Circular dichroism filter, optical element, display, and method for manufacturing circular dichroism filter

Abstract

To provide a high-performance circular dichroic filter that can be operated in a visible and a near infrared ranges, being suppressed in reflection, being excellent in selective absorption of circularly polarized light, can be made thin, and being easily manufactured.SOLUTION: A circular dichroic filter comprises a plurality of structures arranged side by side in a plane. The structure comprises two arms extending from two proximal ends that are arranged at different positions from each other in a direction intersecting the plane.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a circular dichroism filter, an optical element, a display, and a method for producing a circular dichroism filter. [Background technology]

[0002] Circular dichroism is a phenomenon in which a difference in absorbance occurs between left-handed circularly polarized light (sometimes written as "LCP") and right-handed circularly polarized light (sometimes written as "RCP") when circularly polarized light passes through a certain medium. Circular dichroism enables optical manipulations such as converting linearly polarized light into elliptically polarized light (including circularly polarized light) or rotating the plane of polarization (optical rotation). In addition, measuring the circular dichroism of a substance is widely used for identifying the structure of the substance, analyzing its chirality, and analyzing its purity. As will be described later, it can also be applied to anti-reflection in optical elements and displays.

[0003] The circular dichroism of ordinary materials is not very large, and a certain optical thickness is required to obtain a sufficient absorption difference between left and right circularly polarized light, making it difficult to miniaturize optical devices or implement them in flat or flexible displays. Therefore, a circular dichroism filter using metamaterials is desired. Metamaterials are made of artificial structures smaller than the wavelength of the target electromagnetic wave, and since they exhibit unique properties such as a negative refractive index, they have attracted much attention as a new optical design technology. In particular, by arranging the structures on a flat surface, it is possible to express huge birefringence and optical rotation using a film thinner than the wavelength of light (subwavelength), so there are high expectations for the realization of ultrathin optical functional films and ultrasmall optical elements. In addition, since the structures are tiny, it may be possible to realize ultrathin optical films that are resistant to repeated bending and folding.

[0004] A technique has been proposed for achieving circular dichroism using a repeating structure of a relatively simple planar metamaterial (having a flat U-shaped structure) (Patent Document 1). In addition, a technique has been proposed for achieving a thin subwavelength circular dichroism filter using a metal material with a negative dielectric constant (Patent Document 2). Patent Document 3 proposes a technique for applying a circular dichroism filter made of a metamaterial with a minute helical or lattice structure to the anti-reflection of an organic electroluminescence display.

[0005] In addition, a circular dichroism filter has been proposed that includes a planar structure in which a number of conductive nanohelices are arranged side by side in a plane, the plurality of conductive nanohelices are biased to either right-handed or left-handed, and at least some of the plurality of conductive nanohelices have a helical axis that is tilted with respect to the normal to the plane formed by the planar structure (Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-138985 A [Patent Document 2] JP 2012-123327 A [Patent Document 3] JP 2019-66633 A [Patent Document 4] JP 2020-160440 A [Non-patent literature]

[0007] [Non-Patent Document 1] JK Gansel,et al.,Science,325,1513(2009) [Non-Patent Document 2] HMLi,et al., J.Phys.D:Appl.Phys.,47,185102(2014) Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, there is a strong demand for optical elements to be thin and small. In addition, for example, organic EL displays are required to be bendable (flexible, bendable) and foldable. However, the conventional circular polarizing plate used for external light antireflection is composed of a laminate of a linear polarizing plate and a quarter-wave plate, and the linear polarizing plate has a structure in which, for example, a stretched polyvinyl alcohol film dyed with iodine is sandwiched between triacetyl cellulose films, so it has a certain thickness and lacks flexibility. In addition, for example, a stretched film of a polymer such as polycarbonate or an oriented polymer liquid crystal film is used for the quarter-wave plate, and since the birefringence of the polymer material is not so large, a certain thickness is required to achieve the required phase difference, and the flexibility is also low. As such, the conventional external light antireflection filter has limitations in terms of thinning and imparting flexibility.

[0009] An example of an attempt to utilize circular dichroism is the technology described in Patent Document 1, but in order to realize circular dichroism, the angle of incidence of the incident light on the flat substrate must be inclined from the normal direction of the substrate, which limits the optical arrangement and makes it difficult to apply this to general flat displays. In addition, the technology described in Patent Document 2 requires lamination of an anisotropic transmission plate and a quarter-wave plate, resulting in a complex structure.

[0010] A technology has been proposed that uses a minute helical structure to selectively transmit circularly polarized light (Non-Patent Document 1). However, for example, when transmitting right-handed circularly polarized light, left-handed circularly polarized light is reflected, so it cannot be applied to an anti-reflection mechanism. In addition, this technology uses the selective reflection of circularly polarized light, and is closer to the selective reflection of circularly polarized light well known in cholesteric liquid crystals than to circular dichroism in the strict sense.

[0011] The technology described in Patent Document 3 uses a three-dimensionally complicated structure such as a minute spiral structure, and it is not easy to fabricate such a minute structure uniformly over a large area.

[0012] A circular dichroism filter has been proposed in which metamaterials, which are L-shaped structures arranged in a swastika shape and stacked twice with their orientation changed, are arranged on a two-dimensional plane (Non-Patent Document 2). However, the structure is complex and difficult to manufacture, and it is not possible to obtain an effective response in the visible range by simply scaling it down, making it difficult to apply to optical elements that operate in the visible or near-infrared range.

[0013] An object of the present invention is to provide a high-performance circular dichroism filter that can operate in the visible light region and near-infrared region, has reduced reflection, has excellent selective absorption of circularly polarized light, can be made thin, and is easy to manufacture. [Means for solving the problem]

[0014] In view of the above problems, the inventors conducted extensive research and found that the above problems can be solved by configuring a circular dichroism filter to include a plurality of structures arranged side by side in a plane, each of which has two arms extending from two base ends that are arranged at different positions in a direction intersecting with the plane, the arrangement of these two arms satisfying specific conditions, and the opening angle 2α of the two arms satisfies the condition 0°<2α<180° when viewed in a direction intersecting with the plane, thereby completing the present invention.

[0015] According to the present invention, the following circular dichroism filter and the like can be provided. 1. A circular dichroism filter including a plurality of structures arranged side by side in a plane, the structures comprising: Constructed of conductive material , each extending from two base ends arranged at different positions in a direction intersecting the plane Same shape It has two arms, (i) the base ends of the two arms are connected by a support having a central axis in a direction intersecting the plane; (ii) the base ends of the two arms are in contact with each other in a direction intersecting the plane; or (iii) the two arms are separated from each other, and the distance between the base ends of the two arms is less than or equal to 0.2 times the height of the structure when viewed in a direction intersecting the plane; When viewed in a direction intersecting the plane, the opening angle 2α of the two arms satisfies the condition 0°<2α<180°. death , the structure is composed of four unit cells arranged in a C4 rotational symmetry, and when a repeat pitch of the unit cells composed of the four structures in the plane is P and a wavelength of the operating electromagnetic wave that maximizes the circular dichroism is λ, P / λ is 0.3 to 1.2. Circular dichroism filter. 2. 2. The circular dichroism filter according to 1, wherein the P / λ is 0.4 to 1.0. 3. 3. The circular dichroism filter according to claim 1 or 2, wherein the structures are made of the same conductive material. 4. When the length of the arm is L and the height of the structure is H, the value of L / H is 0.5 to 2. The above 4. The circular dichroism filter according to any one of 1 to 3. 5. The central axis of the support is approximately perpendicular to the plane on which the multiple structures are arranged. The above 5. The circular dichroism filter according to any one of 1 to 4. 6. The two arms extend from one end and the other end of the support, The above 6. The circular dichroism filter according to any one of 1 to 5. 7. The two arms are each plate-shaped. The above 7. The circular dichroism filter according to any one of 1 to 6. 8. The plate surfaces of the two arms are approximately parallel to each other. The above 8. A circular dichroism filter according to claim 7. 9. The plate surfaces of the two arms are approximately parallel to the plane on which the multiple structures are arranged. The above 9. A circular dichroism filter according to claim 7 or 8. 10. When viewed in a direction intersecting the plane, the shape of each of the two arms is semi-rectangular, rectangular, or oval. The above 10. The circular dichroism filter according to any one of 1 to 9. 11. The opening angle 2α of the two arms satisfies the condition 15°≦2α≦120°. The above 11. The circular dichroism filter according to any one of 1 to 10. 12. The opening angle 2α of the two arms satisfies the condition 30°≦2α≦90°. The above 12. The circular dichroism filter according to any one of 1 to 11. 13. An optical element comprising the circular dichroism filter according to any one of 1 to 12 above. 14. The above A display comprising the optical element according to claim 13. 15. The above 13. A method for producing a circular dichroism filter according to any one of 1 to 12, comprising the steps of: preparing one of the two arms of the structure; and producing the other of the two arms of the structure, in this order. 16. The method includes, in this order, fabricating one of the two arms of the structure, fabricating the support of the structure, and fabricating the other of the two arms of the structure. The above 16. A method for producing a circular dichroism filter according to 15. 17. The method includes, in this order, fabricating the one arm portion of the plurality of structures, and fabricating the other arm portion of the plurality of structures. The above 16. A method for producing a circular dichroism filter according to 15. 18. The method includes, in this order, fabricating the one arm portion of the plurality of structures, fabricating the support column of the plurality of structures, and fabricating the other arm portion of the plurality of structures. The above 18. A method for producing a circular dichroism filter according to 17. 19. Lithography is used to fabricate the structure; The above 1 5 19. A method for producing the circular dichroism filter according to any one of claims 1 to 18. Effect of the Invention

[0016] According to the present invention, it is possible to provide a circular dichroism filter that can operate in the visible and near infrared regions, has reduced reflection, has excellent selective absorption of circularly polarized light, can be thinned, and is easy to manufacture. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram illustrating an example of a structure included in the circular dichroism filter according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of a unit cell that can be included in the circular dichroism filter according to the first embodiment. [Diagram 3]FIG. 2 is a diagram illustrating an example of a circular dichroism filter according to the first embodiment. [Figure 4] FIG. 1 is a diagram illustrating a configuration example (semi-rectangular type) of a structure. [Diagram 5] FIG. 1 is a diagram illustrating a configuration example (rectangular type) of a structure. [Figure 6] FIG. 1 is a diagram for explaining a configuration example (oval shape) of a structure. [Figure 7] FIG. 1 is a diagram illustrating a configuration example (elliptical type) of a structure. [Figure 8] 11A to 11C are diagrams illustrating examples of structures included in a circular dichroism filter according to a second embodiment. [Figure 9] FIG. 11 is a diagram illustrating an example of a unit cell that can be included in a circular dichroism filter according to a second embodiment. [Figure 10] 13A to 13C are diagrams illustrating examples of structures included in a circular dichroism filter according to a third embodiment. [Figure 11] FIG. 13 is a diagram illustrating an example of a unit cell that can be included in the circular dichroism filter according to the third embodiment. [Figure 12] 1A to 1C are diagrams illustrating an example of a method for producing a structure. [Figure 13] FIG. 1 is a diagram showing the principle of antireflection of external light when the circular dichroism filter of the present invention is used in an organic EL element. [Figure 14] FIG. 14 is a diagram showing the principle by which light emitted from an organic EL layer of the organic EL element in FIG. 13 passes through a circular dichroism filter and is extracted. [Figure 15] FIG. 2 is a diagram illustrating a unit cell according to the first embodiment. [Figure 16] FIG. 1 is a diagram showing calculation results of Example 1. [Figure 17] FIG. 13 is a diagram showing the calculation results of Example 2. [Figure 18] FIG. 13 is a diagram illustrating a unit cell according to a third embodiment. [Figure 19] FIG. 13 is a diagram showing the calculation results of Example 3. [Figure 20] FIG. 13 is a diagram showing the calculation results of Example 4. [Figure 21] FIG. 13 is a diagram showing the calculation results of Example 5. [Figure 22] FIG. 13 is a diagram showing the calculation results of Example 6. [Diagram 23] FIG. 13 is a diagram showing the calculation results of Example 7. [Figure 24] FIG. 13 is a diagram showing the calculation results of Example 8. [Diagram 25] FIG. 13 is a diagram showing the calculation results of Example 9. [Figure 26] FIG. 13 is a diagram showing the calculation results of Example 10. [Figure 27] FIG. 2 is a diagram illustrating a structure of Comparative Example 1. [Figure 28] FIG. 13 is a diagram showing calculation results of Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The circular dichroism filter, the optical element, the display, and the method for producing the circular dichroism filter of the present invention will be described in detail below. In this specification, "x to y" represents a numerical range of "not less than x and not more than y". The upper and lower limit values ​​described in relation to the numerical range can be arbitrarily combined. In addition, a combination of two or more of the individual embodiments of the present invention described below is also an embodiment of the present invention. In this specification, "approximately parallel" means not only completely parallel, but also substantially parallel, that is, it allows deviation from completely parallel within a range of ±10° due to manufacturing errors, placement errors, etc. In this specification, "approximately vertical" means not only completely vertical but also substantially vertical, that is, it allows deviation from the completely vertical within a range of ±10° due to manufacturing errors, arrangement errors, etc.

[0019] 1. Circular dichroism filter A circular dichroism filter according to one aspect of the present invention is a circular dichroism filter including a plurality of structures arranged side by side in a plane, each of the structures including two arms extending from two base ends disposed at different positions in a direction intersecting the plane, (i) the base ends of the two arms are connected by a support having a central axis in a direction intersecting the plane; (ii) the base ends of the two arms are in contact with each other in a direction intersecting the plane; or (iii) the two arms are separated from each other, and the distance between the base ends of the two arms is less than or equal to 0.2 times the height of the structure when viewed in a direction intersecting the plane; When viewed in a direction intersecting the plane, the opening angle 2α between the two arms satisfies the condition 0°<2α<180°. Such a circular dichroism filter can operate in the visible and near infrared regions, suppresses reflection, and has excellent selective absorption of circularly polarized light. In addition, the shapes of the elements constituting the structure are simple and mainly planar, so that it can be easily manufactured by existing established lithography such as lift-off. Furthermore, it is also suitable for reducing the thickness of the circular dichroism filter.

[0020] In the following description, the above embodiments (i) to (iii) will be referred to as first to third embodiments.

[0021] (i) First embodiment In the first embodiment, the circular dichroism filter includes a plurality of structures arranged side by side in a plane, each of which includes a support and two arms extending from the support, and when viewed in the direction of the central axis of the support, an opening angle 2α between the two arms satisfies the condition 0°<2α<180°.

[0022] (structure) FIG. 1 is a diagram illustrating an example of a structure included in the circular dichroism filter according to the first embodiment, where (A) is a perspective view, (B) is a plan view (top view), and (C) is a side view.

[0023] As shown in Fig. 1, the structure 1 includes a support 4 and two plate-like arms 2 and 3 extending from the support 4. The structure 1 is generally made of a conductive material.

[0024] The two plate-like arms 2, 3 extend from the support 4 so as to form a rectangular parallelepiped. The plate surfaces of the two plate-like arms 2, 3 are approximately parallel to each other. The "plate surface" here refers to at least one of the upper surface and the lower surface (bottom surface), and preferably both. In the illustrated example, the upper surfaces of the two plate-like arms 2, 3 are approximately parallel to each other, and the bottom surfaces are also arranged approximately parallel to each other. In order to exhibit circular dichroism, it is not essential that the two arm portions have their plate surfaces substantially parallel to each other, but considering the ease of fabricating the structure, it is preferable that they are substantially parallel. When the plate surfaces of the two arm portions are not substantially parallel, the angle they form is, for example, 30° or less or 20° or less. In this specification, when an arm is referred to as being "plate-like," it means that the upper and lower surfaces of the arm are approximately parallel to each other. It is not essential that the upper and lower surfaces of the arm are approximately parallel (the arm is plate-like), but considering the ease of fabricating the structure, it is preferable that they are approximately parallel. When the upper and lower surfaces of the arm are not approximately parallel, the angle they form is, for example, 30° or less or 20° or less.

[0025] In the illustrated example, the support 4 is a cylinder. The two plate-like arms 2, 3 extend from one end and the other end of the support 4, respectively. Here, it can be said that each of the two plate-like arms 2, 3 extends from a base end provided adjacent to one end and the other end of the support 4 in the central axis direction of the support 4 (a direction intersecting with an xy plane described later). This base end can be regarded as a component of the arms 2, 3. The two base ends are arranged at different positions from each other in the direction intersecting with an xy plane described later (the central axis direction of the support 4).

[0026] When viewed in the direction of the central axis of the support 4 (indicated by a dashed line in FIG. 1) (a direction intersecting with the xy plane described later), the opening angle 2α between the two plate-like arms 2 and 3 satisfies the condition 0°<2α<180°. This allows selectivity for left- and right-handed circular polarization to be expressed. In the example of Figure 1(B), the "opening angle 2α of arms 2 and 3" corresponds to the angle between the long axes a and b, where a is the line segment (long axis of arm 2) that passes through the central axis of support 4, is perpendicular to the central axis, and is parallel to the long side of the rectangular prism formed by one (upper) arm 2, and b is the line segment (long axis of arm 3) that is parallel to the long side of the rectangular prism formed by the other (lower) arm 3.

[0027] The opening angle 2α of the arms 2, 3 satisfies, for example, the condition 15°≦2α≦120° or the condition 30°≦2α≦90°. In the first embodiment, the opening angle 2α of the arms 2, 3 is preferably 15°≦2α≦90°, and more preferably 30°≦2α≦60°, which further improves the selectivity between left and right circularly polarized light.

[0028] As shown in FIG. 1(B), c is a line segment that bisects the angle 2α (0°<2α<180°) between line segments a and b, and is a vector pointing outward from the center of the support 4. The direction of this vector c is called the direction of the structure. d is a perpendicular line drawn from the center of the support 4 to the "axis of rotation" (described later), and β is the angle between vector c and line segment d. β is measured as a positive value in the counterclockwise direction and a negative value in the clockwise direction, and is in the range of -180°<β≦180°.

[0029] In one embodiment, the following structural parameters are defined for Structure 1. The parameters of the structure depend on the electromagnetic wavelength at which the structure operates as a circular dichroism filter, but the parameters suitable for operation from the near ultraviolet region to the visible light region and up to the near infrared region are, for example, as follows. The length of the arms 2 and 3 including the support 4 (the length from the support 4 portion to the tip of the arms 2 and 3) is designated as L. L can be, for example, 20 nm to 10 μm. The width of the arms 2 and 3 is W. W can be, for example, 20 nm to 5 μm. The thickness of the arms 2 and 3 is t, which can be, for example, 5 nm to 3 μm. The gap between the arms 2 and 3 is designated as g. In the first embodiment, g may be, for example, 5 nm to 3 μm. The diameter of the support 4 is defined as D. D can be, for example, 10 nm to 5 μm. The height of the structure 1 (corresponding to the height of the support 4 including the base ends of the arms 2 and 3 in the first embodiment) is defined as H. H may be, for example, 15 nm to 9 μm. The height of the structure 1 is the height (length) of the structure 1 in a direction intersecting an xy plane described below (corresponding to the central axis direction of the support 4 in the first embodiment).

[0030] The length L, width W and thickness t of the arms 2 and 3 may be the same as or different from each other.

[0031] In the example of FIG. 1, the width W of the arms 2 and 3 and the diameter D of the support 4 are W=D, but W may be greater than D. <Dであってもよい。

[0032] 1 shows the case where the support 4 is cylindrical, but the shape of the support 4 is not limited to a cylinder. For example, it may be a triangular prism, a square prism, an n-sided prism (n is a natural number of 5 or more), or a right-angled prism whose side is perpendicular to the bottom. If the support 4 is not cylindrical, the diameter D of the support 4 is the diameter of a circle when the cross-sectional area perpendicular to the central axis of the support 4 is converted. The following description will be mainly directed to the case where the support 4 is a cylinder, but the same applies to cases where the support 4 has other shapes, such as a right-angled cylinder.

[0033] In one embodiment, the thickness t of the arms 2, 3, the gap g between the arms 2, 3 and the height H of the structure 1 satisfy the condition H=2t+g.

[0034] 1, the positional relationship between the upper arm 2 and the lower arm 3 is such that, in a plan view, the arm 3 is arranged at an angle 2α clockwise relative to the arm 2 (twisted), but conversely, the arm 3 may be arranged at an angle 2α counterclockwise relative to the arm 2. This makes it possible to reverse the selectivity for left- and right-handed circularly polarized light.

[0035] (Unit cell) FIG. 2 is a diagram illustrating an example of a unit cell that can be included in the circular dichroism filter according to the first embodiment, where (A) is a perspective view and (B) is a plan view (top view).

[0036] 2, a set of unit cells 5 includes four structures 1. The structures 1 are the same as those shown in FIG.

[0037] The four structures 1 are arranged in a plane along a two-dimensional plane (xy plane). The central axis of the support 4 of the structure 1 is oriented in a direction intersecting this plane (xy plane), and in this example, it is oriented approximately perpendicular to the xy plane (z direction). In addition, the plate surfaces of the two plate-like arms 2 and 3 of the structure 1 are approximately parallel to the xy plane.

[0038] The four structures 1 included in one unit cell 5 are arranged so as to have four-way rotational symmetry (C4 rotational symmetry) with respect to the rotation axis. That is, an arrangement rotated 90° around the rotation axis overlaps with the original arrangement (in other words, the four structures 1 are arranged in such a way that such a rotation axis can be imagined).

[0039] The bottom surfaces of the two plate-like arms 2 and 3 of the structure 1 are substantially perpendicular to the rotation axis. The formation surfaces of the four structures 1 included in one unit cell 5 (also referred to as the bottom surfaces of the unit cells 5) are substantially perpendicular to the rotation axis.

[0040] The value of β, which represents the orientation of the structure 1 described with reference to Fig. 1, is not particularly limited, and good circular polarization selectivity is exhibited at any angle. Fig. 2 shows the case where β=0°.

[0041] In the circular dichroism filter, a plurality of structures 1 are arranged at a predetermined inter-structure distance p in each of the x-axis direction and the y-axis direction in the xy plane. The inter-structure distance p can be obtained as the center-to-center distance of the support posts 4. p can be, for example, from 20 nm to 10 μm. In the circular dichroism filter, the unit cells 5 are repeatedly arranged at a predetermined pitch (also called "unit cell pitch" or "repeated width of unit cells") P in each of the x-axis direction and the y-axis direction in the xy plane. P can be, for example, 40 nm to 50 μm.

[0042] (Circular dichroism filter) FIG. 3 is a diagram illustrating an example of a circular dichroism filter according to the first embodiment. The circular dichroism filter 6 shown in Fig. 3 includes a plurality of structures 1 arranged side by side in a plane along the xy plane. In the example of Fig. 3, the circular dichroism filter 6 can also be said to include a plurality of unit cells 5 arranged side by side in a plane along the xy plane. There is no particular limitation on the means for supporting (fixing) the planar structure formed as an assembly of the structures 1. For example, the planar structure may be provided on a substrate of some kind, or may be encapsulated in a dielectric medium.

[0043] The structure 1 is not limited to those shown in Figures 1 to 3. The structure 1 preferably has two plate-like (flat rod-like) arms 2 and 3 twisted at a certain angle (2α), and the ends of the arms are bonded (connected) by a support 4, forming an optically chiral form. This allows selective absorption of left- and right-handed circularly polarized light.

[0044] 4 to 7 are diagrams for explaining configuration examples of the structure. Here, the shapes of the arms 2 and 3 are mainly illustrated. Here, the shapes of the arms 2 and 3 are mainly shapes (planar shapes) when viewed in a direction intersecting the above-mentioned xy plane.

[0045] The structure 1 shown in Fig. 4 is the one shown in Fig. 1 to Fig. 3 and is called a "semi-rectangular type" (one end side of the rectangle is arc-shaped). In the example of Fig. 4, the joints (base end sides) of the arms 2, 3 with the support 4 are formed in an arc shape, but the base end side may be formed in a rectangular shape and the tip side in an arc shape.

[0046] The structure 1 shown in FIG. 5 has arms 2 and 3, both of which have rectangular distal end and proximal end portions, and is referred to as a "rectangular type."

[0047] The structure 1 shown in Figure 6 is a rectangle formed by the arms 2 and 3 of the structure 1 shown in Figure 5, with rounded corners, and is called an "oval shape" (it is also sometimes called a "rounded rectangle").

[0048] The structure 1 shown in FIG. 7 has arms 2 and 3 that are elliptical, and is referred to as an "elliptical structure."

[0049] When any of the structures 1 illustrated in FIGS. 4 to 7 constitute a circular dichroism filter, a unit cell in which four of these are arranged in C4 rotational symmetry can be repeatedly arranged in a plane.

[0050] 4 to 7, the lower arm 3 is twisted clockwise relative to the upper arm 2 when viewed from above, but it may be twisted counterclockwise instead. This allows the selectivity for left- and right-handed circularly polarized light to be reversed.

[0051] The circular dichroism filter according to this embodiment is effective for ultraviolet, visible, and near-infrared electromagnetic waves. The size of the structure or unit cell can be appropriately selected depending on the wavelength λ of the electromagnetic wave for which circular dichroism is desired to be exhibited.

[0052] The repeat pitch P of the unit cells is equal to or less than the desired operating wavelength (the resonant wavelength at which the circular dichroism is maximized). Specifically, P / λ is preferably 0.3 to 1.2, more preferably 0.4 to 1.0. When P / λ is 1.2 or less, the transmitted component of light can be reduced, and sufficient circular dichroism can be suitably obtained. When P / λ is 0.3 or more, the structures are spaced apart from each other, preventing the reflected component from increasing, suppressing interference between the structures, suitably obtaining sufficient circular dichroism, and preventing the absorption spectrum from becoming complicated.

[0053] The ratio L / λ of the length L of the arms including the supports in the structure to the operating wavelength λ is preferably 0.1 to 0.5, more preferably 0.1 to 0.3. When L / λ is 0.5 or less, the diffraction of light by the structure is prevented and the reflected component can be reduced. When L / λ is 0.1 or more, sufficient selectivity between left and right circularly polarized light can be suitably obtained.

[0054] Taking the aspect ratio L / H (H is the height of the structure) as an index of the shape of the structure, it is preferable that the aspect ratio is 0.5 to 2, and more preferably 0.8 to 1.7.

[0055] The gap g between the upper and lower arms is preferably 0.1 to 0.6, and more preferably 0.2 to 0.4, in relation to the height H of the structure, that is, g / H. Within this range, the resonance effect of the upper and lower arms is strengthened, and the selectivity between left and right circularly polarized light is improved.

[0056] (ii) Second embodiment In the second embodiment, the circular dichroism filter is a circular dichroism filter including a plurality of structures arranged side by side in a plane, the structures having two arms each extending from two base ends arranged at different positions in a direction intersecting the plane, the base ends of the two arms being in contact with each other in a direction intersecting the plane, and when viewed in a direction intersecting the plane, an opening angle 2α of the two arms satisfies the condition 0°<2α<180°.

[0057] FIG. 8 is a diagram illustrating an example of a structure included in the circular dichroism filter according to the second embodiment, and FIG. 9 is a diagram illustrating an example of a unit cell that can be included in the circular dichroism filter according to the second embodiment.

[0058] The circular dichroism filter of the second embodiment is the circular dichroism filter of the first embodiment in which the support 4 of the structure 1 (the portion corresponding to the gap g between the arms 2 and 3) is omitted and the gap g between the arms 2 and 3 of the structure 1 is set to zero.

[0059] In the second embodiment, the lower surface of the base end of arm 2 (the surface facing arm 3) and the upper surface of the base end of arm 3 (the surface facing arm 2) face each other and are in contact with each other and are electrically joined (integrated as a conductor).

[0060] In the second embodiment, the opening angle 2α of the arms 2, 3 is preferably 15°≦2α≦120°, and more preferably 30°≦2α≦90°, which further improves the selectivity between left and right circularly polarized light.

[0061] As for the other configuration of the circular dichroism filter according to the second embodiment, the description of the first embodiment is applicable, and detailed description thereof will be omitted here.

[0062] (iii) Third embodiment In a third embodiment, the circular dichroism filter is a circular dichroism filter including a plurality of structures arranged side by side in a plane, the structures having two arms each extending from two base ends arranged at different positions in a direction intersecting the plane, the two arms are separated from each other, the distance between the base ends of the two arms is less than or equal to 0.2 times the height of the structures when viewed in the direction intersecting the plane, and an opening angle 2α of the two arms when viewed in the direction intersecting the plane satisfies the condition 0°<2α<180°.

[0063] FIG. 10 is a diagram illustrating an example of a structure included in the circular dichroism filter according to the third embodiment, and FIG. 11 is a diagram illustrating an example of a unit cell that can be included in the circular dichroism filter according to the third embodiment.

[0064] The circular dichroism filter according to the third embodiment is the circular dichroism filter according to the first embodiment, in which the support column 4 of the structure 1 (the portion corresponding to the gap g between the arm portions 2 and 3) is omitted, and the base end portions of the arm portions 2 and 3 are separated by a separation distance corresponding to the gap g. Referring to FIG. 10 for further explanation, the separation distance corresponds to the gap g, and the height H of the structure 1 corresponds to the length obtained by combining the thicknesses t of the two arm portions 2 and 3 and the gap g, that is, H = 2t + g. Therefore, the above-mentioned "the two arm portions are separated from each other, and the separation distance between the base end portions of the two arm portions is 0.2 times or less of the height of the structure when viewed in the direction intersecting the plane" can be rephrased as "the separation distance g satisfies 0 < g / H ≦ 0.2 with respect to the height H of the structure 1 including the two arm portions 2 and 3". Even if the arm portions 2 and 3 are separated from each other, if the separation distance is within the above range, these arm portions 2 and 3 are regarded as forming one structure 1.

[0065] In the third embodiment, the separation distance (gap g) can be appropriately set according to the target operating light wavelength. For example, it can be 5 μm or less, 3 μm or less, 1 μm or less, or 0.5 μm or less. The lower limit is not limited as long as g > 0. In the case of g = 0, it corresponds to the second embodiment.

[0066] In the third embodiment, the lower surface of the base end portion of the arm portion 2 (the surface on the side of the arm portion 3) and the upper surface of the base end portion of the arm portion 3 (the surface on the side of the arm portion 2) face each other and are separated by the above-mentioned separation distance and are not electrically connected (not integrated as a conductor).

[0067] In one embodiment, the lower surface of the base end portion of the arm portion 2 and the upper surface of the base end portion of the arm portion 3 are each formed as a flat surface and are parallel to each other.

[0068] In the third embodiment, the opening angle 2α of the arm portions 2 and 3 is preferably 15° ≦ 2α ≦ 120°, and more preferably 30° ≦ 2α ≦ 90°. Thereby, the selectivity of the left and right circularly polarized lights is further improved.

[0069] As for the other configuration of the circular dichroism filter according to the third embodiment, the description of the first embodiment is applicable, and detailed description thereof will be omitted here.

[0070] 2. Manufacturing method of circular dichroism filter A method for manufacturing a circular dichroism filter according to one embodiment of the present invention is a method for manufacturing a circular dichroism filter according to one embodiment of the present invention, which includes, in this order, producing one of two arms of a structure, and producing the other of two arms of the structure.

[0071] Hereinafter, the methods for producing the circular dichroism filters according to the first to third embodiments will be described in order.

[0072] (i) First embodiment A method for manufacturing a circular dichroism filter according to the first embodiment is a method for manufacturing a circular dichroism filter according to the first embodiment, which includes, in this order, fabricating one of two arms of a structure, fabricating a support for the structure, and fabricating the other of two arms of the structure.

[0073] In one embodiment, a method for manufacturing a circular dichroism filter includes, in order, fabricating one arm of a plurality of structures, fabricating a support for the plurality of structures, and fabricating the other arm of the plurality of structures.

[0074] The method for producing the structure is not particularly limited, and for example, lithography is preferably used. As the lithography, a method known per se can be used.

[0075] 12 is a diagram for explaining an example of a method for producing a structure. Here, an example will be explained in which a structure 1 similar to that shown in FIG.

[0076] First, as shown in FIG. 12(A), a resist 8 is formed on a substrate 7 so as to form a shape corresponding to the lower arm portion 3 of the structure 1.

[0077] 12(B), a conductive material (here, a metal) 9 that will be the material of the structure 1 is applied (formed into a film) on the substrate 7 on which the resist 8 has been formed. The method for forming a film of the conductive material is not particularly limited, and for example, a method known per se such as a vacuum deposition method, an electron beam deposition method, a sputtering method, a plating method, or the like can be used.

[0078] 12(C), the resist 8 is removed (peeled off, lifted off) so that the lower arm 3 made of the conductive material 9 remains on the substrate 7.

[0079] Next, as shown in Fig. 12(D), the substrate 7 on which the lower arm portion 3 is formed is covered with a filling material 10. The method for forming the filling material is not particularly limited, and for example, a coating process (coating method) can be used. As the coating process, for example, a method known per se (for example, a coating process) such as a spin coating method, a die coating method, a screen printing method, an inkjet method, an aerosol spray method, etc. can be used.

[0080] Next, as shown in FIG. 12(E), the embedding material 10 is removed (ground) by a known removal process such as dry etching, mechanical polishing, etc. until the upper surface of the lower arm portion 3 is exposed and the entire surface is flat.

[0081] Next, as shown in FIG. 12(F), a resist 11 is formed so as to form a mold corresponding to the support pillar 4 portion of the structure 1.

[0082] Next, as shown in FIG. 12(G), a conductive material (also a metal in this case) 12 is applied (formed into a film) on the substrate 7 on which the resist 11 has been formed.

[0083] 12(H), the resist 11 is removed (peeled off, lifted off). The lower arm 3, the support 4 (conductive material 12), and the filling material 10 remain on the substrate 7.

[0084] Next, as shown in FIG. 12(I), the substrate 7 on which the lower arm 3 and the support 4 are formed is again covered with a filling material 13.

[0085] Next, as shown in FIG. 12(J), the filling material 13 is removed (shaved) by a removal process until the top surface of the support 4 is exposed and the entire surface is flat.

[0086] Next, as shown in FIG. 12(K), a resist 14 is formed so as to form a shape corresponding to the upper arm portion 2 of the structure 1.

[0087] Next, as shown in FIG. 12(L), a conductive material (also a metal in this case) 15 is applied (formed into a film) onto the substrate 7 on which the resist 14 has been formed.

[0088] 12(M), the resist 14 is removed (peeled off, lifted off). The lower arm 3, the support 4, the upper arm 2 (conductive material 15), the embedding material 10 and the embedding material 13 remain on the substrate 7. In this manner, the structure 1 can be formed.

[0089] 12(N), the substrate 7 on which the structure 1 is formed is again covered with the embedding material 16. In this manner, a metamaterial structure in which the structure 1 is embedded in the embedding materials 10, 13, and 16 can be formed.

[0090] The above (including substrate 7) can be used as a circular dichroism sheet, but if necessary, substrate 7 can be removed (peeled off) to produce a circular dichroism sheet in which structure 1 is embedded in an embedding material.

[0091] Although Figure 12 shows the process of producing one structure 1, multiple other structures 1 for constituting a circular dichroism filter together with the structure 1 can also be produced on the same substrate 7 in the same manner as and simultaneously with the structure 1.

[0092] The structure is made of a conductive material. The conductive material is not particularly limited, and examples thereof include metals, conductive oxides (conductive metal oxides) such as indium tin oxide (ITO), and conductive carbon materials such as carbon nanotubes and graphene. The metal is not particularly limited, and may be silver, gold, copper, iron, aluminum, nickel, titanium, tungsten, alloys thereof, and combinations of these metals. The conductive materials described above may be used alone or in combination. Different materials may be used for the arms and supports of the structure.

[0093] The plurality of structures may be arranged along the upper surface of a substrate that serves as a support. The substrate can hold the plurality of structures. The substrate is preferably transparent, thin, uniform, and has little optical anisotropy. The substrate is made of a dielectric material (insulator).

[0094] The material of the substrate is not particularly limited, and may be, for example, a polymer, glass, etc. The polymer is not particularly limited, and may be, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polycarbonate (PC), polystyrene (PS), polyimide (PI), etc. Furthermore, the glass may be, for example, a thin and flexible glass substrate.

[0095] The substrate includes transparent polyimide, which not only has excellent transparency but also exhibits good heat resistance against heat generation, etc., associated with the absorption of circularly polarized light by a circular dichroism filter.

[0096] The shape of the substrate is not particularly limited, but can be, for example, a sheet-like shape. For example, a polymer (also called a "film") formed into a sheet shape can be used as the substrate. The thickness of the sheet-like substrate is not particularly limited, but is preferably thin from the viewpoint of imparting flexibility, and can be, for example, 100 μm or less, 70 μm or less, or 50 μm or less. The lower limit is not particularly limited, and can be, for example, 10 μm or more.

[0097] The structures may be held in a potting material, which not only keeps the structures in place but also protects the structure's material from oxygen, water, and the like in the environment.

[0098] Examples of the medium constituting the embedding material include thermoplastic resin, hardening resin, etc. For applications that do not require much flexibility, glass materials are also suitable.

[0099] Thermoplastic resins include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polylactic acid, polyurethane, fluororesins (including polytetrafluoroethylene, perfluoroalkoxyalkane resins, ethylene-tetrafluoroethylene copolymers, perfluoroethylene-propene copolymers, polyvinylidene fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, and ethylene-tetrafluoroethylene copolymers), ABS (acrylonitrile-butadiene-styrene) resins, AS (acrylonitrile-styrene) resins, polyacrylic acid, polyacrylates, polymethyl methacrylates, polyamides (including nylon and aramid), polybutylene, and polyesters (polyethylene terephthalate). poly(ethylene ether), poly(trimethylene terephthalate), poly(butylene terephthalate), polyethylene naphthalate, polybutylene naphthalate), polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, polyarylate, liquid crystal polymer, polyether ether ketone, thermoplastic polyimide, polyetherimide, polyamide imide, polyacetal, polyvinyl alcohol, polyphenylene ether, cyclic polyolefin, polyethyl vinyl acetate, SMA (styrene-maleic anhydride) resin, petroleum resin, natural rubber, synthetic rubber (including isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene propylene rubber, chlorosulfonated polyethylene, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, silicone rubber), etc.

[0100] Examples of the curable resin include polyimide, polybenzoxazole, polybenzoximidazole, polyphenylene benzobisthiazole, curable polyphenol resin, epoxy resin, melamine resin, urea resin, diallyl phthalate resin, unsaturated polyester resin, alkyd resin, polyurethane, curable polyimide, curable acrylic resin, curable methacrylic resin, silicone resin, vinyl ester resin, etc. Post-curable polyimide varnish, etc. are particularly suitable.

[0101] When using, for example, a thermosetting resin, a photocurable resist material, silicone rubber, or the like as the embedding material, the medium is applied in liquid form to cover the structure to form a thin film, and then the thin film can be cured by any stimulus (for example, heating or irradiation with active energy rays such as ultraviolet rays, etc.). In addition, the cured thin film (medium) including the structure can be peeled off and attached to another desired member.

[0102] The resist mentioned in the method for producing the structure may be a resist that is generally used in lithography, and is preferably a resist for photoresist or electron beam resist.

[0103] (ii) Second embodiment The method for producing a circular dichroism filter according to the second embodiment is similar to the method for producing a circular dichroism filter according to the first embodiment, except that the production of the supports of the structure is omitted.

[0104] The method for producing a circular dichroism filter according to the second embodiment includes, in this order, producing one of the two arms of the structure, and then producing the other of the two arms of the structure, such that the base ends of the two arms are in contact with each other.

[0105] For example, the circular dichroism filter according to the second embodiment can be manufactured by omitting the steps shown in Figures 12(F) to (J) in the manufacturing method described with reference to Figure 12. In this case, arm 3 is exposed on the surface in the step shown in Figure 12(E), and then arm 2 is formed on arm 3 in the steps shown in Figure 12(K) and subsequent steps.

[0106] As for other configurations of the method for producing a circular dichroism filter according to the second embodiment, the explanation given for the first embodiment is applicable, and detailed explanation will be omitted here.

[0107] (iii) Third embodiment The method for producing a circular dichroism filter according to the third embodiment is similar to the method for producing a circular dichroism filter according to the first embodiment, except that the production of the supports of the structure is omitted.

[0108] The method for producing a circular dichroism filter according to the third embodiment includes, in this order, producing one of the two arms of a structure, and then producing the other of the two arms of the structure, such that the distance between the base ends of the one arm and the other arm is 0.2 times or less the height of the structure (the structure including the two arms that is finally formed).

[0109] For example, in the manufacturing method described with reference to Fig. 12, the steps shown in Figs. 12(F)-(H) and (J) can be omitted to manufacture the circular dichroism filter according to the third embodiment. In this case, the arm 3 is exposed to the surface in the step shown in Fig. 12(E), and then a layer of embedding material 13 is formed on the arm 3 in the step shown in Fig. 12(I). Next, the arm 2 is formed on the layer of embedding material 13 in the steps shown in Fig. 12(K) and subsequent steps. Here, the thickness of the layer of embedding material 13 corresponds to the above-mentioned separation distance (gap g), so the separation distance (gap g) can be adjusted by adjusting the thickness of this layer.

[0110] In this manner, a filling material (for example, the layer of filling material 13 described above) can be interposed between the two arms 2 and 3 (including the portion where the support 4 was provided in the first embodiment). The medium described in the first embodiment can be used as the filling material.

[0111] As for the other configurations of the method for producing a circular dichroism filter according to the third embodiment, the explanation given for the first embodiment is applicable, and detailed explanation will be omitted here.

[0112] 3. Anti-reflection principle The principle of using a circular dichroism filter according to one embodiment of the present invention for antireflection of an optical element will be described by taking an example of application to an organic EL element. FIG. 13 is a diagram showing the principle of antireflection of external light when a circular dichroism filter of the present invention is used in an organic EL element. "1" and "0.5" in FIG. 13 indicate approximate light intensity when the incident light intensity is set to 1. FIG. 13 illustrates an example in which a left-handed circular dichroism filter (which selectively absorbs left-handed circularly polarized light) is used, but the following discussion also applies to a right-handed circular dichroism filter (which selectively absorbs right-handed circularly polarized light) by replacing "left" with "right."

[0113] External incident light can be considered as a collection of unpolarized light, that is, linearly polarized light polarized in random directions. Each linearly polarized light can be considered as the sum of right-handed circularly polarized light and left-handed circularly polarized light, each of equal intensity. The right-handed circularly polarized light component of the external incident light does not interact with the circular dichroism filter and passes through. On the other hand, the left-handed circularly polarized light is absorbed by the circular dichroism filter, converted to heat, and attenuated. The right-handed circularly polarized light that passes through the circular dichroism filter passes through the organic EL layer and then reaches the reflective layer. The right-handed circularly polarized light is converted to left-handed circularly polarized light by reflection, passes through the organic EL layer again, and is absorbed by the circular dichroism filter and attenuated.

[0114] Fig. 14 is a diagram showing the principle by which light emitted from the organic EL layer of the organic EL element in Fig. 13 passes through a circular dichroism filter and is extracted. The light emitted from the organic EL element is approximately unpolarized, and the unpolarized light can be considered as the sum of right-handed circularly polarized light and left-handed circularly polarized light. In Fig. 14, of the light (unpolarized light) emitted from the organic EL layer, including the light reflected by the reflective layer, which travels toward the circular dichroism filter (-z axis direction), the right-handed circularly polarized light component can pass through the circular dichroism filter and be extracted to the outside, but the left-handed circularly polarized light is absorbed and attenuated.

[0115] When an organic EL element having the circular dichroism filter of the present embodiment is compared with an organic EL element having a conventional external light reflection antireflection filter consisting of a linear polarizer and a quarter-wave plate, the two have in common that roughly half of the EL light is extracted, but the external light reflection antireflection filter can be made thinner, and the organic EL element can be given flexibility and bendability. The circular dichroism filter of the present invention is also suitable for incorporation into ultra-compact optical sensors, laser devices, and the like.

[0116] 4. Optical elements An optical element according to an aspect of the present invention includes a circular dichroism filter according to an aspect of the present invention, which suppresses reflection, has excellent selective absorption of circularly polarized light, can be made thin, and is easy to manufacture.

[0117] 5. Display A display according to an aspect of the present invention includes the optical element according to an aspect of the present invention, which has reduced reflection, excellent selective absorption of circularly polarized light, can be made thin, and is easy to manufacture. The form of the display is not particularly limited, and may be, for example, an organic EL display (organic EL element). EXAMPLES

[0118] The following describes examples of the present invention, but the present invention is not limited to these examples. Table 1 shows the shape of the arms of the structures used in each example and comparative example, their structural parameters, and an overview of the calculation results (resonance wavelength, absorption amount at the resonance point of left and right circularly polarized light, and the ratio of absorption amounts).

[0119] Example 1 A unit cell shown in FIG. 15 was defined, and its optical properties were calculated using an electromagnetic field simulator (COMSOL Multiphysics (registered trademark) manufactured by COMSOL, Inc.). The arms of the structure are semi-rectangular as shown in FIG. 4, and the supports are cylindrical. The material of the structure was set to gold. The gas surrounding the structure was set to air. The substrate was omitted. The positional relationship between the upper and lower arms is such that, when viewed from above, the lower arm is rotated 20° clockwise relative to the upper arm. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 16(A). It can be seen that 87% of the left-handed circularly polarized light is absorbed at the wavelength of 625 nm, which is the resonance point (labeled "LCP absorption" in the figure). The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 16(B). It can be seen that the absorption of right-handed circularly polarized light at a wavelength of 625 nm was 10% (in the figure, this is indicated as "RCP absorption"). The ratio of maximum absorption of left-handed circularly polarized light to that of right-handed circularly polarized light, which is an index of circular dichroism, was 9.1, indicating good selective absorption properties.

[0120] "LCP reflection" in FIG. 16(A) represents the reflected component when left-handed circularly polarized light is incident. According to the calculation results, in accordance with the definition of circular polarization that takes into account the propagation direction of light, the reflected component is right-handed circularly polarized light. In FIG. 16(A), since the sum of the intensities of "LCP reflection", "LCP transmission", and "LCP absorption" is 1, the reflected component of left-handed circularly polarized light was almost 0. Similarly, the component of "RCP reflection" in FIG. 16(B) is left-handed circularly polarized light, and the reflected component of right-handed circularly polarized light was almost 0. The same applies to the examples and comparative examples described below.

[0121] Example 2 The optical characteristics were calculated in the same manner as in Example 1, except that the shape of the arms of the structure was changed to a rectangular shape as shown in FIG. 5 and the structural parameters were changed as shown in Table 1. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 17(A). It can be seen that 90% of the left-handed circularly polarized light is absorbed at a wavelength of 12.94 μm, which is the resonance point. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 17(B). It can be seen that the absorption of right-handed circularly polarized light at a wavelength of 12.94 μm is 7%. The ratio of maximum absorption of left-handed circularly polarized light to that of right-handed circularly polarized light was 13.5, indicating good selective absorption properties. In addition, it was found that the structure can be suitably applied to the infrared region by increasing its size.

[0122] Example 3 A unit cell shown in Fig. 18 was defined. That is, the optical characteristics were calculated in the same manner as in Example 1, except that the shape of the arms of the structure was changed to the oval shape shown in Fig. 6 and the structural parameters were changed as shown in Table 1. The positional relationship between the upper and lower arms is such that, when viewed in a plane, the lower arm is rotated 30° counterclockwise relative to the upper arm. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 19(A). It can be seen that 93% of the left-handed circularly polarized light is absorbed at a wavelength of 526 nm, which is the resonance point. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 19(B). It can be seen that the absorption of right-handed circularly polarized light at a wavelength of 526 nm is 4%. The ratio of maximum absorption of left-handed circularly polarized light to that of right-handed circularly polarized light was 22.6, indicating good selective absorption properties.

[0123] Example 4 The positional relationship of the upper and lower arms was reversed from that of Example 3. That is, the lower arm was rotated 30° clockwise relative to the upper arm when viewed in a plan view, but the optical characteristics were calculated in the same manner as in Example 3. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 20(B). It can be seen that 93% of the right-handed circularly polarized light is absorbed at a wavelength of 526 nm, which is the resonance point. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 20(A). It can be seen that the absorption of left-handed circularly polarized light at a wavelength of 526 nm is 4%. The ratio of maximum absorption of left-handed circularly polarized light to that of right-handed circularly polarized light was 21.5, and good selective absorption characteristics were obtained. Comparing Examples 3 and 4, it can be seen that the transmission characteristics and absorption characteristics for left-handed circularly polarized light are swapped by reversing the twist relationship of the arms.

[0124] Example 5 The optical properties were calculated in the same manner as in Example 3, except that the structural parameters were changed as shown in Table 1. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 21(A). It can be seen that 45% of the left-handed circularly polarized light is absorbed at a wavelength of 428 nm, which is the resonance point. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 21(B). It can be seen that the absorption of right-handed circularly polarized light at a wavelength of 428 nm is 2%. Although an increase in the transmitted component was observed when left-handed circularly polarized light was incident, the maximum absorption ratio between left-handed circularly polarized light and right-handed circularly polarized light was a good 25.1. It was found that by reducing the size of the structure, it can also be applied to light in the purple region.

[0125] Example 6 The optical characteristics were calculated in the same manner as in Example 3, except that the opening angle 2α between the upper and lower arms was changed from 0 to 180°. The absorption intensity, transmission intensity, reflection intensity, and the ratio of resonance wavelength to absorption amount when 2α is changed are shown in Figures 22(A) to (D). At 2α = 45°, 95% of left-handed circularly polarized light was absorbed, while the absorption of right-handed circularly polarized light was 3% (Figure 22(A)). Correspondingly, the transmission component at 2α = 45° was 2% left-handed circularly polarized light and 94% right-handed circularly polarized light (Figure 22(B)). At this time, the reflection component was the smallest, with both left-handed and right-handed circularly polarized light at 2% (Figure 22(C)). The selectivity of left-handed and right-handed circularly polarized light decreased whether 2α was larger or smaller than 45°. Moreover, the resonance wavelength gradually decreased as the opening angle increased (Figure 22(D)). When 2α is 15≦2α≦90°, the ratio of maximum absorption of left-handed circularly polarized light to that of right-handed circularly polarized light is 3.6 or more, and the selectivity of left-handed circularly polarized light is very good. On the other hand, when 2α=0° and 180°, it is found that the selectivity of absorption of left-handed circularly polarized light is not obtained. This is because the structure loses chirality (Figure 22(D)).

[0126] Example 7 The optical characteristics were calculated in the same manner as in Example 3, except that the orientation β of the structures was changed from 0 to 180°. The absorption intensity, transmission intensity, reflection intensity, and the ratio of the resonance wavelength to the amount of absorption when β is changed are shown in Figures 23(A) to (D). As shown in Figures 23(A) and (B), a slight decrease in the selectivity for left and right circular polarization is observed at β=45°, but this is sufficient for practical use, and as shown in Figure 23(C), the reflection component is 10% or less over the entire range of β, and as shown in Figure 23(D), the absorption ratio is 22.5 or more over the entire range of β, indicating good characteristics.

[0127] Example 8 The optical properties were calculated in the same manner as in Example 3, except that the structural parameters were changed as shown in Table 1. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 24(A). It can be seen that 76% of the left-handed circularly polarized light is absorbed at a wavelength of 12.2 μm, which is the resonance point. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 24(B). It can be seen that the absorption of right-handed circularly polarized light at a wavelength of 12.2 μm is 5%. It has been found that the effects of the present invention are achieved even when the support pillars are omitted and the gap g is zero.

[0128] Example 9 The optical properties were calculated in the same manner as in Example 2, except that the structural parameters were changed as shown in Table 1. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 25(A). It can be seen that 68% of the left-handed circularly polarized light is absorbed at a wavelength of 12.2 μm, which is the resonance point. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 25(B). It can be seen that the absorption of right-handed circularly polarized light at a wavelength of 12.2 μm is 4%. It has been found that the effects of the present invention are achieved even when the support pillars are omitted and the gap g is zero. The difference between this embodiment and embodiment 8 is the shape of the arms (embodiment 8: oval, embodiment 9: rectangular).

[0129] Example 10 The optical properties were calculated in the same manner as in Example 2, except that the structural parameters were changed as shown in Table 1. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 26(B). It can be seen that 83% of the right-handed circularly polarized light is absorbed at a wavelength of 554 nm, which is the resonance point. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 26(A). It can be seen that the absorption of left-handed circularly polarized light at a wavelength of 554 nm was 2%. In this embodiment, the distance g between the base ends is 10 nm, the height H of the structure is 150 nm, and the ratio g / H is 0.067. It was found that even when the support pillar is omitted, the effects of the present invention can be achieved as long as the distance (gap g) between the base ends of the two arms is 0.2 times or less the height H of the structure including the arms.

[0130] Comparative Example 1 Except for the absence of the support pillars, the optical properties were calculated in the same manner as in Example 3. The defined structure is shown in FIG. The calculation results for the case where left-handed circularly polarized light is incident are shown in Figure 28(A). It can be seen that 65% of the left-handed circularly polarized light is absorbed at a wavelength of 461 nm, which is the resonance point. The calculation results for the case where right-handed circularly polarized light is incident are shown in Figure 28(B). It can be seen that the absorption of right-handed circularly polarized light is 23%. The ratio of maximum absorption between left-handed circularly polarized light and right-handed circularly polarized light is low at 2.9, and it is found that the selectivity for left-handed circularly polarized light is significantly reduced and the spectrum near the resonance point is complicated.Compared with Example 10, in this comparative example, the separation distance (gap g) between the base ends of the two arms exceeds 0.2 times (equivalent to 0.33 times) the height H of the structure including the arms, and therefore good selectivity cannot be obtained.

[0131] [Table 1] [Explanation of symbols]

[0132] 1: Structure 2, 3: Arms 4: Prop 5: Unit cell 6: Circular dichroism filter

Claims

1. A circular dichroism filter including a plurality of structures arranged side by side in a plane, the structure is made of a conductive material and includes two arms of the same shape extending from two base ends disposed at different positions in a direction intersecting the plane; (i) the base ends of the two arms are connected by a support having a central axis in a direction intersecting the plane; (ii) the base ends of the two arms are in contact with each other in a direction intersecting the plane; or (iii) the two arms are separated from each other, and the distance between the base ends of the two arms is equal to or less than 0.2 times the height of the structure when viewed in a direction intersecting the plane; When viewed in a direction intersecting the plane, the opening angle 2α of the two arms satisfies the condition 0°<2α<180°, the structure is composed of a set of four unit cells arranged in C4 rotational symmetry, and when a repeat pitch of the unit cells composed of the set of four structures in the plane is P and a wavelength of the operating electromagnetic wave that maximizes the circular dichroism is λ, P / λ is 0.3 to 1.2; Circular dichroism filter.

2. The P / λ is 0.4 to 1.

0.

2. The circular dichroism filter of claim 1.

3. The structures are made of the same conductive material.

3. The circular dichroism filter according to claim 1 .

4. When the length of the arm portion is L and the height of the structure is H, the value of L / H is 0.5 to 2. The circular dichroism filter according to any one of claims 1 to 3.

5. The central axis of the support is approximately perpendicular to the plane on which the plurality of structures are arranged. The circular dichroism filter according to any one of claims 1 to 4.

6. The two arms extend from one end and the other end of the support pole, The circular dichroism filter according to any one of claims 1 to 5.

7. Each of the two arms is plate-shaped. The circular dichroism filter according to any one of claims 1 to 6.

8. The plate surfaces of the two arms are approximately parallel to each other.

8. The circular dichroism filter of claim 7.

9. The plate surfaces of the two arms are approximately parallel to a plane on which the multiple structures are arranged side by side.

9. The circular dichroism filter according to claim 7 or 8.

10. When viewed in a direction intersecting the plane, the shape of each of the two arms is semi-rectangular, rectangular, or oval. The circular dichroism filter according to any one of claims 1 to 9.

11. The opening angle 2α of the two arms satisfies the condition of 15°≦2α≦120°. The circular dichroism filter according to any one of claims 1 to 10.

12. The opening angle 2α of the two arms satisfies the condition 30°≦2α≦90°. The circular dichroism filter according to any one of claims 1 to 11.

13. An optical element comprising the circular dichroism filter according to any one of claims 1 to 12.

14. A display comprising the optical element according to claim 13.

15. A method for producing a circular dichroism filter according to any one of claims 1 to 14, comprising the steps of: Creating one of the two arms of the structure; and and creating the other arm of the two arms of the structure, in this order. A method for producing a circular dichroism filter.

16. Creating one of the two arms of the structure; Creating the struts of the structure; and and creating the other arm of the two arms of the structure, in this order. A method for producing the circular dichroism filter according to claim 15.

17. creating the one arm of a plurality of the structures; and and creating the other arm of the plurality of structures, in this order. A method for producing the circular dichroism filter according to claim 15.

18. Creating the one arm of a plurality of the structures; creating a plurality of said struts of said structure; and and creating the other arm of the plurality of structures, in this order. A method for producing the circular dichroism filter according to claim 17.

19. Utilizing lithography to fabricate the structure; A method for producing the circular dichroism filter according to any one of claims 15 to 18.

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