JP2010197764A - Polarization controlling element and image display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polarization controlling element which can control the phase shift quantity and has high polarization controllability regardless of a mechanically stable structure. <P>SOLUTION: Metallic structures 4, each of which has the size smaller than the wavelength of incident light and which have the same shape, are arrayed two-dimensionally on the surface of a supporting substrate 2 while interposing an undercoat film 3, which consists of a metallic material for forming a solid solution on the interface between the metallic material and a material of the supporting substrate 2. Since metallic structures are arrayed so that the nearest distance between the metallic structures 4 becomes smaller than the size of each of metallic structures 4, the polarization controlling element 1 has mechanical stability and the phase shift quantity is made variable by making variable the thickness of the undercoat film 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a polarization control element having a phase shift function, high light utilization efficiency, and miniaturization and thinning, and an image display for reducing the number of optical elements and simplifying an optical system using the same. It relates to the device.

  Polarization control elements are widely used in display devices that control on / off using polarized light, such as liquid crystal projectors and liquid crystal displays. Further, it is used for optical signal detection such as an optical pickup of a disk device and analysis / evaluation equipment such as an ellipsometer. The polarization control element includes a polarization selection element that extracts only one of two orthogonal polarization components of incident light, a polarization separation element that separates the optical path of the two polarization components, and one phase of the two polarization components. There is a phase shift element or a wave plate for delaying the delay time.

  Many polarization selective elements are composed of organic materials, and they are absorbed by dyeing and adsorbing dichroic materials such as iodine and organic dyes on a substrate film such as polyvinyl alcohol, and by highly stretching and orienting them. The polarization selection function is realized by developing dichroism. As described above, the polarization control element using the absorption by the organic material is easily affected by heat, and has problems such as a decrease in transparency, scorching, and melting, and the amount of irradiation light cannot be increased. In addition, the operating temperature conditions are strict, and when used in a liquid crystal projector or the like, there is a problem that a cold air mechanism is necessary and it is difficult to reduce the size of the apparatus, and image quality defects are caused due to adhesion of dust and the like.

  In addition, there is an element that realizes the polarization selection function by bonding optical crystal materials, such as Glan-Thompson polarizer, but the polarization control element itself is controlled by adjusting the film thickness, that is, the optical path difference. Since the optical crystal material is expensive, it is difficult to reduce the size and thickness of the device, and the price of the device itself using the polarization control element increases.

  The phase shift element uses a birefringent optical crystal material such as calcite or quartz to modulate the phase difference between two orthogonal polarization components using the difference in refractive index between ordinary and extraordinary rays. Thus, functions such as a ½ wavelength plate where the optical path difference between the ordinary ray and the extraordinary ray becomes ½ wavelength and a ¼ wavelength plate where the wavelength becomes ¼ wavelength are realized. Since this polarization control element also controls the polarization state based on the film thickness of the optical crystal material, it is difficult to reduce the size and thickness of the polarization control element itself, and the optical crystal material is expensive. It has been difficult to reduce the price of the device itself that uses the element.

  In order to solve such a problem, the inventors of the present application have proposed a polarization control element having excellent heat resistance and environmental resistance, and having high light transmittance or reflectance, such as Patent Document 1, Patent Document 2, Patent Document 3, and Patent. This is disclosed in Document 4. As shown in FIG. 15A, the polarization control element 30 disclosed in Patent Document 1 has a metal microstructure 31 having a size that is equal to or smaller than the diffraction limit of incident light on a support substrate 2 that is equal to or smaller than the wavelength of incident light. It is formed by periodically arranging metal composite structures 32 arranged adjacent to a region, has a structure in which an interaction by near-field light works, has high light transmittance, and gives a sufficient phase difference. Is possible. The polarization control element 30 can obtain a large polarization control characteristic with an extremely thin planar structure by utilizing collective motion (plasmon) of electrons in the metal generated when light enters the metal structure 31. .

  As shown in FIG. 15 (b), the polarization control element 30 disclosed in Patent Document 2 is made of a metal that has a wavelength higher than that of light incident on the flat surface of the support substrate 2 made of a dielectric material such as a transparent glass substrate. The microstructures 31 are two-dimensionally arranged at a distance smaller than the wavelength of incident light so that the light transmittance is high and a sufficient phase difference can be given.

  As shown in FIG. 15C, the polarization control element 30 disclosed in Patent Document 3 includes a first glass particle 33a and a second metal particle 33a formed on the surface of the support substrate 2 made of a transparent dielectric material such as a transparent glass substrate. A pattern of the metal particles 33b is continuously formed to form a wave plate that generates a phase difference in the polarization component of transmitted light or reflected light.

  As shown in FIG. 15D, the polarization control element 30 shown in Patent Document 4 has a periodic structure whose height is periodically modulated, and the periodic structure has a period smaller than the wavelength of incident light. Forming a metal composite structure 32 composed of two or more metal microstructures 31 arranged in a region below the wavelength of incident light and periodically arranged on the surface of the configured support substrate 2; Strong evanescent light is generated on the surface layer of the support substrate 2 and the near-field light and the evanescent light are combined to generate light emission and light absorption more strongly, thereby improving the control performance of the optical characteristics.

  In Non-Patent Document 1, an electron beam lithography technique is used to produce asymmetric nano-particles having a gold L-shaped structure at a pitch below the wavelength on a substrate, and when this metal microstructure is irradiated with linearly polarized light, phase shift And elliptically polarized light is obtained as reflected or transmitted light.

  Patent Document 5 discloses that as a technology to be used as a high-sensitivity sensing device, strong wavelength selectivity and polarization selectivity can be obtained by a metal microstructure in which metal nanorod arrays are arranged in a uniaxial direction at constant minute intervals. Is described. Here, in order to enhance the adhesion between the metal and the substrate and prevent the structure from peeling off, Cr is disposed as an underlayer on the interface between the metal and the substrate.

  Although the polarization control elements described in Patent Documents 1 to 4 exhibit polarization control characteristics depending on the shape and height of the metal structure, the effect of the base film or base structure that joins the metal structure and the support is achieved. There are disadvantages in that the polarization controllability is low and the mechanical stability in the manufacturing process is insufficient.

  Further, Non-Patent Document 1 describes a metal microstructure having a phase shift function, but a very large phase shift effect is not obtained, and characteristics that are practical as a polarization control element cannot be obtained.

  Further, Patent Document 5 discloses a metal structure having high wavelength selectivity and high polarization selectivity, but it is not a polarization control element having a function of controlling the phase, and two phase shift effects are orthogonal to each other. Since it is a characteristic using both polarization components, it has a disadvantage that it is impossible to achieve both polarization selectivity and phase shift effect.

  The present invention provides a polarization control element that improves such disadvantages and has a mechanically stable structure and can control the amount of phase shift and has high polarization controllability, and an image display device using the same. It is the purpose.

  In the polarization control element of the present invention, the metal structure having the same shape and having a size smaller than the wavelength of the incident light is provided on the surface of the support made of a material transparent to incident light or on the plane in the support. Two-dimensionally arrayed on the support through a base structure made of a metal material that forms a solid solution at the interface with the body material, and the closest distance between the metal structures is smaller than the size of the metal structure It arrange | positions so that it may become.

  The thickness of the base structure is variable according to the phase shift amount.

  The base structure has the same two-dimensional shape as the metal structure, and has an isolated structure at the arrangement position of each metal structure.

  Further, the underlying structure having the same two-dimensional shape as the metal structure has a uniform thickness in all the metal structures arranged.

  Furthermore, the base structure is formed to have a uniform thickness on the entire surface of the support or the flat surface in the support.

  The metal structure has a pattern periodically arranged in a one-dimensional direction.

  Further, a plurality of the metal structures are arranged such that the closest approach distance is smaller than the size of the metal structure to constitute a metal structure unit, and the metal structure unit is periodically arranged in a two-dimensional plane. Or you may arrange | position at random.

  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 according to the present invention is a metal material that forms a solid solution on the surface of a support or a plane in the support with the same shape of a metal structure having a size smaller than the wavelength of incident light at the interface with the support material. Are arranged two-dimensionally on the support via the base structure made of the metal structure and disposed so that the closest distance between the metal structures is smaller than the size of the metal structure. In addition to having stability, the phase shift amount can be varied by varying the thickness of the underlying structure. In addition, by having a planar element structure, it is possible to reduce the number of optical elements, reduce the size of the optical device, and reduce the price.

  Further, the controllability of the phase shift amount can be improved by making the base structure the same shape as the metal structure.

  Furthermore, the thickness of the base structure having the same two-dimensional shape as that of the metal structure is made uniform in all metal structures, or the base structure is uniformly formed on the surface of the support or on the entire surface of the support. Thus, a spatially uniform phase shift can be given to the polarization control element.

  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.

It is a block diagram of the 1st polarization control element of this invention. It is a schematic diagram which defines the size of the metal structure which comprises a polarization control element. It is process drawing which shows the preparation methods of a polarization control element. It is sectional drawing which shows the structure of the polarization control element which has a protective film in a surface layer part. It is a block diagram which shows the model for verifying operation | movement of a polarization control element. It is a change characteristic view of the phase difference and the amplitude ratio with respect to the wavelength obtained as a result of verifying the operation of the polarization control element. It is a change characteristic figure of an operation center wavelength to the film thickness of a ground film. It is a change characteristic figure of phase contrast by the height of a metal structure. It is a block diagram of the 2nd polarization control element. It is a block diagram of a 3rd polarization control element. It is a change characteristic figure of phase contrast to a wavelength obtained as a result of verifying operation of the 3rd polarization control element. It is a block diagram of the 4th polarization control element. It is a top view which shows the arrangement | sequence of the metal structure unit of a 4th 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 control element.

  1A and 1B show a configuration of a first polarization control element according to the present invention. FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line AA in FIG. As shown in the figure, in the first polarization control element 1, a base film 3 is formed on the surface of a support substrate 2, and a plurality of cylindrical metal structures 4 having a diameter d are applied to the surface of the base film 3 in the x direction. Two-dimensionally arranged with a period of px and y direction py.

  The material used as the support substrate 2 of the first 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. Boron such as quartz glass, BK7, and Pyrex (registered trademark) is preferable. Silicate glass uses optical crystal materials such as CaF2, ZnSe, Al2O3, and the like. Further, FIG. 1 is described assuming a transmission type polarization control element. However, the first polarization control element 1 may have a reflection type configuration, and in that case, Al is provided below the support substrate 2. And a reflective film made of a metal material such as Au. 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. Further, a reflection structure by total reflection coating with a dielectric multilayer film may be used.

  The base film 3 constituting the first polarization control element 1 improves the mechanical stability when the support substrate 2 and the metal structure 4 are bonded, and improves the controllability of the phase shift function. Is. Therefore, a material having high adhesion between the material of the support substrate 2 and the material of the metal structure 4 is suitable, and Ti, Cr, which increases the strength and hardness by forming a solid solution at the interface with the material of the support substrate 2. Metal materials such as Ta, V, Zr, Al, Mg, Mo, Co, Cu, and Ni can be used. Further, in order to give a spatially uniform phase shift to the polarization control element 1, the base film 3 needs to have a uniform thickness in all the metal structures 4. Here, the uniform thickness means that variation is suppressed with an accuracy of several nm, preferably with an accuracy of 2 nm or less, as will be described later.

  The metal structure 4 constituting the first polarization control element 1 has a size d smaller than the wavelength of the incident light, and the closest distance between the metal structures 4 is smaller than the size d of the metal structure 4. Is arranged. Here, the reason why the size d of the metal structure 4 is set to be equal to or smaller than the wavelength of the incident light is to avoid the influence of diffraction due to the periodic arrangement of the metal structure 4. As shown in FIGS. 1 and 2 (a), the shape of the metal structure 4 is not limited to the cylindrical metal structure 4, and (b) to (e) of the plan view of the metal structure 4 in FIG. An elliptical column shape, a triangular column shape, a quadrangular column shape, an asymmetric column shape, a spherical shape, a hemispherical shape, a conical shape, or the like may be used. Moreover, the size of the metal structure 4 cannot be uniquely determined if the shape is other than the cylindrical shape shown in FIG. 1 or FIG. Therefore, as shown in FIG. 2 (a), the metal structure has a diameter d of a circle having the same area as that of the metal structure 4 and a major axis d1 and a minor axis d2 of an ellipse 5 having the same area as that of the metal structure 4. A size of 4 is specified.

  By arranging such a metal structure 4 in contact with the base film 3, it is difficult to peel off and a mechanically stable configuration can be realized. With respect to the height h1 of this metal structure 4, that is, the size in the direction perpendicular to the paper surface in FIGS. 1A and 2, it is assumed that the polarization direction of the incident light is in a plane parallel to the paper surface. If it is assumed that light is incident perpendicular to the paper surface, the height h1 of the metal structure 4 does not affect the distance of interaction via the near-field light, and thus it is not necessary to define the height h1. Here, the near-field light means an electromagnetic field generated in the vicinity of the metal structure 4. The polarization control element 1 is characterized by a large amount of phase shift. This is because near-field light is strongly generated near the metal structure 4 due to the effect of surface plasmon or localized surface plasmon, and the metal structure 4 is unidirectional. This is because a large phase shift through near-field light occurs due to the fact that the metal structures 4 are arranged at intervals smaller than the size of the metal structure 4. Here, the surface plasmon is a collective motion of electrons excited on the metal side of the interface region between the metal and the dielectric, and the localized surface plasmon is the entire metal material when the structure of the metal becomes minute. This is the collective motion of electrons excited. Hereinafter, both surface plasmons and localized surface plasmons are expressed as plasmons. Therefore, the metal structure 3 needs to be a material that can excite plasmons. As a metal material that can excite plasmons, any one of Au, Ag, Pt, Al, Ni, Cr, Cu, or a combination thereof, or these Alloy materials / mixed materials can be used.

  Next, a method for manufacturing the first polarization control element 1 will be described with reference to the process diagram of FIG. For producing the 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. 3, parallel flat optical glass such as SiO2 is used as the support substrate 2, and an underlayer 6 such as Ti and a metal layer 7 such as Au are sequentially formed on the flat surface by sputtering or vacuum deposition. A photoresist layer 8 is formed on the surface of the metal layer by deposition. Next, as shown in step 2, the photoresist layer 8 is exposed by electron beam drawing so as to leave a metal arrangement pattern, thereby forming an exposure pattern 9. Thereafter, as shown in Step 3, unnecessary portions of the metal layer 7 and the underlayer 6 are etched by reactive ion etching (RIE) or the like using the exposure pattern 9 as a mask, and then remained as shown in Step 3. The exposure pattern 9 of the photoresist layer 8 is removed. In this way, a two-dimensional array pattern in which the base film 3 having the same size as the metal structure 4 is arranged between the support substrate 2 and the metal structure 4 can be formed. When the unnecessary portions of the metal layer 7 and the underlayer 6 are removed by etching, as shown in the steps 3a and 4a, the support substrate 2 may be etched (overetching), but overetching is performed. However, it has been confirmed by numerical simulation that the characteristics of the polarization control element 1 do not change greatly. Further, instead of forming the two-dimensional array pattern of the metal structures 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 two-dimensional array pattern of the metal structures 4. The method of forming is also effective.

  Further, the metal structure 4 of the first polarization control element 1 is exposed in the air as shown in FIG. 1, but the surface layer portion of the metal structure 4 as shown in the sectional view of FIG. A protective film 10 and a protective structure may be provided on the substrate, whereby resistance to mechanical deterioration and damage, metal oxidation, and the like can be improved.

  Next, a numerical simulation performed for verifying the operation of the first polarization control element 1 will be described with reference to FIGS. As the numerical simulation method, a finite difference time domain method (FDTD method) is used in which the Maxwell equation describing the time-space response of an electromagnetic field is differentiated into a time domain and a spatial domain. FIG. 5A is a plan view of a model of the polarization control element 1 used in the numerical simulation, and FIG. 5B is a BB cross-sectional view of FIG. In this numerical simulation, in order to obtain the spectral characteristics of transmitted light, 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 support substrate 2 (SiO 2) interface 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. Further, by adopting a rectangular Au structure as the metal structure 4 and using a dielectric function in which the Drude model and the Lorentz model are superimposed in order to describe the response of the electrons in the Au to the photoelectric field, Introduced chromatic dispersion characteristics. Although the cylindrical metal structure 4 is illustrated in FIG. 1, the same effect can be obtained even with a quadrangular prism-shaped Au structure. Therefore, in this numerical simulation, a quadrangular prism-shaped Au structure 4 that is easy to model. The results will be described. As the underlying film 3, a Ti film having a thickness of h2 is assumed, and a dielectric function of Ti is given by the Drude model. In order to obtain a phase difference between two polarization components orthogonal to the arrangement direction of the Au structure 4, the incident polarized light is inclined by 45 degrees with respect to each side of the Au structure 4, as shown in FIG. Set to direction.

  The simulation parameters used in this numerical simulation are as follows: the Au structure 4 is formed in a disk shape with a vertical and horizontal size of 152 nm and a height of 60 nm. In the plan view of FIG. In the case where the direction is the y direction, the simulation was carried out by switching the thickness h2 of the base film 3 from 0 to 20 nm by arranging the gap in the x direction with a narrow pitch direction of 200 nm and the y direction with a wide pitch direction of 400 nm. 6A is a spectral characteristic of a phase difference of transmitted light obtained by simulation, and FIG. 6B is a diagram in which the amplitude ratio Ax / Ay component of polarized light in the x direction and y direction is plotted. As a result of this simulation, as shown in FIG. 6 (a), the thickness h2 of the underlying film 3 made of Ti is switched from 0 nm to 20 nm, so that the phase difference can be varied in multiple steps from approximately 107 degrees to 40 degrees. Confirmed that it can be controlled. When this polarization control element 1 is used as a phase shift element, the amplitudes of two orthogonal polarization components need to be approximately equal. Therefore, the transmitted light amplitude ratio Ax / Ay shown in FIG. 6B needs to be in the vicinity of 1.0. FIG. 7 is a graph plotting the results of calculating the wavelength (operation center wavelength) at which the amplitude ratio Ax / Ay is 1.0 by interpolation processing. Since the wavelength band in which the magnitude of the phase difference in FIG. 6A is shifted from about 107 degrees to 40 degrees is about 100 nm, the thickness h2 of the Ti underlayer 3 is set to a wavelength that falls within 50 nm of 50% thereof. When set, the thickness h2 of the base film 3 needs to be 10 nm or less as shown by the broken line in FIG. Even if the base film 3 is formed using a material other than Ti, the characteristics do not change greatly. Therefore, the polarization control element 1 adjusts the thickness h2 of the base film 3 to 10 nm or less to thereby adjust the phase shift amount. Can be controlled flexibly.

  Further, as a result of a numerical simulation of the dependency of the height of the metal structure 4 on the phase difference, the vertical and horizontal sizes of the Au structure 4 are 152 nm in height as shown in the spectral characteristics of the phase difference of transmitted light in FIG. It has been found that when h1 is switched from 20 nm to 100 nm, the position where the phase difference changes as the height h1 of the metal structure 4 increases shifts to the short wavelength side and has a function of adjusting the operating band.

  As described above, the first polarization control element 1 can improve the mechanical stability by two-dimensionally arranging the metal structure 4 on the support substrate 2 via the base film 3. Further, the thickness h2 of the base film 3 is made smaller than 10 nm, the phase shift amount can be controlled by adjusting the thickness h2, and the height h1 of the metal structure 4 can be adjusted to adjust the thickness h2. The adjustment range of the phase shift amount can be expanded with a simple element configuration, a thin polarization control element can be realized, and the number of optical elements can be reduced and the optical device can be miniaturized. Furthermore, since the first polarization control element 1 is made of an inorganic material, it has excellent light resistance and heat resistance with respect to light intensity, and can be widely used in projection display devices and the like.

  In the above description, the case where the shape of the base film 3 on the surface orthogonal to the propagation direction of the incident light is formed in the same two-dimensional shape as that of the metal structure 4 is illustrated in FIG. As shown in FIG. 9B, which is an AA cross-sectional view of FIG. 9A, a base layer 6 having a uniform thickness h2 is formed on the entire surface of the support substrate 2, and a plurality of base layers 6 are formed on the surface of the base layer 6. The second polarization control element 1a may be configured by two-dimensionally arranging the metal structures 4 in a cycle of the horizontal direction px and the vertical direction py.

  The material used for the support substrate 2, the underlayer 6 and the metal structure 4 constituting the second polarization control element 1a may be the same material as that of the first polarization control element 1. The manufacturing method of the second polarization control element 1a is the same as the manufacturing method of the first polarization control element 1 except that the underlayer 6 is not removed in the etching step.

  In the second polarization control element 1a, the metal structure 4 also has a size equal to or smaller than the wavelength of the incident light in a plane perpendicular to the propagation direction of the incident light, and the closest distance between the metal structures 4 is the metal structure 4. It is arranged to be smaller than the size of. With such an arrangement, plasmons are excited in the metal structure 4, and an interaction by near-field light acts on the arrangement direction of the metal structure 4, and the phase shift depends on the anisotropy of the arrangement. The function can be exhibited, and the thickness h2 of the underlayer 6 is made smaller than 10 nm, and the phase shift amount can be controlled by adjusting the thickness h2.

  The polarization control elements 1, 1 a are formed by forming a metal structure 4 in a disk shape and using a vibration component having a wave vector in a plane parallel to the plasmon support substrate 2 excited in the metal structure 4. As described above, next, the ratio of the height of the metal structure 4 to the size of the cross section parallel to the support substrate 2 (diameter in the case of a cylindrical shape), that is, the aspect ratio is, for example, 1 or more, the height h1 of the metal structure 4 The third polarization control element 1b used by exciting the vibration component plasmon having a wave vector in the propagation direction of the incident light and using it will be described.

  As shown in the plan view of FIG. 10A and the AA cross-sectional view of FIG. 10B, the third polarization control element 1b has a base film 3 or a base layer 6 (hereinafter referred to as a base film) on the surface of the support substrate 2. The metal structure 4 is formed in contact with the base film 3. The material used for the support substrate 2, the base film 3, and the metal structure 4 constituting the third polarization control element 1 b may be the same material as that of the first polarization control element 1.

  The size of the metal structure 4 and the base film 3 of the third polarization control element 1b also has a size d smaller than the wavelength of the incident light, and the closest distance between the metal structures 4 is larger than the size d of the metal structure 4. It is arranged to be smaller. When the metal structure 4 is arranged in this way, plasmons are excited in the metal structure 4 and an interaction by near-field light acts on the arrangement direction of the metal structure 4 and the base film 3, Depending on the anisotropy, the phase shift function appears. This operation principle can be confirmed by the numerical simulation results shown in FIG.

  The manufacturing method of the third polarization control element 1b is the same as the manufacturing method of the first polarization control element 1, and includes a method using electron beam lithography, DUV / EUV lithography, nanoimprinting, etching utilizing alteration of material properties, and the like. Available. In addition, a protective film or a protective structure may be provided on the surface layer portion, which makes it possible to improve resistance to mechanical deterioration and damage, metal oxidation, and the like.

  Next, the principle that the polarization control characteristic can be improved by the configuration of the third polarization control element 1b will be described. The first polarization control element 1 and the second polarization control element 1a use a vibration component having a wave number vector in a plane parallel to the support substrate 2 of plasmon excited in the metal structure 4. The polarization control element 1b increases the height h1 of the metal structure 4 by setting the metal structure 4 to a high aspect ratio, so that plasmons of vibration components having a wave vector in the propagation direction of incident light are excited.

  In the numerical simulation carried out to verify the operation of the third polarization control element 1, as shown in the spectral characteristic of the phase difference of transmitted light in FIG. When the thickness h1 is switched from 20 nm to 200 nm, if the aspect ratio of the metal structure 4 exceeds 1, a large phase difference is obtained due to the resonance effect in the height direction near the wavelength of 580 nm, and an extremely large phase shift amount in a narrow band. Was confirmed to occur. Furthermore, it has been confirmed that as the height h1 of the metal structure 4 increases, a higher-order vibration component appears, which causes a large phase shift on the short wavelength side. Therefore, if a metal structure 4 having a high aspect ratio is used, a larger phase shift function can be obtained as compared with the disk-shaped metal structure 4, and the thickness (height) of the base film 3 is further increased. ) By adjusting h2, the magnitude of the phase shift amount can be controlled.

  As described above, the third polarization control element 1b has a metal structure with a high aspect ratio in which the metal structure 4 having a large height h1 is two-dimensionally arranged on the support substrate 2 with the base film 3 or the base layer 6 interposed therebetween. By using the body 4, the polarization control characteristics are improved and high controllability can be obtained. In addition, since the base film 3 and the base layer 6 are provided, the mechanical stability is improved, and a large phase shift effect can be obtained despite the two-dimensional element configuration. This can be realized, and the number of optical elements can be reduced and the optical device can be miniaturized. Further, since the third polarization control element 1b is also made of an inorganic material, it is excellent in light resistance and heat resistance with respect to light intensity, and can be widely used for projection display devices and the like.

  The first polarization control element 1, the second polarization control element 1 a, and the third polarization control element 1 b each have a metal structure 4 having a metal structure 4 having a size d smaller than the wavelength of the incident light, and the closest distance is a metal structure. Although the case where it arrange | positioned so that it may become smaller than the size d of the body 4 was demonstrated, next, the 4th polarization control element 1c which has arrange | positioned the metal structure unit which the several metal structure 4 made the pair is demonstrated.

  As shown in the plan view of FIG. 12A and the AA cross-sectional view of FIG. 12B, the fourth polarization control element 1c includes two metal structures 4 having a size d equal to or smaller than the wavelength of incident light. The metal structure unit 11 paired with a minute gap g is formed on the surface of the support substrate 2 in the x direction px1 and the y direction py via the base film 3 or the base layer 6 (hereinafter collectively referred to as the base film 3). They are arranged in a two-dimensional manner with a period. The two metal structures 4 are arranged such that the distance g between the two metal structures 4 constituting the metal structure unit 11 is smaller than the size d of the metal structure 4.

  The material used for the support substrate 2, the base film 3, and the metal structure 4 constituting the fourth polarization control element 1 c may be the same material as that of the first polarization control element 1. Further, the manufacturing method is the same as the manufacturing method of the first polarization control element 1, and a method using electron beam lithography, DUV / EUV lithography, nanoimprinting, etching utilizing alteration of material properties, and the like can be used. In addition, a protective film or a protective structure may be provided on the surface layer portion, which makes it possible to improve resistance to mechanical deterioration and damage, metal oxidation, and the like.

  In the fourth polarization control element 1c, the two metal structures 4 constituting the metal structure unit 11 have a size d equal to or smaller than the wavelength of incident light, and the distance g between the metal structures 4 is a metal structure. Therefore, the plasmon is excited in the metal structure 4 and the near field with respect to the arrangement direction of the metal structure 11 and the base film 3 in the metal structure unit 11 is arranged. The interaction by light works, and the phase shift function appears depending on the anisotropy of the array. This phase shift function depends on the interval g between the metal structures 4 constituting the metal structure unit 11, and the operating wavelength band can be controlled without changing the filling rate of the metal structures 4.

  As described above, the fourth polarization control element 1 c includes the metal structure unit 11 formed on the surface of the support substrate 3 via the base film 3 or the base layer 6, and two metal structures constituting the metal structure unit 11. The body 4 is arranged close to the size d or less of the metal structure 4, and the metal structure unit is two-dimensionally arranged to improve the polarization control characteristic and have high controllability. be able to. In addition, since the base film 3 or the base layer 6 is provided, the mechanical stability is improved, and a large phase shift effect can be obtained while having a two-dimensional element configuration. Thus, the number of optical elements can be reduced and the optical device can be miniaturized. Further, since the fourth polarization control element 1c is also made of an inorganic material, it is excellent in light resistance and heat resistance with respect to light intensity, and can be widely used for projection display devices and the like.

  In the above description, the case where the metal structure unit 11 is constituted by two metal structures 4 has been described, but the metal structure unit 11 may be constituted by three or more metal structures 4. Thus, by increasing the number of the metal structures 4 included in the metal structure unit 11, more complicated polarization anisotropy can be designed. Further, the metal structure 4 constituting the metal structure unit 11 is made to have a high aspect ratio metal structure 4 like the third polarization control element 1c, thereby improving the polarization control characteristic and having high controllability. be able to.

  Further, as shown in FIG. 13A, the metal structure units 11 constituting the fourth polarization control element 1c may be arranged on the lattice points of a square lattice or as shown in FIG. As shown in FIG. 13B, the metal structure units 11 may be arranged on lattice points of a rectangular lattice. By arranging the metal structure units 11 in this way, anisotropy occurs in a direction parallel to or perpendicular to the arrangement direction of the metal structures 4 in the metal structure unit 11, and the polarization control characteristic is arranged. Can be controlled. Moreover, if the interval between the metal structure units 11 is set to be equal to or less than the interval between incident lights, the influence of diffraction is not included, and a polarization control element having no spatial intensity unevenness can be realized. On the contrary, if the interval of the metal structure units 11 is arranged so as to be larger than the wavelength of the incident light, the angle dependency and the wavelength dependency can be controlled.

  Similar effects can be obtained by arranging the metal structure units 11 on a hexagonal lattice as shown in FIG. 13C, or by forming two metal structure units 11 as shown in FIG. 13D. The metal structure units 11 are arranged at equal intervals on a line orthogonal to the arrangement direction of the metal structures 4, or two metal structures constituting the metal structure unit 11 as shown in FIG. It can also be obtained by arranging the metal structure units 11 at equal intervals on a line connecting the four arrangement directions. Further, when the metal structure units 11 are arranged on a hexagonal lattice as shown in FIG. 13C, the filling rate of the metal structure units 11 with respect to the support substrate 2 can be maximized, and a large phase shift effect can be realized. it can. Furthermore, as shown in FIG. 13F, when the metal structure units 11 are randomly arranged, the polarization anisotropy can be determined only in the arrangement direction of the metal structures 4 in the metal structure unit 11.

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

  FIG. 14 shows a schematic configuration of a liquid crystal projector 20 using, for example, the first polarization control element 1. As shown in the figure, the liquid crystal projector 20 includes three color image forming units 21R, 21G, and 21B of R, G, and B, a light combining prism 22, a projection lens 23, and a screen 24. The image forming units 21R, 21G, and 21B are formed by laminating a light source 25, a polarization control element 1, a liquid crystal panel 26, and a polarizing plate 27, respectively.

  When the liquid crystal projector 20 projects an image on the screen 24, the light emitted from the light source 25 of each of the image forming units 21R, 21G, and 21B is transmitted from the polarization control element 1 through the liquid crystal panel 26 and the polarizing plate 27. The light is combined by the light combining prism 22 and the combined light is projected onto the screen 24 by the projection lens 23 to display an image. When this image is displayed, a full-color image can be continuously projected on the screen 24, and a high-quality image can be stably displayed. Further, the liquid crystal projector 20 can be manufactured with a simple configuration, and the liquid crystal projector 20 can be provided at a low price.

  In the above description, the liquid crystal projector 20 has been described as an image display device. However, when any one of the polarization control elements 1 to 1c is disposed on the front surface of the LED array and used as a backlight of a liquid crystal display, a diffusion plate, a color filter, and a polarizing plate are used. Can be eliminated, and the configuration of the liquid crystal display can be simplified.

DESCRIPTION OF SYMBOLS 1; Polarization control element, 2; Support substrate, 3; Underlayer film, 4; Metal structure, 6: Underlayer,
10; Protective film, 11; Metal structure unit, 20; Liquid crystal projector.

JP 2006-330105 A JP 2006-330106 A JP 2006-330107 A JP 2006-330108 A W02006 / 092963

Optics Express, 12, 5418-5423 (1004) `` Linear and Nonlinear Optical Responses Influenced by Broken Symmetry in an Array of Gold Nanoparticles '' Brian K. Canfield, et.al

Claims (8)

  On the surface of the support formed of a material transparent to incident light or on a plane in the support, a metal structure having the same shape having a size smaller than the wavelength of the incident light is solid solution at the interface with the support material. Two-dimensionally arranged on the support through a base structure made of a metal material forming the metal structure, and arranged so that the closest distance between the metal structures is smaller than the size of the metal structure A polarization control element. The polarization control element according to claim 1,
A polarization control element, wherein the thickness of the base structure is variable in accordance with a phase shift amount. The polarization control element according to claim 1 or 2,
The polarization control element according to claim 1, wherein the base structure has a two-dimensional shape that is the same as that of the metal structure, and has an isolated configuration at an arrangement position of each metal structure. The polarization control element according to claim 3,
The polarization control element, wherein the base structure has a uniform thickness in all the metal structures arranged. The polarization control element according to claim 1 or 2,
The polarization control element according to claim 1, wherein the base structure is formed with a uniform thickness on the surface of the support or the entire surface of the support. The polarization control element according to any one of claims 1 to 5,
The said metal structure has a pattern periodically arranged in the one-dimensional direction, The polarization control element characterized by the above-mentioned. The polarization control element according to any one of claims 1 to 5,
A plurality of the metal structures are arranged such that the closest approach distance is smaller than the size of the metal structure to constitute a metal structure unit, and the metal structure units are periodically or randomly arranged in a two-dimensional plane. A polarization control element characterized by being arranged in the above.   8. An image display device comprising the polarization control element according to claim 1 laminated on a liquid crystal layer.

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