Electromagnetic wave control element

Abstract

This electromagnetic wave control element is provided with: a conductor; and a metasurface structure in which a plurality of microstructures are arranged, each microstructure including a movable part in which the distance from the conductor changes in accordance with a voltage applied to the piezoelectric element, the piezoelectric element having a piezoelectric film, and a first electrode and a second electrode that are disposed on both sides of the piezoelectric film in the thickness direction and that apply the voltage, the first electrode and the second electrode being disposed on both sides of the piezoelectric film in the thickness direction. The electromagnetic wave control element acts on an electromagnetic wave having a frequency of 0.1-0.3 THz.

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 (Longqing Cong et al., Adv. Optical Mater. 2016, DOI: 10.1002 / adom.201600716) describes an electromagnetic wave control element that utilizes a metasurface structure to change the reflection direction of electromagnetic waves to a direction other than specular reflection, or to dynamically change the reflection direction. This type of electromagnetic wave control 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 change the resonance conditions of a microstructure, the electromagnetic wave control element described in the non-patent literature displaces the microstructure. Changing the spacing between the microstructure and the substrate on which it is mounted, for example, alters the resonance conditions of the microstructure. By utilizing this phenomenon, the electromagnetic wave control element described in the non-patent literature controls the amount of phase modulation of electromagnetic waves by displacing the microstructure.

[0006] Electromagnetic wave control elements described in non-patent literature use electrostatic MEMS (Micro Electro Mechanical Systems) as a driving unit for displacing a microstructure. Electrostatic MEMS uses static electricity generated by accumulated charge to displace the microstructure using the repulsive force generated by the static electricity. Summary of the Invention

[0007] Technical issues to be solved by the invention

[0008] 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.

[0009] The technology of the present invention provides an electromagnetic wave control element having a metasurface structure using MEMS, 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.

[0010] Means for solving technical problems

[0011] The electromagnetic wave control element involved in the technology of the present invention comprises: a conductor; and a metasurface structure, which is composed of a plurality of arranged microstructures, the microstructure including a movable part whose distance from the conductor changes according to the voltage applied to the piezoelectric element, the piezoelectric element having a piezoelectric film and a first electrode and a second electrode arranged on both sides of the piezoelectric film in the thickness direction and used to apply voltage, the electromagnetic wave control element acts on electromagnetic waves with a frequency of 0.1 to 0.3 THz.

[0012] As independent elements from the movable portion, a first electrode and a second electrode may be provided.

[0013] The movable portion may also serve as one of the first electrode and the second electrode.

[0014] The region of the conductor facing the plurality of fine structures may be formed integrally.

[0015] The conductor may be formed by being divided into a plurality of regions, and each region may face a part of the plurality of microstructures.

[0016] The microstructure may contain metal.

[0017] The microstructure may include an oxide semiconductor.

[0018] It may be a reflective type that reflects electromagnetic waves.

[0019] The conductor can also serve as a reflective layer that reflects electromagnetic waves.

[0020] 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.

[0021] An opening for emitting electromagnetic waves may be formed in a portion of a wall surface defining the waveguide.

[0022] A portion of the waveguide component constituting the waveguide may also serve as a conductor.

[0023] Effects of the Invention

[0024] According to the electromagnetic wave control element according to the technology of the present invention, in an electromagnetic wave control element having a metasurface structure using MEMS, 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

[0025] Figure 1 This is a diagram showing an example of use of an electromagnetic wave control element.

[0026] Figure 2 This is a diagram showing an example of a metasurface structure used in an electromagnetic wave control element.

[0027] 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.

[0028] Figure 4 This is a diagram conceptually showing an example of an electromagnetic wave controlling element.

[0029] Figure 5 This is a diagram conceptually showing a state in which the distance between the movable portion and the conductor in the electromagnetic wave controlling element changes.

[0030] Figure 6 This is a diagram showing the relationship between the applied voltage and the amount of phase delay of the electromagnetic wave.

[0031] Figure 7 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0032] Figure 8 This is a diagram conceptually showing another example of an electromagnetic wave controlling element.

[0033] Figure 9 This is a diagram showing a leaky-wave antenna using an electromagnetic wave controlling element.

[0034] Figure 10 It is conceptually shown Figure 9 A plan view of an example of an electromagnetic wave control element.

[0035] Figure 11 It is conceptually shown Figure 10 A three-dimensional diagram of a subunit of an electromagnetic wave control element.

[0036] Figure 12 It is conceptually shown Figure 11 A diagram of an example of a subunit of .

[0037] Figure 13 It is conceptually shown Figure 9 Figure 2 is a diagram of another example of an electromagnetic wave control element. DETAILED DESCRIPTION

[0038] exist Figure 1 The 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.

[0039] like Figure 2As 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. The microstructure 14 is composed 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 resonate an alternating current. The phase of the incident electromagnetic wave RW changes due to the resonance of the microstructure 14. Furthermore, by actively changing the resonance conditions of the microstructure 14 through various methods, the phase delay of the electromagnetic wave RW can be controlled. Furthermore, as materials forming the microstructure 14, a composite composed of metal particles and a binder, or an oxide semiconductor can also be used, at least in part.

[0040] 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.

[0041] 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 plurality of electromagnetic waves RW.

[0042] Furthermore, it is conceivable that, in the electromagnetic wave control element 10, for example, the phase delay of the electromagnetic wave RW incident on and reflected by each of the multiple unit cells UC arranged in a one-dimensional manner is gradually increased as it moves from the unit cells UC in the right direction toward the unit cells UC in the left direction. In this way, even if 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 the unit cells UC will be tilted relative to the reflection surface. In other words, the direction of travel of the electromagnetic wave RW emitted from the reflection surface, i.e., the emission direction OUT, changes only by an angle θ relative to the incident direction IN of the electromagnetic wave RW. In this way, by phase modulating each unit cell UC, i.e., controlling the phase delay, the direction of travel of the electromagnetic wave RW can be controlled.

[0043] 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.

[0044] As an example, Figure 4 As conceptually shown in the figure, the electromagnetic wave control element 10 uses a piezoelectric element 42 as a piezoelectric MEMS as a requirement for actively changing the resonance conditions of the microstructure 14 of the metasurface structure 12. The electromagnetic wave control element 10 has a supporting substrate 47, a conductive layer 46 and a metasurface structure 12 including a plurality of microstructures 14, in order from the bottom of the figure. The conductive layer 46 is provided on the supporting substrate 47. In this example, the conductive layer 46 is formed by a layer shared by a plurality of microstructures 14. Specifically, it has a region opposite to all the microstructures 14. The conductive layer 46 is an example of a "conductor" involved in the technology of the present invention.

[0045] The microstructure 14 is composed of a movable portion 41 and a piezoelectric element 42. The movable portion 41 is a cantilever beam with one end fixed to the conductive layer 46 by a spacer 43 and the other end being a free end. The movable portion 41 can be deformed starting from the fixed end. The piezoelectric element 42 is provided on the surface of the movable portion 41 opposite to the surface facing the conductive layer 46. The piezoelectric element 42 is an element that deforms according to the applied voltage and functions as a driving portion that deforms the movable portion 41. That is, in the microstructure 14, the movable portion 41 deforms according to the voltage applied to the piezoelectric element 42, and the distance D from the conductive layer 46 changes due to the deformation of the movable portion 41. As an example, a microstructure 14 of this example includes a pair of movable portions 41 arranged in a posture with their free ends facing each other.

[0046] Each unit cell UC is composed of a microstructure 14, a conductive layer 46, and a support substrate 47. Microstructure 14 is provided separately for each unit cell UC. The other conductive layers 46 and support substrate 47 are not independent structures for each unit cell UC, but are formed integrally with the regions corresponding to the plurality of unit cells UC.

[0047] The electromagnetic wave control element 10 is a reflective type, and the conductive layer 46 also serves as a reflective layer for reflecting the electromagnetic wave RW. The conductive layer 46 is a metal layer. The support substrate 47 is, for example, a silicon substrate.

[0048] like Figure 5 As shown in FIG. 4 , the piezoelectric element 42 includes a piezoelectric film 42A, a first electrode 42B, and a second electrode 42C, and has a structure in which the second electrode 42C, the piezoelectric film 42A, and the first electrode 42B are stacked in this order from the movable portion 41 side. That is, the first electrode 42B and the second electrode 42C are arranged on both sides of the piezoelectric film 42A in the thickness direction and are used to apply voltage to the piezoelectric film 42A. Figure 5 In order to facilitate visual recognition, the film thickness of each layer or their ratio is appropriately changed and depicted, which does not necessarily reflect the actual film thickness or ratio. Figure 5 The same applies to other drawings.

[0049] The first electrode 42B and the second electrode 42C are connected to the power supply 28. When the power supply 28 applies a voltage V to the piezoelectric film 42A, the piezoelectric film 42A deforms. Figure 5 In FIG, the upper diagram shows a state where voltage V is not applied, and the lower diagram shows a state where voltage V is applied. Figure 4 In the figure, the unit cell UC on the left also shows a state where voltage V is not applied, and the unit cell UC on the right also shows a state where voltage V is applied. When voltage V is applied, the distance D between the free end of the movable portion 41 and the conductive layer 46 changes from D1 to D2. D2 is greater than D1. The distance D2 changes depending on the magnitude of voltage V.

[0050] By changing the distance D between the microstructure 14 and the conductive layer 46 in each unit cell UC, the resonance condition of the microstructure 14 changes, and the change in the resonance condition of the microstructure 14 is manifested as a change in the phase delay of the electromagnetic wave RW. The distance D between the microstructure 14 in each unit cell UC changes according to the voltage V applied to the piezoelectric element 42 of the microstructure 14 in each unit cell UC. Therefore, as an example, the relationship between the voltage V and the phase delay of the electromagnetic wave RW is as follows: Figure 6 shown.

[0051] like Figure 3As shown, if the electromagnetic wave RW is incident on the electromagnetic wave control element 10 from the microstructure 14 side, the electromagnetic wave RW will pass through the microstructure 14. Then, the electromagnetic wave RW is reflected at the conductive layer 46, which also serves as a reflective layer, and again passes through the microstructure 14 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, the electromagnetic wave RW that passes through each unit cell UC is phase modulated by the resonance of the microstructure 14. More specifically, in each unit cell UC, the resonance condition of the microstructure 14 is determined according to the distance D, and the phase modulation of the electromagnetic wave RW is generated by the resonance corresponding to this condition.

[0052] 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 .

[0053] Also like Figure 3 As 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.

[0054] 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.

[0055] For example, consider the following situation: Figure 3 As shown, when there are multiple unit cells UC arranged in one direction, the phase delay of the central unit cell UC is increased, while the phase delay decreases toward the sides. In this case, the wavefronts of the electromagnetic wave RW that pass through each unit cell UC are connected, forming a V-shape, thereby focusing the emitted electromagnetic wave RW. Conversely, consider the case where the phase delay of the central unit cell UC is decreased, while the phase delay increases toward the sides.

[0056] In this case, if the wavefronts of the electromagnetic waves RW passing through each unit cell UC are connected, they form a mountain shape (an inverted V shape), thereby diverging the emitted electromagnetic waves RW. The degree of such focusing and divergence can also be adjusted by controlling the amount of phase delay of the electromagnetic waves RW passing through each unit cell UC by adjusting the magnitude of the applied voltage.

[0057] The metasurface structure 12 is similar to a known metasurface structure, and is formed by two-dimensionally arranging microstructures 14 as metamaterials. 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.

[0058] The movable portion 41 also functions as a substrate supporting the piezoelectric element 42. The movable portion 41 is, for example, a silicon substrate. Various silicon wafers can be used as the silicon substrate. The concept of silicon wafer here includes wafers having a SiO2 layer in a portion, such as SOI (Silicon-On-Insulator) substrates. Furthermore, substrates having the same Young's modulus as commonly available commercial silicon substrates can also be used as appropriate.

[0059] In the piezoelectric element 42, the thickness of the first electrode 42B and the second electrode 42C is not particularly limited, but is preferably 50 nm to 300 nm, for example, approximately 200 nm. The thickness of the piezoelectric film 42A is preferably 1 μm to 10 μm, for example, 1 μm to 5 μm.

[0060] The film formation method of the first electrode 42B, the second electrode 42C, and the piezoelectric film 42A is not particularly limited, but a vapor phase growth method is preferred, and sputtering is particularly preferred.

[0061] The first electrode 42B, the second electrode 42C, and the piezoelectric film 42A can be made of any known material as appropriate.

[0062] Examples of the piezoelectric film 42A include piezoelectric films containing one or two or more perovskite-type oxides (P) represented by the following formula.

[0063] General formula AaBbOc(P)

[0064] (The symbols in the formula are as follows.

[0065] A: is an element at the A position, and is at least one element selected from the group consisting of Pb, Ba, La, Sr, Bi, Li, Na, Ca, Cd, Mg, and K.

[0066] B: is an element at the B position, and is at least one element selected from the group consisting of Ti, Zr, V, Nb, Ta, Sb, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni.

[0067] O: is an oxygen atom.

[0068] The standard is a:b:c = 1:1:3, but their molar ratios may deviate from the standard molar ratio within a range that allows for a perovskite structure.

[0069] The piezoelectric film 42A preferably contains a perovskite-type oxide containing lead as a main component. Here, the main component refers to a component that accounts for 80 mol% or more of the constituent components.

[0070] Examples of the lead-containing perovskite oxide include one or two or more perovskite oxides (PX) represented by the following formula.

[0071] Aa(Zrx、Tiy、Mb-xy)bOc(PX)

[0072] (The symbols in the formula are as follows.

[0073] A: is an element at the A position, and is at least one element including Pb. M is at least one element selected from the group consisting of V, Nb, Ta, and Sb.

[0074] 0<x<b, 0<y<b, 0≤bxy, a:b:c=1:1:3 are the standards, but their molar ratios can deviate from the standard molar ratios within the range that allows the perovskite structure to be obtained.

[0075] The perovskite-type oxide represented by the general formula (PX) is preferred because it has a large dielectric constant.

[0076] Piezoelectric films composed of perovskite-type oxides represented by the general formulas (P) and (PX) have a high piezoelectric strain constant (d31 constant), and thus piezoelectric elements incorporating such piezoelectric films exhibit excellent displacement characteristics. Furthermore, perovskite-type oxides represented by the general formula (PX) are more preferred because their piezoelectric constant is higher than that of perovskite-type oxides represented by the general formula (P).

[0077] Furthermore, a piezoelectric element comprising a piezoelectric film composed of perovskite oxides represented by general formulas (P) and (PX) exhibits voltage-displacement characteristics with excellent linearity within the driving voltage range. These piezoelectric materials exhibit excellent piezoelectric properties when the technology of the present invention is implemented.

[0078] In this example, the movable portion 41 is described using a cantilever beam as an example, but the movable portion 41 is not limited to a cantilever beam and may be a double-support beam, a diaphragm structure, or the like.

[0079] As an example, a method for manufacturing the metasurface structure 12 including the piezoelectric element 42 is as follows: First, a silicon substrate constituting the movable portion 41 is prepared, and the second electrode 42C is formed on the surface of the silicon substrate by sputtering.

[0080] Next, the piezoelectric film 42A is formed on the second electrode 42C by sputtering, and the first electrode 42B is further formed on the piezoelectric film 42A.

[0081] Then, the second electrode 42C, the piezoelectric film 42A, and the first electrode 42B are patterned by photolithography and etching. In addition, at this time, electrode wiring, electrode pads, etc. can be formed on the silicon substrate.

[0082] Next, the silicon substrate with the patterned piezoelectric element 42 and the supporting substrate 47 with the conductive layer 46 are bonded together using an adhesive. The silicon substrate constituting the movable portion 41 is bonded so that the surface opposite the piezoelectric element 42 faces the conductive layer 46. The adhesive serves as the spacer 43. For example, an optically clear adhesive (OCA) that transmits electromagnetic waves RW is used.

[0083] After the silicon substrate on which the piezoelectric element 42 is formed and the support substrate 47 are bonded together, the silicon substrate is patterned into the shape of the movable portion 41. In this way, the electromagnetic wave controlling element 10 is completed.

[0084] As described above, the metasurface structure 12 is formed by two-dimensionally arranging the microstructures 14 as metamaterials on a plane. More specifically, it is basically composed of an arrangement of unit cells UC, each of which is composed of a microstructure 14 and the space around the microstructure 14.

[0085] 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 movable portion 41 is used as in this example, phase modulation occurs due to the interaction between the distance D between the movable portion 41 and the conductive layer 46 and the microstructure 14 . The phase modulation amount is determined by the resonance characteristics of the microstructure 14 that change based on the distance D.

[0086] 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.

[0087] 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.

[0088] Furthermore, in this example, one microstructure 14 is configured to include two movable portions 41 , but the number of movable portions 41 may be one or three or more.

[0089] 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.

[0090] And, as Figure 3 As shown, the preferred embodiment of the metasurface structure 12 is a configuration in which identical microstructures 14 having all identical structures 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 thereto. As described above, a variety of microstructures may be used simultaneously, and the arrangement intervals and arrangements of the microstructures 14 may also be different in the surface direction of the support substrate 47. However, if the controllability of the reflection direction of the electromagnetic wave when a voltage is applied to the piezoelectric element 42 is taken into consideration, the metasurface structure 12 preferably uses all identical 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.

[0091] The conductive layer 46 is not limited; as long as it has sufficient conductivity and can reflect electromagnetic waves RW with a frequency of 0.1 to 0.3 THz, a sheet made of various known materials can be used. Examples of the conductive 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 of the aforementioned frequencies.

[0092] The thickness of the conductive layer 46 is also not limited, and may be appropriately set according to the material forming the conductive layer 46 so as to reflect the electromagnetic wave to be controlled at a desired reflectivity.

[0093] As described above, as an example, the electromagnetic wave control element 10 according to the technology of the present invention includes a conductor represented by a conductive layer 46 and a metasurface structure 12 formed by arranging a plurality of microstructures 14, and is responsive to electromagnetic waves with a frequency of 0.1 to 0.3 THz. Furthermore, the microstructure 14 includes a movable portion 41 whose distance D from the conductive layer 46 changes depending on the voltage applied to the piezoelectric element 42. The piezoelectric element 42 includes a piezoelectric film 42A and a first electrode 42B and a second electrode 42C arranged on either side of the piezoelectric film 42A in the thickness direction. In the electromagnetic wave control element 10, by supplying power to the piezoelectric element 42 of each microstructure 14, the distance D between the movable portion 41 and the conductive layer 46 is changed, thereby forming regions with different resonance conditions in the microstructure 14 for each unit cell UC, thereby reflecting the electromagnetic wave RW with a frequency of 0.1 to 0.3 THz in a desired direction. Furthermore, by changing the power supplied to each fine structure 14 , that is, the voltage applied to the piezoelectric element 42 , the reflection direction of the incident electromagnetic wave RW can be switched.

[0094] Compared to conventional electrostatic MEMS, piezoelectric MEMS, such as the piezoelectric element 42, have better responsiveness. Therefore, in the electromagnetic wave control element 10 having the metasurface structure 12 using MEMS, the emission direction of electromagnetic waves RW with a frequency of 0.1 to 0.3 THz can be switched in a shorter time than before.

[0095] 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 example shown, the conductive layer 46, which is an example of a conductor, is formed integrally with the region facing the plurality of fine structures 14. Figure 7 The conductors may be divided into a plurality of regions, as shown in FIG. 1 . Each conductor 46A corresponding to the divided region faces a portion of the plurality of fine structures 14 .

[0096] And, in Figure 5 In the embodiment, the first electrode 42B and the second electrode 42C of the piezoelectric element 42 are provided as independent elements from the movable portion 41. Figure 8 As shown, the movable portion 41 may also function as the second electrode of the piezoelectric element 42 .

[0097] In the above embodiment, as the type of electromagnetic wave control element, Figure 41 shows an example of a reflective electromagnetic wave control element 10. Furthermore, an example of using the electromagnetic wave control element as a component of an electromagnetic wave reflecting device 2 is shown. The applications of the electromagnetic wave control element are not limited to those described above and may also include applications other than those described above. For example, the electromagnetic wave control element can be used as a component of a so-called leaky wave antenna by combining it with a waveguide that conducts electromagnetic waves RW.

[0098] As an example, Figure 9 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.

[0099] 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.

[0100] As an example, Figure 10 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.

[0101] As an example, Figure 11 and Figure 12 As shown, the 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 is in the shape of a rectangular parallelepiped as a whole. The waveguide component 120 is arranged with its long side direction along the arrangement direction of the microstructure 14. The waveguide component 120 is, for example, a tubular component in the shape of a square tube with a rectangular cross-section. The internal space defined by the inner wall of the waveguide component 120 constitutes a waveguide 120A for conducting the electromagnetic wave RW. The microstructure 14 constituting the metasurface structure 12 is provided on one side of the waveguide component 120. The waveguide component 120 is, for example, made of metal, and a part of the waveguide component 120, more specifically, the surface opposite to the movable portion 41 of the microstructure 14 also serves as Figure 4 A conductor such as the conductive layer 46 shown.

[0102] 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 an electromagnetic wave RW into the waveguide 120A. The waveguide 120A conducts the electromagnetic wave RW sent 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 on the side of the spacer 43, 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.

[0103] In the electromagnetic wave control element 110, the unit cell UC is formed to include at least one fine structure 14 and an opening 121. Figure 4 Similar to the electromagnetic wave controlling element 10 shown, the electromagnetic wave controlling element 110 can control the phase delay of the electromagnetic wave RW by controlling the voltage applied to each unit cell UC. This can control the emission direction of the electromagnetic wave RW emitted from the opening 121 and transmitted through the microstructure 14.

[0104] The metasurface structure 12 can piezoelectrically move the movable portion 41, and thus has a higher responsiveness than conventional devices. Consequently, the electromagnetic wave control element 110 can switch the emission direction of electromagnetic waves RW with a frequency of 0.1 to 0.3 THz in a shorter time than conventional devices.

[0105] exist Figure 12 In the example, a part of the waveguide component 120 is configured to also serve as a conductor, but the conductor may be provided separately from the waveguide component 120.

[0106] And, as Figure 11 and Figure 12 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 11 and Figure 12 structures other than those shown. For example, Figure 13 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 12As shown, the waveguide member is provided with an opening portion for emitting a portion of the electromagnetic wave RW propagating in the waveguide in a direction intersecting with the arrangement direction of the fine structures 14 .

[0107] As a result, electromagnetic waves RW are emitted.

[0108] The electromagnetic wave controlling element 110 used in the leaky wave antenna 100 may also be Figure 7 and Figure 8 Applicable portions of the modified examples shown for the reflective electromagnetic wave controlling element 10 are appropriately combined.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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."

[0114] The disclosure of Japanese Patent Application No. 2023-013603, 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.

[0115] The above-mentioned embodiments further disclose the technologies related to the following supplementary items.

[0116] Supplementary Item 1

[0117] An electromagnetic wave control element comprising:

[0118] electrical conductors; and

[0119] The super surface structure is composed of a plurality of micro structures arranged in an array.

[0120] The microstructure includes a movable portion whose distance from the conductor changes according to the voltage applied to the piezoelectric element.

[0121] The piezoelectric element includes a piezoelectric film and a first electrode and a second electrode disposed on both sides of the piezoelectric film in a thickness direction and for applying a voltage.

[0122] The electromagnetic wave control element acts on electromagnetic waves with a frequency of 0.1 to 0.3 THz.

[0123] Supplementary Item 2

[0124] The electromagnetic wave controlling element according to Supplementary Note 1 includes the first electrode and the second electrode as independent elements from the movable portion.

[0125] Supplementary Item 3

[0126] The electromagnetic wave control element according to Supplementary Note 1 or 2, wherein

[0127] The movable portion also serves as one of the first electrode and the second electrode.

[0128] Supplementary Item 4

[0129] The electromagnetic wave control element according to any one of Supplementary Notes 1 to 3, wherein

[0130] The region of the conductor facing the plurality of fine structures is formed integrally.

[0131] Supplementary Item 5

[0132] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 4, wherein

[0133] The conductor is divided into a plurality of regions, and each region faces a portion of the plurality of microstructures.

[0134] Supplementary Item 6

[0135] The electromagnetic wave control element according to any one of Supplementary Notes 1 to 5, wherein

[0136] The microstructure includes metal.

[0137] Supplementary Item 7

[0138] The electromagnetic wave control element according to any one of Supplementary Notes 1 to 6, wherein

[0139] The microstructure includes an oxide semiconductor.

[0140] Supplementary Item 8

[0141] The electromagnetic wave controlling element according to any one of Supplementary Notes 1 to 7, which is a reflection type that reflects electromagnetic waves.

[0142] Supplementary Item 9

[0143] The electromagnetic wave control element according to Supplementary Note 8, wherein

[0144] The conductor also serves as a reflective layer that reflects electromagnetic waves.

[0145] Supplementary Item 10

[0146] An electromagnetic wave control element according to any one of appendixes 1 to 9, 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.

[0147] Supplementary Item 11

[0148] The electromagnetic wave control element according to Supplementary Item 10, wherein:

[0149] An opening for emitting electromagnetic waves is formed in a portion of a wall surface defining the waveguide.

[0150] Supplementary Item 12

[0151] The electromagnetic wave control element according to Supplementary Note 11, wherein

[0152] A portion of the waveguide member constituting the waveguide also serves as a conductor.

Claims

1. An electromagnetic wave control element comprising: electrical conductors; and The super surface structure is composed of a plurality of micro structures arranged in an array. The microstructure includes a movable portion whose distance from the conductor changes according to a voltage applied to a piezoelectric element. The piezoelectric element includes a piezoelectric film and a first electrode and a second electrode disposed on both sides of the piezoelectric film in a thickness direction and for applying the voltage. The electromagnetic wave control element acts on electromagnetic waves with a frequency of 0.1 to 0.3 THz. 2 . The electromagnetic wave control element according to claim 1 , comprising the first electrode and the second electrode as independent elements from the movable portion.

3. The electromagnetic wave control element according to claim 1, wherein The movable portion also serves as one of the first electrode and the second electrode.

4. The electromagnetic wave control element according to claim 1, wherein The region of the conductor facing the plurality of fine structures is formed integrally.

5. The electromagnetic wave control element according to claim 1, wherein The conductor is divided into a plurality of regions, and each region faces a portion of the plurality of microstructures.

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

7. The electromagnetic wave control element according to claim 1, wherein The microstructure includes an oxide semiconductor. The electromagnetic wave controlling element according to claim 1 , which is a reflection type that reflects the electromagnetic wave.

9. The electromagnetic wave control element according to claim 8, wherein The conductor also serves as a reflective layer for reflecting electromagnetic waves.

10. 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.

11. The electromagnetic wave control element according to claim 10, wherein: An opening for emitting the electromagnetic wave is formed in a portion of a wall surface defining the waveguide.

12. The electromagnetic wave control element according to claim 11, wherein A portion of the waveguide member constituting the waveguide also serves as the conductor.

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