Electromagnetic wave control element

Abstract

This electromagnetic wave control element is provided with: a liquid crystal layer in which the alignment state of a liquid crystal compound changes in accordance with a voltage; a metasurface structure in which a plurality of fine structures are arranged; and an electrode pair that is configured from a first electrode and a second electrode and that applies a voltage, the electromagnetic wave control element acts on electromagnetic waves having a frequency of 0.1-0.3 THz, and the liquid crystal layer contains a methine compound.

Description

Technical Field

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

[0002] Electromagnetic waves, such as high-frequency radio waves (millimeter waves and terahertz waves) required for high-capacity wireless communications, tend to be highly linear. Therefore, reflectors are needed that can bend the direction of travel of electromagnetic waves into any desired orientation. However, conventional reflectors reflect electromagnetic waves in a fixed, mirror-like manner with equal angles of incidence and emission. This significantly limits the range of electromagnetic wave direction changes, making it difficult for the waves to reach the intended destination.

[0003] Therefore, a non-patent document (Jingbo Wu et al., Liquid crystal programmable metasurface for terahertz beam steering, Applied Physics Letters, 116, 131104 (2020)) describes an electromagnetic wave steering element that, by utilizing a metasurface structure, can change the reflection direction of electromagnetic waves to a direction other than specular reflection, or actively change the reflection direction. This type of electromagnetic wave steering element is also known as a beam steering element.

[0004] Metasurface structures utilize metamaterials. Metamaterials are artificial substances that exhibit properties not found in naturally occurring materials, such as a negative refractive index for electromagnetic waves. Metasurface structures are composed of an arrangement of multiple microstructures that function as metamaterials. These microstructures resonate with transmitted electromagnetic waves, modulating the phase of the electromagnetic waves through resonance. By changing the resonance conditions of the microstructures, the amount of phase modulation of the electromagnetic waves can be varied. Electromagnetic wave control elements control the phase of incident electromagnetic waves using metasurface structures to control their direction of travel.

[0005] To alter the resonance conditions of a microstructure, electromagnetic wave control elements described in non-patent literature use a liquid crystal layer. Within the liquid crystal layer, the refractive index relative to electromagnetic waves changes by altering the orientation of the liquid crystal compounds. This change in refractive index alters the resonance conditions of the microstructure. By exploiting this phenomenon, the electromagnetic wave control elements described in non-patent literature control the amount of phase modulation of electromagnetic waves by varying the refractive index of the liquid crystal layer. Summary of the Invention

[0006] Technical issues to be solved by the invention

[0007] One of the performance indicators of electromagnetic wave control components is the switching time of the electromagnetic wave's emission direction, such as the reflection direction of the electromagnetic wave. By shortening the emission direction switching time, for example, it is possible to more quickly respond to changes over time in areas with a high concentration of wireless communication users. With the expected increase in user demand for wireless communication, there is a need to further shorten the emission direction switching time.

[0008] The technology of the present invention provides an electromagnetic wave control element having a metasurface structure using a liquid crystal layer, which can switch the emission direction of electromagnetic waves with a frequency of 0.1 to 0.3 THz in a shorter time than before.

[0009] Means for solving technical problems

[0010] The electromagnetic wave control element involved in the technology of the present invention comprises: a liquid crystal layer, the orientation state of the liquid crystal compound of which changes according to the voltage; a metasurface structure composed of a plurality of arranged microstructures; and an electrode pair composed of a first electrode and a second electrode, and used to apply voltage. 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 a methyl compound.

[0011] The methine compound may have a methine structure.

[0012] The liquid crystal layer may include a liquid crystal compound having a methine structure.

[0013] At least one of the first electrode and the second electrode may be a microstructure.

[0014] The first electrode and the second electrode may be provided as independent elements from the microstructure.

[0015] One of the first electrode and the second electrode may be a pattern electrode.

[0016] The microstructure may contain metal.

[0017] The microstructure may include an oxide semiconductor.

[0018] An electric field caused by a voltage can be generated in the thickness direction of the liquid crystal layer.

[0019] An electric field caused by the voltage can be generated in a direction intersecting the thickness direction of the liquid crystal layer.

[0020] It may be a reflective type that reflects electromagnetic waves.

[0021] One of the first electrode and the second electrode may also serve as a reflection layer that reflects electromagnetic waves.

[0022] It may be a transmission type that transmits electromagnetic waves.

[0023] A waveguide may be provided for guiding incident electromagnetic waves in a direction along the arrangement direction of the microstructures, and for emitting a portion of the electromagnetic waves guided in the waveguide in a direction intersecting the arrangement direction.

[0024] An opening for emitting electromagnetic waves may be formed in a portion of a wall surface defining the waveguide.

[0025] The waveguide member constituting the waveguide can function as the first electrode or the second electrode.

[0026] The opening can function as a microstructure.

[0027] Effects of the Invention

[0028] According to the electromagnetic wave control element of the present invention, in an electromagnetic wave control element having a metasurface structure using a liquid crystal layer, the reflection direction of electromagnetic waves with a frequency of 0.1 to 0.3 THz can be switched in a shorter time than before. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram showing an example of use of an electromagnetic wave control element.

[0030] Figure 2 This is a diagram showing an example of a metasurface structure used in an electromagnetic wave control element.

[0031] Figure 3 This is a diagram explaining the mechanism by which the emission direction of electromagnetic waves is changed in the electromagnetic wave controlling element.

[0032] Figure 4 This is a diagram conceptually showing an example of an electromagnetic wave control element.

[0033] Figure 5 This is a diagram conceptually showing an example of a liquid crystal alignment pattern in an electromagnetic wave controlling element.

[0034] Figure 6 This is a diagram showing the relationship between the applied voltage and the amount of phase delay of the electromagnetic wave.

[0035] Figure 7 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0036] Figure 8 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0037] Figure 9 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0038] Figure 10 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0039] Figure 11 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0040] Figure 12 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0041] Figure 13 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0042] Figure 14 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0043] Figure 15 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0044] Figure 16 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0045] Figure 17 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0046] Figure 18 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0047] Figure 19 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0048] Figure 20 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0049] Figure 21 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0050] Figure 22 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0051] Figure 23 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0052] Figure 24 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0053] Figure 25 This is a diagram conceptually showing another example of a liquid crystal alignment pattern in an electromagnetic wave controlling element.

[0054] Figure 26This is a diagram conceptually showing another example of a liquid crystal alignment pattern in an electromagnetic wave controlling element.

[0055] Figure 27 This is a diagram conceptually showing another example of a liquid crystal alignment pattern in an electromagnetic wave controlling element.

[0056] Figure 28 This is a diagram conceptually showing another example of a liquid crystal alignment pattern in an electromagnetic wave controlling element.

[0057] Figure 29 This is a diagram conceptually showing another example of a liquid crystal alignment pattern in an electromagnetic wave controlling element.

[0058] Figure 30 This is a diagram showing a leaky-wave antenna using an electromagnetic wave controlling element.

[0059] Figure 31 It is conceptually shown Figure 30 A plan view of an example of an electromagnetic wave control element.

[0060] Figure 32 It is conceptually shown Figure 31 A three-dimensional diagram of a subunit of an electromagnetic wave control element.

[0061] Figure 33 It is conceptually shown Figure 32 A diagram of an example of a subunit of .

[0062] Figure 34 It is conceptually shown Figure 32 A diagram of another example of a subunit of .

[0063] Figure 35 It is conceptually shown Figure 30 Figure 2 is a diagram of another example of an electromagnetic wave control element.

[0064] Figure 36 This is a diagram schematically showing a method for measuring switching time. DETAILED DESCRIPTION

[0065] exist Figure 1The electromagnetic wave reflecting device 2 shown utilizes an electromagnetic wave control element 10 according to the present invention. The electromagnetic wave reflecting device 2 is capable of reflecting highly linear electromagnetic waves RW radiated from an antenna ANT located behind a building BL toward an area AR1 in front of the building BL, which is shaded when viewed from the antenna ANT. Furthermore, the electromagnetic wave reflecting device 2 is capable of varying the reflection direction of the electromagnetic waves RW to different directions in multiple areas AR1 and AR2. For example, the user concentration area may vary depending on the time of day, such as the number of users utilizing wireless communication being more concentrated in area AR1 during daytime hours and more concentrated in area AR2 during nighttime hours. In this case, the electromagnetic wave reflecting device 2 can change the area to which the electromagnetic waves RW are supplied by varying the reflection direction of the electromagnetic waves RW according to the time of day.

[0066] like Figure 2 As shown, the electromagnetic wave control element 10 is a reflective electromagnetic wave control element having a metasurface structure 12 and reflecting the direction of travel of the electromagnetic wave RW in the desired direction. The metasurface structure 12 is a structure that utilizes a metamaterial. Metamaterials refer to artificial substances that exhibit properties not found in natural materials, such as a negative refractive index for electromagnetic waves. The electromagnetic wave control element 10 is a structure composed of a plurality of unit cells UC arranged in two dimensions, and the two-dimensional plane formed by the arrangement of the plurality of unit cells UC serves as a reflection surface for the electromagnetic wave RW. Each unit cell UC includes a microstructure 14 as a metamaterial, which constitutes the smallest unit on the reflection surface that can actively change the phase of the electromagnetic wave RW. As an example, the microstructure 14 is made of metal. The microstructure 14 has a size on the order of less than the wavelength of the incident electromagnetic wave RW and functions as a resonator that resonates through interaction with the incident electromagnetic wave RW. Electrically, the microstructure 14 can be considered to be equivalent to a resonant circuit in which a coil and a capacitor are connected in series to cause an alternating current to resonate. The phase of the incident electromagnetic wave RW changes due to the resonance of the microstructure 14. Furthermore, the delay amount of the phase of the electromagnetic wave RW can be controlled by actively changing the resonance conditions of the microstructure 14 using various methods.

[0067] The electromagnetic wave control element 10 acts on electromagnetic waves RW with a frequency of 0.1 to 0.3 THz. The electromagnetic waves RW in this frequency band are also called high-frequency radio waves (millimeter waves or terahertz waves), etc., which can perform high-capacity wireless communication. On the other hand, they have high straightness. In the electromagnetic wave control element 10, the metasurface structure 12 is configured to act on electromagnetic waves RW with a frequency of 0.1 to 0.3 THz. The wavelength of the electromagnetic wave RW with a frequency of 0.1 to 0.3 THz is 1 to 3 mm. As an example, the size of the fine structure 14 constituting the metasurface structure 12 is on the order of about 1 / 2 of the wavelength. By setting the size of the fine structure 14 to be less than the wavelength of the electromagnetic wave RW, the fine structure 14 resonates through the transmitted electromagnetic wave RW and acts as a phase modulation element that modulates the phase of the electromagnetic wave RW.

[0068] exist Figure 3 In the figure, as exemplified by the incident direction IN and the emission direction OUT, the overall traveling direction of the electromagnetic wave RW can be considered to be the normal direction relative to the straight line connecting the wavefronts of the multiple electromagnetic waves RW. Moreover, it can be considered that in the electromagnetic wave control element 10, for example, the phase delay amount of the electromagnetic wave RW incident on and reflected on each of the multiple unit cells UC arranged in one dimension is gradually increased from the unit cell UC in the right direction toward the unit cell UC in the left direction. In this way, even when the straight line connecting the wavefronts of the incident electromagnetic waves RW is parallel to the reflection surface, the straight line connecting the wavefronts of the electromagnetic waves RW reflected in each unit cell UC will be tilted relative to the reflection surface. That is, the traveling direction of the electromagnetic wave RW emitted from the reflection surface, that is, the emission direction OUT, only changes by an angle θ relative to the incident direction IN of the electromagnetic wave RW. In this way, by performing phase modulation on each unit cell UC, that is, controlling the phase delay amount, the traveling direction of the electromagnetic wave RW can be controlled.

[0069] As a result, while conventional reflectors can only change the direction of electromagnetic wave RW to the direction of specular reflection, the electromagnetic wave reflecting device 2 can change the direction of electromagnetic wave RW to directions other than specular reflection by using the metasurface structure 12. Furthermore, by actively changing the phase delay in each unit cell UC, the direction of electromagnetic wave RW can be actively changed.

[0070] As an example, Figure 4As conceptually shown in FIG, the electromagnetic wave control element 10 uses a liquid crystal layer 20 as a key element for actively changing the resonance conditions of the microstructures 14 of the metasurface structure 12. The electromagnetic wave control element 10 includes, from the bottom of the figure, a first electrode layer 26, a liquid crystal layer 20, and a metasurface structure 12 including a plurality of microstructures 14. The liquid crystal layer 20 is provided on a support 24. Furthermore, the first electrode layer 26 is provided so as to entirely cover the surface of the support 24 opposite to the liquid crystal layer 20.

[0071] Each unit cell UC is composed of a microstructure 14, a liquid crystal layer 20, and a first electrode layer 26. The microstructure 14 is provided separately for each unit cell UC. The remaining components, including the support 16, liquid crystal layer 20, support 24, and first electrode layer 26, are not separate structures for each unit cell UC but are formed integrally with the regions corresponding to the multiple unit cells UC.

[0072] In the electromagnetic wave control element 10, the first electrode layer 26 and the support 24, and the liquid crystal layer 20 and the support 16 are bonded together using an adhesive (tackifier or adhesive) as needed. The bonding method is not limited, and various known methods that allow the electromagnetic wave to be controlled by the electromagnetic wave control element 10 to pass through can be used, such as using an optical clear adhesive (OCA) that allows the electromagnetic wave to be controlled by the electromagnetic wave control element 10 to pass through.

[0073] As an example, the microstructure 14 is formed of a conductive material and also serves as an electrode that forms an electrode pair with the first electrode layer 26. In addition, a power supply 28 for applying a voltage between the microstructure 14 and the first electrode layer 26 is connected to each microstructure 14. Therefore, the magnitude of the voltage applied to each unit cell UC can be controlled. The first electrode layer 26 is a common electrode shared by each unit cell UC, and the microstructure 14 of each unit cell UC functions as an individual electrode. The first electrode layer 26 that functions as a common electrode is an example of the "first electrode" involved in the technology of the present invention, and the individual electrode that is also used by the microstructure 14 is an example of the "second electrode". The microstructure 14 that serves as the second electrode and the first electrode layer 26 that serves as the first electrode are an example of an "electrode pair for applying a voltage."

[0074] The electromagnetic wave controlling element 10 is a reflection type, and the first electrode layer 26 also serves as a reflection layer that reflects the electromagnetic wave RW.

[0075] The liquid crystal layer 20 changes its orientation state (hereinafter also referred to as an orientation pattern) by applying a voltage. The arrangement direction of the fine structure 14 of each unit cell UC is a direction (X direction or Y direction in the figure) orthogonal to the thickness direction of the liquid crystal layer 20 (Z direction in the figure). The fine structure 14 and the first electrode layer 26 are arranged on both sides of the thickness direction of the liquid crystal layer 20. By supplying power from the power supply 28, a voltage is applied between the fine structure 14 of each unit cell UC and the first electrode layer 26. By applying the voltage, an electric field is generated in the thickness direction of the liquid crystal layer 20, thereby changing the orientation state of the liquid crystal compound LC of each unit cell UC. In addition, by adjusting the voltage applied to each unit cell UC, the orientation state of the liquid crystal compound LC of each unit cell UC can be adjusted.

[0076] like Figure 5 As shown in FIG, the cross section of the liquid crystal compound LC is substantially elliptical with a major axis and a minor axis. For example, when no voltage is applied between the microstructure 14 and the first electrode layer 26, which function as an electrode pair, no electric field is generated in the liquid crystal layer 20. In this state, as shown in FIG. Figure 5 As conceptually shown in the upper section of FIG, the liquid crystal compound LC is aligned with its major axis along the thickness direction of the liquid crystal layer 20. In the following description, this alignment state is also referred to as "vertical alignment."

[0077] When a voltage is applied between the fine structure 14 and the first electrode layer 26 in this state, an electric field is generated in the liquid crystal layer 20, and the alignment state of the liquid crystal compound LC changes. Figure 5 As conceptually shown in the lower section of FIG, the liquid crystal compound LC in the region corresponding to the fine structure 14 changes its orientation state according to the magnitude of the applied voltage and tilts relative to the thickness direction of the liquid crystal layer 20. Figure 5 The example shown in the lower section of FIG. 1 shows a state in which the tilt angle of the liquid crystal compound LC is at its maximum. In this state, the liquid crystal compound LC is aligned with its major axis perpendicular to the thickness direction of the liquid crystal layer 20. In the following description, the alignment state in which the tilt angle is at its maximum is also referred to as "horizontal alignment."

[0078] The larger the tilt of the liquid crystal compound LC is, that is, the closer the long axis of the liquid crystal compound LC is to the main surface direction of the liquid crystal layer 20 (in the direction of the liquid crystal layer 20). Figure 5 The larger the angle (in the X direction or Y direction in the figure), the greater the refractive index of the liquid crystal layer 20. Conversely, the smaller the tilt of the liquid crystal compound LC, that is, the closer the long axis of the liquid crystal compound LC is to the thickness direction of the liquid crystal layer 20 (the Z direction in the figure), the smaller the refractive index of the liquid crystal layer 20. By changing the refractive index of the liquid crystal layer 20 in each unit cell UC, the resonance condition of the fine structure 14 changes, and the phase delay of the incident electromagnetic wave RW changes. In this example, Figure 5 The phase delay of the lower unit cell UC is greater than Figure 5 The unit cell UC in the upper section is large.

[0079] That is, in the liquid crystal layer 20 located around the microstructure 14 of each unit cell UC, if the orientation state of the liquid crystal compound LC changes, the refractive index of the liquid crystal layer 20 with respect to the electromagnetic wave RW that transmits each unit cell UC changes. Moreover, since there is a positive correlation between the refractive index and the dielectric constant, the resonance condition of the microstructure 14 that acts as a resonator changes due to the change in the refractive index of the liquid crystal layer 20. The change in the resonance condition of the microstructure 14 is reflected in the form of a change in the phase delay of the electromagnetic wave RW. Therefore, by changing the refractive index of the liquid crystal layer 20, the phase delay of the electromagnetic wave RW can be changed. Moreover, the change in the refractive index of the liquid crystal layer 20 itself also causes a change in the phase delay of the electromagnetic wave RW. The refractive index of the liquid crystal layer 20 of each unit cell UC changes according to the voltage V applied to each unit cell UC, so as an example, the relationship between the voltage V and the phase delay of the electromagnetic wave RW becomes as follows. Figure 6 shown.

[0080] like Figure 3 As shown, if the electromagnetic wave RW is incident on the electromagnetic wave control element 10 from the side of the microstructure 14, the electromagnetic wave RW sequentially transmits the microstructure 14 and the liquid crystal layer 20. Moreover, the electromagnetic wave RW is reflected at the first electrode layer 26 which also serves as a reflective layer, and sequentially transmits the liquid crystal layer 20 and the microstructure 14 again, and is emitted from the electromagnetic wave control element 10. The electromagnetic wave RW is reflected through this incident / emission path. In the incident / emission path, for the electromagnetic wave RW that transmits each unit cell UC, phase modulation caused by the resonance of the microstructure 14 and phase modulation caused by the transmission of the liquid crystal layer 20 are generated. In more detail, in each unit cell UC, the resonance condition of the microstructure 14 is determined according to the refractive index of the liquid crystal layer 20, and the phase modulation of the electromagnetic wave RW is generated by the resonance corresponding to the condition. In addition, phase modulation of the electromagnetic wave RW corresponding to the magnitude of the refractive index of the liquid crystal layer 20 is also generated.

[0081] according to Figure 6 According to the relationship shown, the phase delay amount of the electromagnetic wave RW is controlled for each unit cell UC by the applied voltage V, thereby controlling the reflection direction of the electromagnetic wave RW reflected by the electromagnetic wave controlling element 10 .

[0082] Also like Figure 3As shown, in a conventional reflector, the propagation direction of the electromagnetic wave RW can only be changed to the direction of specular reflection. As a result, by using the metasurface structure 12 in the electromagnetic wave control element 10, the propagation direction of the electromagnetic wave RW can be changed to directions other than specular reflection. Furthermore, by actively changing the phase delay in each unit cell UC, the propagation direction of the electromagnetic wave RW can be actively changed.

[0083] Furthermore, the direction of travel of the electromagnetic wave RW emitted from the electromagnetic wave control element 10 is controlled in addition to the following Figure 3 In addition to controlling the reflected electromagnetic wave RW so that it travels straight in one direction as a whole, as in the example shown, various other examples are possible. For example, the electromagnetic wave RW emitted from the electromagnetic wave control element 10 can be focused toward a focal point or diverged in the opposite direction. Controlling the direction of travel of the emitted electromagnetic wave RW can be achieved by adjusting the voltage applied to each unit cell UC to adjust the phase delay of the electromagnetic wave RW for each unit cell UC.

[0084] For example, consider the following situation: Figure 3 As shown, in the case where there are multiple unit cells UC arranged in one direction, the phase delay amount of the central unit cell UC is increased, and the phase delay amount is reduced toward both sides. In this case, if the wavefront of the electromagnetic wave RW that passes through each unit cell UC is connected, it becomes a V shape, so that the emitted electromagnetic wave RW can be focused. And, on the contrary, consider the following situation: reduce the phase delay amount of the central unit cell UC, and increase the phase delay amount toward both sides. In this case, if the wavefront of the electromagnetic wave RW that passes through each unit cell UC is connected, it becomes a mountain shape (inverted V shape), so that the emitted electromagnetic wave RW can be diverged. The degree of such focusing and divergence can also be adjusted by adjusting the magnitude of the applied voltage to control the phase delay amount of the electromagnetic wave RW that passes through each unit cell UC.

[0085] Similar to the known metasurface structure, the metasurface structure 12 is formed by two-dimensionally arranging the microstructure 14 as the metamaterial on the support 16. In the metasurface structure 12 shown in the figure, Figure 2 As shown, the fine structures 14 are two-dimensionally arranged at equal intervals in the mutually orthogonal X and Y directions. In addition, in the metasurface structure 12, as an example, all the fine structures 14 are identical.

[0086] The support 16 is not limited, and any known sheet-like material can be used as long as it can support the microstructure 14 and transmit the electromagnetic wave RW having a frequency of 0.1 to 0.3 THz, which is the control target of the electromagnetic wave control element 10. Examples of the support 16 include a metal substrate having an oxide insulating layer such as a silicon substrate containing silicon oxide, a support composed of an oxide such as silicon oxide, a support composed of a semiconductor such as germanium or chalcogenide glass, a polyacrylic resin film such as polymethyl methacrylate, a cellulose resin film such as cellulose triacetate, a cycloolefin polymer film (e.g., "ARTON" manufactured by JSR Corporation, "ZEONOR" manufactured by Zeon Corporation), a resin film such as polyethylene terephthalate (PET) film, a polycarbonate film, and a polyvinyl chloride film, and a glass plate.

[0087] The thickness of the support 16 is also not limited, as long as it can support the microstructure 14 and provide sufficient transmittance for electromagnetic waves RW with a frequency of 0.1 to 0.3 THz, and further provide sufficient strength depending on the application of the electromagnetic wave control element 10. The thickness of the support 16 can be appropriately set according to the material forming the support 16 to meet these conditions.

[0088] Furthermore, in the electromagnetic wave control element 10 according to the present invention, the support 16 is not an essential component of the metasurface structure 12 and may be absent. For example, if possible, the metasurface structure 12 may be formed by directly arranging the microstructure 14 on the surface of the liquid crystal layer 20.

[0089] As described above, the metasurface structure 12 is a structure in which the fine structures 14 as metamaterials are separated and two-dimensionally arranged on a plane. More specifically, it is basically composed of an arrangement of unit cells UC, each of which is a fine structure 14 and the space around the fine structure 14.

[0090] In the electromagnetic wave control element 10 involved in the technology of the present invention, the morphology of the metasurface structure is basically the same as the known metasurface structure. Therefore, in the electromagnetic wave control element 10 involved in the technology of the present invention, various known metasurface structures can be used. That is, in the technology of the present invention, there are no restrictions on the shape and forming material of the fine structure 14, the arrangement of the fine structure 14, and the spacing, i.e., the pitch, of the fine structure 14. Moreover, the metasurface structure 12 can be designed according to the wavelength of the electromagnetic wave RW that is the control object of the electromagnetic wave control element 10 and the target reflection characteristics (for example, the range of the reflection direction that can be controlled) and by a known method. As an example, commercially available simulation software is used to calculate the amplitude and phase of the electromagnetic wave RW reflected by the fine structure 14 used, and the arrangement of the fine structure 14 can be set in a manner that becomes the distribution of the target phase modulation amount. When the liquid crystal layer 20 is used as in this example, phase modulation occurs due to the refractive index and the interaction between the refractive index and the fine structure 14 , and the phase modulation amount is determined by the resonance characteristics of the fine structure 14 that change based on the refractive index.

[0091] The electromagnetic wave control element 10 involved in the technology of the present invention controls electromagnetic waves RW with a frequency of 0.1 to 0.3 THz. Therefore, in the metasurface structure 12, the microstructures 14 are selected in such a way as to impart a desired phase difference to the electromagnetic waves RW of this frequency, and the arrangement of the microstructures is then set. Specifically, when the electromagnetic waves RW with a frequency of 0.1 to 0.3 THz are used as the control target, the wavelength range of the electromagnetic waves RW is approximately 1 to 3 mm, so the size of the microstructures 14 is also selected to be below this wavelength range.

[0092] The number of microstructures 14 contained in a single unit cell UC is essentially one, but the technology of the present invention is not limited to this. Specifically, in the electromagnetic wave control element according to the technology of the present invention, a single unit cell UC may contain multiple microstructures 14 as needed, depending on the reflection characteristics, the size, material, and shape of the microstructures 14, and the size of the unit cell UC. In this case, a single unit cell UC may have different microstructures 14. However, since the unit cell UC is the smallest unit capable of actively changing the phase of the electromagnetic wave RW, even when a single unit cell UC contains multiple microstructures 14, the phase modulation amount is determined for each unit cell UC.

[0093] Furthermore, the forming material of the microstructure 14 is not limited, and various materials used as microstructures in known metasurface structures can be used. As the forming material of the microstructure 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. Furthermore, as the forming material of the microstructure 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 in consideration of the fact that the refractive index is large and the phase modulation amount can be increased. In addition, as Figure 4 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.

[0094] Similarly, the shape of the microstructure 14 is not limited, and various shapes used as microstructures in known metasurface structures can be used. As an example, there can be illustrated: a cross-shaped solid such as a cross of rectangular prisms, a rectangular prism, a cylindrical shape, a V-shaped solid such as connecting rectangular prisms at the ends as shown in Japanese Patent Publication No. 2018-046395, a roughly H-shaped solid such as an H-shaped steel, and a roughly C-shaped solid such as a C-shaped channel. In addition, as shown in Japanese Patent Publication No. 2018-046395, the V-shaped solid and the cross-shaped solid can utilize various shapes by adjusting the angle between the two rectangular prisms. In addition, it is also possible to utilize "Appl.Sci.2018,8(9),1689; https: / / doi.org / 10.3390 / app8091689" Figure 5 The three-dimensional object with the bottom shape shown, etc.

[0095] In the metasurface structure 12, such microstructures 14 may be of the same type, or multiple types of microstructures 14 may be used simultaneously. Furthermore, the same microstructures 14 may be arranged in the same orientation on the XY plane, or in different orientations. Furthermore, microstructures 14 in the same orientation and microstructures 14 in different orientations may be mixed. However, in the electromagnetic wave control element 10 according to the present invention, it is preferred that only one type of microstructure 14 be used, and all microstructures 14 be arranged in the same orientation.

[0096] And, as Figure 3As shown, the preferred embodiment of the metasurface structure 12 is a method in which the same microstructures 14 having all the same structure are arranged in two dimensions at equal intervals in the X and Y directions orthogonal to each other. However, the technology of the present invention is not limited to this. As mentioned above, multiple microstructures can also be used at the same time, and the arrangement intervals and arrangements of the microstructures 14 can also be different in the surface direction of the support 16. However, if the controllability of the reflection direction of the electromagnetic wave RW when a voltage is applied to the liquid crystal layer 20 is taken into account, the metasurface structure 12 preferably uses all the same microstructures 14. Moreover, the metasurface structure 12 preferably has the microstructures 14 spaced equally apart from each other, and further preferably has the microstructures 14 spaced equally apart in the orthogonal X and Y directions.

[0097] The liquid crystal layer 20 is a layer in which the liquid crystal compound LC is aligned in a predetermined state. As described above, the alignment state of the liquid crystal compound LC changes by application of a voltage.

[0098] When no voltage is applied, Figure 4 The liquid crystal compound LC in the liquid crystal layer 20 shown in the example is vertically aligned. When a voltage is applied to the liquid crystal layer 20, the liquid crystal compound LC is aligned tilted relative to the thickness direction according to the voltage, with a maximum horizontal alignment. Furthermore, in the electromagnetic wave control element 10, the change in the alignment of the liquid crystal compound LC is not limited to changing from a vertical alignment to a horizontal alignment or vice versa. The alignment can also change from a tilted state relative to the thickness direction to a horizontal or vertical alignment, from a horizontal or vertical alignment to a tilted state relative to the thickness direction, or from a tilted state relative to the thickness direction to a tilted state relative to the thickness direction, with the angle changing.

[0099] Furthermore, the liquid crystal layer 20 may be formed on the surface of an alignment film to be described later by, for example, a known method.

[0100] In the electromagnetic wave control element 10 according to the present invention, the liquid crystal layer 20 contains a methine compound. The inclusion of the methine compound in the liquid crystal layer 20 improves the responsiveness of the electromagnetic wave control element 10, enabling it to quickly switch the reflection direction of electromagnetic waves RW with a frequency of 0.1 to 0.3 THz. These points will be described in detail later.

[0101] In the electromagnetic wave controlling element 10, the liquid crystal layer 20 is formed on a support 24. The support 24 is basically the same as the support 16 described above.

[0102] Here, the support 24 forming the liquid crystal layer 20 may be composed primarily of the support 16 and further include an alignment film on the surface of the support forming the liquid crystal layer 20 for aligning the liquid crystal compound LC in a predetermined state. Various known alignment films can be used as the alignment film. Examples include rubbing-treated films composed of organic compounds such as polymers, obliquely deposited films of inorganic compounds, films having microgrooves, and films formed by depositing Langmuir-Blodgett (LB) films of organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate using the Langmuir-Blodgett method.

[0103] Furthermore, as an alignment film, a so-called photo-alignment film can be formed by irradiating a photo-alignment material with polarized light or non-polarized light. These alignment films can be formed by a known method corresponding to the main forming material.

[0104] The entire surface of the support 24 on which the liquid crystal layer 20 is formed, which is opposite to the liquid crystal layer 20, is covered by a first electrode layer 26. 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 reflective layer that reflects electromagnetic waves RW with a frequency of 0.1 to 0.3 THz incident from the metasurface structure 12 side.

[0105] The first electrode layer 26 is not limited; as long as it has sufficient conductivity and can reflect electromagnetic waves with a frequency of 0.1 to 0.3 THz, a sheet made of various known materials can be used. Examples of the first electrode layer 26 include metal layers such as copper, aluminum, gold, and silver; inorganic conductive materials such as ITO (tin-doped indium oxide); organic conductive materials such as polythiophene represented by PEDOT (poly-3,4-ethylenedioxythiophene); and graphene. Inorganic conductive materials, organic conductive materials, and graphene are transparent to visible light, but they function as reflective layers for electromagnetic waves with the aforementioned frequencies.

[0106] 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 electromagnetic wave to be controlled at a desired reflectivity.

[0107] As described above, the electromagnetic wave control element 10 according to the present invention is a reflective electromagnetic wave control element comprising a metasurface structure 12 and a liquid crystal layer 20. In this element 10, power is supplied to each microstructure 14 to alter the alignment of the liquid crystal compound LC in the corresponding region of the liquid crystal layer 20, forming regions with different refractive indices for each unit cell UC. This allows electromagnetic waves RW with a frequency of 0.1 to 0.3 THz to be reflected in a desired direction. Furthermore, by varying the power supplied to each microstructure 14, i.e., the voltage applied to the liquid crystal layer 20, the direction of reflection of the incident electromagnetic wave RW can be switched.

[0108] As mentioned above, conventional electromagnetic wave control elements using metasurface structures and liquid crystal layers, such as those described in non-patent literature, take time to switch the reflection direction of electromagnetic waves RW. In contrast, the electromagnetic wave control element 10 according to the present invention ensures high responsiveness by including a methine compound in the liquid crystal layer 20, preferably including a liquid crystal compound having a methine structure, and more preferably forming the liquid crystal layer 20 from a liquid crystal compound having a methine structure, thereby enabling rapid switching of the reflection direction of incident electromagnetic waves RW.

[0109] That is, in the technology of the present invention, by including a methine compound in the liquid crystal layer 20, it is possible to increase Δn, an index of the anisotropy of the refractive index (also called birefringence) in the liquid crystal layer 20. Δn is the difference between the refractive index when the posture of the liquid crystal compound LC in the liquid crystal layer 20 is in the vertical direction and the refractive index when it is in the horizontal direction. By including a methine compound, Δn can be increased, so in the technology of the present invention, the thickness of the liquid crystal layer 20 required to give the electromagnetic wave RW the desired refractive index, that is, the desired phase difference, can be thinned. By thinning the liquid crystal layer 20, the orientation of the liquid crystal compound LC changes rapidly when the applied voltage is changed. As a result, the electromagnetic wave control element 10 involved in the technology of the present invention can speed up the response speed relative to the change of the voltage applied to the liquid crystal layer 20, thereby switching the reflection direction of the incident electromagnetic wave RW in a short time.

[0110] As a methine compound, as long as it is a compound containing a methine structure (-C(Rc1)=C(Rc2)-C(Rc3)=), it is not particularly limited. Here, Rc1~Rc3 each independently represent a hydrogen atom or a substituent, and Rc1~Rc3 can be bonded to form a ring structure. The number of methine structures possessed by the methine compound is not particularly limited, as long as it is 1 or more, preferably 2 or more. The upper limit of the number of methine structures is not particularly limited, but the case of less than 7 is more common, and the case of less than 5 is more common. The methine compound can be a compound that shows liquid crystal properties, or a compound that does not show liquid crystal properties, and is preferably a compound that shows liquid crystal properties. That is, the methine compound is preferably a liquid crystal compound having a methine structure.

[0111] As the methine compound, a compound represented by formula (1) is preferred.

[0112] [Chemical Formula 1]

[0113]

[0114] In formula (1), Rc1 to Rc3 each independently represent a hydrogen atom or a substituent, and Rc1 to Rc3 may be bonded to form a ring structure.

[0115] n represents an integer of 1 to 7. When n is 2 or greater, Rc1 to Rc3 may be the same or different. n is preferably 1 to 5, more preferably 1 to 4.

[0116] A1 and A2 each independently represent a ring structure that may have a substituent, and A1 (and its substituent) and Rc1, A2 (and its substituent) and Rc3 can be bonded to form a ring structure. The ring structure can be a monocycle, or a condensed ring of more than two rings, or a ring (for example, a biphenyl ring, a terphenyl ring) formed by a plurality of monocycles bonded by a single bond. As the above-mentioned ring structure, a hydrocarbon ring or an aromatic ring, a heterocycle can be enumerated, and the heterocycle can form a condensed ring with a hydrocarbon ring or an aromatic ring. As the heteroatom of the heterocycle, preferably an N atom, an O atom, an S atom. Examples of the heterocyclic ring include a pyridine ring, a piperidine ring, a furan ring, a furfuran ring, a thiophene ring, a pyrrole ring, a quinoline ring, a morpholine ring, an indole ring, an imidazole ring, a pyrazole ring, a carbazole ring, a phenothiazine ring, a phenoxazine ring, an indoline ring, a triazine ring, a pyrrolidone ring, a thiazole ring, a pyrazine ring, a thiadiazine ring, a benzoquinoline ring, a thiadiazine ring, and a thienothiazole ring.

[0117] Examples of the substituents possessed by A1 and A2 include alkyl groups, alkenyl groups, aralkyl groups, aryl groups, heterocyclic groups, halogen atoms, cyano groups, nitro groups, mercapto groups, hydroxyl groups, amino groups, amide groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, acyloxy groups, alkylamino groups, dialkylamino groups, carboxamide groups, sulfonamide groups, sulfamoyl groups, oxycarbonylamino groups, oxysulfonylamino groups, urea groups, thiourea groups, acyl groups, oxycarbonyl groups, carbamoyl groups, sulfonyl groups, sulfinyl groups, sulfamoyl groups, carboxyl groups (including salts), sulfo groups (including salts), and combinations thereof. These groups may be further substituted with these groups.

[0118] The methine compound may be a cyanine compound, a squarylium compound, an oxonol compound, a merocyanine compound, a hemicyanine compound, or a streptocyanine compound, and particularly, a squarylium compound and a merocyanine compound are more preferred.

[0119] As the squaric acid compound, a compound represented by the following general formula (2) is preferred.

[0120] [Chemical Formula 2]

[0121]

[0122] Wherein, D1 and D2 each independently represent a substituted or unsubstituted hydrocarbon ring or heterocyclic group. Rc4 and Rc5 each independently represent a hydrogen atom or a substituent, n1 and n2 each independently represent an integer from 0 to 4, and when there are multiple Rc4 or Rc5, they can be the same or different, and there are multiple Rc4, Rc5, Rc4 and D1 or Rc5 and D2 to form a ring. In addition, the square acid compound has a zwitterionic structure within the molecule, but the markings of the cationic atom, anionic atom, single bond and double bond adopt multiple tautomeric structures. Therefore, the bond type and charge structure in the above-mentioned general formula (2) are not explicitly indicated.

[0123] As the merocyanine compound, a compound represented by the following general formula (3) is preferred.

[0124] [Chemical Formula 3]

[0125]

[0126] Wherein, D represents a substituted or unsubstituted donor ring structure, and A represents a substituted or unsubstituted acceptor ring structure. Rc6 to Rc9 represent a hydrogen atom or a substituent, and n represents an integer from 0 to 4. When there are multiple Rc7 or Rc8, they may be the same or different. Multiple Rc7, Rc8, Rc6 and D, or Rc9 and A may form a ring. Preferred structures of D include a 5-membered ring containing a substituted nitrogen atom which may have a substituent and is represented by the following general formula (4) or a 6-membered ring containing a substituted nitrogen atom which may have a substituent and is represented by the following general formula (5).

[0127] [Chemical Formula 4]

[0128]

[0129] [Chemical Formula 5]

[0130]

[0131] Among them, Rc10 in the general formula (4) represents an alkyl group having 1 to 10 carbon atoms which may have a substituent. In addition, the 5-membered ring of the general formula (4) may form a condensed ring structure with other rings. Rc11 in the general formula (5) represents an alkyl group having 1 to 10 carbon atoms which may have a substituent, which may have a condensed ring structure shown by the dotted line. As a preferred structure of A, a 5-membered ring or 6-membered ring containing a carbonyl carbon which may have a substituent and is represented by the following general formula (6) can be cited.

[0132] [Chemical Formula 6]

[0133]

[0134] The ring structure of the general formula (6) may form a fused ring structure with another ring. Specific structures of the general formulas (4), (5), and (6) include those described on pages 194 to 234 of "The Theory of the Photographic Process, 4th Edition (by TH James)".

[0135] The liquid crystal composition of the present invention may also contain liquid crystal compounds other than methine compounds. To adjust the various physical properties for use as an electromagnetic wave control element, known liquid crystal compounds are preferably used as liquid crystal compounds other than methine compounds. While there are no particular limitations on the liquid crystal compound used, a high Δn is preferred to increase the Δn of the liquid crystal composition containing the methine compound. Furthermore, the Δn is preferably 0.20 or greater, more preferably 0.25 or greater, and most preferably 0.30 or greater.

[0136] The content of the methine compound in the liquid crystal composition is not particularly limited, but from the viewpoint of further increasing Δn, it is preferably 3% or more, more preferably 5% or more, and most preferably 10% or more.

[0137] In the electromagnetic wave control element 10 according to the present invention, the Δn of the liquid crystal layer 20 is not limited, but preferably large. In the reflective electromagnetic wave control element 10 of this embodiment, the Δn of the liquid crystal layer 20 is preferably 0.35 or greater. This is preferable from the perspective of enabling faster switching of the reflection direction of the electromagnetic wave RW by reducing the thickness of the liquid crystal layer 20 by setting the Δn of the liquid crystal layer 20 to 0.35 or greater.

[0138] Furthermore, there is no limit to the thickness of the liquid crystal layer 20, as long as the thickness that imparts the desired phase difference to the electromagnetic wave RW is appropriately set according to the material forming the liquid crystal layer 20. Here, as described above, the liquid crystal layer 20 of the electromagnetic wave control element 10 involved in the technology of the present invention contains a methine compound, so the liquid crystal layer 20 can be made thinner. Taking this into consideration, 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. It is preferred from the viewpoint that by setting the thickness of the liquid crystal layer 20 to 200 μm or less, the switching of the reflection direction of the electromagnetic wave RW can be performed more quickly.

[0139] In the electromagnetic wave control element involved in the technology of the present invention, the reflective electromagnetic wave control element is not limited to Figure 4 The structure shown in FIG. 1 can illustrate various structures. For example, Figure 4 In the electromagnetic wave control element 10 shown, the microstructure 14 constituting the metasurface structure 12 also functions as an electrode. However, the technology of 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 (see FIG. Figure 7 In other words, as independent elements from the microstructure 14, the first electrode layer 26 and the second electrode 30 may be provided. The second electrode 30 may be formed of the same material as the first electrode layer 26. In the examples shown below, although illustration is omitted, Figure 4 Similar to the illustrated example, a power source 28 is connected to each electrode or the microstructure 14 serving also as an electrode.

[0140] As the structure, for example, Figure 7 As conceptually shown in FIG. 1 , a structure in which a second electrode 30 is provided on the microstructure 14 can be exemplified. Alternatively, Figure 8 As conceptually shown in FIG, the second electrode 30 may be provided between the microstructure 14 and the support 16. Figure 9It is conceptually shown in Figure 4 In the structure shown, the first electrode layer 26 is patterned as a pattern electrode and provided only in a region corresponding to the fine structure 14. In this structure, electromagnetic waves RW incident on a region without the first electrode layer 26 are transmitted therethrough.

[0141] Furthermore, in the electromagnetic wave control element according to the present invention, in a reflective electromagnetic wave control element, the microstructure 14 may be provided adjacent to the liquid crystal layer 20, and the metasurface structure 12 may be provided between the layered electrodes. Figure 10 As conceptually shown in FIG, the microstructure 14 can be provided on the liquid crystal layer 20 side of the support 16, and a layered common electrode, i.e., a second electrode 30, which is a common electrode shared by a plurality of unit cells UC, such as the first electrode layer 26, can be provided on the side of the support 16 opposite to the liquid crystal layer 20. In this structure, the second electrode 30 is patterned to have a plurality of openings, so that the electromagnetic wave RW can pass through the second electrode 30. In this structure, as shown in FIG. Figure 11 As conceptually shown in FIG, the fine structure 14 may also be arranged on the support 24, and the metasurface structure 12 may be provided on both surfaces of the liquid crystal layer 20.

[0142] The electromagnetic wave control element involved in the technology of the present invention described above is a reflective electromagnetic wave control element that reflects the incident electromagnetic wave RW and causes it to travel in the desired direction when an electromagnetic wave RW with a frequency of 0.1 to 0.3 THz is incident. However, the technology of the present invention is not limited to this. That is, the electromagnetic wave control element involved in the technology of the present invention may also be a transmissive electromagnetic wave control element that refracts and transmits the electromagnetic wave RW with a frequency of 0.1 to 0.3 THz and causes it to travel in the desired direction. In the following description, unless otherwise specified, the electromagnetic wave RW represents an electromagnetic wave with a frequency of 0.1 to 0.3 THz.

[0143] exist Figure 12 2 conceptually illustrates an example of a transmissive electromagnetic wave controlling element. The transmissive electromagnetic wave controlling element according to the present invention described below, except that it does not include the first electrode layer 26 serving as a reflective layer, is fundamentally the same as the reflective electromagnetic wave controlling element described above, and the functions of its components are also the same. Therefore, identical components are denoted by identical reference numerals, and the description will focus on the differences.

[0144] Figure 12 The transmission type electromagnetic wave control element 36 shown does not have the first electrode layer 26, but has the same Figure 4The structure of the reflective electromagnetic wave control element 10 shown in FIG. 36 is the same. That is, the electromagnetic wave control element 36 includes a metasurface structure 12 and a liquid crystal layer 20. The metasurface structure 12 is formed by two-dimensionally arranging microstructures 14 that serve as resonators on a support 16, and the liquid crystal layer 20 is formed on a support 24. Figure 12 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 adjacent fine structures 14.

[0145] In this electromagnetic wave control element 36, power is supplied from a power source 28 to the microstructures 14, applying a voltage in the in-plane direction to the liquid crystal layer 20 between adjacent microstructures 14. The in-plane direction refers to a direction intersecting the thickness direction of the liquid crystal layer 20. As a result, the alignment of the liquid crystal compound LC in the liquid crystal layer 20 in that region changes according to the applied voltage, thereby changing the refractive index. Furthermore, by varying the power supplied to each microstructure 14, that is, the voltage applied to the corresponding region, regions with different refractive indices in the in-plane direction can be formed.

[0146] Similar to the electromagnetic wave control element 10, if the electromagnetic wave RW is incident on the electromagnetic wave control element 36, the electromagnetic wave RW is phase-modulated by the resonance based on the fine structure 14 when transmitting through the metasurface structure 12, and further, the phase is modulated by transmitting through the liquid crystal layer 20. The electromagnetic wave control element 36 does not have the first electrode layer 26 that serves as a reflective layer, so the electromagnetic wave RW transmits the liquid crystal layer 20 and is emitted from the electromagnetic wave control element 36. Here, as described above, the liquid crystal layer 20 has different refractive indices in the surface direction, so the phase difference given to the electromagnetic wave RW that transmits the liquid crystal layer 20 is different depending on the region in the surface direction. Therefore, the apparent optical path length of the electromagnetic wave RW is different depending on the phase difference given corresponding to the incident region, and the electromagnetic wave RW that transmits the region with a long optical path length is emitted from the liquid crystal layer 20 more slowly than the electromagnetic wave RW that transmits the region with a short optical path length. As a result, electromagnetic wave RW incident on and transmitted through electromagnetic wave control element 36 is not transmitted linearly, but is refracted and transmitted in a manner that aligns the wavefront. For example, electromagnetic wave RW incident from the normal direction is not transmitted in the normal direction, but is transmitted in a direction inclined relative to the normal.

[0147] Furthermore, by changing the power supplied to each microstructure 14, that is, the voltage applied to the liquid crystal layer 20, the refractive index of the transmitted electromagnetic wave RW, that is, the emission direction of the electromagnetic wave RW, can be switched. Furthermore, by adjusting the voltage applied to the liquid crystal layer 20, the transmitted electromagnetic wave RW can be focused or diverged, and the degree of focusing and divergence of the transmitted electromagnetic wave RW can be switched. In the electromagnetic wave control element 36, the liquid crystal layer 20 also contains a methine compound, so the refractive index, that is, the direction of travel of the transmitted electromagnetic wave RW, can be quickly switched.

[0148] In the transmissive electromagnetic wave control element 36 according to the present invention, the Δn of the liquid crystal layer 20 is not limited, but preferably is large. In the transmissive electromagnetic wave control element 36 shown in the figure, the Δn of the liquid crystal layer 20 is preferably 0.2 or greater, more preferably 0.3 or greater, and even more preferably 0.4 or greater. In the electromagnetic wave control element 36, setting the Δn of the liquid crystal layer 20 to 0.2 or greater is preferable because it allows for faster switching of the transmission direction of the electromagnetic wave RW by thinning the liquid crystal layer 20.

[0149] Furthermore, there is no restriction on the thickness of the liquid crystal layer 20, as long as the thickness that imparts the desired phase difference to the electromagnetic wave RW is appropriately set according to the material forming the liquid crystal layer 20. Here, as described above, in the transmission-type electromagnetic wave control element 36, the liquid crystal layer 20 also contains a methyl compound, so the liquid crystal layer 20 can be made thinner. Furthermore, in the technology of the present invention, the target electromagnetic wave RW 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. Taking this into consideration, in the transmission-type electromagnetic wave control element 36, the thickness of the liquid crystal layer 20 is preferably 500 μm or less, more preferably 300 μm or less, and further preferably 200 μm or less. It is preferred from the viewpoint that by setting the thickness of the liquid crystal layer 20 to 500 μm or less, the transmission direction of the electromagnetic wave RW can be switched more quickly.

[0150] In the electromagnetic wave control element involved in the technology of the present invention, the transmission type electromagnetic wave control element is not limited to Figure 12 The electromagnetic wave control element 36 shown in the figure can be illustrated in various structures. Figure 12 As in the example shown, a power source 28 is connected to each electrode or the microstructure 14 serving as an electrode. Figure 12 In the electromagnetic wave control element 36 shown in FIG. 1 , the microstructure 14 constituting the metasurface structure 12 also functions as an electrode. However, the technology of the present invention is not limited thereto, and a first electrode 32 and a second electrode 30 may be provided corresponding to the microstructure 14. As an example of such a structure, Figure 13As conceptually shown in FIG. 1 , a structure in which a first electrode 32 is provided on one of two adjacent microstructures 14 and a second electrode 30 is provided on the other microstructure 14 can be exemplified. Alternatively, Figure 14 As conceptually shown in FIG, 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 .

[0151] Transmission-type electromagnetic wave control elements may also have multiple metasurface structures. Figure 15 As shown, in Figure 12 In 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 to serve as the super surface structure 12. In this example, as an example, the microstructures 14 facing each other with the liquid crystal layer 20 interposed therebetween function as an electrode pair, namely, the first electrode and the second electrode. Figure 15 In the structure shown, the first electrode 32 and the second electrode 30 may be provided corresponding to the microstructure 14. As an example of this structure, Figure 16 As conceptually shown in FIG, a structure can be exemplified in which, of two fine structures 14 constituting an electrode pair facing each other with the liquid crystal layer 20 interposed therebetween, a first electrode 32 is provided on the surface of one fine structure 14 and a second electrode 30 is provided on the surface of the other fine structure 14. Alternatively, as Figure 17 As conceptually shown in FIG, in two fine-structure bodies 14 constituting an electrode pair facing each other with the liquid crystal layer 20 interposed therebetween, a first electrode 32 may be provided between one fine-structure body 14 and the support 24 , and a second electrode 30 may be provided between the other fine-structure body 14 and the support 16 .

[0152] like Figure 18 As conceptually shown in FIG, in a transmission type electromagnetic wave control element having a plurality of metasurface structures, the microstructures 14 constituting the metasurface structure 12 can be arranged in a staggered manner in the surface direction. Figure 15 As in the example shown, as an example, the fine structures 14 facing each other with the liquid crystal layer 20 interposed therebetween function as a first electrode and a second electrode of an electrode pair. Figure 18 In the structure shown, the first electrode 32 and the second electrode 30 may be provided corresponding to the microstructure 14. As an example of this structure, Figure 19 As conceptually shown in FIG, a structure can be exemplified in which, of two microstructures 14 constituting an electrode pair facing each other via a liquid crystal layer 20, 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. Alternatively, as Figure 20 As conceptually shown in FIG, in two fine-structure bodies 14 constituting an electrode pair facing each other with the liquid crystal layer 20 interposed therebetween, 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 24 .

[0153] Moreover, if Figure 21 As conceptually shown in FIG, in a transmission-type electromagnetic wave control element, similar 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 microstructure 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 the electromagnetic wave RW can be transmitted. Moreover, even with a structure such as Figure 21 The structure of the first electrode layer 26A shown in FIG. 1 may also be such that the microstructure 14 does not serve as an electrode. Figure 22 As conceptually shown in FIG, the second electrode 30 is provided on the fine structure 14, and the first electrode layer 26A and the second electrode 30 constitute an electrode pair.

[0154] Furthermore, the transmission type electromagnetic wave control element can be Figure 23 In the figure, the microstructure 14 is conceptually 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. Alternatively, Figure 23 In the structure shown, Figure 24 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 RW may be provided on the side of the dielectric layer 34 opposite to the support 24 .

[0155] In the above example, the orientation pattern of the liquid crystal compound LC in the liquid crystal layer 20 is as follows: when no voltage is applied, the liquid crystal compound LC is vertically oriented. When a voltage is applied, the angle relative to the thickness direction increases according to the applied voltage, and finally becomes horizontally oriented. However, the technology of the present invention is not limited to this, and various liquid crystal orientation patterns can be used. An example is shown below. In addition, in the example shown below, Figure 5Similarly, for the sake of simplicity, only the liquid crystal layer 20, the fine structure 14, and the first electrode layer 26 are shown. In the following example, the fine structure 14 and the first electrode layer 26 are shown as electrodes, but the technology of the present invention is not limited to this. Figure 4 、 Figures 7 to 24 In all the structures shown, the liquid crystal orientation pattern shown below can be used. Figure 5 Same.

[0156] In the electromagnetic wave control element according to the present invention, the liquid crystal alignment pattern of the liquid crystal layer 20 is as follows: Figure 25 As conceptually shown in FIG, the following liquid crystal orientation pattern can also be used: when no voltage is applied, the liquid crystal compound LC is horizontally aligned. When a voltage is applied, the angle with respect to the plane direction of the liquid crystal layer 20 increases according to the applied voltage, and finally becomes vertically aligned. In addition, as the liquid crystal orientation pattern of the liquid crystal layer 20, as shown in FIG. Figure 26 As conceptually shown in FIG, the following liquid crystal orientation pattern can also be used: in the state where no voltage is applied, the liquid crystal compound LC is horizontally aligned and twisted in a spiral shape in the thickness direction. 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. Moreover, as the liquid crystal orientation pattern of the liquid crystal layer 20, as shown in FIG. Figure 27 As conceptually shown in FIG, 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 can also be utilized. In the case of this liquid crystal orientation pattern, as an example, Figure 27 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.

[0157] Furthermore, in the electromagnetic wave control element involved in the technology of the present invention, Figures 12 to 14 As shown in FIG. 1 , a voltage can be applied in a direction intersecting the thickness direction of the liquid crystal layer 20. In this structure, as shown in FIG. Figure 28 As conceptually shown in FIG, 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. When a voltage is applied, the liquid crystal compound LC rotates in the plane direction according to the applied voltage, and finally the length direction is aligned with the horizontal direction in the figure and is horizontally oriented. Or, conversely, as Figure 29 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 a 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.

[0158] The polarization state (i.e., polarization state) of the electromagnetic wave RW, which is the object of control of the electromagnetic wave control element involved in the technology of the present invention, is not limited and can be unpolarized light, linearly polarized light, circularly polarized light, or elliptically polarized light. Furthermore, when the electromagnetic wave RW is linearly polarized light and the microstructures 14 are arranged two-dimensionally in orthogonal X and Y directions, it is preferred that the electromagnetic wave RW be incident so that its polarization direction coincides with the X or Y direction.

[0159] In the above embodiment, as the type of electromagnetic wave control element, Figure 4 An example of a reflective electromagnetic wave control element 10 and Figure 12 , an example of a transmission-type electromagnetic wave control element 36 is shown. Furthermore, examples of each type of electromagnetic wave control element being used as a component of the electromagnetic wave reflection device 2 are shown. The uses of the electromagnetic wave control element are not limited to the above-mentioned uses and may also include uses other than those described above. For example, by combining it with a waveguide that conducts electromagnetic waves RW, it can be used as a component of a so-called leaky-wave antenna.

[0160] As an example, Figure 30 As shown, an electromagnetic wave controlling element 110 is incorporated into the leaky wave antenna 100. The electromagnetic wave controlling element 110 is identical to the electromagnetic wave controlling element 10 in that it has the function of controlling the propagation direction of the electromagnetic wave RW. In the electromagnetic wave controlling element 110, components identical to those of the electromagnetic wave controlling element 10 are denoted by the same reference numerals, and their descriptions are omitted.

[0161] and Figure 1 Similar to the antenna ANT shown, the leaky wave antenna 100 transmits electromagnetic waves RW. The leaky wave antenna 100 can change the emission direction of the electromagnetic waves RW, for example, to emit the electromagnetic waves RW toward the area AR1 during a certain time period and toward the area AR2 during another time period.

[0162] As an example, Figure 31 As shown, the electromagnetic wave control element 110 is composed of multiple subunits 110A and multiple electromagnetic wave generating sources 112. The multiple subunits 110A are rectangular parallelepiped-shaped and arranged in a direction perpendicular to the longitudinal direction. One electromagnetic wave generating source 112 is assigned to each subunit 110A.

[0163] As an example, Figure 32 and Figure 33As shown, subunit 110A is composed of a metasurface structure 12 formed by a one-dimensional arrangement of multiple microstructures 14, and a waveguide component 120, and has an overall rectangular parallelepiped shape. Waveguide component 120 is positioned with its longitudinal side aligned with the arrangement direction of the microstructures 14. Waveguide component 120 is arranged so as to contact a surface of support 24 opposite to liquid crystal layer 20. Waveguide component 120 is, for example, a tubular component with a rectangular cross-section. The internal space defined by the inner wall of waveguide component 120 constitutes waveguide 120A, which conducts electromagnetic wave RW.

[0164] An electromagnetic wave generating source 112 is disposed on one end side of the waveguide component 120, and the electromagnetic wave generating source 112 sends out an electromagnetic wave RW into the waveguide 120A. The waveguide 120A conducts the electromagnetic wave RW sent out from the electromagnetic wave generating source 112 and incident on the waveguide 120A in a direction along the arrangement direction of the microstructures 14. The electromagnetic wave RW propagates in the waveguide 120A while being reflected by the inner wall of the waveguide component 120. In the waveguide component 120, an opening 121 is formed on a portion of the wall surface opposite to the support body 24, which emits the electromagnetic wave RW in a direction intersecting the arrangement direction of the microstructures 14. The opening 121 is formed corresponding to the position of each of the multiple microstructures 14. The opening 121 in this example emits the electromagnetic wave RW in the Z direction, which is the normal direction of the XY plane, which is the arrangement plane on which the microstructures 14 are arranged.

[0165] In the electromagnetic wave control element 110, a unit cell UC is formed by including at least one fine structure 14 and an opening 121. The fine structure 14 and the waveguide member 120 also serve as an electrode pair of a first electrode and a second electrode. By applying a voltage to each unit cell UC, an electric field is generated in the thickness direction of the liquid crystal layer 20. Figure 4 Similar to the electromagnetic wave control element 10 shown, the electromagnetic wave control element 110 can control the phase delay of the electromagnetic wave RW by controlling the voltage applied to each unit cell UC. This allows the direction of the electromagnetic wave RW emitted from the opening 121 and transmitted through the liquid crystal layer 20 and the fine-structure 14 to be controlled.

[0166] As described above, the responsiveness of the liquid crystal layer 20 is higher than before, and therefore the electromagnetic wave controlling element 110 can also switch the emission direction of the electromagnetic wave RW having a frequency of 0.1 to 0.3 THz in a shorter time than before.

[0167] exist Figure 33 In the example, the microstructure 14 and the opening 121 are provided separately. Figure 34As shown, the opening 121 can also function as a microstructure. That is, the opening 121 itself can function as a resonator that causes a phase delay in the electromagnetic wave RW. The opening 121 can also be formed with a size that is smaller than the wavelength of the electromagnetic wave RW, and the shape can be designed to function as a resonator.

[0168] Furthermore, by controlling the resonance condition of the opening 121 according to the change in the refractive index of the liquid crystal layer 20 , the phase delay amount of the electromagnetic wave RW can be controlled for each unit cell UC.

[0169] In this case, as an example, an electrode pair consisting of a first electrode 32 and a second electrode 30 is provided for each unit cell UC between the support 24 and the liquid crystal layer 20. Then, by applying a voltage to these electrode pairs, an electric field is generated in a direction intersecting the thickness direction of the liquid crystal layer 20, thereby changing the refractive index of the liquid crystal layer 20 for each unit cell UC.

[0170] And, as Figure 32 and Figure 33 As shown in the figure, the electromagnetic wave control element 110 is described as an example of being composed of a rectangular subunit 110A, but it can also be Figure 32 and Figure 33 structures other than those shown. For example, Figure 35 As shown, the electromagnetic wave control element 110 can be formed by arranging the metasurface structure 12 in a radial shape with an electromagnetic wave generating source 112 as the center. In this example, the electromagnetic wave generating source 112 generates electromagnetic waves RW in a radial shape. Moreover, a waveguide component (not shown) is provided corresponding to the metasurface structure 12 in which a plurality of fine structures 14 are arranged. Figure 32 As shown, the waveguide member is provided with an opening that emits a portion of the electromagnetic wave RW propagating in the waveguide in a direction intersecting the arrangement direction of the fine structures 14. Thus, the electromagnetic wave RW is emitted.

[0171] The electromagnetic wave controlling element 110 used in the leaky wave antenna 100 may also be Figures 7 to 29 Applicable portions of the various modified examples shown for the reflective or transmissive electromagnetic wave controlling element 10 are appropriately combined.

[0172] Example

[0173] (Preparation of Liquid Crystal Composition 1)

[0174] Liquid crystal composition 1 was prepared with the following composition: Compound 2-1 10.00 parts by mass PTU-3-S 13.48 parts by mass PTU-5-S 13.48 parts by mass PGU-3-S 13.48 parts by mass PPTU-5-S 8.99 parts by mass CPU-2-S 25.18 parts by mass CPU-4-S 15.28 parts by mass D-1c 0.11 parts by mass

[0175] [Chemical Formula 7]

[0176]

[0177] [Chemical Formula 8]

[0178]

[0179] (Preparation of Liquid Crystal Composition 2)

[0180] Liquid Crystal Composition 2 was prepared in the same manner except that Compound 2-2 below was used instead of Compound 2-1 of Liquid Crystal Composition 1.

[0181] [Chemical Formula 9]

[0182]

[0183] (Preparation of Liquid Crystal Composition 3)

[0184] Liquid Crystal Composition 3 was prepared in the same manner except that Compound 2-3 below was used instead of Compound 2-1 of Liquid Crystal Composition 1.

[0185] [Chemical Formula 10]

[0186]

[0187] (Preparation of Liquid Crystal Composition 4)

[0188] Liquid Crystal Composition 4 was prepared in the same manner except that Compound 3-1 below was used instead of Compound 2-1 of Liquid Crystal Composition 1.

[0189] [Chemical Formula 11]

[0190]

[0191] (Preparation of Liquid Crystal Composition 5)

[0192] Liquid Crystal Composition 5 was prepared in the same manner except that Compound 3-2 below was used instead of Compound 2-1 of Liquid Crystal Composition 1.

[0193] [Chemical Formula 12]

[0194]

[0195] (Preparation of Liquid Crystal Composition 6)

[0196] Liquid Crystal Composition 6 was prepared in the same manner except that Compound 3-3 below was used instead of Compound 2-1 of Liquid Crystal Composition 1.

[0197] [Chemical Formula 13]

[0198]

[0199] (Preparation of Liquid Crystal Composition x)

[0200] A liquid crystal composition x of Comparative Example was prepared in the same manner except that the compound 2-1 of the liquid crystal composition 1 was not used.

[0201] (Fabrication of Electromagnetic Wave Control Components)

[0202] (Example 1)

[0203] A patterned gold (Au) film was formed in the center of a 2.5 mm square quartz substrate by vapor deposition, and used as a supersurface structure formed by arranging multiple microstructures. At this time, as the pattern of the microstructure, 40 microstructures of 0.32 mm square were arranged vertically and 40 microstructures were arranged horizontally at a period of 0.4 mm. In addition, in order to apply voltage, the 40 microstructures arranged horizontally were connected with a metal pattern on a thin wire with a width of 0.05 mm and a length of 2.5 mm, which served as the first electrode. An alignment film composed of polyimide was formed on the first electrode.

[0204] Next, a gold (Au) film was formed on the front surface of another 2.5 mm square quartz substrate using the same vapor deposition method to serve as the second electrode. An alignment film made of polyimide was formed on the second electrode. Next, using epoxy resin as a spacer, the quartz substrate with the first electrode formed and the quartz substrate with the second electrode formed were bonded together, with the electrode surfaces facing inward. The spacer thickness was set to a value that resulted in an optical path length (Δn × thickness) of 25 μm.

[0205] Next, the cavity between the electrodes formed by the spacer was filled with the liquid crystal composition 1. Thus, the electromagnetic wave controlling element of Example 1, which functions as a reflector capable of changing the direction of electromagnetic waves like the electromagnetic wave controlling element 10 described above, was produced.

[0206] (Examples 2 to 6 and Comparative Examples)

[0207] Electromagnetic wave control elements of Examples 2 to 6 were produced by the same method as in Example 1, except that the liquid crystal composition 1 was changed to any one of the liquid crystal compositions 2 to 6 shown in Table 1 below.

[0208] (Evaluation of Δn)

[0209] The index Δn of the anisotropy (also called birefringence) of the refractive index was evaluated as follows. Δn was measured for electromagnetic waves with a frequency of 250 GHz (i.e., 0.25 THz) by the method disclosed in Applied Optics, Vol. 44, No. 7, p1150 (2005). Regarding Δn, the above-mentioned composition was filled into a variable short-circuit waveguide and kept in a static magnetic field of 0.3 T for 3 minutes to align the dichroic pigment in the composition. An electromagnetic wave with a frequency of 250 GHz was input into the variable short-circuit waveguide, and the amplitude ratio of the reflected wave to the incident wave was measured. The measurement was performed by changing the direction of the static magnetic field and the tube length of the variable short-circuit waveguide, and the refractive indices ne and no of the two axes were determined. Δn was calculated based on ne-no.

[0210] (Evaluation of switching time)

[0211] pass Figure 36 The method schematically shown in the figure was used to evaluate the switching time of the reflection direction of the electromagnetic wave incident on the electromagnetic wave control element. First, the applied voltage of the electromagnetic wave control element was pre-adjusted so that the electromagnetic wave incident from the normal direction of the reflection surface was reflected in the direction of 30°. Then, in the transmitter, a frequency generator was used to generate a signal with a frequency of about 14 GHz, and the frequency was multiplied by 18 using a frequency multiplier, thereby generating a signal with a frequency of 250 GHz. Figure 36 As shown in the figure, a 250 GHz electromagnetic wave emitted from a transmitter is focused using a resin lens and incident on an electromagnetic wave control element. It then reflects from the electromagnetic wave control element, and the intensity of the reflected electromagnetic wave, focused by the resin lens and horn antenna, is detected using a Schottky diode. Next, by re-adjusting the applied voltage, the direction of electromagnetic wave reflection from the electromagnetic wave control element is changed from a 30° angle to a 0° angle. The time it takes for the electromagnetic wave intensity detected by the Schottky diode to drop to 1 / 10 of its original value is used as the switching time for the electromagnetic wave's reflection direction.

[0212] Table 1 shows the results of evaluating the Δn of the filled liquid crystal composition and the switching time in the reflection direction in the fabricated electromagnetic wave control elements. It was clearly shown that the switching time was shortened in the electromagnetic wave control elements of Examples 1 to 6, in which the liquid crystal layer contained a methine compound. Furthermore, while the examples illustrate reflective electromagnetic wave control elements, similar effects were observed in transmissive electromagnetic wave control elements.

[0213] [Table 1]

[0214]

[0215] The technology of the present invention can also be appropriately combined with the various embodiments and / or various modifications described above. Furthermore, the technology is not limited to the embodiments described above, and various configurations can be adopted without departing from the spirit of the present invention.

[0216] The records and illustrations shown above are detailed descriptions of the parts involved in the technology of the present invention, and are only an example of the technology of the present invention. For example, the descriptions related to the above-mentioned structure, function, action and effect are descriptions related to an example of the structure, function, action and effect of the parts involved in the technology of the present invention. Therefore, without departing from the scope of the technical purpose of the present invention, it is of course possible to delete unnecessary parts of the records and illustrations shown above, or to add or replace new elements. In addition, in order to avoid complex situations and facilitate understanding of the parts involved in the technology of the present invention, descriptions related to technical common sense that does not particularly need to be explained in terms of enabling the implementation of the technology of the present invention are omitted in the records and illustrations shown above.

[0217] In this specification, the 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. In this specification, "same" includes the error range generally allowed in the technical field.

[0218] The figures illustrating the electromagnetic wave control elements and the like described above are all conceptual diagrams, and therefore the shapes, sizes, thicknesses, positional relationships, etc. of the various components do not necessarily correspond to the actual ones.

[0219] In this specification, "A and / or B" has the same meaning as "at least one of A and B." That is, "A and / or B" can mean only A, only B, or a combination of A and B. Furthermore, in this specification, the same concept as "A and / or B" applies when three or more items are linked together using "and / or."

[0220] The disclosure of Japanese Patent Application No. 2023-013602, filed on January 31, 2023, is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, or technical standard were specifically and individually indicated as being incorporated by reference.

[0221] The above-mentioned embodiments further disclose the technologies related to the following supplementary items.

[0222] Supplementary Item 1

[0223] An electromagnetic wave control element comprising:

[0224] a liquid crystal layer in which the orientation state of the liquid crystal compound changes according to a voltage;

[0225] A metasurface structure formed by arranging a plurality of microstructures; and

[0226] An electrode pair, which is composed of a first electrode and a second electrode and is used to apply a voltage,

[0227] 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 a methine compound.

[0228] Supplementary Item 2

[0229] The electromagnetic wave control element according to Supplementary Note 1, wherein:

[0230] The methine compound has a methine structure.

[0231] Supplementary Item 3

[0232] The electromagnetic wave control element according to Supplementary Note 1 or 2, wherein

[0233] The liquid crystal layer contains a liquid crystal compound having a methine structure.

[0234] Supplementary Item 4

[0235] The electromagnetic wave control element according to any one of Supplementary Notes 1 to 3, wherein

[0236] At least one of the first electrode and the second electrode is a microstructure.

[0237] Supplementary Item 5

[0238] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 4, comprising the first electrode and the second electrode as independent elements from the microstructure.

[0239] Supplementary Item 6

[0240] The electromagnetic wave control element according to any one of Supplementary Notes 1 to 5, wherein

[0241] One of the first electrode and the second electrode is a pattern electrode.

[0242] Supplementary Item 7

[0243] The electromagnetic wave control element according to any one of Supplementary Notes 1 to 6, wherein

[0244] The microstructure includes metal.

[0245] Supplementary Item 8

[0246] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 7, wherein:

[0247] The microstructure includes an oxide semiconductor.

[0248] Supplementary Item 9

[0249] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 8, wherein an electric field caused by a voltage is generated in the thickness direction of the liquid crystal layer.

[0250] Supplementary Item 10

[0251] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 9, wherein an electric field caused by a voltage is generated in a direction intersecting with a thickness direction of the liquid crystal layer.

[0252] Supplementary Item 11

[0253] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 10, which is a reflection type that reflects electromagnetic waves.

[0254] Supplementary Item 12

[0255] The electromagnetic wave control element according to Supplementary Note 11, wherein

[0256] One of the first electrode and the second electrode also serves as a reflection layer that reflects electromagnetic waves.

[0257] Supplementary Item 13

[0258] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 12, which is a transmissive type that transmits electromagnetic waves.

[0259] Supplementary Item 14

[0260] An electromagnetic wave control element according to any one of appendixes 1 to 13, comprising a waveguide for conducting incident electromagnetic waves in a direction along the arrangement direction of the microstructures, and for emitting a portion of the electromagnetic waves conducted in the waveguide in a direction intersecting the arrangement direction.

[0261] Supplementary Item 15

[0262] The electromagnetic wave control element according to Supplementary Item 14, wherein:

[0263] An opening for emitting electromagnetic waves is formed in a portion of a wall surface defining the waveguide.

[0264] Supplementary Item 16

[0265] The electromagnetic wave control element according to Supplementary Item 14 or 15,

[0266] The waveguide member constituting the waveguide functions as the first electrode or the second electrode.

[0267] Supplementary Item 17

[0268] The electromagnetic wave control element according to Supplementary Item 15 or 16, wherein:

[0269] The opening functions as a microstructure.

Claims

1. An electromagnetic wave control element comprising: a liquid crystal layer in which the orientation state of the liquid crystal compound changes according to a voltage; A metasurface structure formed by arranging a plurality of microstructures; and an electrode pair consisting of a first electrode and a second electrode for applying the voltage, 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 a methine compound.

2. The electromagnetic wave control element according to claim 1, wherein The methine compound has a methine structure.

3. The electromagnetic wave control element according to claim 1, wherein The liquid crystal layer includes a liquid crystal compound having a methine structure.

4. The electromagnetic wave control element according to claim 1, wherein At least one of the first electrode and the second electrode is the microstructure. 5 . The electromagnetic wave controlling element according to claim 1 , comprising the first electrode and the second electrode as independent elements from the microstructure.

6. The electromagnetic wave control element according to claim 1, wherein One of the first electrode and the second electrode is a pattern electrode.

7. The electromagnetic wave control element according to claim 1, wherein The microstructure includes metal.

8. The electromagnetic wave control element according to claim 1, wherein The microstructure includes an oxide semiconductor.

9. The electromagnetic wave control element according to claim 1, wherein An electric field caused by the voltage is generated in the thickness direction of the liquid crystal layer.

10. The electromagnetic wave control element according to claim 1, wherein An electric field caused by the voltage is generated in a direction intersecting the thickness direction of the liquid crystal layer. The electromagnetic wave controlling element according to claim 1 , which is a reflection type that reflects the electromagnetic wave.

12. The electromagnetic wave control element according to claim 11, wherein One of the first electrode and the second electrode also serves as a reflection layer that reflects electromagnetic waves. 13 . The electromagnetic wave controlling element according to claim 1 , which is a transmission type that transmits the electromagnetic wave.

14. The electromagnetic wave control element according to claim 1 has a waveguide that conducts the incident electromagnetic wave in a direction along the arrangement direction of the microstructure, and emits a part of the electromagnetic wave conducted in the waveguide in a direction intersecting the arrangement direction.

15. The electromagnetic wave control element according to claim 14, wherein An opening for emitting the electromagnetic wave is formed in a portion of a wall surface defining the waveguide.

16. The electromagnetic wave control element according to claim 14, wherein The waveguide member constituting the waveguide functions as the first electrode or the second electrode.

17. The electromagnetic wave control element according to claim 15, wherein: The opening portion functions as the microstructure.

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