Three-dimensional isotropic metamaterial and terahertz region optical element having the same

Abstract

A three-dimensional isotropic metamaterial is formed by gathering a plurality of metamaterial atoms having a three-dimensional structure with a minimum thickness of 1 μm or more in a transparent resin.

Description

Technical Field

[0001] The present invention relates to three-dimensional isotropic metamaterials and terahertz optical elements having the metamaterials. Background Technology

[0002] Terahertz waves are electromagnetic waves with frequencies ranging from approximately 0.1 to 10 THz. They possess inherent fingerprint spectra of matter and high transmittance, and have minimal impact on living organisms. Therefore, they are considered suitable for sensing applications in security and medical fields, and research on them has been actively conducted in recent years. For example, there are reports of successfully identifying drugs in envelopes based on differences in the transmission spectra of terahertz waves (Non-Patent Literature 1).

[0003] However, the application areas of sensing technology in the terahertz region are limited. The main reasons for this are: the limited availability of low-loss materials that can be used as optical elements in the terahertz bands reported to date, and the limited design freedom.

[0004] In this context, metamaterials, which are artificial structures composed of tiny metals smaller than the wavelength, have been proposed as materials capable of controlling the optical properties of terahertz waves, such as transmission and refraction. It has been shown that in the terahertz region, by fabricating patterns of metal wires on a polymer film, a refractive index more than twice that of existing materials can be obtained at specific frequencies (Non-Patent Document 2), which promises applications in small and high-performance lenses, prisms, etc.

[0005] Furthermore, for example, a split ring resonator (SRR) is a structure with a gap in a portion of the ring. It can be considered as an LC resonant circuit where the gap acts as a capacitor, and in principle, it can change the refractive index near the resonant frequency. As a metamaterial using SRR, a three-dimensional isotropic metamaterial is disclosed, characterized by containing a random aggregate of metaatomic sheets formed by embedding SRRs within a transparent resin body (Patent Document 1). According to this three-dimensional isotropic metamaterial, by arranging SRRs in a random direction within the transparent resin, polarization dependence can be eliminated, and a high refractive index with isotropic properties can be exhibited for terahertz waves of a specific frequency.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2020 / 194640

[0009] Non-patent literature

[0010] Non-patent literature 1: Optics Express, Vol. 11, 2549-2554 (2003)

[0011] Non-patent literature 2: Infrared Milli Terahz Waves, Vol. 38, 1130–1139 (2017) Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The technical problem of this invention is to provide a new three-dimensional isotropic metamaterial with the optical properties desired for terahertz wave displays.

[0014] Solution for solving the problem

[0015] To solve the aforementioned technical problems, the inventors conducted in-depth research and discovered that a three-dimensional isotropic metamaterial, composed of multiple metaatoms with specific minimum thicknesses different from SRRs, can exhibit unique refractive index and transmission characteristics for terahertz waves. This invention was completed based on further repeated research using this insight.

[0016] That is, the above-mentioned technical problems of the present invention are solved by the following methods.

[0017] 〔1〕

[0018] A three-dimensional isotropic metamaterial is formed by aggregating multiple metaatoms with a minimum thickness of 1 μm or more in a transparent resin.

[0019] 〔2〕

[0020] According to the three-dimensional isotropic metamaterial described in [1], wherein, The meta-atoms with a three-dimensional structure are selected from the following (A) to (C). The three-dimensional isotropic metamaterial is a meta-atom embedded sheet formed by assembling multiple meta-atoms of the following (A) or meta-atoms of the following (B) in transparent resin A, or formed by assembling multiple meta-atoms of the following (C) in transparent resin B.

[0021] (A) A superatomic structure formed by overlapping two or more layers of multiple rods arranged on the same plane such that the rods are not connected to each other in the vertical direction of the plane.

[0022] (B) Hexagonal intersecting superatoms.

[0023] (C) Bulk superatoms.

[0024] 〔3〕

[0025] According to the three-dimensional isotropic metamaterial described in [2], wherein, When viewed from above, the superatoms of (A) are arranged in a consistent configuration with each other in the vertical direction.

[0026] 〔4〕

[0027] According to the three-dimensional isotropic metamaterial described in [2], wherein, The superatom of (B) is a prism-shaped or cylindrical rod that extends from the center of the superatom along a hexagonal cross direction.

[0028] 〔5〕

[0029] According to the three-dimensional isotropic metamaterial described in [2], wherein, Each metaatom in (A) to (C) is a dielectric, semiconductor material, or conductive substance.

[0030] 〔6〕

[0031] According to the three-dimensional isotropic metamaterial described in [5], wherein, The metaatoms of the dielectric or semiconductor material have a dielectric constant greater than that of the transparent resin B, and the maximum diameter of the metaatoms is shorter than the wavelength of the terahertz wave incident on the three-dimensional isotropic metamaterial.

[0032] 〔7〕

[0033] According to any one of [2] to [6], the three-dimensional isotropic metamaterial, wherein, The three-dimensional isotropic metamaterial is formed by randomly aggregating multiple metaatoms into a block or metaatoms of (C) in the transparent resin B.

[0034] 〔8〕

[0035] A terahertz optical element comprising a three-dimensional isotropic metamaterial according to [7].

[0036] 〔9〕

[0037] According to any one of [2] to [6], the three-dimensional isotropic metamaterial, wherein, The three-dimensional isotropic metamaterial is formed by embedding multiple metaatoms in the transparent resin B in a neatly arranged manner along the same direction, or by embedding metaatoms of (C).

[0038] 〔10〕

[0039] A terahertz optical element comprising a three-dimensional isotropic metamaterial according to [9].

[0040] 〔11〕

[0041] An article comprising a three-dimensional isotropic metamaterial according to any one of [1] to [7] and [9].

[0042] Invention Effects

[0043] The three-dimensional isotropic metamaterial of the present invention has the desired optical properties for terahertz waves (isotropy, refractive index controllability, and transmittance controllability). Attached Figure Description

[0044] Figure 1 This is an example of a schematic diagram representing a three-dimensional representation of a meta-atom embedded block. A meta-atom embedded block is formed by embedding multiple rod-shaped bodies arranged on the same plane, which are stacked in two layers in the vertical direction of the plane, into a transparent resin A.

[0045] Figure 2 This is a schematic representation of viewing the object from the front along the z-axis. Figure 1 The diagram shows the state of the metaatomic embedded block (viewed from above).

[0046] Figure 3 It schematically represents the view from the side towards the y-axis. Figure 1 The diagram shows the state of the meta-atomic embedded block sheet.

[0047] Figure 4 This is an example of a schematic diagram representing another embodiment of a meta-atom embedded sheet in three dimensions. Hexagonal intersecting meta-atoms are embedded in transparent resin A to form a meta-atom embedded sheet.

[0048] Figure 5 This is a schematic representation of viewing the object from the front along the z-axis. Figure 4 The diagram shows the state of the meta-atomic embedded block sheet.

[0049] Figure 6 This is a schematic diagram of a three-dimensional isotropic metamaterial consisting of multiple cubic-shaped metaatoms that exhibit a higher refractive index to terahertz waves than transparent resin B, aggregated in transparent resin B. The diagram shows a structure formed by cutting out and stereoscopically representing a cubic-shaped metaatom and transparent resin B with a similar shape covering it.

[0050] Figure 7 This is a schematic representation of viewing the object from the front along the z-axis.Figure 6 A diagram showing the state of the structure.

[0051] Figure 8 This is an example of a three-dimensional isotropic metamaterial composed of multiple cubic metaatoms that exhibit a higher refractive index to terahertz waves than transparent resin B. It is a schematic diagram showing a structure formed by cutting out and stereoscopically representing a cubic metaatom with a through hole on one side facing the opposite side and transparent resin B with a similar shape covering it.

[0052] Figure 9 It schematically represents the view from the side towards the x-axis. Figure 8 A diagram showing the state of the structure.

[0053] Figure 10 This is an illustrative diagram illustrating an example of a manufacturing process related to a metaatom embedding block formed by embedding two layers of metaatoms arranged on the same plane in a transparent resin A.

[0054] Figure 11 This is an illustrative diagram illustrating an example of a manufacturing process related to a metaatom embedding block formed by embedding hexagonal metaatoms in transparent resin A.

[0055] Figure 12 This is an illustrative diagram illustrating an example of the manufacturing process of a cuboid-shaped metaatom.

[0056] Figure 13 This is an illustrative diagram illustrating another example of the manufacturing process of a superatomic structure in the shape of a cuboid.

[0057] Figure 14 This is an illustrative diagram illustrating an example of a manufacturing process in which metaatoms (C) are embedded in a block or aggregated in a transparent resin B to obtain a three-dimensional isotropic metamaterial.

[0058] Figure 15 This is an illustrative diagram illustrating another example of the manufacturing process of obtaining a three-dimensional isotropic metamaterial by aggregating multiple sheets formed by embedding metaatoms or (C) metaatoms and transparent resin B.

[0059] Figure 16 This is an illustrative diagram illustrating another example of the manufacturing process of obtaining a three-dimensional isotropic metamaterial by aggregating multiple sheets formed by embedding metaatoms or (C) metaatoms and transparent resin B.

[0060] Figure 17This is a graph showing the simulation results of the optical properties of the meta-atom embedded block of Experimental Example 1 relative to terahertz waves.

[0061] Figure 18 This is a graph showing the simulation results of the optical properties of the meta-atom embedded block of Experiment Example 2 relative to terahertz waves.

[0062] Figure 19 This is a graph showing the simulation results of the optical properties of the meta-atom embedded block of Experiment Example 3 relative to terahertz waves.

[0063] Figure 20 This is a graph showing the simulation results of the optical properties of the meta-atom embedded block of Experiment Example 4 relative to terahertz waves.

[0064] Figure 21 This is a graph showing the simulation results of the optical properties of the meta-atom embedded block of Experimental Example 5 relative to terahertz waves.

[0065] Figure 22 This is a graph showing the simulation results of the optical properties of the meta-atom embedded block of Experiment Example 6 relative to terahertz waves.

[0066] Figure 23 This is a graph showing the simulation results of the optical properties of the metaatoms of Experimental Example 7 (C) relative to terahertz waves.

[0067] Figure 24 This is a graph showing the simulation results of the optical properties of the metaatoms of Experimental Example 8 (C) relative to terahertz waves. Detailed Implementation

[0068] Preferred embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below except as specified herein.

[0069] [Three-dimensional isotropic metamaterial]

[0070] The three-dimensional isotropic metamaterial of the present invention (hereinafter also referred to as "the metamaterial of the present invention") exhibits a unique and isotropic (substantially direction-independent) optical response to terahertz waves. The metamaterial of the present invention can be used, for example, as a high-refractive-index material relative to terahertz waves, a wavelength-dispersive material, or a material that blocks or transmits terahertz waves of a specific frequency.

[0071] It should be noted that, for the three-dimensional isotropic metamaterial of the present invention, regardless of the three-dimensional structure of the intrinsic metaatoms, the resulting metamaterial exhibits three-dimensional isotropy. For example, in the case where the intrinsic metaatoms exhibit anisotropy (three-dimensional anisotropy), by randomly aggregating multiple such metaatoms in a transparent resin, or in the case where the intrinsic metaatoms themselves exhibit isotropy (three-dimensional isotropy), by randomly or regularly (along the same direction) aggregating multiple such metaatoms in a transparent resin, the resulting metamaterial can exhibit three-dimensional isotropic optical properties.

[0072] The metamaterial of the present invention is a three-dimensional isotropic metamaterial formed by aggregating multiple metaatoms with a minimum thickness of 1 μm or more in a transparent resin (Embodiment-1). The three-dimensional structure is formed by the metaatoms creating various structures, resulting in an overall three-dimensional structure, with a minimum thickness of 1 μm or more. Therefore, the metaatoms in the metamaterial of the present invention differ from the SRR described in International Publication No. 2020 / 194640.

[0073] In this invention or specification, the "minimum thickness" of the metaatom having a three-dimensional structure refers to the length of the shortest side of the smallest cuboid shape circumscribed by the metaatom. For example, when the metaatom is a metaatom formed by a single structure (e.g., the metaatom of (B) or (C) described later), the length of the shortest side of the smallest cuboid shape circumscribed by that single structure is 1 μm or more. Furthermore, when the metaatom is formed by multiple independent structures (e.g., the metaatom of (A) described later), the multiple independent structures are considered as a whole as "one structure," and with the arrangement of each structure fixed, the length of the shortest side of the smallest cuboid shape circumscribed by that "one structure" is 1 μm or more.

[0074] The meta-atoms have a three-dimensional structure with a minimum thickness of 1 μm or more. The meta-material of the present invention exhibits a unique and isotropic optical response to terahertz waves by aggregating multiple of these meta-atoms.

[0075] In the metamaterial of the present invention, the minimum thickness is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. Furthermore, the minimum thickness can be 850 μm or less, 700 μm or less, or 600 μm or less. Therefore, the minimum thickness can be set to 2–850 μm, preferably 5–700 μm, and even more preferably 10–600 μm.

[0076] Regarding Embodiment 1 of the metamaterial of the present invention described above, as a more preferred embodiment, the following embodiments (Embodiment 2) can be listed.

[0077] A three-dimensional isotropic metamaterial is formed by aggregating multiple metaatoms in a transparent resin, which are: metaatoms consisting of multiple rod-shaped structures stacked on the same plane in two or more layers and having a thickness (with stacking thickness) in the stacking direction; or metaatoms consisting of multiple rods extending from the center in different directions and having a thickness as the distance from one end of one rod to the other; or metaatoms consisting of blocky metaatoms with a thickness of 1 μm or more.

[0078] Furthermore, regarding the metamaterial of the present invention, when further specifically describing Embodiment-1 or Embodiment-2, it can be determined as the following embodiment (Embodiment-3).

[0079] A three-dimensional isotropic metamaterial, wherein the metaatoms having a three-dimensional structure are metaatoms selected from (A) to (C) below. The three-dimensional isotropic metamaterial is formed by aggregating multiple metaatoms of (A) below or metaatoms of (B) below in transparent resin A to form a metaatom embedding sheet, or by aggregating multiple metaatoms of (C) below in transparent resin B.

[0080] (A) A superatomic structure formed by overlapping two or more layers of multiple rods arranged on the same plane (on the same two-dimensional plane) in such a way that the rods arranged in the vertical direction of the plane do not touch each other in the vertical direction.

[0081] (B) Hexagonal intersecting superatoms.

[0082] (C) Bulk superatoms.

[0083] It should be noted that the reason for embedding the metaatoms of (A) or (B) in transparent resin A to form metaatom embedding blocks, and then aggregating multiple of these blocks in transparent resin B, is due to the advantage of manufacturing efficiency. That is, there is a background to this: it is technically difficult to independently manufacture the metaatoms of (A) or (B) and maintain their original aggregation in transparent resin B. The metamaterials of Embodiment 3 described above are all three-dimensional isotropic metamaterials with a structure in which multiple metaatoms selected from (A) to (C) with specific structures are aggregated in transparent resin B. They share a common technical feature with the prior art in that they exhibit a unique and isotropic optical response to terahertz waves that is significantly different from existing materials.

[0084] The shape of the metaatoms used in this invention is not particularly limited, as long as they exhibit the desired optical responsiveness to terahertz waves and, as a whole, have a minimum thickness of 1 μm or more as described above. The number, size, volume ratio, and other elements of the metaatoms in the metamaterial of this invention can be appropriately set according to the purpose. For example, when using the metamaterial of this invention as an optical element exhibiting specific optical properties in the terahertz region, the above elements can be appropriately adjusted to achieve characteristics and ease of use more suitable for use as such an optical element. Specific examples of such optical elements will be described later.

[0085] Hereinafter, regarding the metamaterial of the present invention, taking the above-described embodiment-3 as a preferred embodiment as an example, each constituent element will be described in the following content.

[0086] <Metaatom embedding slice>

[0087] The shape of the meta-atom embedding block is not particularly limited. For example, it can be a cuboid, a cube, a cuboid or cube with rounded corners or sides, a prism, a cylinder, a sphere, or an ellipsoid. The size of the meta-atom embedding block can be appropriately set according to the frequency of the irradiated terahertz wave, the type and size of the embedded meta-atoms. For example, when the meta-atom embedding block is a cube, the length (period) of one side is preferably 10 to 3000 μm, more preferably 30 to 1500 μm, and even more preferably 50 to 1000 μm. Furthermore, when the meta-atom embedded block is a cuboid shape other than a cube, it is preferable that the width is 10-3000 μm, the height is 10-3000 μm, and the thickness (depth) is 10-3000 μm; more preferably, the width is 30-1500 μm, the height is 30-1500 μm, and the thickness is 30-1500 μm; even more preferably, the width is 50-1000 μm, the height is 50-1000 μm, and the thickness is 50-1000 μm.

[0088] It should be noted that, in this specification, the metaatom embedding block formed by embedding the metaatoms of (A) in transparent resin A is also referred to as the "metaatoms (A) embedding block". Furthermore, the metaatom embedding block formed by embedding the metaatoms of (B) in transparent resin A is also referred to as the "metaatoms (B) embedding block". The metaatoms of (A) and (B) can be disposed at any position within the metaatom embedding block, with a preferred placement in the central portion.

[0089] The structures of the superatoms in (A) and (B) above will be described in the following content.

[0090] ((A) metaatom)

[0091] The meta-atom described in (A) is particularly useful as a wavelength-dispersing material at specific terahertz frequencies, and is a meta-atom formed by overlapping two or more layers of multiple rod-shaped bodies arranged in the same plane such that the rod-shaped bodies are not connected to each other in the vertical direction of the plane. The cross-sectional shape of the "rod-shaped body" perpendicular to its long dimension is not particularly limited. This cross-sectional shape can be, for example, circular, elliptical, rectangular, square, or a rectangle or square with rounded corners or sides, or a polygon with five or more sides, or a polygon with rounded corners or sides. For example, it can also be as follows: Figure 1 The high aspect ratio plate-like (thin film-like) shape is shown. Referring to the accompanying drawings, an example of the shape of the metaatomic atom in (A) is illustrated.

[0092] As an example Figure 1 This is a schematic diagram showing the state of the meta-atom (A) embedded block 10 viewed from an oblique angle, wherein the meta-atom (A) embedded block 10 has in transparent resin A11: a first layer of meta-atoms 12, configured such that four rods arranged on the same plane form a square; and a second layer of meta-atoms 13, similarly configured such that four rods arranged on the same plane form a square. Figure 2 This is a schematic representation of viewing the object from the front along the z-axis. Figure 1 The diagram shows the structure of the superatoms (A) embedded in the sheet 10. Figure 3 It schematically represents the view from the side towards the y-axis. Figure 1 The diagram shows the structure of the superatoms (A) embedded in the sheet 10. The combination of the four superatoms 12 in the first layer and the four superatoms 13 in the second layer corresponds to the superatoms of (A).

[0093] In this invention, the superatoms in (A) are anisotropic superatoms.

[0094] The minimum thickness of the superatoms in (A) is set as the length of the shortest side of the smallest cuboid shape (a cuboid shape that includes the concept of a cube shape) that is circumscribed by the three-dimensional structure when the superatoms in (A) are considered as a whole. For example, for Figures 1 - 3 Regarding the minimum thickness of the superatoms in (A), since the four superatoms 12 in the first layer and the four superatoms 13 in the second layer are combined as a whole and regarded as a single structure, i.e., a "superatom with a three-dimensional structure", the thickness t of the superatoms 12 is... 12The thickness t of the superatomic 13 13 The sum of the distances d between the rods becomes Figures 1 - 3 The minimum thickness of the superatomic atoms shown in (A).

[0095] In the metaatoms of (A), regarding the rod-shaped bodies of each layer overlapping in the z-axis direction, the shape of the rod-shaped bodies of each layer is preferably uniform when viewed from above in the z-axis direction. Therefore, when the metaatoms of (A) are viewed from the front along the z-axis direction, as... Figure 2 As shown, the shape of the meta-atom 12 in the first layer is the same as the shape of the meta-atom 13 in the second layer, thus the meta-atom 12 in the first layer is hidden by the meta-atom 13 in the second layer. It should be noted that this example illustrates the case where the rod-shaped bodies in each layer have the same shape when viewed from above in the z-axis direction, but the rod-shaped bodies in each layer could also have the same shape when viewed from above in the x-axis and y-axis directions, or even when viewed from above in a specified direction. By overlapping the rod-shaped bodies in two or more layers, the transmittance of the meta-atom embedded block with this meta-atom in a specific frequency domain of the terahertz band can be further improved compared to the case of a single layer. In the meta-atom described in (A), the number of overlapping rod-shaped layers is two or more, and can be four or more, or even six or more. Furthermore, the upper limit of this number of layers can be appropriately set according to the size of the meta-atom embedded block and the distance between the rod-shaped bodies in each layer.

[0096] In the meta-atom of (A), the distance d between two adjacent layers (the distance between rods in two adjacent layers) can be set to 1–300 μm, 5–150 μm, or 10–75 μm. In the meta-atom of (A), the transmittance of the embedded block can be controlled by controlling the distance between the rods.

[0097] The size of the rod can be appropriately set according to the irradiated terahertz wave. Preferably, the maximum diameter (length in the longitudinal direction) of the rod is shorter than the wavelength (incident wavelength) of the terahertz wave within the transparent resin A11. By controlling the maximum diameter of the rod, the resonant frequency of the metaatoms can be controlled. For example, the length in the longitudinal direction of the rod can be set to 7–2100 μm, 21–1050 μm, or 35–700 μm.

[0098] Preferably, the plurality of rods arranged on the same plane are configured to surround the central portion of the plane. The ends of the plurality of rods arranged on the same plane may be connected to each other or may have gaps. Figures 1 - 3In one example shown, the rods are arranged separately with their ends not touching each other. The number of rods in each layer is not particularly limited, but is preferably three or more, more preferably four or more. Furthermore, it is preferable that the number and arrangement of rods in each layer are the same. For example, in layers overlapping in the z-axis direction, it is preferable that each rod in each layer exists on the same coordinate in a coordinate system consisting of the x-axis and y-axis.

[0099] There are no particular limitations on the material of the rod. For example, it can be a rod made of a conductive material, a dielectric, or a semiconductor, preferably a rod made of a conductive material.

[0100] Examples of conductive materials include metals, conductive metal oxides, conductive polymers, and nanomaterials (e.g., graphene, carbon nanotubes), with materials exhibiting low conductor loss being preferred. Examples of metals or conductive metal oxides include gold, silver, copper, aluminum, iron, nickel, chromium, titanium, tungsten, stainless steel, oxides of these metals (e.g., conductive titanium oxide, tungsten oxide), and other conductive metal oxides (indium tin oxide (ITO), indium zinc oxide (IZO), etc.). Specifically, the conductive material preferably contains at least one metal selected from gold, silver, copper, aluminum, iron, nickel, chromium, titanium, tungsten, stainless steel, indium, tin, and zinc. These metals only need to be conductive and can be in the form of compounds (oxides, etc.). On the other hand, examples of conductive polymers include known conductive polymers.

[0101] The rod-shaped body can use one type of conductive material alone, or it can use a combination of two or more materials. From the perspective of raw material cost and process cost, it is more preferable that the conductive material includes aluminum, copper and / or gold.

[0102] Furthermore, when the rod-shaped body is a dielectric or semiconductor material, it is preferable that the dielectric or semiconductor material is a dielectric (high dielectric) or semiconductor material having a higher dielectric constant than the transparent resin A described later. By using a high dielectric, for example, a high refractive index material can be realized, thereby being effective for the thinning of optical elements. In addition, the interaction with the incident wave becomes stronger, thereby obtaining strong optical modulation. Examples of high dielectrics include ceramics such as silicon, alumina, zirconium oxide, silicon carbide, aluminum nitride, silicon nitride, yttrium oxide, and barium titanate, as well as compounds containing such ceramics. The rod-shaped body may use only one dielectric or semiconductor material, or a combination of two or more.

[0103] ((B) metaatom)

[0104] The metaatom in (B) is a hexagonal interlocking metaatom. This metaatom can reduce the transmittance of terahertz waves at a specific frequency to approximately zero and make the transmittance in other terahertz regions approximately 100%. Therefore, it is useful as a basic unit of metamaterials with filtering capabilities. An example of the shape of the metaatom in (B) is illustrated with reference to the accompanying drawings.

[0105] As an example Figure 4 This is a schematic diagram showing the structure of the superatoms (B) of the superatoms 22 with a hexagonal cross shape embedded in the transparent resin A21 when viewed from an oblique angle. Figure 5 This indicates viewing from the front towards the z-axis. Figure 4 The diagram shows the structure when the metaatoms (B) are embedded in the sheet 20. [The following is a description of the structure:] ... Figure 4 , Figure 5 The shape of the superatom shown is called a hexagonal cross shape, and the superatom 22 of the hexagonal cross shape is equivalent to the superatom of (B).

[0106] The minimum thickness of the superatoms in (B) is set as the length of the shortest side of the smallest cuboid shape circumscribed by the three-dimensional structure when the superatoms in (B) are considered as a whole as the "superatoms with a three-dimensional structure". For example, as Figure 4 and Figure 5 As shown, in a hexagonal cross shape composed of rods of the same shape, the minimum thickness of the superatoms of (B) is equivalent to the length of one rod × (2 / 3) of the length.

[0107] The hexagonal cross shape is described in detail, such as... Figure 4As shown, the shape of the three rods extending from the center along the positive and negative directions (opposite directions) of the x-axis, y-axis, and z-axis respectively (extending from the center of the meta-atom along the hexagonal intersection direction) is a hexagonal intersection shape. That is, this hexagonal intersection shape refers to the shape that forms an intersection (cross-shaped) when viewed from above in the x-axis, y-axis, and z-axis directions respectively. The shape of the rods extending from the center is not particularly limited, for example, it can be cylindrical or prismatic. That is, the cross-sectional shape perpendicular to the long dimension of the rod can be, for example, circular, elliptical, rectangular, square, rectangular or square with rounded corners or sides, polygonal with more than five sides, or polygonal with more than five sides with rounded corners or sides. In addition, its size can also be appropriately set according to the terahertz wave being irradiated. Preferably, the maximum diameter of the hexagonal intersection shape (the distance from one point on the surface of the hexagonal intersection shape to another point where the distance is the largest) is shorter than the wavelength (incident wavelength) of the terahertz wave in the transparent resin A. For example, when the cross-sectional shape is quadrilateral, the rod extending from the center in one direction can be configured with a length of 4.2–420 μm (the overall length of the rod extending in opposite directions from the center is approximately twice that, i.e., 8.4–840 μm), a width of 0.42–42 μm, and a height of 0.42–42 μm; alternatively, it can be configured with a length of 42–420 μm, a width of 2.1–21 μm, and a height of 2.1–21 μm; or it can be configured with a length of 84–210 μm, a width of 4.2–10.5 μm, and a height of 4.2–10.5 μm. By controlling the length of the rod, the resonant frequency of a terahertz wave at a specific frequency can be controlled.

[0108] The superatom in (B) can be either an isotropic or anisotropic, preferably an isotropic superatom. That is, as... Figure 4 As shown, the hexagonal cross shape is preferably composed of identical rods that extend equally along the positive and negative directions of the x-axis, y-axis, and z-axis (in which case the hexagonal cross shape exhibits isotropy). However, the length of the rods on each single or double axis can also be different from the length of the rods on other axes (in which case the hexagonal cross shape exhibits anisotropy).

[0109] In addition, Figure 4 In the superatoms shown in (B), the rods extend along the positive and negative directions of the x-axis, y-axis, and z-axis, respectively. However, the direction of the rods' extension is not limited to the x-axis, y-axis, and z-axis. They can also extend from the center point at a specified angle (0° < θ < 90°) relative to the x-axis, y-axis, and z-axis.

[0110] In this case, it is preferable that, in the superatoms of (B), the distance between one end of at least one rod extending from the center in different directions from one end of the other rod is more than 1 μm.

[0111] By adjusting the hexagonal cross-shaped structure as described above, the transmittance of terahertz waves at a specific frequency of the obtained three-dimensional metamaterial can be controlled to the desired value.

[0112] The material of the metaatom in (B) is not particularly limited. For example, it can be a metaatom formed of a conductive material, a dielectric, or a semiconductor material, preferably a metaatom formed of a conductive material. As the conductive material, the conductive material described above can be used. Furthermore, when the metaatom in (B) is a dielectric or semiconductor material, it is preferable that the dielectric or semiconductor material has a dielectric constant higher than that of the transparent resin A described later, and the dielectric or semiconductor material described above can be used.

[0113] (Transparent resin A)

[0114] In this invention, the material of the transparent resin A, which embeds (inner) the metaatoms of (A) or (B), is not particularly limited as long as it is a non-conductive material that is substantially transparent to electromagnetic waves in the terahertz region. Examples include polymethylpentene, polyethylene, cyclic olefin polymers (COP), silicone (polydimethylsiloxane: PDMS, etc.), polytetrafluoroethylene (Teflon; registered trademark), SiO2, etc. Among these, COP is preferred.

[0115] ((C) metaatom)

[0116] The metaatom in (C) is a bulk metaatom. The metaatom in (C) is adapted to control its refractive index relative to a terahertz wave of a specific frequency. In this invention, "bulk" refers to a shape that is not rod-shaped or arranged in a regular pattern like the metaatom in (A) or (B). For example, it is a block with a size of 1 μm or more and 850 μm or less, and may also have cavities within the block. An example of the shape of the metaatom in (C) will be described with reference to the accompanying drawings.

[0117] As an example Figure 6 This diagram shows a single superatom (C) and the surrounding transparent resin B31 integrally arranged, with the superatom (C) being cubic in shape (hereinafter, the superatom is also referred to as "the superatom of (C)"). In this invention or specification, the superatom (C) 32A and the surrounding transparent resin B31 together are referred to as the superatom (C) embedded block 30.Figure 7 This indicates viewing from the front towards the z-axis. Figure 6 The diagram shows the structure of the superatom (C1) embedded in the sheet 30. The cubic-shaped superatom corresponds to the superatom 32A of (C1). It should be noted that, in this invention, the superatom 32A of (C1) is an isotropic superatom.

[0118] Furthermore, as another example, Figure 8 The diagram shows a superatom (C2) with the superatom 32B being a cube in shape and having a through hole 33 of a square shape around a hole in the opposite face. The superatom and the transparent resin B31 covering it are shown together (hereinafter, the superatom is also referred to as "the superatom of (C2)"). Figure 9 This indicates viewing from the side along the x-axis. Figure 8 The diagram shows the structure of the superatom (C2) embedded in the sheet 30. The superatom with a square-shaped through-hole 33 surrounding a hole in one face facing the opposite face corresponds to the superatom 32B of (C2). It should be noted that, in this invention, the superatom 32B of (C2) is an anisotropic superatom.

[0119] The minimum thickness of the superatoms in (C) is set as the length of the shortest side of the smallest cuboid shape circumscribed by the three-dimensional structure when the superatoms of (C) as a whole are considered as the "superatoms with a three-dimensional structure". For example, as Figure 6 and Figure 7 As shown, when the superatoms of (C) are cube-shaped, the minimum thickness of the superatoms of (C) is equivalent to the length (l) of each side of the cube shape.

[0120] It should be noted that, in this invention, for metamaterials having (C) metaatoms, as described above, the (C) metaatoms can be formed by directly aggregating multiple of them in the transparent resin B without forming metaatom embedding sheets. On the other hand, when investigating the optical properties of the metamaterial of this invention having multiple (C) metaatoms aggregated in the transparent resin B, if the optical properties are investigated using the aforementioned "metaatom (C) embedding sheet 30" as the basic unit, the optical properties of the metamaterial of this invention having multiple (C) metaatoms aggregated can be theoretically understood. Therefore, for ease of understanding this invention, for convenience, Figures 6 - 9 The image shows a superatomic (C) embedded block 30.

[0121] When the metaatom in (C) is cuboid in shape, it can be a cube with all sides equal, or it can be a shape with rounded corners or edges. The dimensions of the cuboid shape can be appropriately set according to the irradiated terahertz wave. Preferably, the maximum diameter of the cuboid shape (the distance from one point on the surface of the cuboid to another point where the distance is greatest) is shorter than the wavelength (incident wavelength) of the terahertz wave within the transparent resin B31. For example, when the metaatom is a cube, the length of one side can be set to 1–850 μm, 2–700 μm, or 10–600 μm.

[0122] The material of the metaatoms in (C) is not particularly limited. For example, it is preferably formed of a conductive material, a dielectric, or a semiconductor material, more preferably a dielectric or semiconductor material. As a conductive material, for example, the metals and metal oxides described above can be used. In addition, as a semiconductor material, for example, silicon or silicon nitride can be used. Furthermore, as a dielectric, it is preferable to have a dielectric constant that is higher than that of the transparent resin B described later (high dielectric material). Examples of such high dielectric materials include ceramics such as silicon, alumina, zirconium oxide, silicon carbide, aluminum nitride, silicon nitride, yttrium oxide, and barium titanate, as well as compounds containing ceramics.

[0123] The metaatoms of (C) are preferably high-refractive-index materials relative to light in the terahertz region. By setting them in this way, a plurality of metaatoms of (C) are aggregated in a desired amount within a transparent resin B, which has a low refractive index relative to light in the terahertz region. This results in a metamaterial exhibiting a desired refractive index between the refractive index of the transparent resin B and the refractive index of the metaatoms of (C). From this perspective, silicon, with a much higher refractive index than transparent resin B, is a useful metaatomic material.

[0124] In the metaatoms of (C), "blocky" can include, for example, cuboid shapes (including cube shapes), cylindrical shapes, prismatic shapes, spherical shapes, etc., but is not limited to these shapes. That is, it can also be a shape with rounded corners, an arc, or a shape with corners formed on a plane. Furthermore, the metaatoms of the above shapes can have recesses, holes, or voids inside. When the metaatoms have recesses, the shape of the recess is not particularly limited. When the recess is viewed from above, the shape around the recess can be, for example, a square, rectangle, ellipse, triangle, polygon, etc. Furthermore, the shape in the depth direction of the recess is not particularly limited. For example, it can be formed perpendicular to the surface of the metaatoms, or it can be a conical shape that is pointed in the depth direction relative to the surface. The interior of the recess can be filled with air, or it can be filled with a resin such as transparent resin B described below, or both air and transparent resin B can coexist. When the metaatoms have holes, the shape around the holes can be, for example, a square, rectangle, ellipse, triangle, polygon, etc. The shape of the pore in the depth direction can be perpendicular to the surface of the metaatomic structure, or it can be a tapered shape that is pointed in the depth direction relative to the surface. The pore can be filled with air, or it can be filled with a resin such as transparent resin B described below, or both air and transparent resin B can coexist.

[0125] It should be noted that the metaatoms in (C) can be metaatoms of the same type and shape in terms of particle size (size), and they only need to be within the subwavelength size. The particle size of the metaatoms can also have deviations and distributions.

[0126] <Transparent resin B>

[0127] The metamaterial of Embodiment 3 described above has multiple superatomic embedded sheets or superatoms of (C) aggregated in transparent resin B. The material of transparent resin B is not particularly limited as long as it is a non-conductive material that is transparent to electromagnetic waves in the terahertz region; the material described in transparent resin A can also be used as transparent resin B. Transparent resin A and transparent resin B can be the same or different, but are preferably the same. Preferably, the superatomic atom (A) embedded sheets, the superatomic atom (B) embedded sheets, or the superatoms of (C) are uniformly dispersed in transparent resin B.

[0128] It should be noted that the "transparent resin" in Embodiment-1 and Embodiment-2 above is the same resin as the "transparent resin B" in Embodiment-3 above.

[0129] The metamaterial of the present invention exhibits three-dimensional isotropic optical properties due to its structure composed of aggregated metaatoms. For example, in the metamaterial of Embodiment-3 described above, the number of metaatomic embedded sheets or metaatoms in (C) aggregated in the transparent resin B is not particularly limited, and can be aggregated within the range where the metamaterial of the present invention has the desired isotropic optical properties. The content of metaatoms contained in the metamaterial of the present invention can be set to 0.1% by volume or more, or 1 to 99% by volume, or 10 to 90% by volume.

[0130] In particular, by controlling the content of the metaatoms of (C) in the metamaterial, the refractive index of terahertz waves with specific frequencies can be freely controlled.

[0131] As described above, regardless of the structure of the metaatoms contained therein, the three-dimensional isotropic metamaterial of the present invention exhibits isotropy. The method of aggregating metaatoms can be appropriately determined taking into account the structure of the metaatoms and in a way that the resulting metamaterial has three-dimensional isotropy. For example, in the case where the metaatoms exhibit anisotropy, by aggregating multiple metaatoms (or forming metaatomite sheets by embedding metaatoms) in a random orientation in transparent resin B, the resulting metamaterial can be made into a metamaterial with isotropic optical properties. Furthermore, in the case where the metaatoms themselves exhibit isotropy, whether multiple metaatoms (or forming metaatomite sheets by embedding metaatoms) are aggregated in a random orientation in transparent resin B, or are aggregated in a uniform orientation (or forming metaatomite sheets by embedding metaatoms) in the same orientation, the resulting metamaterial can be made into an isotropic metamaterial.

[0132] In the metamaterial of Embodiment 3 described above, the metaatoms (A) to (C) can be used individually or in combination. By using the same type of metaatoms, the optical properties of the metamaterial of the present invention can be enhanced or weakened. Furthermore, by combining different types of metaatoms, the metamaterial of the present invention can also produce the desired properties. Therefore, in Embodiment 3 described above, "a plurality of metaatomium-embedded sheets or metaatoms (C) formed by embedding metaatoms of (A) or (B) in transparent resin A are aggregated in transparent resin B" means that the metaatoms (A) to (C) can be used individually or in appropriate combinations.

[0133] As described above, the metamaterials according to the present invention, by fabricating metamaterials having multiple metaatoms in a combined manner, allow for the control of terahertz waves at specific frequencies and the free setting and design of refractive index and transmittance. Therefore, structures with desired properties can be obtained without designing new metamaterials.

[0134] [Method for manufacturing embedding slices of metaatom (A), embedding slices of metaatom (B), and metaatom (C)] [Method]

[0135] The meta-atom (A) embedded wafer, the meta-atom (B) embedded wafer, and the meta-atoms in (C) used in the above embodiment-3 can be manufactured using conventional semiconductor manufacturing techniques. As an example, Figures 10 - 13 The diagram shows an outline of the process for manufacturing the superatoms (A), (B), or (C) embedded blocks of the superatoms.

[0136] (Method for manufacturing embedding slice of metaatom (A))

[0137] use Figure 10 An example of a process for manufacturing metaatomic (A) embedded blocks is illustrated.

[0138] A double-sided adhesive tape 42 and a cutting tape 43 attached to the double-sided adhesive tape 42 are laid on the wafer 41 to form a strip substrate. Figure 10 of (a) Figure 10 (b) Next, a transparent resin film 44 (COP film) is deposited on the strip substrate. Figure 10 (c)) A film (e.g., an Au film) formed of a metaatomic material 45 is formed on the transparent resin film 44. Figure 10 (d)). Next, a resist film 46 is formed. Figure 10 (e)) The film formed by metaatomic material 45 is etched by photolithography. Figure 10 of (f), Figure 10 (g)). After etching, the resist film 46 ( Figure 10 (h)), coated with transparent resin solution 47 (COP solution) ( Figure 10 (i)). Then, the transparent resin film 44 (COP film) is laid again ( Figure 10 (j)), to dry ( Figure 10 (k)), thereby enabling the embedding of metaatoms within transparent resin A. This process is repeated multiple times (in... Figure 10 (This is to be done again) Figure 10 The process described in (d) to (k) is after ( Figure 10 (l)), cut, and then remove the cutting strip 43 ( Figure 10 of (m), Figure 10(n)), from which the superatomic (A) embedded block 10 can be obtained.

[0139] It should be noted that cutting into Figure 10 The method of embedding the (m) block is not limited to cutting. It can also be done by cutting with a pressing blade, cutting with a cutting knife, die stamping with a pressing mold, cutting with a wire saw, or precision machining with cutting tools such as a lathe tool.

[0140] (Method for manufacturing embedding slice of metaatom (B))

[0141] use Figure 11 An example of a process for fabricating metaatom (B) embedded blocks will be illustrated. It should be noted that, in Figure 11 In (a) to (k), the right column shows a top view of the superatomic (B) embedded block, and the left column shows the installation of the block in... Figure 11 The end view shown in (a) is cut along a single-dotted line and viewed from the cut surface in the direction of the arrow.

[0142] A transparent resin film 44 (COP film) is adhered to the strip substrate formed by the cutting strip 43. Figure 11 (a), wafer 41 and double-sided tape 42 are not shown). Next, a hole is formed on the upper surface of the transparent resin film 44. Figure 11 (b)), the pore is filled with metaatomic material 45 ( Figure 11 (c)). Then, a film formed of metaatomic material 45 is deposited on the transparent resin film 44. Figure 11 (d) Next, the film formed from metaatomic material 45 is patterned ( Figure 11 (e)), and then a transparent resin film 44 is laminated on it. Figure 11 (f)). Similarly, a hole is formed on the upper surface of the transparent resin film 44. Figure 11 (g)), the pore is filled with metaatomic material 45 ( Figure 11 (h)). Then a transparent resin film 44 is laminated on it. Figure 11 (i)), cut, and then remove the cutting strip 43 ( Figure 11 of (j), Figure 11 (k)), from which superatomic (B) embedded block 20 can be obtained.

[0143] It should be noted that cutting into Figure 11 The method of embedding the (j) block is not limited to cutting. It can also be carried out by cutting with pressing blade, cutting with a cutting knife, die stamping with pressing mold, cutting with a wire saw, or precision machining with cutting tools such as lathe tools.

[0144] (Method for manufacturing metaatom (C))

[0145] Figure 12 and Figure 13 This is an illustrative diagram showing an example of a process for manufacturing the metaatoms of (C).

[0146] exist Figure 12 In the manufacturing method shown, a silicon substrate 48 is deposited on the dicing strip 43. Figure 12 (a)), then proceed with cutting ( Figure 12 (b) can be used to obtain the superatoms of (C) on the cutting band 43.

[0147] In addition, Figure 13 In the manufacturing method shown, a silicon substrate 48 is deposited on the dicing strip 43. Figure 13 (a)), then a resist film 46 is formed. Figure 13 (b) ), the silicon substrate 48 is etched by photolithography ( Figure 13 (c) Figure 13 (d)). After etching, the resist film 46 is removed. Figure 13 (e) can yield (C) superatoms by cutting band 43. It should be noted that in... Figure 13 The process is described using a dicing tape 43, but the metaatoms of (C) can also be obtained without using the dicing tape 43. Alternatively, for example, a dummy substrate can be used instead of the dicing tape 43, on which a silicon substrate 48 is bonded for fabrication.

[0148] It should be noted that, in the case where the surface of the superatom in (C) has a porous shape, for example in Figure 13 In the photolithography process shown in (c), a process for forming is created. Figure 8 and Figure 9 The pattern of the through hole shown is then implemented. Figure 13 The etching process shown in (d) also yields (C) superatoms with pores.

[0149] [Method for manufacturing metamaterial of the present invention]

[0150] The metamaterial of the present invention can be obtained by aggregating multiple metaatoms with a three-dimensional structure having a minimum thickness of 1 μm or more in a transparent resin. Furthermore, in the metamaterial of Embodiment-3 described above, it can be obtained by aggregating multiple metaatoms (A), (B), or (C) in a transparent resin B. Figures 14 - 16This is an explanatory diagram illustrating a summary of an example of a process for manufacturing the metamaterial of the present invention. In particular, when using a material with a high specific gravity, such as silicon, as the material for the metaatoms, it is preferable to employ [a specific process] from the viewpoint of uniformly dispersing the metaatoms in the transparent resin B. Figure 15 and Figure 16 The manufacturing method shown.

[0151] right Figure 14 The illustration shown is used for explanation. An assembly of superatoms 32, with superatoms (A) embedded in sheet 10, (B) embedded in sheet 20, or (C) embedded in sheet 20, is placed into a mold 49 (mold) filled with a transparent resin solution 47. Figure 14 (a)) so that the embedded blocks or meta-atoms are uniformly dispersed. Figure 14 (b)). Then, the transparent resin solution 47 is dried and cured to become transparent resin B31 ( Figure 14 (c)), removing the mold 49, thereby obtaining the metamaterial 40 of the present invention, which is composed of multiple embedded pieces or metaatoms aggregated in transparent resin B31. Figure 14 (d)

[0152] Next, regarding Figure 15 The diagram shown illustrates the process. A block formed by uniformly mixing metaatoms (A) embedded in sheet 10, or metaatoms (B) embedded in sheet 20, or metaatoms (C) embedded in sheet 32, and transparent resin B31 is placed into mold 49. Figure 15 (a) Next, the blocks formed of transparent resin B31 are heated to melt them, the gaps between the blocks are eliminated, and then cooled to solidify them. Figure 15 (b)). Then, the mold 49 is removed, thereby obtaining the metamaterial 40 of the present invention, which is composed of a plurality of embedded pieces or metaatoms aggregated in transparent resin B31. Figure 15 (c)).

[0153] Next, regarding Figure 16 The diagram shown illustrates the process. A block formed by uniformly mixing metaatoms (A) embedded in sheet 10, or metaatoms (B) embedded in sheet 20, or metaatoms (C) embedded in sheet 32, and transparent resin B31 is placed into mold 49. Figure 16 (a)). Next, inject 47 (a) of transparent resin solution. Figure 16 (b) After eliminating the gaps between the blocks, it is allowed to cure, forming transparent resin B31 ( Figure 16 (c)). Then, the mold 49 is removed, thereby obtaining the metamaterial 40 of the present invention, which is composed of a plurality of embedded pieces or metaatoms aggregated in transparent resin B31. Figure 16 (d)

[0154] [Optical properties of metamaterial of the present invention]

[0155] The optical properties of the metamaterial of the present invention can be measured by conventional methods, and can also be analyzed and predicted by the following simulations.

[0156]

[0157] To predict the response of the three-dimensional metamaterial, the S-parameters of the metamaterial are calculated as periodic structures in the xy-plane, yz-plane, and two-dimensional periodic structures in the zx-plane. Simulations can be performed using the Finite Integration Technique (FIT) with SIMULIA CST Studio Suite. The simulation conditions can be set, for example, as described below.

[0158] Solver: Frequency domain solver.

[0159] Mesh shape: tetrahedron.

[0160] Grid size: Automatic.

[0161] Incident wave: pulse.

[0162] Number of data: 1001.

[0163]

[0164] The calculated S-parameters are then expressed as transmission (S... 21 ), reflection (S) 11 The average value is taken and set as the S-parameter when constructing a three-dimensional metamaterial.

[0165] Next, the refractive index is calculated based on the obtained S-parameters.

[0166] Using SIMULIA CST Studio Suite, the frequency characteristics of transmittance, reflectance, and refractive index can be calculated. Here, the method for deriving the refractive index from transmittance and reflectance is explained. Based on the calculation of the periodic structure, the reflectance and transmittance data are calculated and used as the scattering matrix S, respectively. 11 S 21 S 11 S 21 Both are complex numbers. If reflectivity and transmittance are defined as r and t respectively, then the following relationship holds.

[0167] [Formula 1]

[0168] [Formula 2]

[0169] Using these values, the impedance z can be calculated using the following formula.

[0170] [Formula 3]

[0171] Here, if we use the refractive index n, the wave number k0 of free space, and the thickness d of the model (the dimension of one side of the metaatomic embedded block), then the following relationship holds.

[0172] [Formula 4]

[0173] If the above formula is transformed, it becomes the following formula.

[0174] [Formula 5]

[0175] This allows us to derive the refractive index, but when the thickness d increases and the accumulated phase within the model exceeds 2π, the logarithmic function of the real part cannot be correctly calculated. Therefore, using an integer m, we obtain the following formula.

[0176] [Formula 6]

[0177] By setting the integer m to an appropriate value, the refractive index can also be predicted for models with thickness.

[0178] The metamaterial of the present invention allows for free setting of refractive index and transmittance, thus enabling its use as an optical element in the terahertz region. The metamaterial of the present invention exhibits unique optical properties such as high refractive index, large refractive index difference, frequency-dependent high transmittance, and low transmittance in any region at least between 0.1 and 10 THz (preferably at least between 0.1 and 5 THz, more preferably at least between 0.2 and 2 THz). Examples of applications of terahertz optical elements incorporating the metamaterials of this invention include, for example, articles, systems, and devices related to the following applications: terahertz invisibility cloaks, products equipped with invisibility technology (terahertz wave reflection / absorption suppression technology), products equipped with radio wave fault elimination technology (operating the direction of terahertz waves), high-sensitivity ultra-miniature antennas, IC tags, wide-angle beam scanning antennas, near-field microscope devices, high-efficiency detectors, terahertz band optical waveguides / fibers, hazardous material inspection devices, airport security inspection devices, body scanners (used in financial / information terminal rooms / airports, etc.), drug inspection devices, biometric authentication devices (used in financial / information terminal rooms / airports, etc.), food quality and safety inspection devices, food quality management devices, crop inspection devices, drug inspection devices, biochip / DNA analysis devices, cancer diagnosis devices, semiconductor wafer evaluation devices, LSI (Large Scale Integration) defect inspection devices, atmospheric environment analysis devices, etc.

[0179] Example

[0180] The present invention will be described in further detail based on embodiments. The present invention is not limited to the embodiments described below, except as specified herein.

[0181] The response of a meta-atom embedded block, which is formed by embedding the meta-atoms (A) to (C) mentioned above, to terahertz waves is analyzed using the following method (three-dimensional response of the meta-atom embedded block).

[0182] <Analysis method of S parameters>

[0183] To predict the response of three-dimensional metamaterials, S-parameters (Scattering parameters) were calculated for each two-dimensional periodic structure in the xy, yz, and zx planes of each metaatomic embedded sheet. The S-parameters were calculated using the Finite Integration Technique (FIT) and simulations based on the SIMULIA CST Studio Suite (DASSAULT SYSTEMES Co., Ltd.). The simulation conditions are shown below.

[0184] Solver: Frequency domain solver.

[0185] Mesh shape: tetrahedron.

[0186] Grid size: Automatic.

[0187] Incident wave: pulse.

[0188] Number of data: 1001.

[0189] It should be noted that, for the anisotropic metaatoms embedded in sheets or metaatoms (Experimental Examples 1, 2, 7, and 8), the calculated S-parameters (representing the pass-through characteristics from the input side) of the xy, yz, and zx planes are used. 21 And S represents the reflection characteristics on the input side. 11 The arithmetic mean of the values ​​is taken and set as the S-parameter representing the isotropic metaatom embedded sheet. Furthermore, for the isotropic metaatom embedded sheets (Experimental Examples 3-6), the two-dimensional periodic structures in the xy, yz, and zy planes are identical; therefore, the S-parameter relative to any one plane is used as is. 11 S 21 Both are plural.

[0190] <Method for determining refractive index>

[0191] According to the above S 21 S 11 The refractive index is calculated from the parameters.

[0192] Let the reflectivity and transmittance be r and t respectively, and we get the following relationship (Equation 1) and (Equation 2).

[0193] [Formula 7]

[0194] [Formula 8]

[0195] Using these formulas, and with the following (Formula 3), the impedance z is calculated.

[0196] [Formula 9]

[0197] Furthermore, using the refractive index n, the wave number k0 in free space, and the thickness d of the model (the period or thickness of the embedded block), the following relationship (Equation 4) is obtained.

[0198] [Formula 10]

[0199] Furthermore, by transforming the above (Equation 4), we obtain the following (Equation 5).

[0200] [Formula 11]

[0201] Furthermore, considering that the logarithmic function of the real part cannot be correctly obtained when the thickness d increases and the phase accumulated in the model exceeds 2π, the following equation (6) is obtained by using an integer m.

[0202] [Formula 12]

[0203] In the above (Equation 6), the integer m is set to an appropriate value, thereby calculating the refractive index for each meta-atom embedded sheet.

[0204] (Experimental example 1)

[0205] like Figures 1 - 3 As shown, a two-layer metaatomic (A) embedded sheet (A1 embedded sheet) is constructed by embedding four rod-shaped bodies arranged on the same plane in two overlapping layers in transparent resin A. It should be noted that the material of the four rod-shaped bodies is gold, and the transparent resin A is COP (dielectric constant: 2.3, tanδ: 0.00081). The arrangement of the four rod-shaped bodies is as follows... Figures 1 - 3 As shown.

[0206] The parameters of the A1 embedded block are shown in Table 1 below. It should be noted that the minimum thickness of the meta-atom in this embodiment is 50.2 μm, which is obtained by adding the distance between the rods (d) in Table 1 to the thickness (t) of each rod.

[0207] [Table 1]

[0208] For the A1 embedded block, its response to terahertz waves (0.2–0.6 THz) was evaluated using the methods described above. The results are presented below. Figure 17 .

[0209] according to Figure 17 It is known that the A1 embedded block exhibits a transmittance of over 30% in the wavelength region (e.g., 0.3–0.4 THz) expected to utilize next-generation 6G (6th Generation Mobile Communication Technology) communication. Furthermore, it is known that its refractive index (effective refractive index n) in this region is [not specified]. effThe Re value increases broadly from 1.3 to 1.9, for example, demonstrating its usefulness as a wavelength-dispersing material in the 0.3–0.4 THz region.

[0210] (Experimental example 2)

[0211] like Figures 1 - 3 As shown, a two-layer metaatomic (A) embedded sheet (A2 embedded sheet) is constructed by embedding four rod-shaped bodies arranged on the same plane in a double-overlapping manner in transparent resin A. Furthermore, a single-layer metaatomic embedded sheet (A3 embedded sheet) is constructed by embedding four rod-shaped bodies in transparent resin A in the same manner. It should be noted that the material of the four rod-shaped bodies is gold, and the transparent resin A is COP (dielectric constant: 2.3, tanδ: 0.00081).

[0212] The responsiveness was evaluated for each individual block in the same manner as described above. The parameters for the A2 and A3 embedded blocks are shown in Table 2 below. It should be noted that the minimum thickness of the metaatomic atoms in the A2 embedded block is 50.2 μm, obtained by adding the distance between the rods (d) in Table 2 to the thickness (t) of each rod. The results are shown below. Figure 18 .

[0213] [Table 2]

[0214] according to Figure 18 It can be seen that block A2 is embedded ( Figure 18 (a) and A3 buried block ( Figure 18 Compared to (b), the transmittance in the 0.25–0.3 THz region is exceptionally high. Therefore, it can be concluded that by arranging multiple rods in overlapping layers or more, the transmittance of the embedded block can be improved.

[0215] (Experimental example 3)

[0216] like Figure 4 and Figure 5 As shown, a meta-atom embedding block (B1 embedding block) is constructed by embedding hexagonal intersecting meta-atoms in transparent resin A. It should be noted that the material of each rod (quadrangular prism) constituting the meta-atom is gold, and the transparent resin A is COP (dielectric constant: 2.3, tanδ: 0.00081).

[0217] The parameters of the B1 embedded block are shown in Table 3 below. It should be noted that the minimum thickness of the metaatoms in this embodiment is approximately 93 μm.

[0218] [Table 3]

[0219] For the B1 embedded block, its response to terahertz waves (0.2–0.9 THz) was evaluated using the methods described above. The results are presented below. Figure 19 .

[0220] according to Figure 19 It can be seen that for the B1 embedded block, the transmittance drops to near zero around 0.6THz and 0.76THz. Moreover, the transmittance recovers in the region between 0.6 and 0.76THz, and recovers to approximately 100% around 0.7THz.

[0221] Moreover, the refractive index fluctuates between 1.2 and 1.8 around 0.6 THz, showing a refractive index characteristic with a refractive index difference as high as about 0.6.

[0222] (Experimental example 4)

[0223] Next, the parameters of the B1 embedded block were changed to produce B2 and B3 embedded blocks, respectively. The changed parameters are shown in Table 4 below. It should be noted that the minimum thickness of each metaatom in this embodiment is approximately 93 μm (B1 embedded block), approximately 87 μm (B2 embedded block), and 100 μm (B3 embedded block), respectively.

[0224] [Table 4]

[0225] For the embedded blocks B1 to B3, the optical characteristics were calculated in the same manner as above. The results are shown below. Figure 20 .

[0226] like Figure 20 As shown, by reducing the size of the hexagonal cross shape (B2 embedded plate), the resonant frequency can be shifted towards the higher frequency side, and by increasing the size of the hexagonal cross shape, the resonant frequency can be shifted towards the lower frequency side (B3 embedded plate). Therefore, it is shown that by changing the period of the plate and the parameters of the hexagonal cross shape, the frequency of the shielded electromagnetic wave can be arbitrarily changed.

[0227] (Experimental example 5)

[0228] like Figure 6 and Figure 7As shown, a meta-atom embedding body (C1 embedding block) is constructed by embedding cubic-shaped meta-atoms in transparent resin B. It should be noted that the material of the cubic-shaped meta-atoms is silicon (FZ-Si), and the transparent resin B is COP (dielectric constant: 2.3, tanδ: 0.00081).

[0229] The parameters of the C1 embedded block are shown in Table 5 below. It should be noted that the minimum thickness of the metaatom in this embodiment corresponds to the edge (l) in Table 5, which is 300 μm.

[0230] [Table 5]

[0231] For the C1 embedded block, its response to terahertz waves (0.1–0.3 THz) was evaluated using the methods described above. The results are presented below. Figure 21 .

[0232] according to Figure 21 It can be seen that, relative to terahertz waves in the frequency range of 0–0.3 THz, the refractive index of the C1 embedded sheet changes gradually. Furthermore, its refractive index is between that of Si (approximately 3.5) and that of COP (approximately 1.5).

[0233] (Experimental example 6)

[0234] For the C1 embedded sheet, the period p of the sheet is constructed without changing the edge l of the meta-atom as shown in Table 6 below. The response of each embedded sheet to terahertz waves (0.1–0.3 THz) is evaluated in the same manner as described above. It should be noted that the minimum thickness of the meta-atom in each embedded sheet of this embodiment corresponds to the edge (l) in Table 6, which is 300 μm.

[0235] The results of the refractive index relative to the volume ratio of each embedded block ((C) volume ratio of the volume of the meta-atom to the volume of the embedded block, %) are shown in Figure 22 It should be noted that, in Figure 22 In the diagram, points with a volume ratio (horizontal axis) of "0%" represent the refractive index of the COP resin itself, while points with a volume ratio of "100%" represent the refractive index of the silicon itself.

[0236] [Table 6]

[0237] according to Figure 22 It can be seen that by changing the size of the C2 to C9 embedded blocks to adjust the volume ratio, the refractive index can be controlled relative to terahertz waves of any frequency.

[0238] (Experimental example 7)

[0239] like Figure 8 and Figure 9 As shown, a superatomic structure (C2) with a cubic shape and a through-hole is constructed, with one side facing the opposite side. It should be noted that the (C2) superatomic structure is made of silicon (FZ-Si), and the hole is filled with air with a dielectric constant of 1.0. In the (C2) superatomic structure, the... Figure 9 The refractive index (the overall refractive index of the (C2) metaatoms and the through-hole combined) was analyzed when the length b of one side of the hole was varied from 0 to 290 μm. It should be noted that, except for calculating the refractive index of the metaatoms themselves by replacing the embedded sheets with metaatoms, the analysis was performed using the same method as described above. The results are shown below. Figure 23 .

[0240] exist Figure 23 For example, "b50" refers to a (C2) superatom with one side of the hole having a length b of 50 μm. In addition, "Si" refers to a (C2) superatom without a hole (i.e., one side of the hole has a length of 0 μm), and "air" refers to air itself with a dielectric constant of 1.0.

[0241] according to Figure 23 It is known that by adjusting the size of the pore to control the volume occupancy of the pore relative to the overall shape of the meta-atom, the refractive index of the (C2) meta-atom can be any refractive index between the refractive index of air (1.0) and the refractive index of silicon (approximately 3.5).

[0242] (Experimental example 8)

[0243] For the metaatoms of (C2) in Experimental Example 7, the refractive index of the metaatoms of (C2) was analyzed in the same manner as in Experimental Example 7, except that COP was filled into the pores of the through-hole. The results are shown below. Figure 24 .

[0244] according to Figure 24 It is known that by adjusting the size of the aperture to control the volume occupancy of the aperture relative to the overall shape of the meta-atom, the refractive index of the (C2) meta-atom can be any refractive index between the refractive index of COP (approximately 1.5) and the refractive index of silicon (approximately 3.5).

[0245] As shown in Experimental Examples 7 and 8, it is demonstrated that by controlling the refractive index of the metaatom itself of (C) to an arbitrary value, the refractive index of a three-dimensional isotropic metamaterial formed by aggregating multiple metaatoms in transparent resin B can be controlled to an arbitrary value.

[0246] In this way, the three-dimensional isotropic metamaterials of the present invention exhibit unique and isotropic (substantially direction-independent) optical responsiveness to terahertz waves that is significantly different from that of existing materials. The metamaterials of the present invention can be used, for example, as high-refractive-index materials relative to terahertz waves, wavelength-dispersive materials, materials that block or transmit terahertz waves of specific frequencies, etc. With respect to the three-dimensional isotropic metamaterials of the present invention, regardless of the three-dimensional structure of the intrinsic metaatoms, the resulting metamaterials exhibit three-dimensional isotropic optical properties.

[0247] Furthermore, the application fields of terahertz region light for the three-dimensional isotropic metamaterial of the present invention are not particularly limited. For example, applications such as terahertz region optical elements, angle-independent filters, thin lenses, and beam splitters using prisms can be listed. Furthermore, when used in terahertz optical components, it can be used in items, systems, devices, etc., related to applications such as: terahertz invisibility cloaks, products equipped with invisibility technology (terahertz wave reflection / absorption suppression technology), products equipped with radio wave fault elimination technology (direction of terahertz waves), high-sensitivity ultra-miniature antennas, IC tags, wide-angle beam scanning antennas, near-field microscope devices, high-efficiency detectors, terahertz band optical waveguides / fibers, hazardous material inspection devices, airport security inspection devices, body scanners (used in financial / information terminal rooms / airports, etc.), drug inspection devices, biometric authentication devices (used in financial / information terminal rooms / airports, etc.), food quality and safety inspection devices, food quality management devices, crop inspection devices, drug inspection devices, biochip / DNA analysis devices, cancer diagnosis devices, semiconductor wafer evaluation devices, LSI defect inspection devices, atmospheric environment analysis devices, etc.

[0248] The invention and its embodiments have been described together, but it is understood that, unless otherwise specified, the invention is not limited to any of the details described, but should be interpreted broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0249] This application claims priority based on Japanese Patent Application No. 2023-185677, filed on October 30, 2023, the contents of which are incorporated herein by reference as a part of this specification.

[0250] Explanation of reference numerals in the attached figures

[0251] 10: Metaatomic (A) embedded block sheet; 11, 21: Transparent resin A; 12: Superatoms in the first layer; 13: Superatoms in the second layer; 20: Metaatomic (B) embedded block sheet; 22: Superatoms with a hexagonal cross shape; 30: Metaatomic (C) embedded block sheet; 31: Transparent resin B; 32, 32A, 32B: (C) superatoms (bulk superatoms); 33: Through hole; 40: Three-dimensional isotropic metamaterials; 41: Chip; 42: Double-sided tape; 43: Cutting strip; 44: Transparent resin film; 45: Metaatomic materials; 46: Resist film; 47: Transparent resin solution; 48: Silicon substrate; 49: Mold.

Claims

1. A three-dimensional isotropic metamaterial is formed by aggregating multiple metaatoms with a minimum thickness of 1 μm or more in a transparent resin.

2. The three-dimensional isotropic metamaterial according to claim 1, wherein, The metaatoms with a three-dimensional structure are selected from (A) to (C) below. The three-dimensional isotropic metamaterial is a metaatomically embedded sheet formed by assembling multiple metaatoms of (A) below or metaatoms of (B) below in transparent resin A, or formed by assembling multiple metaatoms of (C) below in transparent resin B. (A) A superatomic structure formed by overlapping two or more layers of multiple rod-shaped bodies arranged on the same plane such that the rod-shaped bodies are not connected to each other in the vertical direction of the plane; (B) Hexagonal intersecting superatoms; (C) Bulk superatoms.

3. The three-dimensional isotropic metamaterial according to claim 2, wherein, When viewed from above, the superatoms of (A) are arranged in a consistent configuration with each other in the vertical direction.

4. The three-dimensional isotropic metamaterial according to claim 2, wherein, The superatom of (B) is a prism-shaped or cylindrical rod that extends from the center of the superatom along a hexagonal cross direction.

5. The three-dimensional isotropic metamaterial according to claim 2, wherein, Each metaatom in (A) to (C) is a dielectric, semiconductor material, or conductive substance.

6. The three-dimensional isotropic metamaterial according to claim 5, wherein, The metaatoms of the dielectric or semiconductor material have a dielectric constant greater than that of the transparent resin B, and the maximum diameter of the metaatoms is shorter than the wavelength of the terahertz wave incident on the three-dimensional isotropic metamaterial.

7. The three-dimensional isotropic metamaterial according to any one of claims 2 to 6, wherein, The three-dimensional isotropic metamaterial is formed by randomly aggregating multiple metaatoms into a sheet or by embedding metaatoms of (C) in the transparent resin B.

8. A terahertz optical element comprising the three-dimensional isotropic metamaterial according to claim 7.

9. The three-dimensional isotropic metamaterial according to any one of claims 2 to 6, wherein, The three-dimensional isotropic metamaterial is formed by embedding multiple metaatoms in the transparent resin B in a neatly arranged manner along the same direction, or by embedding metaatoms of (C).

10. A terahertz optical element comprising the three-dimensional isotropic metamaterial according to claim 9.

11. An article comprising a three-dimensional isotropic metamaterial according to any one of claims 2 to 6.

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