JP2012093620A - Polarizing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a user-friendly and novel polarizing element capable of effectively reducing the generation of reflecting light despite using a metal material, and having superior heat resistance, light resistance, and environment resistance.SOLUTION: This polarizing element includes: a transparent tabular support body 10, a structure layer, and a transparent medium layer 14, and both of the tabular support body 10 and the transparent medium layer 14 are formed of an inorganic material. Each of micro metal structures 12 constituting the structure layer has a rectangular parallelepiped shape having the length L1, the width L2(<L1), and the height H, and is formed of a metal material comprising Al as a major component, the height direction being defined as a direction orthogonal to the flat surface of the tabular support body 10. In a two-dimensional array in the structure layer, the length direction and the width direction are formed in parallel to each other such that an interval between adjacent micro metal structures becomes the reference wavelength λ or less, and the length L1, the width L2, and the height H of the micro metal structure 12 satisfy the following expressions, 0<L2≤50 nm, L2<L1≒λ/4, and 200 nm>H≥50 nm.

Description

  The present invention relates to a polarizing element.

  Polarizing elements are widely used in display devices typified by liquid crystal projectors and liquid crystal displays, and by selectively extracting “linearly polarized light components of a specific angle” from light incident on spatial light modulation elements such as liquid crystal panels. It is used to switch pixels on and off.

  In recent years, a polarizing element is provided on or near the surface of the sensor of the image pickup apparatus, and is also used in a polarization measurement technique for extracting an image of a linearly polarized light component having a specific angle.

  Recently, the wire grid polarization has been replaced with the conventionally known “polarizing element in which dichroic materials such as iodine and organic dyes are dyed and adsorbed on a substrate film such as polyvinyl alcohol and are highly stretched and oriented”. Elements and “polarizing elements using aluminum fine particles” have been proposed and put into practical use (Patent Documents 1 to 6).

  All of the polarizing elements described in these patent documents utilize an interaction between light, which is an electromagnetic wave, and a metal.

  An object of the present invention is to provide a novel polarizing element that can effectively reduce the generation of reflected light, is excellent in heat resistance, light resistance, and environment resistance and is easy to handle while using a metallic material.

  The polarizing element of Claim 1 has a flat support body, a structure body layer, and a transparent medium layer.

The “flat support” is a transparent material and has a flat plate shape.
The “structure layer” is configured by two-dimensionally arranging a large number of minute metal structures in parallel to a flat plate surface of a flat plate support (a surface perpendicular to the thickness direction of the support). One or more structure layers are formed.

  The “transparent medium layer” is a layer covering the structure layer.

Both the flat support and the transparent medium layer are made of “inorganic material”.
The “micro metal structure” is formed of a metal material containing Al as a main component. Of course, “a metal material mainly composed of Al” includes “aluminum alone”.

  A fine metal structure formed of a metal material mainly composed of aluminum has a “cuboid shape”. This rectangular parallelepiped shape is a shape of “a rectangular parallelepiped of length: L1, width: L2: height: H rectangular parallelepiped”, but of course, since it is artificially formed, geometrically Needless to say, it is not necessary to be a strict rectangular parallelepiped, and it is needless to say that irregularities in shape and roundness of the ridges are allowed as long as the optical function described later can be exhibited.

  Many fine metal structures having a rectangular parallelepiped shape are two-dimensionally arranged to form a structure layer. In arranging the fine metal structures, the height: H direction of each fine metal structure is defined as “flat plate shape”. The direction of the length: L1 is aligned in one direction, in the direction perpendicular to the flat surface of the support (the surface orthogonal to the heat direction of the flat support). The “flat surface” is a surface orthogonal to the thickness direction of the flat support.

  For example, if orthogonal coordinate axes: ξ, η are set on the flat plate surface of the flat plate support, and coordinate axes: ζ are set orthogonal to the flat plate surface, the individual micrometals arranged two-dimensionally on the ξη plane The structures can be arranged such that the height direction is parallel to the ζ axis, the length direction is parallel to the ξ direction, and the width direction is parallel to the η direction.

  The arrangement of the two-dimensionally arranged fine metal structures is performed such that “the distance between adjacent fine metal structures is a reference wavelength: λ or less”.

The length of the fine metal structure: L1, the width: L2, the height: H
0 <L2 ≦ 50 nm, L2 <L1 ≦ λ / 4, 200 nm> H ≧ 50 nm
Satisfied.

  “Reference wavelength: λ” is a wavelength at which polarization separation is performed by the polarizing element.

  2. The polarizing element according to claim 1, wherein “the fine metal structure constituting one structure layer” can have the same shape (claim 2), but the fine metal structure constituting one structure layer. In addition, “a plurality of types of fine metal structures having different lengths: L1” may be mixed (claim 3).

Since the polarizing element according to claim 1 has one or more structure layers by a two-dimensional arrangement of fine metal structures as described above, it is possible to provide two or more structure layers.
When two or more structure layers are provided, each structure layer is formed so as to form a “multi-layer structure” on the flat plate surface of the flat plate-like support. In this case, the structure layers that overlap each other are filled with the “transparent medium”, and the uppermost structure layer is covered with the transparent medium.

  That is, even when a single structure layer is formed or when a plurality of structure layers are formed, the fine metal structure constituting the structure layer is in a state of being surrounded by a “transparent medium”. .

  Thus, the “transparent medium layer” wraps and covers one or more structural body layers formed on a flat support.

  The polarizing element according to any one of claims 1 to 3, wherein "a first structure layer is provided in contact with one surface of a flat support, and a transparent medium layer is interposed on the first structure layer. The second structure layer is provided, and the second structure layer is further covered with a transparent medium layer ”.

  In the polarizing element according to claim 4, the longitudinal direction of the fine metal structure forming the first structure layer and the longitudinal direction of the fine metal structure forming the second structure layer are in the same direction. The longitudinal direction of the minute metal structure forming the first structure layer and the longitudinal direction of the minute metal structure forming the second structure layer are orthogonal to each other. It can also be oriented (claim 6).

  The “two-dimensional arrangement of the fine metal structures in the structure layer” in the polarizing element according to any one of claims 1 to 6 may be regular (claim 7) or random. (Claim 8).

The material which comprises a polarizing element is demonstrated.
As described above, both the flat support and the transparent medium layer are composed of “inorganic material”, but these are of course “both transparent”.
The material for the plate-like support is preferably a transparent material generally used for optical elements, such as quartz glass, borosilicate glass such as BK7 and Pyrex (registered trademark), CaF ₂ , ZnSe, Al ₂ O _{3 and the} like. An optical crystal material or the like can be used.
The transparent medium layer controls the light absorption characteristics of the metal microstructure and "a protection function that prevents the metal structure formed of a metal material containing aluminum as a main component from oxidation and direct action of physical force". As the material, a glass material having a refractive index in the vicinity of 1.5 is suitable, and quartz glass generally used for optical elements as a “low-absorption coating material” , Pyrex (registered trademark), and borosilicate glass, such as _{ZnS-SiO 2, CaF 2,} Si, ZnSe, it is possible to use a material such as Al ₂ O 3, ZnO. In addition, a “spin-on-glass material” containing a glass material as a main component can also be used.

Al is most suitable as the “metal material mainly composed of Al” used for the fine metal structure, but an alloy / mixed material mainly composed of Al may be used. This is because when the size of the fine metal structure made of the Al material is reduced to “below the wavelength order of light”, the absorption characteristics can be expressed over a wide band.
Depending on the operating wavelength band, the same effect as that of the polarizing element of the present invention can be expected in materials other than Al, such as Au, Ag, Pt, and Cu.

A polarization function (referred to as a function of separating incident light into transmitted light and non-transmitted light according to the polarization direction, hereinafter also referred to as “polarized light separation function”) in the polarizing element of the present invention will be described.
The polarization function in the polarizing element of the present invention uses “plasmon resonance absorption”.
Consider a “small rectangular parallelepiped” that is one minute metal structure.
The light that is polarized and separated is incident as incident light from the height direction of the rectangular parallelepiped. Since light is a transverse wave, the vibration direction of the incident light is parallel to the flat plate surface. Therefore, as the vibration direction of the electric field, the “direction parallel to the length direction” and the “direction parallel to the width direction” of the rectangular parallelepiped are considered.

  The vibration of the electric field causes electrons in the minute metal structure to vibrate in a plasma state, but when the width of the rectangular parallelepiped: L2 is 50 nm or less, the polarization component due to the electric field oscillating parallel to the width direction is “absorbed almost by the minute metal structure. Therefore, the polarization component that vibrates in the electric field parallel to the width direction of the rectangular parallelepiped transmits through the transparent medium layer, the structure layer, and the flat plate support with high transmittance.

  On the other hand, the polarization component that vibrates in the electric field parallel to the length direction of the rectangular parallelepiped produces a resonance state called “plasmon resonance” when the amplitude of the vibration of electrons that vibrate in the plasma state is close to the length in the length direction: L1. The polarization component of the reference wavelength: λ that vibrates in the electric field parallel to the width direction of the rectangular parallelepiped is absorbed by the fine metal structure with a high absorption rate, and the light energy is changed to heat.

  Therefore, when viewed as a polarizing element, the polarization component that vibrates in an electric field parallel to the length direction of the minute metal structure is absorbed and does not pass through the polarizing element.

  In this manner, the “deflection component that vibrates in the electric field in parallel with the width direction” and the “polarization component that vibrates in the electric field in parallel with the length direction” are separated by polarization.

  As described above, in the polarizing element of the present invention, the polarization separation is performed using “resonance absorption by the minute metal structure”, and the reflection component reflected by the polarizing element is extremely small. Therefore, the problem of “return light”, which is a problem in a conventional polarizing element (for example, a wire grid polarizing element) that generates reflected light, is effectively reduced.

  As described above, the polarization component that vibrates in the electric field parallel to the length direction of the minute metal structure is absorbed by the minute metal structure and converted into heat, so that heat is generated in the structure layer. Since it is composed of a metal material mainly composed of aluminum and an inorganic material, even if such heat generation occurs, it is not damaged by heat.

  In addition, since the polarizing element does not contain an organic material, functional deterioration with time due to light irradiation does not occur. Furthermore, the fine metal structure is sandwiched between the transparent medium layer and the flat plate support, and since both the transparent medium layer and the flat plate support are inorganic materials and hard, physical force from the outside Even if there is an effect of the above, the fine metal structure is not damaged.

  Moreover, since the wavelength which can carry out polarization separation can be set by the length: L1 of the minute metal structure, it is possible to easily design and manufacture according to the wavelength used.

  As apparent from the above description, the width L2 in the rectangular parallelepiped shape of the minute metal structure may be 50 nm or less, but L2 can be further reduced as desired. Actually, the lower limit of L2 is determined by the formation conditions of the rectangular parallelepiped. Formable rectangular parallelepiped width: The lower limit of L2 is considered to be about 10 nm.

  Further, when the height of the rectangular parallelepiped: H is smaller than 50 nm, the light absorption effect becomes insufficient. In consideration of the depth of skin through which the electric field penetrates into the metal material, the height: H needs to be 50 nm or more. Also, the upper limit of the height: H is considered to be about 200 nm from the formation conditions.

  As described above, according to the present invention, a novel polarizing element can be realized. As described above, this polarizing element can be easily designed and manufactured in accordance with the wavelength used, has excellent heat resistance and light resistance, is excellent in environmental resistance, and is strong against mechanical external force, so that it is easy to handle. Also, the problem of return light due to reflected light is effectively reduced. In addition, since it is a thin flat plate type and avoids the generation of reflected light, it is advantageous in a laminated structure.

It is a figure explaining 1st Embodiment of a polarizing element. It is a figure explaining the specific structure of the polarizing element of 1st Embodiment. It is a figure explaining the modification of the polarizing element of 1st Embodiment. It is a figure explaining the model of numerical simulation. It is a figure explaining the result of numerical simulation. It is a figure which shows the numerical simulation result of the operation principle of the polarizing element of 1st Embodiment. It is a figure explaining 2nd Embodiment of a polarizing element. It is sectional drawing and top view explaining 3rd Embodiment of a polarizing element. It is a figure explaining the model of the numerical simulation with respect to the polarizing element of 3rd Embodiment. It is a figure explaining the numerical simulation result with respect to 3rd Embodiment. It is a figure explaining 4th Embodiment of a polarizing element.

Hereinafter, embodiments will be described.
FIG. 1 is a perspective view illustratively showing a “first embodiment” of a polarizing element.
In FIG. 1, reference numeral 10 denotes a flat plate support, reference numeral 12 denotes a fine metal structure, and reference numeral 14 denotes a transparent medium layer.

The flat support 10 is a parallel flat plate made of a transparent inorganic material (SiO ₂ ) having a refractive index of 1.51.
The minute metal structure 12 is a minute rectangular parallelepiped made of aluminum, and is formed so as to be regularly arranged two-dimensionally on the flat plate surface of the flat plate-like support 10.

The transparent medium layer 14 is formed of a transparent inorganic dielectric (SOG) having a refractive index of 1.38. A large number of minute gold image structures 12 constituting the structure layer are in a state of being embedded in the transparent medium layer 14.
With this configuration, the fine metal structure 12 is not “exposed to the outside air” and is not subject to external damage due to a physical external force.
FIG. 2 is a diagram for explaining a structure layer formed by the fine metal structure 12.
FIG. 2A is an explanatory view showing an arrangement state of the minute metal structures 12 forming the structure layer as seen through the transparent medium layer 14, and FIG. An imaginary sectional view taken along a plane parallel to the thickness direction (AA ′ sectional view of FIG. 2A) ”is illustratively shown.

  Each of the minute metal structures 12 has a rectangular parallelepiped shape (which is of course identical to each other) (of course, irregular shapes due to manufacturing accuracy, roundness of the ridges, etc. are allowed), and as shown in FIG. The bottom of the rectangle of length: L1 and width: L2 has a height: H as shown in FIG.

  L1, L2, and H have a size smaller than the reference wavelength: λ, and the distance between the minute metal structures is also smaller than the reference wavelength: λ. This is to avoid spatial intensity distribution unevenness due to the light diffraction phenomenon and to ensure high transmittance.

  FIG. 2 shows an example in which the fine metal structures 12 are “orderedly arranged in a two-dimensional lattice”, but the two-dimensional arrangement of the fine metal structures is not limited to this, and FIG. As shown in FIG. 3, “the arrangement in the left-right direction is the same interval” of the fine metal structures 12, and this arrangement may be arranged by shifting by a displacement amount: S in the vertical direction, as shown in FIG. Alternatively, the arrangement may be such that the micro metal structures 12 are “randomly arranged”.

  However, in any of these arrangements, the length of the fine metal structure 12: L1 (the vertical direction in FIG. 3) is aligned in one direction.

  As described above, the arrangement of the minute metal structures 12 is not limited to the “regular arrangement”, but “only the length direction needs to be aligned” is that the polarization selection characteristic of the polarizing element is the individual minute metal structures 12. This is because it depends on the absorption of light in and does not depend on the arrangement of the fine metal structures.

Here, a method for manufacturing the polarizing element shown in FIGS. 1 to 3 will be described.
For the production of a fine metal structure having a reference wavelength: λ or less, a “method with processing accuracy below 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.
A “method by electron beam lithography” will be described as a general method, but the manufacturing method is of course not limited thereto.
A parallel plate-like optical material is used as the plate-like support 10, Al is deposited on the plate surface with a thickness: H by sputtering or vacuum evaporation, and a photoresist film is formed thereon.
At this time, in order to improve the adhesion of the Al film at the interface between Al and the flat plate surface, an underlayer such as Ti or Cr may be provided. Subsequently, the “negative pattern” is exposed so as to leave a “rectangular Al film pattern of length: L1 and width: L2 (two-dimensionally arranged)” by electron beam drawing.
Thereafter, unnecessary Al film portions are etched by RIE or the like, and the remaining photoresist pattern is removed, whereby a large number of rectangular parallelepiped minute metal structures can be formed at the support substrate interface. Instead of forming a pattern of a fine metal structure by etching, it is also effective to form a pattern of a fine metal structure by using a lift-off method in which an Al material is deposited on a photoresist pattern and then the photoresist is removed. .
In this way, a “structure layer” based on a two-dimensional arrangement of micro metal structures (Al film) is formed on the flat plate surface of the flat plate support.

  Subsequently, a “transparent film” that coats a two-dimensional array of fine metal structures is deposited by sputtering or coating using a transparent inorganic dielectric material to form a transparent medium layer, thereby obtaining a polarizing element. it can.

  As described above, the shape of the fine metal structure 12 is defined by the length: L1, the width: L2, and the height: H. When the width: L2 is 50 nm or less, the electric field is oscillated parallel to the width direction. The polarized light component is hardly absorbed by the fine metal structure and passes through the polarizing element with a high transmittance.

In the polarization component that vibrates in the electric field parallel to the length direction, a phenomenon (plasmon resonance) that resonates with the electric field vibration occurs when the length: L1 is just “close to the electronic vibration amplitude in the metal”.
As a result, “strong resonance absorption with respect to a polarized component that vibrates in an electric field parallel to the length direction” occurs, light energy is converted into heat, and the transmittance of the polarizing element is greatly reduced. In this way, “polarization anisotropy having strong wavelength dependency” is manifested.
Since the wavelength of light that causes absorption depends on the length L1, polarization anisotropy can be expressed at a desired wavelength.

  The height of the fine metal structure 12: When H is low, the absorption effect becomes insufficient. Therefore, the fine metal structure needs to have an appropriate height, and the skin depth at which the electric field penetrates into the metal material. To a height of 50 nm or more.

The polarization separation operation of the polarizing element described above in the embodiment was verified by numerical simulation. This numerical simulation will be described with reference to FIGS.
For the numerical simulation method, the “finite difference time domain method (FDTD method) that solves the Maxwell equation describing the time-space response of the electromagnetic field by differentiating it into the time domain and the spatial domain” was used.
FIG. 4 is a diagram for explaining the “polarizing element model” used in the numerical simulation.
FIG. 4A is a plan view showing a region including the minute metal structure 12 made of aluminum, and this surface is called an XY plane. The X direction is the width direction of the minute metal structure 12, and the Y direction is the length direction of the minute metal structure 12.
As shown in FIG. 4, the “region including the minute metal structure 12” has a length Px in the X direction and a length Py in the width direction.

The refractive index of SiO ₂ constituting the flat support 10 is 1.51, and the refractive index of the dielectric material SOG forming the transparent medium layer 14 is 1.38.

By imposing periodic boundary conditions on the “computation region boundary” shown in FIG. 4, the two-dimensional array structure continues indefinitely in the plane direction (X direction, Y direction) parallel to the flat plate surface of the flat plate-like support 10. A periodic structure was adopted.
In the numerical simulation, in order to obtain the polarization characteristics of the transmitted light spectrum, “linear polarization in the X direction perpendicular to the length direction” of the minute metal structure 12 shown in the plan view (XY plane) of FIG. FIG. 4B and FIG. 4C show a plane wave pulse having a sufficiently short time width (spectrum width sufficiently spread in the visible light region) as “linearly polarized light in the Y direction parallel to the length direction”. In this way, it is assumed that the incident light is incident on a plane 920 nm away from the flat plate surface (“plane wave source” in the figure) in the flat plate support 10, and the electric field amplitude subjected to spatial averaging on the observation plane 1000 nm away from the plane wave source. The polarization characteristics of the transmitted light were calculated by Fourier transforming the time variation of the transmitted light.
The wavelength dispersion characteristic of the dielectric function of Al was given by the Drude model often used in the calculation of metal materials.

The shape parameters of the fine metal structure 12 were set to length: L1 = 96 nm, width: L2 = 16 nm, height: H = 108 nm, arrangement period Px = 192 nm, and Py = 160 nm.
The reference wavelength: λ was 450 nm.

FIG. 5 shows the result of the numerical simulation.
FIG. 5A is a diagram in which the “transmittance” of the polarization component (Txx) perpendicular to the longitudinal direction of the fine metal structure and the horizontal polarization component (Tyy) are plotted (the solid line 5-2 is “Txx component”, The wavy line 5-1 is “Tyy component”).
As shown in FIG. 5A, a sharp decrease in transmittance of the Tyy component is observed in the vicinity of the wavelength: 450 nm. Moreover, it can be seen that the transmittance of the Txx component is approximately 1.0, indicating extremely high transmission characteristics.
FIG. 5B is a diagram in which “extinction ratio (= Txx / Tyy)”, which is one of the indexes representing the optical performance of the polarizing element, is plotted against the wavelength of incident light. Generally, the extinction ratio of a commercially available polarizing plate is about several hundreds, but the extinction ratio of the polarizing element in the description is “high enough to reach 103”.
FIG. 6 shows the transmittance (curve 6-1), reflectance (curve 6-3), and absorptance (curve 6) for the electric field vibration component parallel to the length direction (Y direction) of the fine metal structure 12. 2) is plotted. “Absorptance” is “a value obtained by subtracting the sum of transmittance and reflectance from 1.0”.

  As shown in FIG. 6, the change of the reflectance with the wavelength is relatively small in the wavelength region where the transmittance of the Tyy component is greatly reduced.

  From this, it can be recognized that the cause of the steep decrease in the “transmissivity of the Tyy component” is the absorption characteristic, and that most of the Tyy component is consumed as light absorption by the fine metal structure. .

As an example of the use of such a polarizing element, there is a projection type image display device such as a liquid crystal projector, but the conventional “polarizing element having a high extinction ratio” generates reflected light, which may adversely affect image formation. there were. On the other hand, in the polarizing element of the present invention, since the polarized light on the blocking side is removed by absorption of the minute metal structure, the generation of return light (reflected light) is extremely small, and not only the performance of the image display device is improved. , The ease of design can be improved.
The operating wavelength band is limited due to the use of resonance absorption of metal, but in recent years, light sources using LEDs with a narrow spectral band are often used due to good color reproducibility, and a polarizing element with a somewhat narrow operating band. Even so, if it has good polarization characteristics, it will be used frequently.
In addition, since the influence of reflected light can be ignored, it is advantageous also in an optical device of a type in which flat optical elements are stacked at a short distance. In recent years, development of an optical apparatus in which optical elements are arranged in multiple stages on an image sensor surface such as a wafer level camera has been developed, and the polarizing element of the present invention can be applied to such a new optical device.

  A “second embodiment” obtained by modifying the first embodiment will be described below.

  The polarizing element of the second embodiment has “polarization anisotropy in a wide band”.

  The polarizing element of this embodiment is structurally similar to that described above, but is characterized in that, as shown in FIG. 7, the minute metal medium 120 constituting the structural body layer is “width and width”. “Height is the same”, but multiple types of different lengths are mixed.

  The “structure layer” by the two-dimensional arrangement of the fine metal structures 120 is formed on the flat plate surface of the flat plate support and covered with the transparent medium layer, as in the embodiment described above.

In the above-described “example of two-dimensional arrangement of minute metal structures 12 having the same shape”, it has been explained that the length of the fine metal structure: L1 determines the absorption wavelength, but the length: L1 is different. When a plurality of things are mixed and the length has a distribution, the wavelength band for absorbing the transmitted light can be expanded according to the distribution state.
That is, it is possible to realize a polarizing element having a band design or having a polarization anisotropy in a wide band. Specifically, it is preferable to give the size of the fine metal structure by “the length of the fine metal structure: normal distribution centering on L1” corresponding to the design center wavelength (the aforementioned reference wavelength: λ).
In FIG. 7, “an example in which the fine metal structures 120 are arranged in a line in the length direction” is shown as an example of the arrangement of the minute metal structures 120. However, as shown in FIGS. Alternatively, it may be arranged in a random position with the length direction aligned.

The constituent materials are the same as those in the embodiment described with reference to FIGS.
Also, the manufacturing method of the polarizing element is the same as that of the above embodiment, and a method using electron beam lithography, DUV / EUV lithography, nanoimprint, etching utilizing alteration of material physical properties, or the like is used.

The polarizing element of the second embodiment is a polarizing element having a polarization selectivity over a wide band in a projection type image display device such as a liquid crystal projector using a “light source having a continuous spectral distribution such as a lamp”. Is available as
In such an image display device, when the return light (reflected light) is generated, the image display performance is deteriorated. However, the influence of the reflected light can be reduced by using the “polarizing element of the second embodiment” described above. At the same time, the ease of design can be improved. It can also be used for applications such as optical measurement using polarized light.

Next, a “third embodiment” of the polarizing element will be described.
The polarizing element of this embodiment is “to achieve a high extinction ratio”.
The characteristic part is shown in FIG.

FIG. 8A is a plan view showing the configuration of the polarizing element of the embodiment, FIG. 8B is a sectional view taken along line AA ′ in FIG. 8A, and FIG. 8C is a sectional view taken along line BB ′.
In the polarizing element of this embodiment, the fine metal structures 121 are two-dimensionally arranged on the flat surface of the flat support 10 to form a “first structure layer”, and the first structure layer is used as a transparent medium layer. 141, and further, a fine metal structure 122 is two-dimensionally arranged on the upper surface (a surface parallel to the flat plate surface) of the transparent medium layer 141 to form a “second structure layer”. This second structure The layer is further covered with a transparent medium layer 142.
The first transparent medium layer 141 and the second transparent medium layer 142 are integrated to form a “single transparent medium layer”.

  The cross-sectional view shown in FIG. 8C shows a two-dimensional arrangement of the fine metal structures 121 forming the first structure layer, and the cross-sectional view shown in FIG. 8B forms the second structure layer. A two-dimensional arrangement of the fine metal structures 122 is shown.

  In the example shown in FIG. 8, the case where the minute metal structures 121 and 122 are regularly arranged in a two-dimensional lattice shape is shown, but the two-dimensional arrangement of these minute metal structures 121 and 122 is shown in FIG. ) Or (b), an arrangement shifted from the lattice arrangement or an arrangement “arranged in the longitudinal direction at random positions” may be used.

  The material constituting the polarizing element of the embodiment of FIG. 8 is the same as that of the first and second embodiments, and the manufacturing method is the same as that of the first and second embodiments. Methods, DUV / EUV lithography, nanoimprinting, etching utilizing alteration of material properties, and the like can be used.

The effect produced by the third embodiment will be described.
As described in connection with the first embodiment, the minute metal structure absorbs the polarization component parallel to the length direction and transmits the polarization component parallel to the width direction, thereby polarizing anisotropy. Therefore, it is difficult to be affected by reflected light.
In the polarizing element of the third embodiment, since the structure layer is provided in two layers, the product of “transmittance of each polarization component” in each structure layer becomes the transmittance as the polarizing element. . As a result, the “transmittance of the polarization component to be blocked (polarization component parallel to the length direction)” can be significantly reduced, and a polarizing element having an extremely high extinction ratio can be realized.

The characteristics of the polarizing element of the third embodiment were examined by numerical simulation.
As a numerical simulation method, the FDTD method is used as in the first embodiment. The optical constants of the flat support and the transparent medium layer (dielectric material), and the “parameters used for simulation” such as the light source position (“plane wave source”) and the observation surface position are also shown in the first embodiment and FIG. The same as described.

  FIG. 9 is a diagram for explaining a numerical simulation model for this polarizing element. FIG. 9A shows a case where there is only a single-layer structure layer made of the fine metal structure 121, and FIG. , 122 is a cross-sectional view showing a case of having two structure layers.

In this numerical simulation, the two-dimensional arrangement pattern of the minute metal structures is the same in the first structure layer of the minute metal structure 121 and the second structure layer of the minute metal structure 122 (the minute metal structure). When viewed from the height direction of the body, the arrangement of the minute metal structures of both structure layers overlap each other.) The parameters of each rectangular parallelepiped shape are as follows: length: L1 = 96 nm, width: L2 = 48 nm, high S: H = 108 nm.
Width: The width L2 is set to “3 times larger” than L2 = 16 nm used in the first embodiment in order to confirm the improvement in characteristics due to the lamination of the structure layers.
The arrangement period Px = 192 nm and Py = 160 nm of the minute metal structures are the same as those in the first embodiment.

The simulation result is shown in FIG.
As shown in FIG. 10 (a), when the fine metal structure is arranged in a single layer (“single layer structure” in the figure), the blocking characteristic of the polarizing element is slightly in the vicinity of the wavelength indicating the resonance characteristic: 400 nm. It is bad and the transmittance is somewhat low.
When the structure layer with a two-dimensional arrangement of fine metal structures is configured in two layers, the transmittance of the polarized light component parallel to the length direction acts as the product of the transmittance of each structure layer. The characteristics are much improved (about 2%).
FIG. 10B is a plot of the extinction ratio, which is improved from about 7 in the case of a single layer configuration to about 40 in the case of a two layer configuration.

  As is clear from this, the extinction ratio can be further improved by stacking three or more structure layers in the same manner as in this embodiment.

  The curves shown as “(single layer) 2” in FIGS. 10A and 10B are “plotted by squaring the transmittance and extinction ratio in the case of a single layer configuration”, as described above. It can be seen that when the structure layer is stacked in two layers, the transmittance is given by “the product of the transmittance of the two layers” in the operating wavelength region.

Finally, the “fourth embodiment” of the polarizing element will be described.
The fourth polarizing element has a “function as a notch filter that makes the light transmittance at a resonant wavelength close to zero”. In FIG. 11, (a) is a virtual sectional view in which the polarizing element is cut in the thickness direction, and (b). (BB) sectional drawing in (a), (c) is AA 'sectional drawing.

  In the polarizing element of this embodiment, as shown in FIG. 11, a first structure layer is formed on a flat surface of a flat support 10 by a two-dimensional arrangement of fine metal structures 121, and this is formed on a transparent medium. 141, and a second structure layer having a two-dimensional arrangement of the fine metal structures 122 is further formed thereon. The second structure layer is covered with the transparent medium 142, and the transparent medium 141 and 142 are integrated to form a transparent medium layer. It has a structured structure.

  Although it is the same as in the case of the third embodiment in that it has two structural layers on the flat support 10, the first structural layer is configured in the fourth embodiment. In the length direction (vertical direction in FIG. 11C) in the two-dimensional arrangement of the fine metal structures 121 and in the length direction (FIG. 11B) of the fine metal structures 122 constituting the second structure layer. The horizontal direction is different from the third embodiment in that they are orthogonal to each other.

  The arrangement of the minute metal structures 121 and 122 is not limited to the regular arrangement shown in FIG. 11, and as shown in FIGS. 3A and 3B, the arrangement form deviated from the lattice arrangement and the length direction An arrangement form in which the orientations are aligned at random positions may be used.

  The material constituting the polarizing element of the fourth embodiment is the same as that of the first and second embodiments, and the manufacturing method is the same as that of the first and second embodiments. Methods, DUV / EUV lithography, nanoimprinting, etching utilizing alteration of material properties, and the like can be used.

The operation of the polarizing element of the fourth embodiment will be described.
As already described, the fine metal structure constituting the single structure layer absorbs light having a resonant wavelength. In the fourth embodiment, since the length directions of the minute metal structures 121 and 122 constituting the two structure layers are orthogonal to each other, the polarization component (the minute metal medium) that passes through the second structure layer is used. The polarization component parallel to the length direction of 122) is absorbed by the minute metal structure 121 constituting the first structure layer.

  In other words, the minute metal structure 121 and the minute metal structure 122 absorb polarized components of incident light that are orthogonal to each other. Therefore, the “light transmittance at the resonating wavelength” can be brought close to zero. That is, this operation is an “optical notch filter” and can cut only light in a predetermined wavelength band.

  The fine metal structures 121 and 122 are the same as each other in the example of FIG. 11, but they may have a rectangular parallelepiped shape different from each other, and the two-dimensional arrangement of the two layers of the structure layers may be different from each other. Also good.

10 Flat support
12 Micro metal structure
14 Transparent media layer

Special table 2003-502708 gazette JP 2007-148344 A JP 2002-519743 A JP 2000-147253 A JP 2006-58615 A JP 2008-26807 A

Claims (8)

A transparent plate-like support;
One or more structure layers formed by two-dimensionally arranging a large number of fine metal structures parallel to the flat plate surface of the flat plate support;
A transparent medium layer covering the structure layer,
The flat support and the transparent medium layer are both formed of an inorganic material,
Each of the minute metal structures forming the structure layer is a rectangular parallelepiped shape having a length: L1, a width: L2 (<L1), and a height: H, and is formed of a metal material mainly composed of Al. The height direction is a direction perpendicular to the flat plate surface of the flat plate-like support, and in the two-dimensional arrangement in the structure layer, the length direction and the width direction are parallel to each other, and adjacent micro metal structures are between , The reference wavelength is arranged to be λ or less,
The fine metal structure has a length L1, a width L2, and a height H.
0 <L2 ≦ 50 nm, L2 <L1≈λ / 4,> H ≧ 50 nm
A polarizing element characterized by satisfying The polarizing element according to claim 1,
A polarizing element characterized in that the minute metal structures constituting one structure layer have the same shape. The polarizing element according to claim 1,
A polarizing element characterized in that a plurality of kinds of minute metal structures having different lengths: L1 are mixed in a minute metal structure constituting one structure layer. The polarizing element according to any one of claims 1 to 3,
A first structure layer is provided in contact with one surface of the plate-like support, and a second structure layer is provided on the first structure layer via a transparent medium layer. A polarizing element, wherein the body layer is further coated with a transparent medium layer. The polarizing element according to claim 4, wherein
A polarizing element characterized in that the longitudinal direction of the fine metal structure forming the first structure layer and the longitudinal direction of the fine metal structure forming the second structure layer are in the same direction. The polarizing element according to claim 4, wherein
A polarizing element characterized in that the longitudinal direction of the fine metal structure forming the first structure layer and the longitudinal direction of the fine metal structure forming the second structure layer are perpendicular to each other. The polarizing element according to any one of claims 1 to 6,
A polarizing element characterized in that a two-dimensional arrangement of fine metal structures in a structure layer is regular. The polarizing element according to any one of claims 1 to 6,
A polarizing element, wherein the two-dimensional arrangement of the fine metal structures in the structure layer is random.

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