Structure and terahertz wave band electromagnetic wave oscillation device

Abstract

The present invention provides a structure that improves radiation efficiency of terahertz waves. The present invention comprises: an AC generation source; a first electrode and a second electrode that are stacked so as to have the AC generation source interposed therebetween to apply voltage and current to the AC generation source, the second electrode having a smaller area than the first electrode; and a constricted portion that is electrically connected to at least one of the first electrode and the second electrode, the constricted portion being more constricted than the at least one of the first electrode and the second electrode to which the constricted portion is connected.

Description

Structure and terahertz-band electromagnetic wave oscillator

[0001] This disclosure relates to a structure and a terahertz-band electromagnetic wave oscillator.

[0002] In recent years, electromagnetic waves in the terahertz (THz) band, which lies in the electromagnetic wave region between light and radio waves, have attracted attention (Non-Patent Document 1).

[0003] The terahertz wave band (0.1 THz to 10 THz) has the property of penetrating nonpolar materials such as paper and plastic, allowing for non-contact analysis of the material's unique vibration spectrum. By utilizing this property, terahertz waves can be used to non-destructively image and sense the internal information of materials. Terahertz waves can be applied to a wide range of industrial fields, including non-destructive testing, medical applications such as lesion detection, and high-speed communications. Furthermore, terahertz waves can be applied to fields such as checking the freshness of food, verifying the contents of envelopes, airport security checks, and determining the authenticity of paintings.

[0004] M. Tonouchi, Nature Photonics 1, 97 (2007)

[0005] A structure according to one embodiment of the present disclosure comprises an AC source, a first electrode and a second electrode having a smaller area than the first electrode, which are stacked on either side of the AC source and to which a voltage and current are applied, and a constricted portion which is electrically connected to at least one of the first electrode and the second electrode and is narrower than at least one of the connected first electrode and second electrode.

[0006] This is an exploded perspective view of the structure relating to this disclosure. This is a schematic perspective view of the first electrode, the second electrode, and the AC source. This is a schematic perspective view of an electromagnetic wave generator according to one embodiment of this disclosure. This is an exploded perspective view of a conventional structure. This is a diagram showing the analysis results of the distribution of effective gain in the structure relating to this disclosure and in a conventional structure. This is a diagram showing the analysis results of the distribution of effective gain in the two second electrodes relating to this disclosure. This is a diagram showing the change in radiation efficiency when the width of the second electrode is changed. This is a diagram showing the analysis results of the distribution of effective gain when the presence or absence of a third electrode and the position of the third electrode are changed. This is a diagram showing the analysis results of the distribution of effective gain and radiation efficiency when the size of the first electrode is changed. This is a diagram showing the analysis results of the distribution of effective gain in the two second electrodes relating to this disclosure. This is an analysis result showing the surface current density in the two second electrodes relating to this disclosure. This is a diagram showing the surface current density distribution along the longitudinal direction in the two second electrodes relating to this disclosure. This is a diagram showing the surface current density distribution along the longitudinal direction in the two second electrodes relating to this disclosure. This is a schematic diagram for explaining the shape of another second electrode relating to this disclosure. This is a block diagram of a terahertz wave electromagnetic wave oscillator relating to this disclosure.

[0007] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. First, for ease of understanding, an electromagnetic wave generator 1 comprising the structure 10 according to the present disclosure will be described with reference to Figure 3. Next, the structure 10 will be described with reference to Figures 1, 2, etc.

[0008] Figure 3 is a schematic perspective view of an electromagnetic wave generator 1 according to one embodiment of the present disclosure. Figure 3 shows XYZ coordinates. In the XYZ coordinates, the X axis indicates the short direction of the rectangular second electrode 14. The Y axis indicates the long direction of the second electrode 14. The Z axis indicates the direction perpendicular to the XY axis. With respect to the structure 10, the upper jig 22 side is defined as the upper side and the lower jig 21 side is defined as the lower side.

[0009] As shown in Figure 3, the electromagnetic wave generator 1 comprises a structure 10 and a jig 20. The electromagnetic wave generator 1 is connected to a power supply 30 that applies DC current and voltage to an AC source 15 via a first electrode 13, a second electrode 14, wiring 18, and wiring 19.

[0010] As will be described in detail later, in the electromagnetic wave generator 1, electromagnetic waves emitted from the second electrode 14 pass through the second substrate 12, through the hole 22a of the upper jig 22, are focused by the hemispherical lens 23, and are emitted upward. In Figure 3, for convenience, the hemispherical lens 23 is shown above the upper jig 22, but in reality it is located in contact with the top of the second substrate 12. Also, since the degree of penetration into a material changes depending on the wavelength (or frequency) of the electromagnetic wave, the wavelength (frequency) of the electromagnetic wave is adjusted as appropriate according to the purpose of use. Possible purposes of use include checking the freshness of food, verifying the contents of envelopes, airport security checks, or determining the authenticity of paintings.

[0011] [Structure 10] Structure 10 is composed of a first substrate 11, a second substrate 12, a first electrode 13, a second electrode 14, and an AC source 15. These components are stacked from top to bottom along the Z-axis direction (stacking direction) in the order of second substrate 12, second electrode 14, AC source 15, first electrode 13, and first substrate 11. The AC source 15 is sandwiched between the first electrode 13 and the second electrode 14. Alternatively, the AC source 15 is sandwiched between at least one of the first electrode 13 and the second electrode 14 via a conductor. The conductor may be a thin film formed on the AC source 15 in which Ag and Au are stacked.

[0012] The structure 10 does not necessarily have to include a first substrate 11 and / or a second substrate 12. In this case, the first electrode 13 and / or the second electrode 14 can be made of a metal plate or the like. Hereinafter, the structure 10 will be described assuming that it includes a first substrate 11 and a second substrate 12.

[0013] The first substrate 11 has a first electrode 13 to which wiring 19 is connected on its upper surface. The second substrate 12 has a second electrode 14 to which wiring 18 is connected on its lower surface.

[0014] The second substrate 12 efficiently transmits electromagnetic waves generated in the structural parts of the first electrode 13, the second electrode 14, and the AC power source 15.

[0015] The first substrate 11 and the second substrate 12 support the AC power source 15 and dissipate the heat generated in the AC power source 15.

[0016] The first electrode 13 and the second electrode 14 serve as introduction points for applying DC current and voltage in the thickness direction (Z-axis direction) of the AC power source 15. Therefore, the first substrate 11 and the second substrate 12 may be made of materials with high resistance or insulating properties.

[0017] Therefore, the first substrate 11 may be made of a material that has high resistance, is a semiconductor or an insulator, and has a higher thermal conductivity than the AC source 15. The second substrate 12 may be made of a material that has high resistance, is a semiconductor or an insulator, and has a higher thermal conductivity than the AC source 15. For example, as the AC source 15, a single crystal of layered superconductor BSCCO (bismuth strontium calcium copper oxide) may be used. ２ Sr ２ CaCu ２ O ８＋δ Let's assume that Bi2212 is used. The thermal conductivity of Bi2212 at room temperature is known to be 1 to 5 W / (m·K) (hereinafter, the thermal conductivity at room temperature will be referred to as "κ"). Therefore, examples of materials for the first substrate 11 and the second substrate 12 in this case include semi-insulating gallium-arsenide substrates (κ = 55 W / m·K), sapphire substrates (κ = 27 W / (m·K)), germanium substrates (κ = 60 W / (m·K)), and high-resistance silicon substrates (κ = 163 W / (m·K)). Substrates with high thermal conductivity, such as aluminum nitride substrates (κ = 150 W / (m·K)) and diamond substrates (κ = 2000 W / (m·K)), may also be used. It should be noted that the thermal conductivity at room temperature is useful as a reference for extremely low temperatures (superconducting state).

[0018] The first substrate 11 may be made of a conductive material such as a metal, or it may be made of a dielectric material. The second substrate 12 may be made of a ceramic material that transmits electromagnetic waves in the terahertz wave band, or it may be made of a dielectric material.

[0019] The first substrate 11 and the second substrate 12 are not particularly limited in shape and may be circular, rectangular, or square when viewed from the Z-axis direction.

[0020] The second substrate 12 may be appropriately set to be transmissive to electromagnetic waves according to the wavelength or intensity of the electromagnetic waves generated in the structural portions of the first electrode 13, the second electrode 14, and the AC power source 15.

[0021] The AC power source 15 is disposed between the first electrode 13 and the second electrode 14. Voltage and current are applied to the AC power source 15 from the first electrode 13 and the second electrode 14. Thereby, the second electrode 14, the AC power source 15, and the first electrode 13 are configured to be energizable in the thickness direction (Z-axis direction) of the AC power source 15.

[0022] The AC power source 15 may be a superconducting element using a single crystal or polycrystal of a superconductor. The AC power source 15 is, for example, an element having a Josephson junction that utilizes the Josephson effect manifested by weakly coupling two superconductors. As an example of the structure of the Josephson element, there are structures in which two superconductors are separated by a metal or insulator layer, or structures in which a narrow constriction or step is formed between two superconductors.

[0023] The AC power source 15 is, for example, one using a intrinsic Josephson junction contained in a single crystal of a layered superconductor BSCCo (bismuth strontium calcium copper oxide) having a multi-layered Josephson junction. The BSCCo single crystal may be any that can produce the AC Josephson effect. As an example of such a chemical formula, the aforementioned Bi ２ Sr ２ CaCu ２ O ８＋δ (Bi2212), or Bi ２ Sr ２ Ca ２ Cu ３ O １０＋δ (Bi2223), etc.

[0024] The AC power source 15 functions as a current source that generates an alternating current when a direct current and voltage are applied.

[0025] A voltage is applied to the intrinsic Josephson junction inside the AC generator 15 via the first electrode 13 and second electrode 14, which are positioned above and below the AC generator 15. This generates an alternating current inside the AC generator 15 due to the AC Josephson effect. The frequency of the generated AC current is determined solely by the voltage applied to the AC generator 15, and the intensity of the radiated electromagnetic waves depends on the degree of agreement with the resonant frequency determined by the shape of the AC generator 15, as well as the AC current density and impedance matching with free space. Although not shown in the figures, the region between the first electrode 13 and the second electrode 14 surrounding the AC generator 15 may be filled with a dielectric material with a low dielectric constant to achieve impedance matching with free space and maintain mechanical strength.

[0026] Wires 18 and 19 may be made of wire material such as gold wire or copper wire. Wires 18 and 19 have a diameter of, for example, 10 μm, but are not limited to this. As an example, wire 18 is crimped so as to touch the second electrode 14, and wire 19 is crimped so as to touch the first electrode 13, and wires 18 and 19 each constitute external wiring.

[0027] [Jig 20] The jig 20 houses the structure 10 inside, and Figure 3 shows an example thereof. The jig 20 consists of a lower jig 21, an upper jig 22, and a hemispherical lens 23. The lower jig 21 and the upper jig 22 may be engaged (fixed) to each other by fixing means. The fixing means is, for example, a bolt. The jig 20 is housed, for example, inside a refrigerator. Furthermore, the refrigerator is provided with a window to allow terahertz waves to pass to the outside, and current introduction terminals for connecting wiring 18 and 19 to the power supply 30.

[0028] The lower jig 21 presses the first substrate 11 upward when it engages with the upper jig 22. At this time, the first substrate 11 is placed on the upper surface 24 of the lower jig 21. The upper jig 22 presses the second substrate 12 downward when it engages with the lower jig 21. In this way, the jig 20, with the lower jig 21 and the upper jig 22, presses the structure 10 from above and below, stably housing the structure 10 within the jig 20.

[0029] The lower jig 21 and the upper jig 22 may have a heat dissipation function for dissipating heat from the structure 10, and may be made of a metal such as copper.

[0030] The hemispherical lens 23 is provided on the upper surface of the second substrate 12. Electromagnetic waves generated by the structural components of the first electrode 13, the second electrode 14, and the AC power source 15 pass through the second substrate 12 and through the hole 22a that penetrates the upper jig 22 in the Z-axis direction. The hemispherical lens 23 focuses the electromagnetic waves that have passed through the hole 22a and radiates them upward. The size of the hemispherical lens 23 is not particularly limited and may be set as appropriate.

[0031] [First Electrode 13 and Second Electrode 14] Next, the positional relationship of the first electrode 13, the second electrode 14, and the AC source 15 will be explained with reference to Figure 2. Figure 2 is a schematic perspective view of the first electrode 13, the second electrode 14, and the AC source 15. In Figure 2, the figure indicated by reference numeral 200 is a schematic perspective view of the second substrate 12. The figure indicated by reference numeral 201 is a schematic perspective view of the first substrate 11 and the AC source 15. The figure indicated by reference numeral 202 is a schematic perspective view of the first substrate 11, the second substrate 12, and the AC source 15. In Figure 2, the first substrate 11 and the second substrate 12 are assumed to be circular when viewed from the Z-axis direction.

[0032] First, the first electrode 13 and the second electrode 14 will be described. The first electrode 13 is located below the AC power source 15 when viewed from the Z-axis direction. The second electrode 14 is located above the AC power source 15 when viewed from the Z-axis direction. The first electrode 13 and the second electrode 14 apply voltage and current to the intrinsic Josephson junction inside the AC power source 15. The first electrode 13 is connected to wiring 19, and the second electrode 14 is connected to wiring 18. Wiring 18 and wiring 19 are connected to a power supply 30, which supplies DC current and voltage to the first electrode 13 and the second electrode 14.

[0033] The first electrode 13 and the second electrode 14 are not particularly limited as long as they function as electrodes. The first electrode 13 and the second electrode 14 are connected to the AC power source 15. For example, metals such as gold, silver, and copper, which have low electrical resistivity and are commonly used as electrodes, may be used as the electrode materials. The first electrode 13 and the second electrode 14 may each be formed by depositing a thin film on the surfaces of the first substrate 11 and the second substrate 12 by vacuum evaporation or sputtering, etc.

[0034] In FIG. 2, the wiring electrode 60 connected to the end of the second electrode 14 in the Y-axis direction and the wiring electrode 61 connected to the end of the first electrode 13 in the Y-axis direction are shifted in the X-axis direction. This is to prevent the wiring 18 and the first electrode 13, and the wiring 19 and the second electrode 14 from short-circuiting when the wiring 18 and the wiring 19 are used as wire materials.

[0035] In the example of FIG. 2, the wiring electrode 60 and the wiring electrode 61 are drawn out in the Y-axis direction, but they may both be drawn out in the X-axis direction, or may be drawn out separately in the X-axis direction and the Y-axis direction. Also, the wiring electrode 60 and the wiring electrode 61 are each provided as two on the second electrode 14 and the first electrode 13 for symmetry, but each may be one. The wiring electrode 60 in FIG. 2 also functions as a constriction portion 16A. The width of the constriction portion 16A is narrower than the width of the second electrode 14 so that the inductance component in the terahertz waveband generated in the constriction portion 16A is sufficiently larger than the radiation impedance to the space. Thereby, while allowing the current from the power source 30 to pass through the second electrode 14, it has the function of concentrating the current in the terahertz waveband generated in the AC power source 15 on the second electrode 14 without flowing to the power source 30.

[0036] Referring to the figure indicated by the reference numeral 200, the second substrate 12 has a second surface 12A corresponding to the lower surface of the second substrate 12 and a fourth surface 12B corresponding to the upper surface of the second substrate 12. On the second surface 12A, a rectangular second electrode 14 having a longitudinal direction in the Y-axis direction is provided. In FIG. 2, the second electrode 14 has a width W2 in the X-axis direction and a length L2 in the Y-axis direction.

[0037] Next, referring to the figure indicated by reference numeral 201, the first substrate 11 has a first surface 11A corresponding to the upper surface of the first substrate 11 and a third surface 11B corresponding to the lower surface of the first substrate 11. A rectangular first electrode 13 is provided on the first surface 11A. The first electrode 13 has a width of W1 in the X-axis direction and a length of L1 in the Y-axis direction, and W1 > W2 and L1 < L2. The relationship L1 < L2 is to prevent the wiring 18 from short-circuiting with the first electrode 13 when the wiring 18 is made of a wire material such as a gold wire or a copper wire. Also, if the positions of the wiring electrodes 60 and 61 in the X-axis direction are sufficiently shifted with respect to the diameter of the wire material, the wiring 18 and the first electrode 13 will not short-circuit, so L1 > L2 can also be set.

[0038] Incidentally, the relationships W1 > W2 and L1 < L2 are described in relation to FIG. 2, and the structure 10 according to the present disclosure does not necessarily always satisfy W1 > W2 and L1 < L2.

[0039] The AC power source 15 is located above the first electrode 13 and below the second electrode 14. In FIG. 2, as an example, the AC power source 15 has a rectangular parallelepiped shape. The AC power source 15 is positioned such that the short side direction is in the X-axis direction and the long side direction is in the Y-axis direction.

[0040] Incidentally, the AC power source 15 may be positioned such that the short side direction is in the Y-axis direction and the long side direction is in the X-axis direction. Also, the AC power source 15 may be square in the XY plane.

[0041] Next, referring to the figure indicated by reference numeral 202, in the structure 10, the first substrate 11 and the second substrate 12 are arranged such that the first surface 11A of the first substrate 11 and the second surface 12A of the second substrate 12 face each other.

[0042] When viewed from the Z-axis direction (lamination direction), the first electrode 13 has a superimposed region R1 where the second electrode 14 is superimposed and a non-superimposed region R2 where the second electrode 14 is not superimposed. The AC power source 15 is arranged between the superimposed region R1 and the second electrode 14 superimposed on the superimposed region R1. As is clear from FIG. 2, the area of the first electrode 13 viewed from the Z-axis direction is larger than the area of the second electrode 14 viewed from the Z-axis direction.

[0043] Areas S13 and S14 may be calculated as follows. Specifically, the first electrode 13 has a width in the X-axis direction of W1 and a length in the Y-axis direction of L1, so its area S13 = W1 × L1. The second electrode 14 has a width in the X-axis direction of W2 and a length in the Y-axis direction of L2, so its area S14 = W2 × L2.

[0044] The ratio of the area of ​​the first electrode 13 (area S13) as viewed from the stacking direction to the area of ​​the second electrode 14 (area S14) as viewed from the stacking direction may be 2 or more. In Figure 2, as viewed from the Z-axis direction, the first electrode 13 may encompass the second electrode 14. Also, as viewed from the Z-axis direction, the width of the first electrode 13 may be greater than the width of the AC source 15 in the longitudinal direction (Y-axis direction) of the second electrode 14.

[0045] With each of the above configurations, structure 10 can improve the terahertz wave radiation efficiency compared to the conventional structure 40, which will be described later with reference to Figure 4.

[0046] [Second Electrode 16] The second electrode according to this disclosure is not limited to the shape described with reference to Figure 2. Other second electrodes 16 according to this disclosure will be described below with reference to Figure 1. Figure 1 is an exploded perspective view of the structure 10 according to this disclosure. In Figure 1, the first substrate 11, the second substrate 12, and the AC source 15 are shown at a distance from each other for ease of viewing, but in reality they are connected to each other as shown in Figure 2. It should be noted that this also applies to Figure 4 and others described later.

[0047] Referring to Figure 1, a wiring electrode 60 is connected to the end of the second electrode 16 in the longitudinal direction (Y-axis direction). The wiring electrode 60 is located on the second substrate 12 and connects the wiring 18 (not shown) to the end of the second electrode 16 in the longitudinal direction (Y-axis direction). The second electrode 16 has an overlapping portion 16R on which the AC generation source 15 is superimposed when viewed from the stacking direction.

[0048] Viewed from the stacking direction, the superimposed portion 16R is located in a region that includes the central position of the second electrode 16 in the longitudinal direction. However, there may be cases where the AC source 15 is not located in the central position of the second electrode 16 in the longitudinal direction. In that case, depending on the position of the AC source 15, the superimposed portion 16R is located in a region that includes a position different from the central position of the second electrode 16 in the longitudinal direction, as viewed from the stacking direction.

[0049] Furthermore, the second electrode 16 may have the following configuration. Specifically, the second electrode 16 has a wiring electrode 60 connected to its end in the longitudinal direction (Y-axis direction). In this case, a constricted portion 16A is connected between the second electrode 16 and the wiring electrode 60. The width of the constricted portion 16A in the short direction (X-axis direction) is narrower than the width of the second electrode 16 in the short direction (X-axis direction) of the superimposed portion 16R.

[0050] The wiring electrode 60 is an electrode for applying voltage and current to the AC power source 15, and is located in a place where it has little influence on the radiation characteristics. For this reason, the wiring electrode 60 can also serve as part of the constricted section 16A. The same applies to the wiring electrode 61, which will be described later.

[0051] The structure 10 has a constricted portion 16A, which reduces the current density of the electromagnetic wave current of the second electrode 16 at the connection point between the second electrode 16 and the wiring electrode 60, thereby improving radiation efficiency.

[0052] The width of at least one side of the second electrode 16 in the short direction (X-axis direction) may be configured to decrease as it approaches the end side in the long direction (Y-axis direction) of the second electrode 16.

[0053] Here, the explanation assumes that the constricted portion 16A is connected to the second electrode 16, but the constricted portion (not shown) may be connected to the first electrode 13 instead of the second electrode 16, or together with the second electrode 16. For example, the constricted portion may be connected to the end of the first electrode 13 in the Y-axis direction. The wiring electrode 61 is connected to the end of the first electrode 13 in the Y-axis direction, and this wiring electrode 61 can also be considered as the constricted portion. Furthermore, the wiring electrode 60 may be led out from the second electrode 16 in the X-axis direction, and the wiring electrode 61 may be led out from the first electrode 13 in the X-axis direction. Moreover, the leading directions of the wiring electrode 60 and the wiring electrode 61 may be separated into the X-axis direction and the Y-axis direction.

[0054] The width of the second electrode 16 in the short direction (X-axis direction) may decrease as it approaches the end side in the long direction (Y-axis direction). By making the second electrode 16 tapered, fluctuations in radiation efficiency corresponding to changes in oscillation frequency can be tolerated. The second electrode 16 is not limited to a tapered shape and may have other shapes such as a stepped shape or an elliptical shape.

[0055] When the oscillation frequency is fixed, the second electrode 16 may have a shape in which the width in the X-axis direction is discontinuously narrowed, rather than a tapered shape in which the width in the X-axis direction is continuously and gradually narrowed. For example, the second electrode 16 may have a shape in which the width in the X-axis direction is stepped.

[0056] [Third Electrode 17] As will be described later with reference to Figure 8, the electromagnetic wave generator 1 may further be provided with a third electrode 17 in order to radiate more terahertz waves upward in the Z-axis direction. As described with reference to Figure 2, the structure 10 according to the present disclosure comprises a first substrate 11 having a first surface 11A and a second substrate 12 having a second surface 12A, and the first substrate 11 and the second substrate 12 are superimposed such that the first surface 11A and the second surface 12A face each other. The first electrode 13 is located on the first surface 11A and the second electrode 14 is located on the second surface 12A. The first substrate 11 has a third surface 11B on the side opposite to the first surface 11A. The third electrode 17 may be located on the third surface 11B.

[0057] In Figure 3, the first substrate 11 is placed on the surface 24, which is the upper surface of the lower jig 21. In the example of Figure 3, if the surface 24 or the lower jig 21 is made of a metal such as copper, the surface 24 can function as the third electrode 17. The surface 24 does not need to be grounded and may be electrically floating, and the third electrode 17 does not necessarily need to be grounded.

[0058] [Summary] The configuration of the structure 10 according to this disclosure has been described above. By having the above-described configurations, the structure 10 can improve the radiation efficiency of the structure 10 compared to the conventional structure 40. For reference, the effects of the structure 10 will be explained in comparison with the conventional structure 40 with reference to Figure 4.

[0059] Figure 4 is an exploded perspective view of a conventional structure 40. The structure 40 is composed of a first substrate 41, a second substrate 42, a first electrode 43, a second electrode 44, and an oscillator 45. These components are stacked from top to bottom along the Z-axis direction (stacking direction) in the order of second substrate 42, second electrode 44, oscillator 45, first electrode 43, and first substrate 41. The first substrate 41, second substrate 42, and oscillator 45 may have the same configuration as the first substrate 11, second substrate 12, and AC source 15, respectively, so the first electrode 43 and second electrode 44 will be described below.

[0060] The first electrode 43 is provided on the upper surface of the first substrate 41. The first electrode 43 has a rectangular shape with the X-axis direction as its longitudinal direction. The second electrode 44 is provided on the lower surface of the second substrate 42. The second electrode 44 has a rectangular shape with the Y-axis direction as its longitudinal direction. The oscillation element 45 is located in the superposition region between the first electrode 43 and the second electrode 44.

[0061] The inventors of this application have found that, compared to the conventional structure 40, the structure 10 according to this disclosure can adjust the matching between the AC source 15 and free space by increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 16. As a result, the structure 10 can significantly increase the radiation efficiency compared to the conventional structure 40. Furthermore, the structure 10 can increase the proportion of terahertz waves radiated upward in the Z-axis direction by increasing the area of ​​the first electrode 13 provided on the first substrate 11.

[0062] [Analysis] The structure 10 according to this disclosure has a higher radiation efficiency than the conventional structure 40 described with reference to Figure 4. This is shown by the analysis results using an analytical model.

[0063] [Analysis Model] In the analysis model of this disclosure, the following material properties are used as an example in the calculations: 1. First substrate 11 - Sapphire substrate: Diameter 7 mm, thickness 0.5 mm, relative permittivity ε = 10 (isotropic) 2. Second substrate 12 - Sapphire substrate: Diameter 7 mm, thickness 0.5 mm, relative permittivity ε = 10 (isotropic) 3. AC source 15 - Rectangular parallelepiped (80 μm (X-axis direction) × 400 μm (Y-axis direction) × 5 μm (Z-axis direction)) - Superconductor: ρa = 10 －９ [Ω・m], ρb = 10 －９ [Ω・m] (plane direction), ρc = 5 [Ω・m], relative dielectric constant ε = 17 (isotropic) - Contact surface with first electrode 13 and second electrode 14: gold, 4.1×10 ７ [S / m] ・Current port 1: 1.25Ω, 0.5W. Set on the yz plane at the +x side end of AC source 15. ・Current port 2: 1.25Ω, 0.5W. Set on the yz plane at the -x side end of AC source 15. ・Insulator. Between current port 1 and the superconductor, and between current port 2 and the superconductor: relative permittivity ε = 17 4. First electrode 13 4mm × 4mm (standard size in this analysis) ・Gold, 4.1 × 10 ７ [S / m]5. Second electrode 14 / second electrode 16 ・Gold, 4.1×10 ７ [S / m] 6. Calculation frequency for analysis: 0.43 THz The current ports mentioned above are set as virtual connection points for analysis and are not actually present.

[0064] [Comparison with conventional structures] The effects obtained by structure 10 will be explained below with reference to Figure 5, etc.

[0065] Figure 5 shows the results of the analysis of the distribution of effective gain in the structure 10 according to this disclosure and the conventional structure 40. Of Figure 5, the figure indicated by reference numeral 500 shows the results of the analysis of the distribution of effective gain in the structure 10, which was explained with reference to Figure 1. The figure indicated by reference numeral 501 shows the results of the analysis of the distribution of effective gain in the conventional structure 40, which was explained with reference to Figure 4. The surroundings of the structure 10 and the structure 40 are assumed to be air.

[0066] First, let's explain radiation efficiency and realized gain. Radiation efficiency is the ratio of the power supplied to the antenna to the total radiated power, and the total radiated power includes material losses and reflected power from the antenna. Realized gain is the directivity of the radiated power for an omnidirectional antenna, and the total radiated power includes material losses and reflected power from the antenna.

[0067] According to the analysis results, structure 10 had a radiation efficiency of 75.3% and an effective gain of 10.8 dBi in the +Z axis direction. Structure 40 had a radiation efficiency of 32.1% and a gain of 0.9 dBi in the +Z axis direction. This indicates that structure 10 has significantly improved radiation efficiency compared to structure 40, that the power output in the +Z axis direction is approximately 10 times greater for the same input power, and that the overall performance of structure 10 has significantly improved.

[0068] In structure 10, the matching between the AC source 15 and free space is adjusted by increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 16. As a result, structure 10 has a significantly higher radiation efficiency compared to the conventional structure 40. Furthermore, in structure 10, the width of the second electrode 16 in the short direction (X-axis direction) decreases as it approaches the end from the overlapping portion 16R. As a result, structure 10 forms a constricted portion 16A at the connection point between the second electrode 16 and the wiring electrode 60 connected to the second electrode 16, blocking the high-frequency current flowing from the second electrode 16 to the wiring electrode 60. In this example, the wiring electrode 60 also serves as the constricted portion 16A. This allows the high-frequency current that is the source of terahertz waves to be concentrated on the second electrode 16, improving radiation efficiency. In addition, by increasing the area of ​​the first electrode 13, structure 10 can increase the proportion of terahertz waves radiated upward in the Z-axis direction. For these reasons, it is believed that the aforementioned effects were obtained by the structure 10.

[0069] [Shape of the second electrode and structure of the first electrode] Figure 6 is a diagram showing the analysis results of the distribution of effective gain in the second electrode 14 and the second electrode 16 according to this disclosure. In Figure 6, the first electrode 13 is formed by making the entire first substrate 11 a metal plate (copper plate).

[0070] In Figure 6, the figure indicated by reference numeral 600 shows the analysis results of the distribution of effective gain when the second electrode 14 described with reference to Figure 2 is used and the entire first substrate 11 is made of metal. The figure below reference numeral 600 shows the effective gain (dBi).

[0071] The figure shown by reference numeral 601 shows the analysis results of the distribution of effective gain when the second electrode 16 described with reference to Figure 1 is used and the entire first substrate 11 is made of metal. The figure below reference numeral 601 shows the effective gain (dBi).

[0072] Referring to reference numeral 600, the radiation efficiency was 73.0% when the second electrode 14 was used. Referring to reference numeral 601, the radiation efficiency was 76.2% when the second electrode 16 was used. In both cases, the radiation efficiency was significantly improved compared to the conventional structure 40, and the effective gain of terahertz waves in the +Z axis direction was also shown to be higher. Furthermore, the second electrode 16 showed a higher effective gain than the second electrode 14.

[0073] [Width of the second electrode] Figure 7 shows the change in radiation efficiency when the width of the second electrode 16 is changed. The figure indicated by reference numeral 700 is an exploded perspective view of the second electrode 16 as described with reference to Figure 1. The figure indicated by reference numeral 701 shows a graph with the width W2 [μm] of the second electrode 16 on the horizontal axis and the radiation efficiency [%] on the vertical axis.

[0074] Referring to the figure shown by reference numeral 700, the second electrode 16 is formed in a tapered shape, gradually narrowing in width towards the end in the Y-axis direction. Here, the maximum width of the second electrode 16 in the X-axis direction is defined as width W2. The graph shown by reference numeral 701 shows the results of analyzing the radiation efficiency of the structure 10 when W2 is varied between 320 μm and 400 μm.

[0075] From this graph, it can be seen that the radiation efficiency of the structure 10 changes with the change in the width W2 of the second electrode 16. Therefore, it can be seen that there is a suitable value for the width W2 of the second electrode 16 that increases the radiation efficiency of the structure 10, depending on the shape or size of the AC source 15, the shapes of the first electrode 13 and the second electrode 16, etc.

[0076] [Presence and position of the third electrode] Figure 8 shows the results of the analysis of the distribution of effective gain when the presence or absence of the third electrode 17 and the position of the third electrode 17 are changed. The first electrode 13 is a 4 mm x 4 mm square.

[0077] In Figure 8, the figure indicated by reference numeral 800 shows the analysis results of the effective gain distribution when the second electrode 16 described with reference to Figure 1 is used. The figure indicated by reference numeral 801 shows the analysis results of the effective gain distribution when the third electrode 17 is provided on the lower surface of the first substrate 11 and the second electrode 16 described with reference to Figure 1 is used. The figure indicated by reference numeral 802 shows the analysis results of the effective gain distribution when the third electrode 17 is provided on the upper surface of the second substrate 12 and the second electrode 16 described with reference to Figure 1 is used.

[0078] Referring to the diagram shown in reference numeral 800, the radiation efficiency in this case was 77.5%. By increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 16, the matching between the AC source 15 and free space was adjusted, resulting in increased radiation efficiency. Furthermore, terahertz waves were radiated in both directions along the Z-axis.

[0079] Referring to the figure shown by reference numeral 801, the effective gain radiation efficiency in this case was 70.4%. In this case as well, by increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 16, the matching between the AC source 15 and free space was adjusted, and the radiation efficiency was increased. Furthermore, it was found that more terahertz waves were radiated upward in the Z-axis direction.

[0080] Referring to the figure shown in reference numeral 802, the effective gain radiation efficiency in this case was 48.6%. Furthermore, it was found that more terahertz waves were radiated downwards along the Z-axis.

[0081] Thus, it has been shown that in the structure 10 according to this disclosure, the distribution of effective gain changes significantly depending on the presence or absence of the third electrode 17, and in particular, the position in which the third electrode 17 is provided. Specifically, it has been shown that when the third electrode 17 is placed on the upper surface of the second substrate 12, the effective gain in the +z direction decreases. This is thought to be due to an increase in the proportion of terahertz waves radiated downward by the third electrode 17.

[0082] [Size of the first electrode] Figure 9 shows the distribution of effective gain and the analysis results of radiation efficiency when the size of the first electrode 13 is changed.

[0083] In Figure 9, the figure indicated by reference numeral 900 shows the analysis results of the distribution of effective gain when using the second electrode 16 described with reference to Figure 1. In this case, the first electrode 13 is a 4 mm x 4 mm square. The figure indicated by reference numeral 901 shows the analysis results of the distribution of effective gain when the first electrode 13, which was a 4 mm x 4 mm square, is shortened by 0.25 mm at both ends in the X-axis direction in the second electrode 16 described with reference to Figure 1. The figure indicated by reference numeral 902 shows a graph where the horizontal axis is the width W1 [mm] of the first electrode 13 in the X-axis direction and the vertical axis is the radiation efficiency [%] of the structure 10.

[0084] Referring to the figure shown in reference numeral 900, the radiation efficiency in this case was 77.5%.

[0085] Referring to the figure shown in reference numeral 901, the radiation efficiency in this case was 75.3%. In addition, the effective gain in the +Z axis direction was 10.8 dBi, and the proportion of terahertz waves radiated upward in the Z axis direction increased.

[0086] These results indicate that the radiation efficiency remains largely unchanged even when the shape of the first electrode 13 is altered. In all cases, increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 16 adjusts the matching between the AC source 15 and free space, thereby increasing the radiation efficiency.

[0087] As explained with reference to Figure 2, the ratio of the area of ​​the first electrode 13 as viewed from the stacking direction to the area of ​​the second electrode 14 as viewed from the stacking direction may be 2 or more, which can improve the terahertz wave radiation efficiency. This will be explained with reference to reference numeral 902 in Figure 9. The figure shown by reference numeral 902 shows a graph with the width W1 [mm] of the first electrode 13 in the X-axis direction as the horizontal axis and the radiation efficiency [%] of the structure 10 as the vertical axis.

[0088] A second electrode 14 with a length of 4 mm and a width of 0.24 mm was prepared. A first electrode 13 with a length of 4 mm was also prepared. The width of the first electrode 13 was varied in four patterns: (A) 0.24 mm, (B) 0.48 mm, (C) 0.72 mm, and (D) 0.96 mm. (A) to (D) are values ​​such that the ratio of the area of ​​the first electrode 13 to the area of ​​the second electrode 14 as viewed from the stacking direction is 1, 2, 3, and 4 times, respectively.

[0089] The radiation efficiencies of (A) to (D) at this time were 62.3% for (A), 76.4% for (B), 75.9% for (C), and 77.2% for (D), as shown in the graph of reference numeral 902. Thus, it can be seen that the terahertz wave radiation efficiency is improved when the ratio of the area of ​​the first electrode 13 as viewed from the stacking direction to the area of ​​the second electrode 14 as viewed from the stacking direction is 2 or more.

[0090] [Surface Current Density 1] Figure 10 shows the results of the analysis of the distribution of effective gain in the second electrode 14 and the second electrode 16 according to the present disclosure. In Figure 10, the first electrode 13 is provided below the second electrode 14 and the second electrode 16 for the analysis.

[0091] In Figure 10, the figure indicated by reference numeral 1000 shows the analysis results of the effective gain distribution when using the second electrode 16, which was described with reference to Figure 1. The figure indicated by reference numeral 1001 shows the analysis results of the effective gain distribution when using the second electrode 14, which was described with reference to Figure 2. The second electrode 14 has a constricted portion 16A at its end.

[0092] Referring to the diagram shown in reference numeral 1000, the radiation efficiency in this case was 77.5%. By increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 16, the matching between the AC source 15 and free space is adjusted, thereby increasing the radiation efficiency.

[0093] Referring to the figure shown by reference numeral 1001, the radiation efficiency in this case was 72.8%. In this case as well, although the radiation efficiency was slightly lower than that of the second electrode 16, the radiation efficiency was increased by adjusting the matching between the AC source 15 and free space after increasing the area of ​​the first electrode 13 and then changing the width of the second electrode 14.

[0094] Next, Figure 11 shows the analysis results illustrating the surface current density in the second electrode 14 and the second electrode 16 according to this disclosure.

[0095] In Figure 11, the figure indicated by reference numeral 1100 shows the analysis results of the surface current density on the second electrode 16 at the top, and the analysis results of the surface current density on the first electrode 13 at the bottom. Similarly, the figure indicated by reference numeral 1101 shows the analysis results of the surface current density on the second electrode 14 at the top, and the analysis results of the surface current density on the first electrode 13 at the bottom.

[0096] By comparing the figure shown with reference numeral 1100 and the figure shown with reference numeral 1101, it can be seen that by making the second electrode tapered, as in the second electrode 16, the current can be more concentrated in the vicinity of the AC source 15. Furthermore, by making the second electrode 16 tapered, the effect of tolerating fluctuations in the oscillation frequency of the AC source 15 can be obtained. In addition, the area of ​​high surface current density is wider in the first electrode 13 shown with reference numeral 1101 than in the first electrode 13 shown with reference numeral 1100.

[0097] These results indicate that by providing a tapered second electrode 16, the region with high surface current density can be further concentrated while maintaining the matching conditions for the antenna, thereby contributing to an improvement in radiation efficiency.

[0098] Referring to the diagrams below reference numeral 1100 and 1101, the wiring electrode 61 is connected to the first electrode 13 at a location that is not in a region of high surface current density on the first electrode 13. This configuration reduces the impact on the antenna's directivity characteristics. Such design considerations also reduce the impact on the distribution of the effective gain of the structure 10. Furthermore, because the wiring electrodes 60 and 61 are located at different positions in the XY plane, a short circuit will not occur between the first electrode 13 and the second electrode 14 or the second electrode 16 if the wiring 18 and 19 are made of gold or copper wire or the like.

[0099] The above configuration can also be expressed as follows: A wiring electrode 61 is connected to the end of the first electrode 13 in the longitudinal direction (Y-axis direction). The wiring electrode 61 is located on the first substrate 11 and connects the wiring 19 (not shown) to the end of the first electrode 13 in the longitudinal direction (Y-axis direction).

[0100] In this case, the AC source 15 has an outer shape with a first side and a second side parallel to the longitudinal direction (Y-axis direction) of the second electrode. The first side has a first end and a second end at both ends in the longitudinal direction of the second electrode. When viewed from the stacking direction, the position where the wiring electrode 61 is connected to the first electrode 13 is located outside the range enclosed by a straight line passing through the first end and perpendicular to the first side, and a straight line passing through the second end and perpendicular to the first side. Depending on the shape of the AC source 15 and the values ​​of the applied voltage and current, the part where the high-frequency current generated by the AC source 15 is large changes. Here, the long side of the AC source 15 is parallel to the longitudinal direction of the second electrode, and a mode is used in which the direction of the generated high-frequency current is directed toward the short side of the second electrode. Conversely, the long side of the AC source 15 may be perpendicular to the longitudinal direction of the second electrode, so that the direction of the generated high-frequency current is toward the short side of the second electrode.

[0101] This configuration reduces the impact on the antenna's directional characteristics. Furthermore, it minimizes the impact on the distribution of the effective gain of the structure 10.

[0102] Figure 12 shows the surface current density distribution along the longitudinal direction of the second electrode 14 and the second electrode 16 according to this disclosure.

[0103] Of the figures in Figure 12, the figure indicated by reference numeral 1200 shows the structure 10 when the second electrode 16 is used (hereinafter referred to as "structure 10A"). The figure indicated by reference numeral 1201 shows the structure 10 when the second electrode 14 is used (hereinafter referred to as "structure 10B"). The figure indicated by reference numeral 1202 shows a graph with the position (L) of the second electrode on the horizontal axis and the surface current density on the vertical axis. Here, position (L) refers to the position in the left-right direction in the Y-axis direction, with the center in the longitudinal direction (Y-axis direction) of the second electrode being zero (the position along the dashed line in reference numerals 1200 and 1201).

[0104] As shown in the figure, structure 10A has a high peak value at position zero. On the other hand, in structure 10B, the peak value is distributed in the range of L from -1 to +1, showing the effect of multiple resonances due to position L. From this, it can be seen that in structure 10A, the portion with a high surface current density is concentrated in the central part of the second electrode 16, more so than in structure 10B.

[0105] [Surface Current Density 2] Figure 13 shows the surface current density distribution along the longitudinal direction in the second electrode 130 and the second electrode 14 according to this disclosure.

[0106] In Figure 13, the figure indicated by reference numeral 1300 shows the structure 10 when the second electrode 130 is used (hereinafter referred to as "structure 10C"). The figure indicated by reference numeral 1301 shows the structure 10 when the second electrode 14 is used. Structure 10 will hereinafter be referred to as "structure 10D". Structure 10D has the same structure as structure 10B shown in Figure 12.

[0107] The figure shown in reference numeral 1302 is a graph with the position (L) of the second electrode on the horizontal axis and the surface current density on the vertical axis. Here, position (L) refers to the position in the left-right direction of the Y-axis, with the center of the second electrode in the longitudinal direction (Y-axis direction) being zero. The position in the left-right direction of the Y-axis is the position along the dashed line in reference numerals 1300 and 1301.

[0108] Referring to the figure shown in reference numeral 1300, the second electrode 130 has a shape in which the width in the X-axis direction narrows in a stepped manner towards the end of the second electrode 130. In the illustrated example, the width in the X-axis direction of the second electrode 130 narrows in four steps from the center to the end in the longitudinal direction (Y-axis direction) of the second electrode 130. In the region of the second electrode 130 with the widest width in the X-axis direction, the width in the X-axis direction is set to W2 and the length in the Y-axis direction is set to T (1 mm). In the next step, the width in the X-axis direction is set to W2 × 3 / 4 and the length in the Y-axis direction is set to 0.5T (0.5 mm). In the next step, the width in the X-axis direction is set to W2 × 2 / 4 and the length in the Y-axis direction is set to 0.5T (0.5 mm). In the next step, the width in the X-axis direction is set to W2 × 1 / 4 and the length in the Y-axis direction is set to 0.5T (0.5 mm).

[0109] As shown in the figure of reference numeral 1302, structure 10C has a high peak value at position zero. On the other hand, structure 10D shows more influence from multiple resonances due to position L than structure 10C. From this, it can be seen that structure 10C concentrates the surface current density in the central part of the second electrode 130 more than structure 10D.

[0110] [Shape of the Second Electrode] The second electrode according to this disclosure is not limited to the shape described with reference to Figures 1 and 2. Other examples of the shape of the second electrode according to this disclosure will be described below with reference to Figure 14. Figure 14 is a schematic diagram for illustrating the shape of other second electrodes according to this disclosure.

[0111] The diagram shown by reference numeral 1400 in Figure 14 shows a schematic diagram of the second electrode 140A according to this disclosure. The second electrode 140A has an overlapping portion 16R on which the AC generation source 15 is superimposed when viewed from the stacking direction. The second electrode 140A has a shape in which the width in the X-axis direction narrows in a stepped manner towards the end of the second electrode 140A. In the illustrated example, the width in the X-axis direction of the second electrode 140A narrows in three steps from the center to the end in the longitudinal direction (Y-axis direction) of the second electrode 140A. The second electrode 130, which was described with reference to Figure 13, narrowed in the X-axis direction in four steps, but the second electrode 140A differs from the second electrode 130 in the number of steps in which the width narrows. The width in the X-axis direction of the second electrode 140A may narrow in two steps, or in five or more steps. The width of the steps in the X-axis direction and the length of the steps in the Y-axis direction may also be set as appropriate. In this example, the wiring electrode 60 also serves as the narrowing portion 16A.

[0112] The diagram shown by reference numeral 1401 in Figure 14 shows a schematic diagram of the second electrode 140B according to this disclosure. The second electrode 140B has multiple superimposed portions 16R on which the AC power source 15 is superimposed when viewed from the stacking direction. In the illustrated example, the second electrode 140B has three superimposed portions 16. In the illustrated example, the second electrode 140B is formed in an elliptical shape with the X-axis direction as the minor axis and the Y-axis direction as the major axis. The lengths of the major and minor axes may be set as appropriate. In this way, in the second electrode 140A and the second electrode 140B, multiple superimposed portions 16R on which the AC power source 15 is superimposed may be provided within a single second electrode. The oscillation power can be increased by providing multiple AC power sources 15. The effect of providing multiple AC power sources 15 can be easily considered in the design by taking it into account in the analysis model.

[0113] The structure 10 according to this disclosure can also improve the terahertz wave radiation efficiency compared to the conventional structure 40 described with reference to Figure 4, by having the shape of the second electrode 140A or the second electrode 140B. In this example as well, the wiring electrode 60 also serves as the constricted portion 16A.

[0114] Furthermore, although the above explanation described the case where there is one second electrode superimposed on the AC source 15, multiple second electrodes superimposed on the AC source 15 may be provided. The role of the constriction is to block the terahertz wave current and allow the DC current from the power supply 30 to pass through. By placing the constriction between multiple second electrodes, the terahertz wave current between the second electrodes can be blocked, and each second electrode can be designed individually. In this case, the far-field directivity of the terahertz waves can be designed by the radiation from multiple second electrodes, the first electrode 13, and the AC source 15. Alternatively, multiple second electrodes may be arranged in the X-axis direction and connected to the same power supply 30. In this case, by making the resonant frequencies of each AC source 15 different, it is possible to switch the AC source 15 that resonates in response to the applied voltage, thereby widening the frequency variable range of the radiated terahertz waves and designing the directivity of the terahertz waves. Thus, the second electrode according to this disclosure is not limited to the shape described with reference to Figures 1 and 2, but can be made into various shapes, and these shapes can also improve the radiation efficiency compared to conventional designs.

[0115] [Terahertz Waveband Electromagnetic Wave Oscillator] Next, with reference to Figure 15, the terahertz waveband electromagnetic wave oscillator 50 according to this disclosure will be described. Figure 15 is a block diagram of the terahertz waveband electromagnetic wave oscillator 50 according to this disclosure.

[0116] The terahertz wave electromagnetic wave oscillator 50 comprises a refrigerator 51, an oscillator / antenna unit 52, and a power supply 53.

[0117] The refrigerator 51 maintains the superconductor constituting the AC source 15 in the superconducting region (below the superconducting transition temperature), controlling and maintaining a temperature range suitable for terahertz wave oscillation. The refrigerator 51 may be replaced by other temperature control mechanisms if this function can be achieved.

[0118] The oscillator / antenna unit 52 is housed inside the refrigerator 51. The oscillator / antenna unit 52 includes a terahertz-wave electromagnetic wave oscillator and an antenna. The oscillator emits terahertz-wave electromagnetic waves using the AC Josephson effect. The antenna may have an antenna function; for example, a second electrode superimposed on the AC source 15 and having a larger area than the AC source 15 may be designed as the antenna. The oscillator / antenna unit 52 may have its function provided by the structure 10.

[0119] The power supply 53 applies current and voltage to the superconductor of the AC power source 15. The power supply 53 may be the power supply 30 described with reference to Figure 3.

[0120] By having the above configuration, the terahertz wave electromagnetic wave oscillator 50 can improve the radiation efficiency of terahertz waves compared to conventional devices.

[0121] (Summary) The structure according to Embodiment 1 of the present disclosure comprises an AC source, a first electrode and a second electrode having a smaller area than the first electrode, which are stacked on either side of the AC source and to which a voltage and current are applied, and a constricted portion which is electrically connected to at least one of the first electrode and the second electrode and is narrower than at least one of the connected first electrode and second electrode.

[0122] According to the above configuration, the structure according to Embodiment 1 of the present disclosure can reduce the current density of the current that becomes an electromagnetic wave in the constricted portion and improve radiation efficiency.

[0123] The structure according to Embodiment 2 of the present disclosure, in Embodiment 1, has a constricted portion and a superimposed portion on which the AC generation source is superimposed when viewed from the stacking direction, wherein the constricted portion is located closer to the end in the longitudinal direction of the second electrode than the superimposed portion, and the width in the short direction of the second electrode is narrower than that of the superimposed portion.

[0124] According to the above configuration, the structure relating to Embodiment 2 of the present disclosure can further improve radiation efficiency.

[0125] In the structure according to embodiment 3 of the present disclosure, in embodiment 2, the width of at least one of the second electrodes in the short direction decreases as it approaches the end side.

[0126] According to the above configuration, the structure relating to Embodiment 3 of the present disclosure can further improve radiation efficiency.

[0127] In the structure according to Embodiment 4 of the present disclosure, in Embodiment 2 or 3, the superimposed portion is located in a region that includes the central position of the second electrode in the longitudinal direction, as viewed from the stacking direction.

[0128] According to the above configuration, the structure relating to Embodiment 4 of the present disclosure can further improve radiation efficiency.

[0129] The structure according to Embodiment 5 of the present disclosure further comprises a first electrode-side wiring electrode connected to the first electrode in any of Embodiments 1 to 4, wherein the external shape of the AC source extends along the longitudinal direction of the second electrode and has a first side having a first end and a second end, and when viewed from the stacking direction, the position where the first electrode-side wiring electrode is connected to the first electrode is located outside the range enclosed by a straight line passing through the first end and perpendicular to the first side and a straight line passing through the second end and perpendicular to the first side.

[0130] According to the above configuration, the structure relating to Embodiment 5 of the present disclosure can further improve radiation efficiency.

[0131] The structure according to Embodiment 6 of the present disclosure further comprises, in any of Embodiments 1 to 5 above, a first substrate having a first surface and a second substrate having a second surface, wherein the first substrate and the second substrate are superimposed such that the first surface and the second surface face each other, the first electrode is arranged on the first surface and the second electrode is arranged on the second surface.

[0132] According to the above configuration, the structure relating to embodiment 6 of the present disclosure can further improve radiation efficiency.

[0133] In the structure according to Embodiment 7 of the present disclosure, in Embodiment 6, the first substrate and the second substrate are formed from at least one selected from the group consisting of gallium arsenide, sapphire, germanium, high-resistivity silicon, aluminum nitride, and diamond.

[0134] According to the above configuration, the structure relating to Embodiment 7 of the present disclosure can further improve radiation efficiency.

[0135] The structure according to embodiment 8 of the present disclosure further comprises a third electrode different from the first electrode and the second electrode in embodiment 6 or 7, the first substrate further has a third surface opposite to the first surface, and the third electrode is arranged on the third surface.

[0136] According to the above configuration, the structure relating to Embodiment 8 of the present disclosure can further improve the effective gain.

[0137] In the structure relating to Embodiment 9 of the present disclosure, the AC source includes a superconductor in any of Embodiments 1 to 8.

[0138] According to the above configuration, the structure relating to embodiment 9 of the present disclosure can further improve radiation efficiency.

[0139] The terahertz wave band electromagnetic wave oscillator according to Embodiment 10 of this disclosure comprises a structure according to any of Embodiments 1 to 9 of this disclosure.

[0140] According to the above configuration, the terahertz-band electromagnetic wave oscillator according to embodiment 10 of the present disclosure can improve radiation efficiency.

[0141] The inventions described in this disclosure have been explained above based on the drawings and embodiments. However, the inventions described in this disclosure are not limited to the embodiments described above. That is, the inventions described in this disclosure can be modified in various ways within the scope shown in this disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the inventions described in this disclosure. In other words, it should be noted that it is easy for those skilled in the art to make various modifications or alterations based on this disclosure. Furthermore, it should be noted that these modifications or alterations are included in the scope of this disclosure.

[0142] 1 Electromagnetic wave generator 10, 10A, 10B, 10C, 10D Structure 11 First substrate 11A First surface 11B Third surface 12 Second substrate 12A Second surface 12B Fourth surface 13 First electrode 14, 16 130, 140A, 140B Second electrode 15 AC source 16A Constricted section 16R Superimposed section 17 Third electrode 18, 19 Wiring 20 Jig 21 Lower jig 22 Upper jig 23 Hemispherical lens 50 Terahertz wave band electromagnetic wave oscillator 51 Refrigerator 52 Oscillator / antenna section 53 Power supply 60, 61 Wiring electrode R1 Superimposed region R2 Non-superimposed region

Claims

1. A structure comprising: an AC source; a voltage and current applied to the AC source, and a first electrode and a second electrode having a smaller area than the first electrode stacked on either side of the AC source; and a constricted portion electrically connected to at least one of the first electrode and the second electrode, and being narrower than at least one of the connected first electrode and second electrode.

2. The structure according to claim 1, wherein the second electrode has a constricted portion and a superimposed portion on which the AC generation source is superimposed when viewed from the stacking direction, the constricted portion is located closer to the end in the longitudinal direction of the second electrode than the superimposed portion, and the width in the short direction of the second electrode is narrower than that of the superimposed portion.

3. The structure according to claim 2, wherein at least one width of the second electrode in the short direction decreases as it approaches the end side.

4. The structure according to claim 2 or 3, wherein, when viewed from the stacking direction, the superimposed portion is in a region that includes the central position of the second electrode in the longitudinal direction.

5. The structure according to any one of claims 1 to 4, further comprising a first electrode-side wiring electrode connected to the first electrode, wherein the external shape of the AC source extends along the longitudinal direction of the second electrode and has a first side having a first end and a second end, and, viewed from the stacking direction, the position where the first electrode-side wiring electrode is connected to the first electrode is located outside the range bounded by a straight line passing through the first end and perpendicular to the first side and a straight line passing through the second end and perpendicular to the first side.

6. The structure according to any one of claims 1 to 5, further comprising: a first substrate having a first surface on which the first electrode is disposed; and a second substrate having a second surface on which the second electrode is disposed and which faces the first surface.

7. The structure according to claim 6, wherein the first substrate and the second substrate are formed from at least one selected from the group consisting of gallium-arsenide, sapphire, germanium, high-resistivity silicon, aluminum nitride, and diamond.

8. The structure according to claim 6 or 7, further comprising a third electrode different from the first electrode and the second electrode, wherein the first substrate further has a third surface opposite to the first surface, and the third electrode is disposed on the third surface.

9. The structure according to any one of claims 1 to 8, wherein the AC source includes a superconductor.

10. A terahertz-band electromagnetic wave oscillator comprising the structure described in any one of claims 1 to 9.

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