B is transmitted through the liquid crystal panel 36 and the polarizing plate 37 from the polarization control element 1. Then, the light is combined by the light combining prism 32, and the combined light is projected onto the screen 33 by the projection lens 32 to display an image. When this image is displayed, a full-color image can be continuously projected on the screen 33, and a high-quality image can be stably displayed. Further, the liquid crystal projector 30 can be manufactured with a simple configuration, and the liquid crystal projector 30 can be provided at a low price.

  In the above description, the liquid crystal projector 30 has been described as the image display device. However, when the polarization control element 1 is disposed on the front surface of the LED array and used as a backlight of the liquid crystal display, a diffusion plate, a color filter, and a polarizing plate are not necessary. The configuration of the liquid crystal display can be simplified.

It is a top view which shows the structure of the polarization control element of this invention. It is a block diagram of the metal structure unit which comprises a polarization control element. It is a schematic diagram which shows the various shapes of the 1st shape metal structure which comprises a polarization control element. It is a schematic diagram which defines the size of the shape of the metal structure which comprises a polarization control element. It is sectional drawing which shows the structure of a polarization control element. It is process drawing which shows the preparation methods of a polarization control element. It is a block diagram which shows the model for verifying operation | movement of a polarization control element. It is a change characteristic figure of the off-diagonal component of the transmittance | permeability obtained as a result of verifying operation | movement of a polarization control element. It is a top view which shows the structure of a 2nd polarization control element. It is a top view which shows the structure of a 3rd polarization control element. It is a block diagram of the 4th polarization control element. It is process drawing which shows the preparation methods of the 4th polarization control element. It is a plane sectional view showing the composition of the 5th polarization control element. It is a plane sectional view showing the composition of the 6th polarization control element. It is a block diagram of the liquid crystal projector which uses a polarization control element. It is a block diagram of the conventional polarization illumination apparatus. It is a block diagram of the conventional polarized light source unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Polarization control element, 2; Support substrate, 3; Metal structure of 1st shape,
4; second shape metal structure, 5; metal structure unit, 6; protective film, 7;

Claims (11)

A structure in which a plurality of metal structures having a maximum size smaller than the wavelength of incident light are arranged on a surface of a support formed of a material transparent to incident light or a plane in the support, The metal structure includes at least two different shapes . One shape has rotational symmetry in a plane perpendicular to the propagation direction of incident light, and the shape folded with respect to a specific axis matches. a shape having no linear symmetry to the other one type of shaped polarization, wherein shape der Rukoto having a linear symmetry as the shape folded back against the particular axis coincides Control element . A polarization control element 請 Motomeko 1 Symbol placement,
A polarization control element characterized in that at least two types of metal structures having different shapes are arranged close to each other at a distance equal to or smaller than the wavelength of incident light in a plane orthogonal to the propagation direction of incident light. The polarization control element according to claim 1 or 2 ,
A polarization control element characterized in that metal structure units in which at least two different types of metal structures are arranged close to each other in the same plane are periodically arranged in a plane perpendicular to the propagation direction of incident light. . The polarization control element according to claim 1 or 2 ,
A polarization control element, wherein at least two types of metal structures having different shapes are randomly arranged in a plane perpendicular to the propagation direction of incident light. The polarization control element according to claim 1 or 2 ,
Of at least two different types of metal structures, one of the metal structures is periodically arranged in a plane perpendicular to the propagation direction of incident light, and the other metal structures are arranged in a periodic array. polarization control element characterized in that it has placed a random position. The polarization control element according to claim 1 or 2 ,
A metal structure in any one of at least two different shapes is periodically arranged in a first plane perpendicular to the propagation direction of incident light, and the metal structure in the first plane is arranged. A metal structure having a shape different from that of the body is periodically arranged in a second plane orthogonal to the propagation direction of incident light, and the first plane and the second plane are arranged at an interval smaller than the wavelength of the incident light. A polarization control element characterized by being laminated. The polarization control element according to claim 1 or 2 ,
Of the at least two different types of metal structures, any shape of the metal structures is randomly arranged in a first plane orthogonal to the propagation direction of incident light, and the metal structures in the first plane The metal structures having shapes different from those of the first and second planes are randomly arranged in a second plane perpendicular to the propagation direction of incident light, and the first plane and the second plane are stacked at an interval smaller than the wavelength of the incident light. A polarization control element. The polarization control element according to claim 1 or 2 ,
A metal structure in any one of at least two different shapes is periodically arranged in a first plane perpendicular to the propagation direction of incident light, and the metal structure in the first plane is arranged. A metal structure having a shape different from that of the body is randomly arranged in a second plane orthogonal to the propagation direction of incident light, and the first plane and the second plane are stacked at an interval smaller than the wavelength of the incident light. A polarization control element characterized by that. The polarization control element according to any one of claims 1 to 8 ,
The said metal structure is comprised by the metal dot aggregate | assembly which combined the some isolated metal dot structure, The polarization control element characterized by the above-mentioned. The polarization control element according to any one of claims 1 to 9 ,
The metal structure is composed of any one of Au, Ag, Pt, Al, Ni, Cr, Cu, a combination thereof, or an alloy material / mixed material containing these as a main component. Polarization control element. The image display apparatus characterized by a laminate of polarization control element according to the liquid crystal layer in one of claims 1 to 1 0.

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