Electromagnetic wave control element

Abstract

The present invention addresses the problem of providing an electromagnetic wave control element capable of switching the traveling direction of an electromagnetic wave having a frequency of 0.1-0.3 THz in a short time. The present invention comprises, in order: a liquid crystal layer in which the alignment state of a liquid crystal compound changes according to a voltage; and a metasurface structure in which a plurality of fine structures are arranged, and in which the liquid crystal layer contains an azo compound.

Description

Technical Field

[0001] The present invention relates to an element for electromagnetic wave control using a metasurface structure. Background Art

[0002] High-frequency radio waves (millimeter waves and terahertz waves) required for high-capacity wireless communications have high straightness. Therefore, for example, in order to transmit radio waves to the entire area of ​​a room, a reflector installed on a wall or the like is required to bend the radio waves in any direction.

[0003] However, a typical reflector is a regular reflector, and the incident angle and the outgoing angle are equal, so there is a problem that, for example, radio waves have difficulty reaching the deep part of the room.

[0004] On the other hand, there has been proposed a device that uses a dynamic element such as liquid crystal to bend and reflect electromagnetic waves in a direction different from regular reflection.

[0005] For example, in non-patent document 1, Fig.29 As conceptually shown in FIG. 1 , an electromagnetic wave control element (light beam steering element) is described in which a liquid crystal layer 104 is sandwiched between a metasurface structure 100 and an electrode layer 102 .

[0006] exist Fig.29 In the electromagnetic wave controlling element shown, the metasurface structure 100 is formed by arranging fine structures 100a that serve as resonators, similarly to known metasurface structures.

[0007] In this electromagnetic wave controlling element, each of the fine structures 100a constituting the metasurface structure 100 functions not only as a reflector but also as an electrode. That is, the fine structures 100a and the electrode layer 102 form an electrode pair.

[0008] Furthermore, the electrode layer 102 also functions as a reflection layer for incident electromagnetic waves.

[0009] As an example, the liquid crystal layer 104 is a layer formed by aligning a liquid crystal compound LC. Fig.29 In the example shown, the liquid crystal compound LC is, as an example, a rod-shaped liquid crystal compound.

[0010] In this electromagnetic wave controlling element, when no voltage is applied between the fine structure 100 a and the electrode layer 102 , the longitudinal direction of the liquid crystal compound LC, that is, the direction of the optical axis, is aligned with the thickness direction.

[0011] When a voltage is applied between the fine-structure body 100 a and the electrode layer 102 in this state, the alignment state of the liquid crystal compound LC changes depending on the magnitude of the applied voltage.

[0012] In the example shown in the figure, as an example, the liquid crystal compound LC is tilted with respect to the thickness direction according to the magnitude of the voltage applied between the fine structure body 100 a and the electrode layer 102 .

[0013] exist Fig.29 As an example, a high voltage is applied to the microstructure 100a on the left side of the figure, and a low voltage is applied to the microstructure 100a on the right side of the figure. As a result, the liquid crystal compound LC in the region of the microstructure 100a on the left side of the figure is greatly tilted, and the length direction is close to the main surface of the liquid crystal layer 104. On the other hand, the liquid crystal compound LC in the region of the microstructure 100a on the right side of the figure is tilted less, and the length direction is close to the thickness direction of the liquid crystal layer 104.

[0014] The greater the tilt of the liquid crystal compound LC, that is, the closer the length direction of the liquid crystal compound LC is to the surface of the liquid crystal layer 104, the greater the refractive index of the liquid crystal layer 104. On the contrary, the smaller the tilt of the liquid crystal compound LC, that is, the closer the length direction of the liquid crystal compound LC is to the thickness direction of the liquid crystal layer 104, the smaller the refractive index of the liquid crystal layer 104.

[0015] Therefore, in this state, the refractive index of the liquid crystal layer 104 is large in the region of the microstructure 100a on the left side of the figure where the inclination of the liquid crystal compound LC is large, and is small in the region of the microstructure 100a on the right side of the figure where the inclination of the liquid crystal compound LC is small.

[0016] Therefore, in the region of the microstructure 100a on the left side of the figure having a large refractive index, the phase of the incident electromagnetic wave changes more greatly than in the region of the microstructure 100a on the right side of the figure having a small refractive index.

[0017] Therefore, in the region of the fine-structure body 100a on the left side in the figure, the optical path of the electromagnetic wave is apparently longer than that of the region of the fine-structure body 100a on the right side in the figure.

[0018] Therefore, when electromagnetic waves are incident from the normal direction of the liquid crystal layer 104, even if the electromagnetic waves are incident at the same time, the electromagnetic waves incident on the area of ​​the microstructure 100a on the left side of the figure where the optical path length is long are emitted from the reflecting device more slowly than the electromagnetic waves incident on the area of ​​the microstructure 100a on the right side of the figure where the optical path length is short.

[0019] As a result, the electromagnetic wave incident on the reflecting device from the normal direction and reflected is reflected obliquely to the left side in the figure so that the wave surfaces are aligned, rather than being specularly reflected in the normal direction.

[0020] Previous technical literature

[0021] Non-patent literature

[0022] Non-patent literature 1: Jingbo Wu et al., Liquid crystal programmable metasurface for terahertz beam steering, Applied Physics Letters, 116, 131104 (2020) Summary of the invention

[0023] Technical issues to be solved by the invention

[0024] exist Fig.29 In the electromagnetic wave control element shown, the alignment state of the liquid crystal compound LC is changed by applying a voltage between the microstructure 100a constituting the metasurface structure 100 and the electrode layer 102. The change in the alignment state differs depending on the voltage applied to the microstructure 100a.

[0025] Therefore, by controlling the voltage applied to each fine structure 100a, the incident electromagnetic wave can be reflected in a desired direction.

[0026] That is, the electromagnetic wave control element using the metasurface structure and the liquid crystal layer can switch the reflection angle of the incident electromagnetic wave by changing the voltage applied to each fine structure 100a.

[0027] However, the electromagnetic wave control element using the conventional metasurface structure and liquid crystal layer takes time to switch the reflection direction of the electromagnetic wave. Therefore, for example, when the electromagnetic wave needs to be transmitted to multiple locations by switching the reflection angle, there is a problem that the reflection direction cannot be switched at a sufficient speed.

[0028] The purpose of the present invention is to solve the problems of the prior art and to provide an electromagnetic wave control element, which uses a metasurface structure and a liquid crystal layer to control the direction of travel of electromagnetic waves and can switch the direction of travel of electromagnetic waves with a frequency of 0.1 to 0.3 THz in a short time.

[0029] Means for solving technical problems

[0030] In order to solve the problem, the present invention has the following structure.

[0031] [1] An electromagnetic wave control element comprising:

[0032] 1st electrode;

[0033] a liquid crystal layer, the orientation state of the liquid crystal compound changes according to a voltage; and

[0034] The super surface structure is composed of multiple micro structures.

[0035] The electromagnetic wave control element acts on electromagnetic waves with a frequency of 0.1 to 0.3 THz, and the liquid crystal layer contains an azo compound.

[0036] [2] The electromagnetic wave control element according to [1], wherein:

[0037] The azo compound has two or more azo structures.

[0038] [3] The electromagnetic wave control element according to [1] or [2], wherein:

[0039] The liquid crystal layer contains a liquid crystal compound having an azo structure.

[0040] [4] The electromagnetic wave control element according to any one of [1] to [3], further comprising a second electrode, the second electrode forming an electrode pair with the first electrode.

[0041] [5] The electromagnetic wave control element according to [4], wherein:

[0042] At least one of the first electrode and the second electrode is a microstructure.

[0043] [6] The electromagnetic wave control element according to any one of [1] to [5], wherein

[0044] The microstructure and the first electrode form an electrode pair.

[0045] [7] The electromagnetic wave control element according to any one of [1] to [6], wherein

[0046] The first electrode reflects electromagnetic waves having a frequency of 0.1 to 0.3 THz.

[0047] [8] The electromagnetic wave control element according to any one of [1] to [7], wherein

[0048] The first electrode is a pattern electrode.

[0049] [9] The electromagnetic wave control element according to any one of [1] to [8], wherein

[0050] The microstructure includes metal.

[0051]

[10] The electromagnetic wave control element according to any one of [1] to [9], wherein

[0052] The microstructure includes an oxide semiconductor.

[0053] Effects of the Invention

[0054] According to the electromagnetic wave controlling element of the present invention, the traveling direction of an electromagnetic wave having a frequency of 0.1 to 0.3 THz can be switched in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a diagram conceptually showing an example of the electromagnetic wave controlling element of the present invention.

[0056] Figure 2 This is a diagram conceptually showing an example of a liquid crystal alignment pattern in the electromagnetic wave controlling element of the present invention.

[0057] Figure 3 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0058] Figure 4 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0059] Figure 5 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0060] Figure 6 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0061] Figure 7 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0062] Figure 8 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0063] Fig. 9 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0064] Fig.10 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0065] Fig.11 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0066] Fig.12 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0067] Fig.13 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0068] Fig.14 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0069] Fig.15 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0070] Fig.16 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0071] Fig.17 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0072] Fig.18 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0073] Fig.19 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0074] Fig. 20 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0075] Fig.21 This is a diagram conceptually showing another example of the liquid crystal alignment pattern in the electromagnetic wave controlling element of the present invention.

[0076] Fig. 22 This is a diagram conceptually showing another example of the liquid crystal alignment pattern in the electromagnetic wave controlling element of the present invention.

[0077] Fig.23 This is a diagram conceptually showing another example of the liquid crystal alignment pattern in the electromagnetic wave controlling element of the present invention.

[0078] Fig.24 This is a diagram conceptually showing another example of the liquid crystal alignment pattern in the electromagnetic wave controlling element of the present invention.

[0079] Fig.25 This is a diagram conceptually showing another example of the liquid crystal alignment pattern in the electromagnetic wave controlling element of the present invention.

[0080] Fig.26 This is a diagram conceptually showing another example of the electromagnetic wave controlling element of the present invention.

[0081] Fig. 27 yes Fig.26 A schematic three-dimensional diagram of an electromagnetic wave controlling element is shown.

[0082] Fig.28 It is a conceptual diagram for explaining an embodiment of the present invention.

[0083] Fig.29 This is a diagram conceptually showing an example of a conventional electromagnetic wave controlling element. DETAILED DESCRIPTION

[0084] Hereinafter, the electromagnetic wave controlling element of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0085] In the present specification, a numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0086] In this specification, “the same” includes an error range generally allowed in the technical field.

[0087] The following figures are conceptual diagrams for explaining the electromagnetic wave control element of the present invention, and therefore, the shape, size, thickness, positional relationship, etc. of each component may not necessarily be the same as the actual one.

[0088] Figure 1 1 conceptually shows an example of the electromagnetic wave controlling element of the present invention.

[0089] The electromagnetic wave control element 10 of the present invention is a reflective electromagnetic wave control element that uses a reflective metasurface structure and a liquid crystal layer to set the traveling direction of electromagnetic waves as a target direction.

[0090] The electromagnetic wave control element of the present invention reflects electromagnetic waves with a frequency of 0.1 to 0.3 THz in a desired direction. That is, the electromagnetic wave control element of the present invention reflects electromagnetic waves with a wavelength of 1 to 3 mm in a desired direction.

[0091] like Figure 1 As shown, the electromagnetic wave control element 10 of the present invention includes a first electrode layer 26, a liquid crystal layer 20, and a metasurface structure 12 in this order from the bottom of the figure.

[0092] The metasurface structure 12 is formed by two-dimensionally arranging the microstructures 14 that serve as resonators on a support 16. In addition, the liquid crystal layer 20 is provided on the support 24.

[0093] Furthermore, the first electrode layer 26 is provided so as to cover the entire surface of the support 24 on the side opposite to the liquid crystal layer 20 .

[0094] In the electromagnetic wave controlling element 10 , the first electrode layer 26 and the support 24 , and the liquid crystal layer 20 and the support 16 (metasurface structure 12 ) are bonded together using an adhesive (adhesive, bonding agent) as necessary.

[0095] The bonding method is not limited, and various known methods that can transmit electromagnetic waves to the electromagnetic wave controlling element 10 can be used, for example, a method using an optical clear adhesive (OCA) that can transmit electromagnetic waves to the electromagnetic wave controlling element 10 .

[0096] As an example, Figure 1 In the electromagnetic wave controlling element 10 shown, the microstructure 14 is made of a conductive material and also serves as an electrode forming an electrode pair with the first electrode layer 26. Each microstructure 14 is connected to a power source 28 for applying a voltage between the microstructure 14 and the first electrode layer 26.

[0097] In the electromagnetic wave controlling element 10 of the present invention, the liquid crystal layer 20 is a layer in which the alignment state of the liquid crystal compound changes by application of a voltage.

[0098] Therefore, by supplying power to each fine structure 14 and applying a voltage to the liquid crystal layer 20 between the fine structure 14 and the first electrode layer 26, the alignment state of the liquid crystal compound LC changes. Furthermore, by adjusting the power supplied to each fine structure 14, the voltage applied to the region of the liquid crystal layer 20 corresponding to the fine structure 14 can be adjusted, thereby adjusting the alignment state of the liquid crystal compound LC between the fine structure 14 and the first electrode layer 26.

[0099] As an example, when no voltage is applied to the liquid crystal layer 20, Figure 2 As conceptually shown in the upper section of FIG. , the liquid crystal compound LC is aligned in the thickness direction of the liquid crystal layer 20. In the following description, this alignment state is also referred to as "vertical alignment".

[0100] When power is supplied to the microstructure 14 and voltage is applied to the liquid crystal layer 20, Figure 2 As conceptually shown in the lower section of FIG. 1 , the liquid crystal compound LC in the region corresponding to the fine structure 14 changes its orientation state according to the intensity of the applied voltage and tilts relative to the thickness direction of the liquid crystal layer 20. Figure 2 In the example shown, the liquid crystal compound LC is aligned most in a direction parallel to the main surface of the liquid crystal layer 20. In the following description, this alignment state is also referred to as "horizontal alignment".

[0101] In addition, Figure 2 In order to simplify the drawing, only the liquid crystal layer 20, the fine structure that becomes the electrode, and the first electrode layer 26 are shown.

[0102] In addition, the thickness direction is the stacking direction of the first electrode layer 26 , the support 24 , the liquid crystal layer 20 , and the support 16 .

[0103] The main surface is the largest surface of a sheet-like object (film, plate-like object, layer), and is usually the two surfaces in the thickness direction of the sheet-like object.

[0104] Furthermore, the normal direction refers to a direction perpendicular to the main surface or the like.

[0105] As mentioned above, Figure 1 The electromagnetic wave controlling element 10 shown utilizes a reflective metasurface structure, and the first electrode layer 26 also serves as a reflective layer for electromagnetic waves.

[0106] When an electromagnetic wave is incident on the electromagnetic wave control element 10 of the present invention having such a structure, the electromagnetic wave is phase-modulated by the resonance of the fine structure 14 (unit cell) when transmitting through the metasurface structure 12 , and is further phase-modulated by transmitting through the liquid crystal layer 20 .

[0107] The electromagnetic wave is then reflected by the first electrode layer 26 which also serves as a reflective layer.

[0108] The electromagnetic wave reflected by the first electrode layer 26 is phase-modulated by transmitting through the liquid crystal layer 20 again, and further phase-modulated by the metasurface structure 12 , and is emitted from the electromagnetic wave controlling element 10 as a reflected electromagnetic wave.

[0109] Here, as described above, the orientation state of the liquid crystal compound LC in the liquid crystal layer 20 , that is, the refractive index, varies depending on the voltage applied to each fine-structure body 14 .

[0110] The refractive index of the liquid crystal layer 20 is minimum when the liquid crystal compound LC is vertically aligned, increases as the inclination of the liquid crystal compound LC with respect to the thickness direction increases, and is maximum when the liquid crystal compound LC is horizontally aligned.

[0111] When no voltage is applied to the liquid crystal layer 20, the liquid crystal compound LC in the liquid crystal layer 20 is vertically aligned. When a voltage is applied to the liquid crystal layer 20, the liquid crystal compound LC in the region corresponding to the fine-structure body 14 is tilted with respect to the thickness direction.

[0112] In the electromagnetic wave control element 10, the larger the voltage applied to the liquid crystal layer 20, the closer the liquid crystal compound LC is to the horizontal orientation, and the larger the refractive index of the liquid crystal layer 20 in the region becomes. That is, in the liquid crystal layer 20, the refractive index of the region corresponding to the fine structure 14, that is, the phase difference given to the transmitted electromagnetic wave can be changed according to the voltage applied to the fine structure 14.

[0113] Therefore, in the electromagnetic wave controlling element 10 of the present invention, by adjusting the power supplied to each fine structure 14 to adjust the voltage applied to the corresponding region, regions with different refractive indices can be generated in the plane direction of the liquid crystal layer 20 .

[0114] As a result, Fig.29 Similarly, the electromagnetic wave control element (beam steering element) of non-patent document 1 illustrated in the specification can reflect the incident electromagnetic wave in a direction different from the mirror reflection. For example, when the electromagnetic wave is incident from the normal direction of the liquid crystal layer 20, the electromagnetic wave is reflected in a direction inclined relative to the normal direction, rather than in the normal direction.

[0115] Furthermore, by changing the power supplied to each fine-structure body 14 to change the voltage applied to the liquid crystal layer 20 , the refractive index at each position in the plane direction can be changed to switch the reflection direction of the incident electromagnetic wave.

[0116] Furthermore, by adjusting the voltage applied to the liquid crystal layer 20, the reflected electromagnetic waves can be concentrated or diffused, and further, the focus and diffusion degree of the reflected electromagnetic waves can be switched.

[0117] Similar to a known supersurface structure, the supersurface structure 12 is formed by two-dimensionally arranging fine structures 14 as fine structures on a support 16 .

[0118] In the illustrated example of the supersurface structure 12, the microstructures 14 are two-dimensionally arranged at equal intervals in the x-direction and the y-direction that are orthogonal to each other. In addition, in the supersurface structure 12, the microstructures 14 are all identical.

[0119] The support 16 is not limited, and any of various known sheet-like materials can be used as long as it can support the fine-structure body 14 and can transmit electromagnetic waves of a frequency of 0.1 to 0.3 THz for which the electromagnetic wave controlling element 10 is intended.

[0120] As the support 16, for example, there can be illustrated a metal substrate having an oxide insulating layer such as a silicon substrate having silicon oxide, a support composed of an oxide such as silicon oxide, a support composed of a semiconductor such as germanium and chalcogenide glass, a polyacrylic resin film such as polymethyl methacrylate, a cellulose resin film such as cellulose triacetate, a cycloolefin polymer film, a polyethylene terephthalate (PET) film, a polycarbonate film, a polyvinyl chloride film, and a glass plate, etc. As the cycloolefin polymer film, for example, the trade name "ARTON" manufactured by JSR Corporation and the trade name "ZEONOR" manufactured by ZEON CORPORATION can be illustrated.

[0121] There is no restriction on the thickness of the support 16, as long as the thickness is appropriately set according to the material forming the support 16 so as to support the microstructure 14, obtain sufficient transmittance to electromagnetic waves with a frequency of 0.1 to 0.3 THz, and further obtain sufficient strength according to the purpose of the electromagnetic wave control element 10.

[0122] In addition, in the electromagnetic wave controlling element 10 of the present invention, the metasurface structure 12 is not limited to having the support 16 .

[0123] That is, in the electromagnetic wave controlling element of the present invention, the microstructure 14 can be directly arranged on the surface of the liquid crystal layer 20 to form the super surface structure 12, if possible.

[0124] The microstructure 14 is arranged on one surface of the support 16. Thus, the supersurface structure 12 is formed.

[0125] The super surface structure 12 is a structure in which a fine structure 14 as a fine structure is divided and two-dimensionally arranged on a plane, and is basically composed of an arrangement of unit cells formed by one fine structure 14 and a space around the fine structure 14 .

[0126] In the electromagnetic wave controlling element 10 of the present invention, the metasurface structure is basically a known metasurface structure (metamaterial). Therefore, in the electromagnetic wave controlling element 10 of the present invention, various known metasurface structures can be used.

[0127] That is, in the present invention, the shape and forming material of the fine structures 14, the arrangement of the fine structures 14, and the intervals (pitch) between the fine structures 14 are not limited.

[0128] Furthermore, the metasurface structure 12 can be designed by a known method according to the reflection characteristics of the electromagnetic wave targeted by the electromagnetic wave control element 10 of the present invention. As an example, the amplitude and phase of the electromagnetic wave reflected by the microstructure 14 used can be calculated using commercially available simulation software, and the arrangement of the microstructure 14 can be set in a manner that achieves the distribution of the target phase modulation amount, i.e., the phase delay amount (refractive index).

[0129] The electromagnetic wave controlling element 10 of the present invention is intended for electromagnetic waves having a frequency of 0.1 to 0.3 THz.

[0130] Therefore, in the metasurface structure 12, the microstructure 14 is selected so as to provide a desired phase difference to the electromagnetic wave of the frequency, and the arrangement of the microstructure is set.

[0131] The metasurface structure 12 is basically composed of an arrangement of unit cells formed by one microstructure 14 and the space around the microstructure 14. The metasurface structure 12 modulates the phase of an incident electromagnetic wave by utilizing the resonance of the microstructure 14 through the arrangement of the unit cells.

[0132] In addition, in the electromagnetic wave control element 10 of the present invention, the number of microstructures 14 in one unit cell is basically one, but the present invention is not limited to this. That is, in the electromagnetic wave control element of the present invention, according to the target optical characteristics, the size of the microstructure 14, the forming material and shape, and the size of the unit cell, one unit cell can have a plurality of microstructures 14 as needed. In this case, one unit cell can have different microstructures 14. However, in the case where one unit cell has a plurality of microstructures 14, basically, the phase modulation amount in the space where each microstructure of the unit cell is located is equal.

[0133] In the electromagnetic wave controlling element 10 of the present invention, the material forming the microstructure 14 constituting the metasurface structure 12 is not limited, and various materials used as microstructures in known metasurface structures can be used.

[0134] As the material for forming the fine structure 14, metals and dielectrics can be exemplified. In the case of metals, copper, gold, and silver can be preferably exemplified from the viewpoint of less optical loss. In addition, as the material for forming the fine structure 14, a composite composed of metal particles and a binder and an oxide semiconductor can also be used. On the other hand, in the case of dielectrics, silicon, titanium oxide, and germanium can be preferably exemplified from the viewpoint of having a large refractive index and being able to perform large phase modulation.

[0135] In addition, if Figure 1 As shown, when the fine structure 14 also serves as an electrode forming an electrode pair with the first electrode layer 26, the fine structure 14 is formed of a conductor.

[0136] Likewise, the shape of the fine structure 14 constituting the super-surface structure 12 is not limited, and various shapes used as fine structures in known super-surface structures can be used.

[0137] As an example, there can be illustrated: a cross-shaped solid in which rectangular blocks are crossed, a rectangular block, a cylindrical shape, a V-shaped solid such as connecting rectangular blocks at the ends as shown in Japanese Patent Gazette No. 2018-046395, a roughly H-shaped solid such as H-shaped steel, and a roughly C-shaped solid such as a C-shaped channel, etc.

[0138] Furthermore, as shown in Japanese Patent Application Publication No. 2018-046395, V-shaped solids and cross-shaped solids can utilize various shapes obtained by adjusting the angle formed by two rectangular parallelepipeds.

[0139] In addition, it is also possible to use the Figure 5 The three-dimensional shape of the bottom surface shown, etc.

[0140] In the super surface structure 12, such a microstructure 14 may be used only one, or may be used in combination of multiple types. Figure 2 As shown, the same microstructures 14 may be arranged in the same orientation, may be arranged in different orientations, or may be a mixture of the same orientation and different orientations.

[0141] However, in the electromagnetic wave controlling element of the present invention, it is preferred that only one type of fine structure body 14 is used and all the fine structure bodies 14 are arranged in the same direction.

[0142] In the example shown in the figure, as a preferred embodiment, in the super-surface structure 12, identical microstructures 14 having all identical structures are two-dimensionally arranged at equal intervals in the x-direction and the y-direction that are orthogonal to each other.

[0143] However, the present invention is not limited thereto, and as described above, a plurality of types of fine structures may be used simultaneously, and the arrangement intervals and arrangements of the fine structures 14 may be different in the surface direction of the support 16 .

[0144] However, if the controllability of the reflection direction of the electromagnetic wave when a voltage is applied to the liquid crystal layer 20 is taken into consideration, it is preferred that all identical microstructures 14 are used in the supersurface structure 12. Moreover, it is more preferred that the identical microstructures 14 of the supersurface structure 12 are arranged two-dimensionally at equal intervals, and it is further preferred that they are arranged two-dimensionally at equal intervals in the orthogonal x-direction and y-direction.

[0145] The liquid crystal layer 20 is a layer in which the liquid crystal compound LC is aligned in a predetermined state, and as described above, the alignment state of the liquid crystal compound LC changes by application of a voltage.

[0146] As described above, the liquid crystal compound LC is vertically aligned when no voltage is applied to the liquid crystal layer 20 shown in the figure. When a voltage is applied to the liquid crystal layer 20, the liquid crystal compound LC is tilted in the thickness direction according to the voltage and is horizontally aligned at most.

[0147] In addition, in the present invention, the change in the orientation of the liquid crystal compound LC is not limited to the change from vertical orientation to horizontal orientation or vice versa, and it can be changed from a state inclined relative to the thickness direction to a horizontal orientation or a vertical orientation, or from a horizontal orientation or a vertical orientation to a state inclined relative to the thickness direction, or from a state inclined relative to the thickness direction to a state inclined relative to the thickness direction, and the angle can change.

[0148] In the present invention, the liquid crystal layer 20 may be formed on the surface of an alignment film described later, for example, by a known method.

[0149] Here, in the electromagnetic wave controlling element 10 of the present invention, the liquid crystal layer 20 contains an azo compound.

[0150] The electromagnetic wave control element 10 of the present invention can improve responsiveness and switch the reflection direction of incident electromagnetic waves with a frequency of 0.1 to 0.3 THz in a short time by including an azo compound in the liquid crystal layer 20 .

[0151] The above viewpoints will be described in detail later.

[0152] In the electromagnetic wave controlling element 10 , the liquid crystal layer 20 is formed on a support 24 .

[0153] The support body 24 is substantially the same as the support body 16 described above.

[0154] Here, the support 24 forming the liquid crystal layer 20 may include the support 16 as a main body, and have an alignment film for aligning the liquid crystal compound LC in a predetermined state on the surface of the main body forming the liquid crystal layer 20 .

[0155] The alignment film can utilize various known alignment films, such as a friction-treated film composed of an organic compound such as a polymer, an oblique vapor-deposited film of an inorganic compound, a film having microgrooves, and a film formed by accumulating an LB (Langmuir-Blodgett) film of an organic compound such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate based on the Langmuir-Blodgett method.

[0156] Furthermore, as the alignment film, a so-called photo-alignment film can be used, in which a material having a photo-alignment property is irradiated with polarized light or non-polarized light to form an alignment film.

[0157] These alignment films may be formed by a known method corresponding to the main forming material.

[0158] The entire surface of the support 24 forming the liquid crystal layer 20 , which is opposite to the liquid crystal layer 20 , is covered with the first electrode layer 26 .

[0159] The first electrode layer 26 is an electrode that changes the orientation of the liquid crystal compound LC in the liquid crystal layer 20 , and as described above, also functions as a reflection layer that reflects electromagnetic waves with a frequency of 0.1 to 0.3 THz incident from the metasurface structure 12 side.

[0160] The first electrode layer 26 is not limited, and a sheet-like material made of various known materials can be used as long as it has sufficient conductivity and can reflect electromagnetic waves with a frequency of 0.1 to 0.3 THz.

[0161] As the first electrode layer 26, for example, there can be illustrated a metal layer such as copper, aluminum, gold, and silver, an inorganic conductive material such as ITO (tin-doped indium oxide), an organic conductive material such as polythiophene represented by PEDOT (poly 3,4-ethylenedioxythiophene), and graphene, etc. Inorganic conductive materials, organic conductive materials, and graphene, etc. are transparent to visible light, but function as a reflective layer for electromagnetic waves of the above frequency.

[0162] The thickness of the first electrode layer 26 is not limited either, and may be appropriately set according to the material forming the first electrode layer 26 so as to reflect the target electromagnetic wave at a desired reflectivity.

[0163] As described above, the electromagnetic wave controlling element 10 of the present invention is a reflection type electromagnetic wave controlling element including the metasurface structure 12 and the liquid crystal layer 20 .

[0164] In the electromagnetic wave control element 10, electric power is supplied to each fine structure 14 to change the orientation state of the liquid crystal compound LC in the corresponding area of ​​the liquid crystal layer 20, thereby forming areas with different refractive indices in the surface direction, thereby reflecting the incident electromagnetic waves with a frequency of 0.1 to 0.3 THz in the desired direction.

[0165] Furthermore, by changing the power supplied to each fine-structure body 14 , that is, the voltage applied to the liquid crystal layer 20 , it is possible to switch the reflection direction of the incident electromagnetic wave.

[0166] Here, as described above, the electromagnetic wave controlling element (light beam steering element) using the conventional metasurface structure and liquid crystal layer as disclosed in Non-Patent Document 1 takes time to switch the reflection direction of the electromagnetic wave.

[0167] In contrast, the electromagnetic wave control element 10 of the present invention includes an azo compound through the liquid crystal layer 20, preferably includes a liquid crystal compound having an azo structure through the liquid crystal layer 20, and more preferably forms the liquid crystal layer 20 with a liquid crystal compound having an azo structure, thereby ensuring high responsiveness and switching the reflection direction of the incident electromagnetic wave in a short time.

[0168] That is, in the present invention, by including an azo compound in the liquid crystal layer 20, Δn (secondary refraction) of the liquid crystal layer can be increased. Therefore, in the present invention, the thickness of the liquid crystal layer required to provide a desired refractive index, that is, a desired phase difference, to electromagnetic waves can be reduced. By reducing the thickness of the liquid crystal layer, when the applied voltage is changed, the orientation of the liquid crystal compound LC changes rapidly.

[0169] As a result, according to the electromagnetic wave controlling element 10 of the present invention, the response speed to the change in the voltage applied to the liquid crystal layer 20 can be increased, and the reflection direction of the incident electromagnetic wave can be switched in a short time.

[0170] The azo compound is not particularly limited as long as it is a compound including an azo structure (—N═N—).

[0171] The number of azo structures in the azo compound is not particularly limited as long as it is 1 or more, and is preferably 2 or more. The upper limit of the number of azo structures is not particularly limited, but is often 5 or less, and more often 3 or less.

[0172] The azo compound may be a compound exhibiting liquid crystallinity or a compound not exhibiting liquid crystallinity, but is preferably a compound exhibiting liquid crystallinity. That is, the azo compound is preferably a liquid crystal compound having an azo structure.

[0173] The azo compound is preferably a compound represented by formula (1).

[0174] [Chemical formula 1]

[0175]

[0176] In formula (1), Ar 1 It represents an aromatic ring with a valence of (m1+1).

[0177] The (m1+1)-valent aromatic ring may be a single ring or a condensed ring of two or more rings. Alternatively, the aromatic ring may be a ring formed by a plurality of single rings bonded together by single bonds (for example, a biphenyl ring or a terphenyl ring).

[0178] Examples of the (m1+1)-valent aromatic ring include an aromatic hydrocarbon ring and an aromatic heterocyclic ring.

[0179] Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, an anthracene ring, a fluorene ring, a biphenyl ring, and an anthracene ring. Among them, a benzene ring is preferred.

[0180] Examples of the aromatic heterocyclic ring include a pyridine ring, a thiophene ring, a furan ring, a quinoline ring, an isoquinoline ring, a thiazole ring, a thienothiophene ring, and a thienothiazole ring.

[0181] For example, when m1 is 1, Ar 1 It represents a divalent aromatic ring.

[0182] In formula (1), Ar 2 It represents an aromatic ring with a valence of (m2+2).

[0183] The (m2+1)-valent aromatic ring may be a single ring or a condensed ring of two or more rings. Alternatively, the aromatic ring may be a ring formed by a plurality of single rings bonded together by single bonds (for example, a biphenyl ring or a terphenyl ring).

[0184] Examples of the (m2+1)-valent aromatic ring include an aromatic hydrocarbon ring and an aromatic heterocyclic ring.

[0185] Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, an anthracene ring, a fluorene ring, a biphenyl ring, and an anthracene ring. Among them, a benzene ring is preferred.

[0186] Examples of the aromatic heterocyclic ring include a pyridine ring, a thiophene ring, a furan ring, a quinoline ring, an isoquinoline ring, a thiazole ring, a thienothiophene ring, and a thienothiazole ring.

[0187] For example, when m2 is 1, Ar 2 It represents a trivalent aromatic ring.

[0188] In formula (1), Ar 3 It represents an aromatic ring with a valence of (m3+1).

[0189] The (m3+1)-valent aromatic ring may be a single ring or a condensed ring of two or more rings. Alternatively, the aromatic ring may be a ring formed by a plurality of single rings bonded together by single bonds (for example, a biphenyl ring or a terphenyl ring).

[0190] Examples of the (m3+1)-valent aromatic ring include an aromatic hydrocarbon ring and an aromatic heterocyclic ring.

[0191] Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, an anthracene ring, a fluorene ring, a biphenyl ring, and an anthracene ring. Among them, a benzene ring is preferred.

[0192] Examples of the aromatic heterocyclic ring include a pyridine ring, a thiophene ring, a furan ring, a quinoline ring, an isoquinoline ring, a thiazole ring, a thienothiophene ring, and a thienothiazole ring.

[0193] For example, when m3 is 1, Ar 3 It represents a divalent aromatic ring.

[0194] In formula (1), R 1 , R 2 and R 3 Each independently represents a substituent.

[0195] In the case of m1 ≥ 2, multiple R 1 They can be the same or different. When m2≥2, multiple R 2 They can be the same or different. When m3≥2, multiple R 3 They may be the same as or different from each other.

[0196] The substituent is a monovalent substituent, and examples thereof include an alkyl group, an alkenyl group, an aralkyl group, an aryl group, a heterocyclic group, a halogen atom, a cyano group, a nitro group, a mercapto group, a hydroxyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acyloxy group, an amino group, an alkylamino group, a dialkylamino group, a carboxamide group, a sulfonamide group, a sulfamoyl group, an oxycarbonylamino group, an oxysulfonylamino group, a urea group, a thiourea group, an acyl group, an oxycarbonyl group, a carbamoyl group, a sulfonyl group, a sulfinyl group, a sulfamoyl group, a carboxyl group (including a salt), a sulfo group (including a salt), and a group formed by combining these groups. These groups may be further substituted by these groups.

[0197] In formula (1), m1, m2 and m3 each independently represent an integer of 0 to 5. m1 is preferably 1 to 3, m2 is preferably 0 to 1, and m3 is preferably 1 to 3.

[0198] In formula (1), n1 represents an integer of 1-4, preferably 1-3, and more preferably 2-3.

[0199] In the electromagnetic wave controlling element 10 of the present invention, Δn of the liquid crystal layer 20 is not limited, but is preferably larger.

[0200] Here, as shown in the example of the figure, in the reflection type electromagnetic wave controlling element 10 , Δn of the liquid crystal layer 20 is preferably 0.35 or more.

[0201] By setting Δn of the liquid crystal layer 20 to 0.35 or more and thereby reducing the thickness of the liquid crystal layer 20 , it is possible to more quickly switch the reflection direction of the electromagnetic wave, which is preferable from such a viewpoint.

[0202] Furthermore, the thickness of the liquid crystal layer 20 is not limited either, and the thickness that provides a required phase difference to the electromagnetic wave may be appropriately set according to the material forming the liquid crystal layer 20 .

[0203] Here, as described above, in the electromagnetic wave control element 10 of the present invention, the liquid crystal layer 20 contains an azo compound, so the liquid crystal layer 20 can be made thinner. Considering this point, the thickness of the liquid crystal layer 20 is preferably 200 μm or less, more preferably 150 μm or less, and further preferably 100 μm or less.

[0204] By setting the thickness of the liquid crystal layer 20 to 200 μm or less, the reflection direction of the electromagnetic wave can be switched more quickly, which is preferable from such a viewpoint.

[0205] In the electromagnetic wave controlling element of the present invention, the reflection type electromagnetic wave controlling element is not limited to Figure 1 The structure shown can exemplify various structures.

[0206] For example, Figure 1In the electromagnetic wave control element 10 shown, the microstructure 14 constituting the super surface structure 12 also functions as an electrode. However, the present invention is not limited to this, and a second electrode 30 constituting an electrode pair with the first electrode layer 26 may be provided corresponding to the microstructure 14. The second electrode 30 only needs to be formed of the same material as the first electrode layer 26.

[0207] In the following examples, although illustration is omitted, Figure 1 In the illustrated example, a power source 28 is connected to each electrode or the microstructure 14 serving as an electrode.

[0208] As the structure, for example, Figure 3 As conceptually shown in FIG. 1 , a structure in which the second electrode 30 is provided on the microstructure 14 can be exemplified.

[0209] Or, if Figure 4 As conceptually shown in FIG. 1 , the second electrode 30 may be provided between the fine-structure body 14 and the support body 16 .

[0210] Moreover, if Figure 5 As shown conceptually in Figure 1 In the structure shown, it is also possible to use a structure in which the first electrode layer 26 is patterned as a pattern electrode and provided only in a region corresponding to the fine structure body 14. In this structure, electromagnetic waves incident on a region without the first electrode layer 26 are transmitted.

[0211] Furthermore, in the electromagnetic wave controlling element of the present invention, the reflective electromagnetic wave controlling element may include the fine structure 14 disposed adjacent to the liquid crystal layer 20 and the super surface structure 12 disposed between the layer electrodes.

[0212] For example, Figure 6 As conceptually shown in FIG. 1 , the microstructure 14 can be disposed on the liquid crystal layer 20 side of the support 16, and a layered (planar) second electrode 30 can be disposed on the side of the support 16 opposite to the liquid crystal layer 20. In this structure, the second electrode 30 is patterned in a manner having a plurality of openings as a pattern electrode so that electromagnetic waves can pass through the second electrode 30.

[0213] In this structure, if Figure 7 As conceptually shown in FIG. 2 , the fine structure 14 may be arranged on the support 24 , and the super-surface structure 12 may be provided on both surfaces of the liquid crystal layer 20 .

[0214] The electromagnetic wave controlling element of the present invention described above is a reflection-type electromagnetic wave controlling element that reflects incident electromagnetic waves having a frequency of 0.1 to 0.3 THz and causes them to travel in a desired direction, but the present invention is not limited thereto.

[0215] That is, the electromagnetic wave controlling element of the present invention may be a transmission-type electromagnetic wave controlling element that refracts and transmits incident electromagnetic waves having a frequency of 0.1 to 0.3 THz to cause them to travel in a desired direction.

[0216] In the following description, unless otherwise specified, electromagnetic waves refer to electromagnetic waves having a frequency of 0.1 to 0.3 THz.

[0217] Figure 8 An example of a transmission-type electromagnetic wave controlling element is conceptually shown in FIG.

[0218] The transmission-type electromagnetic wave controlling element of the present invention described below does not include the first electrode layer 26 serving as a reflective layer, but is basically the same as the above-mentioned reflection-type electromagnetic wave controlling element, and the functions of the respective components are also the same.

[0219] Therefore, the same components are denoted by the same reference numerals, and the description will be mainly focused on different portions.

[0220] Figure 8 The transmission type electromagnetic wave controlling element 36 shown does not have the first electrode layer 26, but has the same Figure 1 The reflection type electromagnetic wave controlling element 10 shown has the same structure.

[0221] That is, the electromagnetic wave controlling element 36 includes the metasurface structure 12 and the liquid crystal layer 20 . The metasurface structure 12 is formed by two-dimensionally arranging the fine structures 14 that serve as resonators on the support 16 , and the liquid crystal layer 20 is formed on the support 24 .

[0222] Here, Figure 8 In the electromagnetic wave controlling element 36 shown, the fine structure 14 serves as both the first electrode and the second electrode. That is, in the electromagnetic wave controlling element 36, the power source 28 is provided to connect the adjacent fine structures 14.

[0223] In the electromagnetic wave controlling element 36 , electric power is supplied from the power source 28 to the fine-structure bodies 14 , so that a voltage in the plane direction is applied to the liquid crystal layer 20 between the adjacent fine-structure bodies 14 .

[0224] As a result, the orientation state of the liquid crystal compound LC in the liquid crystal layer 20 in the region changes according to the applied voltage, thereby changing the refractive index. In addition, by changing the power supplied to each fine structure 14, that is, the voltage applied to the corresponding region, regions with different refractive indices in the plane direction can be formed.

[0225] Similar to the electromagnetic wave control element 10 , when an electromagnetic wave is incident on the electromagnetic wave control element 36 , the electromagnetic wave is phase-modulated by the resonance of the fine structure 14 (unit cell) when transmitting through the metasurface structure 12 , and is further phase-modulated by transmitting through the liquid crystal layer 20 .

[0226] Since the electromagnetic wave controlling element 36 does not include the first electrode layer 26 serving as a reflective layer, the electromagnetic wave transmits through the liquid crystal layer 20 and is emitted from the electromagnetic wave controlling element 36 as a transmitted electromagnetic wave.

[0227] Here, as described above, the liquid crystal layer 20 has different refractive indices in the plane direction, so the phase difference given to the electromagnetic wave passing through the liquid crystal layer 20 is different in each area in the plane direction. Therefore, the apparent optical path length of the electromagnetic wave is different according to the phase difference given corresponding to the incident area, and the electromagnetic wave that passes through the area with a long optical path length is emitted from the liquid crystal layer 20 more slowly than the electromagnetic wave that passes through the area with a short optical path length.

[0228] As a result, the electromagnetic wave incident on the electromagnetic wave controlling element 36 is not transmitted linearly, but refracted and transmitted so that the wave surface is aligned. For example, the electromagnetic wave incident from the normal direction is not transmitted in the normal direction, but is transmitted in a direction inclined relative to the normal.

[0229] Furthermore, by changing the power supplied to each fine structure body 14, that is, the voltage applied to the liquid crystal layer 20, it is possible to switch the refractive index of the transmitted electromagnetic wave, that is, the emission direction of the electromagnetic wave.

[0230] Furthermore, by adjusting the voltage applied to the liquid crystal layer 20 , the transmitted electromagnetic waves can be concentrated or diffused, and further, the focus and diffusion degree of the transmitted electromagnetic waves can be switched.

[0231] Here, in the electromagnetic wave controlling element 36 , the liquid crystal layer 20 also contains an azo compound, and therefore the refractive index, that is, the refraction direction (traveling direction) of the transmitted light can be switched rapidly.

[0232] In the transmission type electromagnetic wave controlling element 36 of the present invention, Δn of the liquid crystal layer 20 is not limited, but is preferably larger.

[0233] Here, in the transmission type electromagnetic wave controlling element 36 as shown in the figure, Δn of the liquid crystal layer 20 is preferably 0.2 or more, more preferably 0.3 or more, and further preferably 0.4 or more.

[0234] In the electromagnetic wave controlling element 36 , it is preferable to make the liquid crystal layer 20 thinner by setting Δn of the liquid crystal layer 20 to 0.2 or more, because the reflection direction of the electromagnetic wave can be switched more quickly.

[0235] Furthermore, the thickness of the liquid crystal layer 20 is not limited either, and the thickness that provides a required phase difference to the electromagnetic wave may be appropriately set according to the material forming the liquid crystal layer 20 .

[0236] Here, as described above, in the transmission type electromagnetic wave control element 36, the liquid crystal layer 20 also contains an azo compound, so the liquid crystal layer 20 can be made thinner. In the present invention, the target electromagnetic wave is an electromagnetic wave with a frequency of 0.1 to 0.3 THz, that is, an electromagnetic wave with a wavelength of 1 to 3 mm.

[0237] Taking this into consideration, in the transmission-type electromagnetic wave controlling element 36 , the thickness of the liquid crystal layer 20 is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less.

[0238] By setting the thickness of the liquid crystal layer 20 to 500 μm or less, the reflection direction of the electromagnetic wave can be switched more quickly, which is preferable from such a viewpoint.

[0239] In the electromagnetic wave control element of the present invention, the transmission type electromagnetic wave control element is not limited to Figure 8 The electromagnetic wave control element 36 shown in the figure can be exemplified by various structures. Figure 8 In the illustrated example, a power source 28 is connected to each electrode or the microstructure 14 serving as an electrode.

[0240] For example, Figure 8 In the electromagnetic wave controlling element 36 shown, the microstructure 14 constituting the metasurface structure 12 also functions as an electrode. However, the present invention is not limited to this, and the first electrode 32 and the second electrode 30 may be provided corresponding to the microstructure 14.

[0241] As an example, the structure Fig. 9 As conceptually shown in FIG. 1 , a structure in which the first electrode 32 is provided on one of two adjacent fine-structure bodies 14 and the second electrode 30 is provided on the other fine-structure body 14 can be exemplified.

[0242] Or, if Fig.10 As conceptually shown in FIG. 1 , in two adjacent fine-structure bodies 14 , the first electrode 32 may be provided between one fine-structure body 14 and the support 16 , and the second electrode 30 may be provided between the other fine-structure body 14 and the support 16 .

[0243] The transmission-type electromagnetic wave controlling element may have a plurality of metasurface structures.

[0244] For example, Fig.11 As shown, in Figure 8In the electromagnetic wave control element 36 shown, the microstructure 14 can be arranged on the surface of the support 24 opposite to the liquid crystal layer 20 as the super surface structure 12. In this example, as an example, the microstructure 14 facing each other across the liquid crystal layer 20 functions as an electrode pair, i.e., the first electrode and the second electrode.

[0245] exist Fig.11 In the illustrated structure, the first electrode 32 and the second electrode 30 may be provided corresponding to the fine structure 14 .

[0246] As an example, the structure Fig.12 As conceptually shown in FIG. 1 , a structure in which a first electrode 32 is provided on the surface of one microstructure 14 and a second electrode 30 is provided on the surface of the other microstructure 14 is exemplified in which two microstructures 14 constituting an electrode pair facing each other via a liquid crystal layer 20 are shown.

[0247] Or, if Fig.13 As conceptually shown in FIG. 1 , in two fine-structure bodies 14 constituting an electrode pair facing each other via the liquid crystal layer 20 , a first electrode 32 may be provided between one fine-structure body 14 and the support 16 , and a second electrode 30 may be provided between the other fine-structure body 14 and the support 16 .

[0248] like Fig.14 As conceptually shown in FIG. 1 , in a transmission-type electromagnetic wave control element having a plurality of metasurface structures, the microstructures 14 constituting the metasurface structures 12 can be arranged in a staggered manner in the surface direction. Fig.11 In the illustrated example, as an example, the fine-structure bodies 14 facing each other with the liquid crystal layer 20 interposed therebetween are made to function as a first electrode and a second electrode of an electrode pair.

[0249] And, in Fig.14 In the illustrated structure, the first electrode 32 and the second electrode 30 may be provided corresponding to the fine structure 14 .

[0250] As an example, the structure Fig.15 As conceptually shown in FIG. 1 , a structure in which a first electrode 32 is provided on the surface of one microstructure 14 and a second electrode 30 is provided on the surface of the other microstructure 14 is exemplified in which two microstructures 14 constituting an electrode pair facing each other via a liquid crystal layer 20 are shown.

[0251] Or, if Fig.16 As conceptually shown in FIG. 1 , in two fine-structure bodies 14 constituting an electrode pair facing each other via the liquid crystal layer 20 , a first electrode 32 may be provided between one fine-structure body 14 and the support 16 , and a second electrode 30 may be provided between the other fine-structure body 14 and the support 16 .

[0252] Moreover, if Fig.17 As conceptually shown in FIG. 1 , in the transmission type electromagnetic wave control element, similarly to the above-mentioned reflection type electromagnetic wave control element, the first electrode layer 26A can be provided to cover the entire surface of the support 24 on the side opposite to the liquid crystal layer 20, and an electrode pair can be formed by the fine structure 14 and the first electrode layer 26A. However, in this case, the first electrode layer 26A is a patterned electrode patterned in a manner having a plurality of openings so that electromagnetic waves can be transmitted.

[0253] Moreover, even with Fig.17 The structure of the first electrode layer 26A shown in FIG. 1 may also be such that the microstructure 14 is not used as the electrode layer, but Fig.18 As conceptually shown in FIG. 1 , the second electrode 30 is provided on the microstructure 14 , and the first electrode layer 26A and the second electrode 30 constitute an electrode pair.

[0254] Furthermore, the transmission type electromagnetic wave control element can be Fig.19 As conceptually shown in FIG. 1 , the microstructure 14 is provided to penetrate the electromagnetic wave control element in the thickness direction, rather than being arranged on the surface of the support. In addition, in this structure, as in the above-mentioned examples, the microstructure 14 can also serve as an electrode, or the first electrode and / or the second electrode can be arranged corresponding to each microstructure 14.

[0255] Or, in Fig.19 In the structure shown, Fig. 20 As shown, a dielectric layer 34 may be provided on the side of the support 24 opposite to the liquid crystal layer 20 , and a first electrode layer 26A patterned to have a plurality of openings for transmitting electromagnetic waves may be provided on the side of the dielectric layer 34 opposite to the support 24 .

[0256] Here, in the above example, the electromagnetic wave controlling element reflects the electromagnetic wave and controls the reflection direction of the electromagnetic wave. However, the electromagnetic wave controlling element of the present invention is not limited to this.

[0257] Fig.26 FIG. 1 is a diagram conceptually showing another example of the electromagnetic wave control element of the present invention. Fig. 27 yes Fig.26 A schematic three-dimensional diagram of an electromagnetic wave controlling element is shown.

[0258] Fig.26 and Fig. 27 The electromagnetic wave control element 50 shown in the figure has a waveguide 52, a liquid crystal layer 20, and a metasurface structure 12 (microstructure 14) in this order from the bottom. The liquid crystal layer 20 is provided on a part of the outer side surface of the waveguide 52. Fig.26 and Fig. 27In the electromagnetic wave controlling element 50 shown, the waveguide 52 is a waveguide tube made of a conductor such as metal, and the waveguide 52 also serves as the first electrode (first electrode layer) in the present invention.

[0259] In addition, Fig.26 and Fig. 27 In the electromagnetic wave control element 50 shown in FIG. Figure 1 The same parts of the electromagnetic wave controlling element 10 shown are denoted by the same reference numerals, and the following description will mainly focus on the different parts.

[0260] and, Fig.26 and Fig. 27 The electromagnetic wave controlling element 50 shown does not include the support 16 and the support 24 , but in this example, it may include the support 16 and / or the support 24 as necessary.

[0261] exist Fig.26 and Fig. 27 In the electromagnetic wave controlling element 50 shown, the waveguide 52 is a cylindrical member having a rectangular cross section and is a metal waveguide that guides the electromagnetic wave RW in a hollow portion.

[0262] The electromagnetic wave RW propagates in the waveguide 52 while forming an electromagnetic field corresponding to the shape and size of the waveguide 52 , the wavelength (frequency) of the electromagnetic wave RW, and the like.

[0263] The waveguide 52 has a plurality of openings 54 communicating between the hollow portion and the outside on the wall portion on which the liquid crystal layer 20 and the fine-structure body 14 are stacked, that is, on the surface facing the fine-structure body 14 and functioning as the first electrode.

[0264] The openings 54 are provided at positions corresponding to the unit cells (ie, the microstructures 14 ), respectively.

[0265] Since the waveguide 52 has a plurality of openings 54 , the electromagnetic wave RW guided in the hollow portion of the waveguide 52 leaks out from the openings 54 and is released to the outside. At this time, the electromagnetic wave RW passes through the liquid crystal layer 20 .

[0266] In the electromagnetic wave control element 50, Figure 1 Similarly, the electromagnetic wave control element 10 shown can control the direction of travel of the electromagnetic wave RW by controlling the phase delay amount for each unit cell through phase modulation. That is, the electromagnetic wave control element 50 can control the emission direction of the electromagnetic wave RW. Furthermore, by actively changing the phase delay amount in each unit cell, the emission direction of the electromagnetic wave RW can be actively changed.

[0267] In addition, Fig.26 and Fig. 27In the example shown, the cross-sectional shape of the waveguide 52 is set to a rectangular shape, but the present invention is not limited to this, and various shapes such as a square, a circle, and a polygon can be set.

[0268] Furthermore, the size of the waveguide 52 is not particularly limited.

[0269] Furthermore, the length of the waveguide 52 is preferably 1 to 10000 mm, and more preferably 3 to 3000 mm.

[0270] And, if Fig.26 and Fig. 27 In the example shown, when the waveguide 52 also serves as the first electrode, the waveguide 52 can be formed of the same material (conductor) as the material forming the first electrode.

[0271] And, in Fig.26 and Fig. 27 In the example shown, the waveguide 52 also serves as the first electrode. However, the present invention is not limited to this, and the waveguide and the first electrode may be separate bodies.

[0272] When the waveguide 52 is separate from the first electrode, the waveguide 52 is disposed on the surface of the first electrode opposite to the liquid crystal layer 20. When the waveguide is separate from the first electrode, the first electrode also has an opening through which the electromagnetic wave RW passes at a position corresponding to each unit cell. In addition, in the waveguide, an emission portion for emitting the electromagnetic wave RW is provided at a position corresponding to the opening of the first electrode.

[0273] As the waveguide when the waveguide and the first electrode are separate bodies, in addition to the waveguide formed of the above-mentioned conductor, a conventionally known waveguide capable of guiding electromagnetic waves such as a stripline line, a microstrip line line, and a coplanar line line can be appropriately used.

[0274] Furthermore, the size of the opening formed in the first electrode is preferably 0.01 to 100,000 mm. 2 , more preferably 0.02 to 80000 mm 2 , more preferably 0.05 to 50000 mm 2 .

[0275] Furthermore, in the example shown in the figure, one opening formed in the first electrode is provided in each unit cell, but the present invention is not limited thereto, and two or more openings may be provided in each unit cell.

[0276] In the above example, the orientation pattern of the liquid crystal compound LC in the liquid crystal layer 20 is the following liquid crystal orientation pattern: when no voltage is applied, the liquid crystal compound LC is vertically oriented. If voltage is applied, the angle relative to the thickness direction becomes larger according to the applied voltage and finally becomes horizontally oriented.

[0277] However, the present invention is not limited to this, and various liquid crystal alignment patterns can be used. An example is shown below.

[0278] In addition, in the example shown below, Figure 2 Similarly, in order to simplify the functions, only the liquid crystal layer 20 , the fine-structure body 14 , and the first electrode layer 26 are shown.

[0279] In the examples shown below, the microstructure 14 and the first electrode layer 26 are shown as an example as electrodes, but the present invention is not limited to this. Figure 1 , Figure 3 to Figure 20 In all the structures shown, the liquid crystal orientation pattern shown below can be used. Figure 2 Same.

[0280] In the electromagnetic wave control element of the present invention, the liquid crystal orientation pattern of the liquid crystal layer 20 is as follows: Fig.21 As conceptually shown in , the following liquid crystal alignment pattern can also be used: when no voltage is applied, the liquid crystal compound LC is horizontally aligned, and when a voltage is applied, the angle with respect to the main surface of the liquid crystal layer 20 increases according to the applied voltage and finally becomes vertically aligned.

[0281] Furthermore, as the liquid crystal orientation pattern of the liquid crystal layer 20, Fig. 22 As conceptually shown in , the following liquid crystal orientation pattern can also be used: when no voltage is applied, the liquid crystal compound LC is horizontally oriented and spirally twisted in the thickness direction. If a voltage is applied, the angle relative to the main surface of the liquid crystal layer 20 becomes larger according to the applied voltage, and finally becomes vertically oriented.

[0282] Furthermore, as the liquid crystal orientation pattern of the liquid crystal layer 20, Fig.23 As conceptually shown in FIG. 1 , it is also possible to utilize a hybrid orientation in which the orientation of the liquid crystal compound LC changes from a horizontal orientation to a vertical orientation in the thickness direction. In the case of this liquid crystal orientation pattern, as an example, Fig.23 As shown, a structure can be exemplified in which, when a voltage is applied from a state where no voltage is applied, the alignment of the liquid crystal compound LC approaches a vertical alignment according to the applied voltage.

[0283] Furthermore, in the electromagnetic wave control element of the present invention, Figure 8 to Figure 10 As shown, a voltage may be applied to the surface direction of the liquid crystal layer 20 .

[0284] In this structure, if Fig.24As conceptually shown in the figure, the following liquid crystal orientation pattern can also be used: when no voltage is applied, the length direction of the liquid crystal compound LC is aligned with the direction perpendicular to the paper surface and is horizontally oriented. If voltage is applied, it rotates in the surface direction according to the applied voltage, and finally the length direction is aligned with the horizontal direction in the figure and is horizontally oriented.

[0285] Or, on the contrary, Fig.25 As conceptually shown in the figure, the following liquid crystal orientation pattern can also be used: when no voltage is applied, the length direction of the liquid crystal compound LC is aligned with the horizontal direction in the figure and is horizontally oriented. If voltage is applied, it rotates in the surface direction according to the applied voltage, and finally the length direction is aligned with the direction perpendicular to the paper surface and is horizontally oriented.

[0286] The polarization state (polarization wave state) of the electromagnetic wave that the electromagnetic wave controlling element of the present invention is used for is not limited, and may be unpolarized light, linearly polarized light, circularly polarized light, or elliptically polarized light.

[0287] When the electromagnetic wave is linearly polarized light and the fine-structure bodies 14 are two-dimensionally arranged in the orthogonal x and y directions, the electromagnetic wave is preferably incident so that the polarization direction of the electromagnetic wave coincides with the x or y direction.

[0288] As mentioned above, the electromagnetic wave controlling element of the present invention has been described in detail, but the present invention is not limited to the above-mentioned examples, and various improvements and changes can be made without departing from the scope of the present invention.

[0289] Example

[0290] Hereinafter, the present invention will be described in further detail based on examples.

[0291] The materials, usage amounts, ratios, treatment contents, and treatment procedures shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following examples.

[0292] [Example]

[0293] Using optical simulation software, we created Fig.28 The model of the electromagnetic wave control element shown (electromagnetic wave control element model 10A) was simulated using finite element method simulation software "COMSOL Multiphysics" by COMSOL.

[0294] The electromagnetic wave control element to be modeled is a structure in which the first electrode layer 26, the liquid crystal layer 20, and the microstructure 14 (supersurface structure 12) are sequentially stacked. The size of one unit cell is set to 1.1 mm×1.1 mm, and the unit cells are infinitely arranged in the in-plane direction by applying periodic boundary conditions.

[0295] The first electrode layer 26 and the fine structure 14 are made of copper and have a thickness of 2 μm. The size of one fine structure 14 is a square of 0.8 mm×0.8 mm and is arranged substantially at the center of the unit cell in the in-plane direction.

[0296] The liquid crystal layer 20 is formed using a liquid crystal composition in which the following compound 1 (liquid crystal compound 1) and compound 2 (liquid crystal compound 2) are mixed at a ratio of 50%:50%.

[0297] Here, Δn of the liquid crystal composition of the example was measured by the following method.

[0298] First, the liquid crystal composition was sealed in a glass cell (10 mm × 10 mm, 1.0 mm thick) formed by sputtering a tin oxide (SnO2) film as an electrode. Then, an optical system for transmission-type terahertz spectroscopy was made, and the time waveform of the photoelectric field was measured under a temperature of 100°C and a humidity of 10% RH. Based on the change in the time waveform of the photoelectric field before and after the voltage was applied, the Δn of the liquid crystal composition sealed in the glass cell was measured. The Δn of the liquid crystal composition was 0.35.

[0299] [Chemical formula 2]

[0300]

[0301] [Chemical formula 3]

[0302]

[0303] [Comparative Example]

[0304] The same electromagnetic wave control element as in Example 1 was modeled except that the liquid crystal compound of the liquid crystal composition for forming the liquid crystal layer was changed to 4′-pentyl-4-biphenylcarbonitrile (5CB).

[0305] In addition, an optical system for transmission-type terahertz spectroscopy was prepared in the same manner as in the example, and the time waveform of the photoelectric field was measured in an environment of temperature 25°C and humidity 10% RH. Based on the change in the time waveform of the photoelectric field before and after the voltage was applied, the Δn of the liquid crystal composition sealed in the glass cell was measured. Δn was 0.2.

[0306] [evaluate]

[0307] Using the simulation software “COMSOL Multiphysics”, the reflection phase of the 100 GHz electromagnetic wave when the 100 GHz electromagnetic wave is incident on and reflected from the model of the electromagnetic wave controlling element of the above-described embodiment and comparative example is calculated.

[0308] The difference in reflection phase accompanying voltage application was calculated for the case where no voltage was applied and the liquid crystal compound LC was horizontally aligned and the case where voltage was applied and the liquid crystal compound LC was vertically aligned. The minimum film thickness at which the difference in reflection phase accompanying voltage application became 180° was calculated for the case where the film thickness of the liquid crystal layer was 10 to 300 μm.

[0309] Furthermore, it is known that the switching time when the alignment state of the liquid crystal compound is changed by applying a voltage to the liquid crystal layer is proportional to the square of the thickness.

[0310] The switching time in the electromagnetic wave controlling element of the comparative example was set to 1, and the switching time in the example and the comparative example was calculated.

[0311] The results are shown in Table 1 below.

[0312] [Table 1]

[0313]

[0314] As can be seen from Table 1, the embodiment of the present invention can achieve both shortening the switching time and suppressing the loss of electromagnetic waves compared with the comparative example.

[0315] Industrial Applicability

[0316] The present invention can be preferably used in a light beam steering device or the like.

[0317] Explanation of symbols

[0318] 10, 36 - element for electromagnetic wave control, 12 - super surface structure, 14, 100a - microstructure, 16, 24 - support body, 20, 104 - liquid crystal layer, 26, 26A - first electrode layer, 28 - power supply, 30 - second electrode, 32 - first electrode, 34 - dielectric layer, LC - liquid crystal compound.

Claims

1. An electromagnetic wave control element, comprising: 1st electrode; a liquid crystal layer, the orientation state of the liquid crystal compound changes according to a voltage; and The super surface structure is composed of multiple micro structures. The electromagnetic wave control element acts on electromagnetic waves with a frequency of 0.1 to 0.3 THz, and the liquid crystal layer contains an azo compound.

2. The electromagnetic wave control element according to claim 1, wherein: The azo compound has two or more azo structures.

3. The electromagnetic wave control element according to claim 1 or 2, wherein: The liquid crystal layer includes a liquid crystal compound having an azo structure.

4. The electromagnetic wave control element according to claim 1 or 2, wherein: The electromagnetic wave controlling element further includes a second electrode, and the second electrode and the first electrode form an electrode pair.

5. The electromagnetic wave control element according to claim 4, wherein: At least one of the first electrode and the second electrode is the microstructure.

6. The electromagnetic wave control element according to claim 1 or 2, wherein: The microstructure and the first electrode form an electrode pair.

7. The electromagnetic wave control element according to claim 1 or 2, wherein: The first electrode reflects electromagnetic waves with a frequency of 0.1 to 0.3 THz.

8. The electromagnetic wave control element according to claim 1 or 2, wherein: The first electrode is a pattern electrode.

9. The electromagnetic wave control element according to claim 1 or 2, wherein: The microstructure includes metal.

10. The electromagnetic wave control element according to claim 1 or 2, wherein: The microstructure includes an oxide semiconductor.

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