Extended logarithmic spiral antenna structure applied to electromagnetic wave energy absorbers, thermoelectric energy harvesters, and photoconductive antennas

Abstract

The extended logarithmic spiral antenna structure includes a first conductive layer, a dielectric layer, and a second conductive layer. The first conductive layer includes a first spiral arm and a plurality of second spiral arms. The first spiral arm has a first initial radius. The second spiral arms are disposed around and connected to the first spiral arm, and each of the second spiral arms has a second initial radius. The dielectric layer has an upper surface and a lower surface, and the upper surface is connected to the first conductive layer. The second conductive layer is connected to the lower surface. The second initial radii of the second spiral arms are different from each other and from the first initial radius.

Description

[Technical Field]

[0001] The present disclosure relates to an augmented logarithmic spiral antenna structure, an electromagnetic energy absorber, a thermoelectric energy harvester, a photoconductive antenna, an array antenna, and a rectenna. More specifically, the present disclosure relates to an augmented logarithmic spiral antenna structure that can extend the absorption bandwidth and can be applied to an electromagnetic energy absorber, a thermoelectric energy harvester, a photoconductive antenna, an array antenna, and a rectenna. [Background technology]

[0002] The increasing demand for direct electromagnetic (EM) energy harvesting from the environment is revolutionizing the lifestyles of today's society. The Earth's long-wavelength infrared (LWIR) and the sun are considered the most abundant energy sources in the IR and visible bands. Capturing such energy and converting it into direct current (DC) electrical form can be used in many low-power electronic applications. Therefore, for practical applications, it is necessary to develop broadband receiving antennas to efficiently harvest IR and visible energy sources. One of the key components of such technology is a planar broadband antenna structure, which has attractive properties such as a wide operating bandwidth, low profile, light weight, low cost, and ease of integration.

[0003] However, achieving good absorber performance often requires not only broadband bandwidth but also high absorption. Therefore, to achieve high-performance antennas, both transmission and reflection should be minimized within the operating frequency range. In addition, increasing the antenna's bandwidth can be achieved at the expense of increased thickness and weight, which is not suitable for certain applications. Furthermore, conventional antennas suffer from unavoidable surface reflections at the interface between free space and the absorbing layer. Another obstacle to broadband IR antennas is the rapid degradation of the plasmonic properties of metal-based structures at long wavelengths. This behavior significantly limits the use of metal arrays as broadband IR light absorbers.

[0004] Typical broadband IR absorbers utilize a sandwich structure consisting of an array of ultrathin metal patterns and a ground plane, separated by a dielectric spacer. Perfect absorption can be achieved when the impedance between the absorber and free space is matched, as the ground layer completely blocks the transmission of the incident wave. However, due to the resonant nature of the structure, such EM absorbers suffer from limited working bandwidth, which significantly limits their practical applications.

[0005] Considering this problem, a method for establishing a perfect broadband absorber that minimizes reflection and transmission and maximizes absorption bandwidth in a wide frequency range is generally highly anticipated in practice and has become the goal and direction of efforts in related industries. Summary of the Invention

[0006] According to one aspect of the present disclosure, an extended logarithmic spiral antenna structure includes a first conductive layer, a dielectric layer, and a second conductive layer. The first conductive layer includes a first spiral arm and a plurality of second spiral arms. The first spiral arm has a first initial radius. The second spiral arms are disposed around and connected to the first spiral arm, and each of the second spiral arms has a second initial radius. The dielectric layer has an upper surface and a lower surface, and the upper surface is connected to the first conductive layer. The second conductive layer is connected to the lower surface. The second initial radii of the second spiral arms are different from each other and from the first initial radius.

[0007] According to another aspect of the present disclosure, an electromagnetic energy absorber includes a nanoantenna, the nanoantenna comprising at least one extended logarithmic spiral antenna structure according to the above-described aspect, the nanoantenna being configured to absorb incident radiation, the incident radiation having a frequency f such that the following condition is satisfied: 4.5 THz. <f≦100THz。

[0008] According to another aspect of the present disclosure, an extended logarithmic spiral antenna structure includes a first conductive layer, a dielectric layer, and a second conductive layer. The first conductive layer has a first pattern and includes a first spiral arm and a plurality of second spiral arms. The first spiral arms have a first initial radius. The second spiral arms are arranged around the first spiral arm and connected to the first spiral arm, and each of the second spiral arms has a second initial radius. A dielectric layer is connected to the first conductive layer and has a second pattern, the second pattern being identical to the first pattern. The second conductive layer is connected to the dielectric layer, and the dielectric layer is disposed between the first conductive layer and the second conductive layer. The second initial radii of the second spiral arms are different from each other and from the first initial radius.

[0009] According to yet another aspect of the present disclosure, an electromagnetic energy absorber includes a nanoantenna, the nanoantenna comprising at least one extended logarithmic spiral antenna structure of the above-described aspect, the nanoantenna being configured to absorb incident radiation, the incident radiation having a frequency f such that the following condition is satisfied: 4.5 THz. <f≦100THz。

[0010] According to yet another aspect of the present disclosure, a photoconductive antenna is configured to replace one of a spiral antenna and a bowtie antenna. The photoconductive antenna includes a first conductive layer, a light-absorbing semiconductor layer, and a second conductive layer of the extended log-spiral antenna structure of the above-described aspect. The light-absorbing semiconductor layer is connected to the first conductive layer, and the structure of the light-absorbing semiconductor layer is identical to the structure of the dielectric layer of the extended log-spiral antenna structure of the above-described aspect. The second conductive layer of the extended log-spiral antenna structure is connected to the light-absorbing semiconductor layer, and the light-absorbing semiconductor layer is disposed between the first and second conductive layers.

[0011] According to yet another aspect of the present disclosure, an array antenna includes a plurality of the extended log-spiral antenna structures of the above-described aspects. The plurality of first conductive layers of the extended log-spiral antenna structure are arranged at intervals. The plurality of dielectric layers of the extended log-spiral antenna structure are arranged at intervals. The plurality of second conductive layers of the extended log-spiral antenna structure are connected to each other or integrally formed.

[0012] According to yet another aspect of the present disclosure, a rectenna for use in a communication or energy harvesting device includes an extended log-spiral antenna structure according to the above aspect and a rectifier module. The extended log-spiral antenna structure receives a radio frequency signal or radiation. The rectifier module is electrically connected to the extended log-spiral antenna structure and converts the radio frequency signal or radiation from alternating current to direct current.

[0013] According to yet another aspect of the present disclosure, a thermoelectric energy harvester includes a first conductive layer, a dielectric layer, a second conductive layer, a contact electrode, and a coaxial cable. The first conductive layer has a first pattern and receives thermal radiation. The first conductive layer includes a first spiral arm and a plurality of second spiral arms. The first spiral arm has a first initial radius. The second spiral arms are disposed around the first spiral arm and connected to the first spiral arm, each of the second spiral arms having a second initial radius. A dielectric layer is connected to the first conductive layer and has a second pattern, the second pattern being identical to the first pattern. The second conductive layer is connected to the dielectric layer, and the dielectric layer is disposed between the first conductive layer and the second conductive layer. A contact electrode is disposed through the dielectric layer and electrically connected between the first conductive layer and the second conductive layer. The coaxial cable is electrically connected to the contact electrode and converts the thermal radiation into direct current in accordance with the Seebeck effect. The second spiral arms have second initial radii different from each other and different from the first initial radii. [Brief explanation of the drawings]

[0014] The present disclosure can be more fully understood from the following detailed description of the embodiments, when read in conjunction with the accompanying drawings, in which:

[0015] [Figure 1A] FIG. 2 shows a three-dimensional schematic diagram of an extended logarithmic spiral antenna structure according to a first embodiment of the present disclosure.

[0016] [Figure 1B] 1B shows an exploded view of the extended logarithmic spiral antenna structure of FIG. 1A.

[0017] [Figure 1C] 1B shows a plan view of the extended log-spiral antenna structure of FIG. 1A.

[0018] [Figure 2A]FIG. 1 shows a three-dimensional schematic diagram of an extended logarithmic spiral antenna structure according to a second embodiment of the present disclosure.

[0019] [Figure 2B] 2B shows an exploded view of the extended logarithmic spiral antenna structure of FIG. 2A.

[0020] [Figure 3] FIG. 10 shows a schematic diagram of an electromagnetic wave energy absorber according to a third embodiment of the present disclosure.

[0021] [Figure 4] FIG. 10 shows a schematic diagram of an electromagnetic wave energy absorber according to a fourth embodiment of the present disclosure.

[0022] [Figure 5] FIG. 10 shows a schematic diagram of a thermoelectric energy harvester according to a fifth embodiment of the present disclosure.

[0023] [Figure 6] FIG. 10 shows a schematic diagram of a photoconductive antenna according to a sixth embodiment of the present disclosure.

[0024] [Figure 7] FIG. 10 shows a two-dimensional schematic diagram of an array antenna according to a seventh embodiment of the present disclosure.

[0025] [Figure 8] 13 shows a schematic diagram of a rectenna according to an eighth embodiment of the present disclosure.

[0026] [Figure 9A] 1B shows the reflectivity and absorptivity curves of the extended logarithmic spiral antenna structure of FIG. 1A under normal incidence of a plane wave.

[0027] [Figure 9B] 1B shows a curve diagram of the transmittance of the extended logarithmic spiral antenna structure of FIG. 1A under normal incidence of a plane wave.

[0028] [Figure 9C]2B shows the reflectivity and absorptivity curves of the extended logarithmic spiral antenna structure of FIG. 2A under normal incidence of a plane wave.

[0029] [Figure 9D] 2B shows a curve diagram of the transmittance of the extended logarithmic spiral antenna structure of FIG. 2A under normal incidence of a plane wave.

[0030] [Figure 10A] 2B shows the curve plot of the absorption spectrum of the extended logarithmic spiral antenna structure of FIG. 2A at different incident angles ranging from 0° to 75° for the transverse electric (TE) mode.

[0031] [Figure 10B] 2B shows the curve plot of the absorption spectrum of the extended logarithmic spiral antenna structure of FIG. 2A at different angles of incidence ranging from 0° to 75° for the transverse magnetic (TM) mode.

[0032] [Figure 10C] 2B shows the curve plot of the absorption spectrum of the extended logarithmic spiral antenna structure of FIG. 2A at different polarization angles ranging from 0° to 90° for the TE mode.

[0033] [Figure 10D] 2B shows the curve plot of the absorption spectrum of the extended logarithmic spiral antenna structure of FIG. 2A at different polarization angles ranging from 0° to 90° for the TM mode.

[0034] [Figure 11A] 2 shows a three-dimensional schematic diagram of the far-field directivity of the extended logarithmic spiral antenna structure of FIG. 1 at 65.75 THz.

[0035] [Figure 11B] 2 shows a polar plot of the far-field directivity of the extended log-spiral antenna structure of FIG. 1 at 67.75 THz.

[0036] [Figure 12A]2B shows a three-dimensional schematic diagram of the far-field directivity of the extended log-spiral antenna structure of FIG. 2A at 65.75 THz.

[0037] [Figure 12B] 2B shows a polar plot of the far-field directivity of the extended log-spiral antenna structure of FIG. 2A at 67.75 THz.

[0038] [Figure 13A] 1B shows a three-dimensional schematic diagram of the far-field gain of the extended log-spiral antenna structure of FIG. 1A at 65.75 THz.

[0039] [Figure 13B] 1B shows a polar plot of the far-field gain of the extended log-spiral antenna structure of FIG. 1A at 67.75 THz.

[0040] [Figure 14A] FIG. 2B shows a three-dimensional schematic diagram of the far-field gain of the extended log-spiral antenna structure of FIG. 2A at 65.75 THz.

[0041] [Figure 14B] 2B shows a polar plot of the far-field gain of the extended log-spiral antenna structure of FIG. 2A at 67.75 THz. DETAILED DESCRIPTION OF THE INVENTION

[0042] The embodiments will be described with reference to the drawings. For clarity, some practical details will be described below. However, it should be noted that the present disclosure should not be limited to these practical details, i.e., in some embodiments, these practical details are not necessary. In addition, to simplify the drawings, some conventional structures and elements are shown in simplified form, and repeated elements may be represented by the same labels.

[0043] When an element (or device) is referred to as "connected to" another element, it will be understood that it may be directly connected to the other element, or it may be indirectly connected to the other element, i.e., there may be intervening elements. In contrast, when an element is referred to as "directly connected to" another element, there are no intervening elements. In addition, terms such as first, second, third, etc. are used herein to describe various elements or components, and these elements or components should not be limited by these terms. Thus, a first element or component discussed below may be referred to as a second element or component.

[0044] Please refer to Figures 1A, 1B, and 1C. Figure 1A shows a three-dimensional schematic view of an extended log-spiral antenna structure 100 according to a first embodiment of the present disclosure. Figure 1B shows an exploded view of the extended log-spiral antenna structure 100 of Figure 1A. Figure 1C shows a plan view of the extended log-spiral antenna structure 100 of Figure 1A. As shown in Figures 1A, 1B, and 1C, the extended log-spiral antenna structure 100 comprises a first conductive layer 200, a dielectric layer 300, and a second conductive layer 400.

[0045] The first conductive layer 200 includes a first spiral arm 210 and a plurality of second spiral arms 220. The first spiral arm 210 has a first initial radius R0 (shown in FIG. 1C). The second spiral arms 220 are disposed around and connected to the first spiral arm 210, and the second spiral arms 220 each have a plurality of second initial radii R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27, R28, R29, R30, R31, R32, R33, R34, R35, R36, R37, R38, R39, R40, R41, R42, R43, R44, R45, R46, R47, R48, R49, R50, R51, R52, R53, R54, R55, R56, R57, R58, R59, R60, R61, R62, R63, R64, R65, R66, R67, R68, R69, R70, R71, R72, R73, R74, R75, R76, R77, R78, R79, R80, R81, R82, R83, R84, R85, R86, R87, R88, R89, R90, R91, R92, R93, R94, R95, R96, R97, R98, R99, R99, R109, R110, R121, R122, R123 10 , R 11 , R 12 (shown in FIG. 1C). The second initial radii R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12are different from each other and are also different from the first initial radius R0. In other words, the length of the first initial radius R0 is different from the length of the plurality of second initial radii R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 The length of the second initial radius R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 Note that the lengths of the first and second conductive layers 200 and 400 are different from each other. The dielectric layer 300 has an upper surface 301 and a lower surface 302, and the upper surface 301 is connected to the first conductive layer 200. The second conductive layer 400 is connected to the lower surface 302 of the dielectric layer 300.

[0046] Conventional log-spiral antennas typically use a multi-layer structure in a single unit cell to absorb electromagnetic (EM) waves over a wide frequency range. However, conventional log-spiral antennas are complex in nature, making their manufacturing process difficult. Additionally, conventional log-spiral antennas are only used for broadband absorption below the infrared (IR) band. The difference between conventional log-spiral antennas and the extended log-spiral antenna structure 100 of the present disclosure is that the extended log-spiral antenna structure 100 can operate in the IR band, from 4.5 THz to 100 THz, and achieve a THz absorption rate of over 88.5% within the operating frequency band due to the hybrid log-spiral structure formed by the first spiral arm 210 and the second spiral arm 220. This hybrid log-spiral structure minimizes the reflection of EM waves from the surface of the first conductive layer 200, significantly improving the absorption bandwidth. Therefore, the extended log-spiral antenna structure 100 not only maintains the absorption bandwidth within the operating frequency range, but also reduces the antenna size.

[0047] Specifically, the first spiral arm 210 shown in FIG. 1C has a first inner curve radius R i0 , first outer curve radius Ro0, the flare rate, the angular position and the phase shift between two consecutive curves of the first spiral arm 210, such that the following equations (1), (2) and (3) are satisfied:

number

[0048] In equations (1), (2) and (3), r0 is the first initial radius R0. r1 is the first inner curve radius R i0 r2 is the first outer curve radius R o0 where α is the flare rate, which controls the rate of increase of the first spiral arm 210 and is related to the number of turns in the first spiral arm 210. φ is the angular position, which varies from 0 to 3π. δ is the phase shift. The flare rate can be expressed in terms of the expansion rate in equation (3), where ε is the expansion rate.

[0049] In particular, the first conductive layer 200 has different radii (i.e., a first initial radius R0 and second initial radii R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 , R 12 The spiral structure is comprised of a multi-arm spiral (i.e., a first spiral arm 210 and a second spiral arm 220) with a logarithmic spiral length and growth rates. The second spiral arm 220 is attached to the outer periphery of the first spiral arm 210 to form a hybrid logarithmic spiral structure.

[0050] For the first spiral arm 210, r0=0.4 μm, α=0.2, and φ=0-3π are adopted for optimal performance of the extended log-spiral antenna structure 100. In FIG. 1C, the number of second spiral arms 220 may be 12, and the flare rate and angular position of each of the second spiral arms 220 may be the same as that of the first spiral arm 210, but the second initial radii R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27, R28, R29, R30, R31, R32, R33, R34, R35, R36, R37, R38, R39, R40, R41, R42, R43, R44, R45, R46, R47, R48, R49, R50, R51, R52, R53, R54, R55, R56, R57, R58, R59, R60, R61, R62, R63, R64, R65, R66, R67, R68, R69, R70, R71, R72, R73, R74, R75, R76, R77, R78, R79, R80, R81, R82, R83, R84, R85, R86, R87, R88, R89, R90, R91, R92, R93, R94, R95, R96, R97, R98, R99, R109, 10 , R11 , R 12 Each of the first spiral arms 210 and the second spiral arms 220 has an optimized structural dimension (μm) set forth in Table 1A and Table 1B, respectively, which is different from the first initial radius R. The optimized structural dimension (μm) of the first spiral arm 210 and the optimized structural dimension (μm) of the second spiral arm 220 are set forth in Table 1A and Table 1B, respectively, and the present disclosure is not limited thereto. [Table 1A] [Table 1B]

[0051] Furthermore, the disclosed extended log-spiral antenna structure 100 can be applied to EM wave absorbers for EM energy harvesting. A perfect EM wave absorber is one in which all incident radiation is efficiently absorbed at the operating wavelength. When radiation is absorbed by the device, it is converted into ohmic heat or other forms of energy. Therefore, reflection, transmission, scattering, and all other wave propagation are not observed when passing through a perfect EM wave absorber. When the first conductive layer 200 absorbs EM energy, electrical and magnetic resonance occurs, resulting in high energy absorption by the hybrid log-spiral structure. When an incident wave interacts with the first conductive layer 200, electronic resonance occurs in the first conductive layer 200, generating oscillating currents that dissipate EM energy throughout the hybrid log-spiral structure. While conventional absorbers are typically constructed from materials with high intrinsic loss, the disclosed extended log-spiral antenna structure 100 can be constructed primarily from precious metals.

[0052] For example, the first conductive layer 200 is made of a lossy metal. The dielectric layer 300 is made of a high-insulation material. The second conductive layer 400 is made of another lossy metal. In particular, the lossy metal is nickel (Ni), the high-insulation material is SU-8 which has a relative permittivity of 2.8, and the other lossy metal is gold (Au). The first conductive layer 200 is patterned, while both the dielectric layer 300 and the second conductive layer 400 are continuous layers, thereby avoiding the transmission of EM waves. The dielectric layer 300 is sandwiched between the first conductive layer 200 and the second conductive layer 400, or in other words, the first conductive layer 200 is laminated on the upper surface 301 of the dielectric layer 300, and the lower surface 302 of the dielectric layer 300 is laminated on the second conductive layer 400.

[0053] In FIG. 1B, the thickness of the first conductive layer 200 is Z1, the thickness of the dielectric layer 300 is Z2, and the thickness of the second conductive layer 400 is Z3, and the following conditions are satisfied: Z1 = Z3 < Z2. The thickness Z1 of the first conductive layer 200 is greater than the skin depth of the first conductive layer 200, the thickness Z2 of the dielectric layer 300 is greater than the penetration depth of the dielectric layer 300, and the thickness Z3 of the second conductive layer 400 is greater than the skin depth of the second conductive layer 400. In FIG. 1C, the length L of the extended logarithmic spiral antenna structure 100 is 17 μm, and the width W of the extended logarithmic spiral antenna structure 100 is 13 μm.

[0054] Specifically, the thickness Z1 of the first conductive layer 200 and the thickness Z3 of the second conductive layer 4 are 0.2 μm. The thickness Z2 of the dielectric layer 300 is 5.5 μm and has a relative permittivity (ε r ) of 2.8. The overall thickness of the extended logarithmic spiral antenna structure 100 is 5.94 μm. The properties of gold (Au), nickel (Ni), and SU-8 are shown in Table 2, but the present disclosure is not limited thereto. [[ID=十三]]

Table 2

[0055] Please refer to Figures 2A and 2B. Figure 2A shows a three-dimensional schematic diagram of an extended log-spiral antenna structure 100a according to a second embodiment of the present disclosure. Figure 2B shows an exploded view of the extended log-spiral antenna structure 100a of Figure 2A. As shown in Figures 2A and 2B, the extended log-spiral antenna structure 100a includes a first conductive layer 200a, a dielectric layer 300a, and a second conductive layer 400a. The first conductive layer 200a has a first pattern and includes a first spiral arm 210a and a plurality of second spiral arms 220a. The second spiral arms 220a are arranged around and connected to the first spiral arm 210a. The first pattern of the first conductive layer 200a, formed by the first spiral arms 210a and the second spiral arms 220a, is identical to the above-described hybrid log-spiral structure of the first conductive layer 200 in FIG. 1C. The dielectric layer 300a is connected to the first conductive layer 200a. The second conductive layer 400a is connected to the dielectric layer 300a, and the dielectric layer 300a is disposed between the first conductive layer 200a and the second conductive layer 400a. In particular, the first conductive layer 200a and the second conductive layer 400a are identical to the corresponding elements of the extended log-spiral antenna structure 100 of the first embodiment, and will not be described again here.

[0056] The difference between the extended logarithmic spiral antenna structure 100a and the extended logarithmic spiral antenna structure 100 is that the dielectric layer 300a has a second pattern, which is identical to the first pattern. In other words, the structure of the dielectric layer 300a is identical to that of the first conductive layer 200a, except that the first conductive layer 200a is made of nickel (Ni) and the dielectric layer 300a is made of SU-8. In addition, the second conductive layer 400a has a surface 401a, and the first conductive layer 200a is laminated on the dielectric layer 300a, with the first pattern aligned with the second pattern, and the dielectric layer is laminated on the surface 401a of the second conductive layer 400a. To achieve good performance of the extended logarithmic spiral antenna structure 100a, an impedance matching network is required. Therefore, proper impedance matching and the superposition of multiple resonances are two important factors for the extended logarithmic spiral antenna structure 100a to achieve full wideband characteristics. In this manner, the reflectivity from the surface of the first conductive layer 200a can be reduced, resulting in improved absorption of the extended log-spiral antenna structure 100a over a wide range of frequencies. Therefore, both the first conductive layer 200a and the dielectric layer 300a are configured in a hybrid log-spiral structure to achieve broadband absorption over the operating frequency range. Therefore, the extended log-spiral antenna structure 100a of the present disclosure not only achieves high absorption and broadband absorption of EM waves, but also is easy to manufacture, has a smaller thickness, and can reduce costs.

[0057] Please refer to FIGS. 1A and 3. FIG. 3 shows a schematic diagram of an electromagnetic wave energy absorber 500 according to a third embodiment of the present disclosure. As shown in FIG. 3, the electromagnetic wave energy absorber 500 includes a nanoantenna 510. The nanoantenna 510 includes at least one extended logarithmic spiral antenna structure 511. In the third embodiment, the number of at least one extended logarithmic spiral antenna structure 511 may be plural (for example, nine), and each of the extended logarithmic spiral antenna structures 511 is the same as the extended logarithmic spiral antenna structure 100 of FIG. 1A. The nanoantenna 510 is configured to absorb incident radiation Ri, the frequency of the incident radiation Ri is f, and the following condition is satisfied: 4.5 THz < f ≦ 100 THz. The incident radiation Ri is incident on the nanoantenna 510 in a perpendicular direction, and the nanoantenna 510 has an average absorption rate corresponding to the incident radiation Ri. The average absorption rate is AA, and the following condition is satisfied: 88.5% ≦ AA. In particular, based on the extended logarithmic spiral antenna structure 100, the nanoantenna 510 has been shown to be a promising candidate for energy harvesting applications in the infrared (IR) to ultraviolet (UV) region by numerical analysis. When testing and simulating the effect on the absorption performance of the electromagnetic wave energy absorber 500, high performance was shown in both the bandwidth and the absorption rate (as shown in FIGS. 9A and 9B in the following paragraphs, an average absorption rate of 88.5% over a wide range from IR to visible light, that is, from 4 THz to 100 THz). In other embodiments, the extended logarithmic spiral antenna structure 511 can also be used in an energy harvesting device used in an antenna. For example, broadband energy harvesting in combination with an antenna can be achieved by directly harvesting (collecting) RF energy into DC using a rectifier, a thermoelectric element, a bolometer, a pyroelectric element, or a quantum detector such as InGaAs and a photoconductive material.

[0058] Please refer to FIGS. 2A and 4. FIG. 4 shows a schematic diagram of an electromagnetic wave energy absorber 500a according to a fourth embodiment of the present disclosure. As shown in FIG. 4, the electromagnetic wave energy absorber 500a includes a nanoantenna 510a. The nanoantenna 510a includes at least one extended logarithmic spiral antenna structure 511a. In the fourth embodiment, the number of at least one extended logarithmic spiral antenna structure 511a may be plural (for example, nine), and each of the extended logarithmic spiral antenna structures 511a is the same as the extended logarithmic spiral antenna structure 100a in FIG. 2A. The nanoantenna 510a is configured to absorb incident radiation Ri, the frequency of the incident radiation Ri is f, and the following condition is satisfied: 4.5 THz < f ≦ 100 THz. The incident radiation Ri is incident on the nanoantenna 510a in a normal direction, and the nanoantenna 510a has an average absorption rate corresponding to the incident radiation Ri. The average absorption rate is AA, and the following condition is satisfied: 88.5% ≦ AA. In particular, based on the extended logarithmic spiral antenna structure 100a, the nanoantenna 510a has been shown to be a promising candidate for energy harvesting applications in the infrared (IR) to ultraviolet (UV) region by numerical analysis. When testing and simulating the effect on the absorption performance of the electromagnetic wave energy absorber 500a, high performance was shown in both the bandwidth and the absorption rate (as shown in FIGS. 9C and 9D in the following paragraphs, an average absorption rate of 88.5% over a wide range from IR to visible light, that is, from 4 THz to 100 THz). In other embodiments, the extended logarithmic spiral antenna structure 511a can also be used in an energy harvesting device for use in an antenna. For example, broadband energy harvesting in combination with an antenna can be achieved by directly harvesting RF energy into DC using a rectifier, a thermoelectric element, a bolometer, a pyroelectric element, or a quantum detector such as InGaAs and a photoconductive material.

[0059] Please refer to FIGS. 2A and 5. FIG. 5 shows a schematic diagram of a thermoelectric energy harvester 600 according to a fifth embodiment of the present disclosure. As shown in FIG. 5, the thermoelectric energy harvester 600 includes a first conductive layer 610, a dielectric layer 620, a second conductive layer 630, a contact electrode 640, and a coaxial cable 650. The structural arrangement between the first conductive layer 610, the dielectric layer 620, and the second conductive layer 630 is identical to that of the corresponding elements of the extended logarithmic spiral antenna structure 100a in FIG. 2A and will not be described again here. However, the dimensions of the first conductive layer 610, the dielectric layer 620, and the second conductive layer 630 may be the same as or different from those of the corresponding elements of the extended logarithmic spiral antenna structure 100a in FIG. 2A.

[0060] The first conductive layer 610 receives the thermal radiation Rh. The contact electrode 640 is disposed through the dielectric layer 620 and is electrically connected between the first conductive layer 610 and the second conductive layer 630. The coaxial cable 650 is electrically connected to the contact electrode 640 and converts the thermal radiation Rh into direct current DC according to the Seebeck effect (diffusion of electrons by the thermal radiation Rh). This direct current DC is then applied to a load R L is supplied to the load R L Provides power to

[0061] The thermoelectric energy harvester 600 can be a portable or wearable thermoelectric generator that can harvest environmental energy from its surroundings by using a flexible, electrically conductive thermoelectric material and an ultra-wideband antenna as one of the heat-receiving ends of a thermoelectric (TE) module. A TE module is essentially a circuit consisting of two different thermoelectric materials, which, when combined, can generate electricity directly from heat. The TE module consists of two different thermoelectric materials joined at their ends. One end is composed of an N-type (electron-rich) semiconductor, and the other end is composed of a P-type (electron-deficient) semiconductor. Specifically, the first conductive layer 610 is composed of a P-type semiconductor, and the second conductive layer 630 is composed of an N-type semiconductor. In particular, the P-type semiconductor of the first conductive layer 610 is composed of nickel or one of several P-type conductive materials, and the N-type semiconductor of the second conductive layer is composed of gold or one of several N-type conductive materials. The first conductive layer 610 utilizes a hybrid logarithmic spiral structure as the heat-receiving end of the thermoelectric energy harvester 600 to improve the energy absorption rate and frequency range. Table 3 lists possible P-type and N-type semiconductor candidates for the first conductive layer 610 and the second conductive layer 630, and their thermoelectric performance. [Table 3]

[0062] Please refer to Figures 2A and 6. Figure 6 shows a schematic diagram of a photoconductive antenna 700 according to a sixth embodiment of the present disclosure. As shown in Figure 6, the photoconductive antenna 700 includes a first conductive layer 710, a light-absorbing semiconductor layer 720, and a second conductive layer 730, and is configured to replace one of a spiral antenna (not shown) or a bowtie antenna (not shown). The first conductive layer 710 is identical to the first conductive layer 200a of the extended logarithmic spiral antenna structure 100a of Figure 2A. The light-absorbing semiconductor layer 720 is connected to the first conductive layer 710, and the structure of the light-absorbing semiconductor layer 720 is identical to the structure of the dielectric layer 300a of the extended logarithmic spiral antenna structure 100a of Figure 2A. The second conductive layer 730 is connected to the light-absorbing semiconductor layer 720, and the structure of the second conductive layer 730 is identical to that of the second conductive layer 400a of the extended logarithmic spiral antenna structure 100a in FIG. 2A. The light-absorbing semiconductor layer 720 is disposed between the first conductive layer 710 and the second conductive layer 730. In short, the structural arrangement between the first conductive layer 710, the light-absorbing semiconductor layer 720, and the second conductive layer 730 is identical to that of the first conductive layer 200a, the dielectric layer 300a, and the second conductive layer 400a of the extended logarithmic spiral antenna structure 100a of the second embodiment, and will not be described again here. In FIG. 6, the photoconductive antenna 700 receives a laser pulse Lp, which excites carriers accelerated by a potential +V. The resulting charge separation generates dipole emission at terahertz frequencies. In particular, the photoconductive antenna 700 essentially utilizes the photoconductive effect to generate electrical energy and transmit and receive radiation (typically in the THz range). The photoconductive antenna 700 consists of a metal antenna (i.e., a first conductive layer 710 and a light-absorbing semiconductor layer 720) patterned on a photoconductive substrate (i.e., a second conductive layer 730). In the sixth embodiment, the photoconductive antenna 700 is not used as an energy harvesting device, but as a transceiver system.

[0063] Please refer to Figures 2A and 7. Figure 7 shows a two-dimensional schematic diagram of an array antenna 800 according to a seventh embodiment of the present disclosure. As shown in Figure 7, the array antenna 800 includes a plurality of extended log-spiral antenna structures 100a shown in Figure 2A. Specifically, the array antenna 800 is configured with a 3x3 array of the extended log-spiral antenna structures 100a. In other words, the extended log-spiral antenna structure 100a is the unit cell antenna structure of the array antenna 800. Regarding the structure of the array antenna 800, the first conductive layers 200a of the extended log-spiral antenna structures 100a are spaced apart, and the dielectric layers 300a of the extended log-spiral antenna structures 100a are spaced apart. The second conductive layers 400a of the extended log-spiral antenna structures 100a are connected to each other or integrally formed. A slot 810 is disposed between each pair of the extended logarithmic-spiral antenna structures 100a and has a width Ws. The slots 810 are connected to each other in a grillage-type configuration. The slots 810 have the same width Ws, and each slot 810 has a width Ws of 0.1 μm. In other embodiments, the first conductive layers of the extended logarithmic-spiral antenna structures may be electrically connected in series and the dielectric layers of the extended logarithmic-spiral antenna structures may be electrically connected in series, thereby increasing the voltage output, or the first conductive layers of the extended logarithmic-spiral antenna structures may be connected in parallel and the dielectric layers of the extended logarithmic-spiral antenna structures may be connected in parallel, thereby increasing the output current.

[0064] Please refer to Figures 2A and 8. Figure 8 shows a schematic diagram of a rectenna 900 according to an eighth embodiment of the present disclosure. As shown in Figure 8, the rectenna 900 can be used for communications or energy harvesting devices and includes an extended log-spiral antenna structure 910 and a rectification module 920. The extended log-spiral antenna structure 910 can include a first conductive layer 911, a dielectric layer 912, and a second conductive layer 913. The structural arrangement between the first conductive layer 911, the dielectric layer 912, and the second conductive layer 913 has the same structural arrangement as the corresponding elements of the extended log-spiral antenna structure 100a in Figure 2A and will not be described again here.

[0065] The first conductive layer 911 of the extended logarithmic spiral antenna structure 910 receives a radio frequency signal Rf or radiation (not shown). The rectification module 920 is electrically connected to the second conductive layer 913 of the extended logarithmic spiral antenna structure 910 and converts the radio frequency signal Rf or radiation from alternating current AC to direct current DC. The direct current DC is then applied to a load R L is supplied to the load R L 9. Specifically, in response to determining that the rectenna 900 is receiving a radio frequency signal Rf, the rectenna 900 can be used for communication. In response to determining that the rectenna 900 is receiving radiation, the rectenna 900 can be used for energy harvesting. The eighth embodiment rectenna 900 is an energy harvesting device that is completely different from the thermoelectric energy harvester 600 of FIG. 5. In FIG. 5, radio frequency radiation (not shown) irradiated to the thermoelectric energy harvester 600 can be absorbed by the thermoelectric energy harvester 600 and converted to direct current (DC) using rectification. In FIG. 8, the radio frequency signal Rf can be converted from alternating current (AC) to direct current (DC) by connecting the extended logarithmic spiral antenna structure 910 to a rectification module 920.

[0066] In the following section, the characteristics of the extended log-spiral antenna structure 100 of FIG. 1A and the extended log-spiral antenna structure 100a of FIG. 2A are tested and the results are described.

[0067] <Reflectance, transmittance and absorption rate testing>

[0068] To clarify the physical origin of ultra-wideband (UWB) absorption, the extended log-spiral antenna structure 100 and the extended log-spiral antenna structure 800a are tested under normal incidence to obtain reflectivity, transmittance, and absorptance. See Figures 9A, 9B, 9C, and 9D. Figure 9A shows the reflectivity and absorptance curves of the extended log-spiral antenna structure 100 of Figure 1A under normal plane wave incidence. Figure 9B shows the transmittance curves of the extended log-spiral antenna structure 100 of Figure 1A under normal plane wave incidence. Figure 9C shows the reflectivity and absorptance curves of the extended log-spiral antenna structure 100a of Figure 2A under normal plane wave incidence. Figure 9D shows the transmittance curves of the extended log-spiral antenna structure 100a of Figure 2A under normal plane wave incidence. 9A and 9B, the extended logarithmic-spiral antenna structure 100 observed an average absorption rate of greater than 88.5% over a broad frequency range from 4.5 THz to 100 THz. In Figures 9C and 9D, the extended logarithmic-spiral antenna structure 100a observed an average absorption rate of greater than 88.5% over a broad frequency range from 4.5 THz to 100 THz.

[0069] 9A and 9B, it is clear that the extended log-spiral antenna structure 100 exhibits multiband and narrowband absorption characteristics, indicating that the extended log-spiral antenna structure 100 is a resonator type. The narrowband absorption by the extended log-spiral antenna structure 100 can be attributed to the impedance mismatch between the material and the surrounding air. The absorption bandwidth of the extended log-spiral antenna structure 100a shown in FIGS. 9C and 9D is dramatically increased. This improvement is due to the geometric asymmetry of the hybrid log-spiral structure and the strong impedance matching between the first conductive layer 200a and the surrounding air. Another reason is that most of the reflected waves destructively interfere with each other within the operating frequency range, reducing the amount of incident waves reflected from the surface of the first conductive layer 200a, resulting in broadband absorption.

[0070] <Transverse electric (TE) mode and transverse magnetic (TM) mode tests>

[0071] For practical applications, polarization-independent performance and a wide incident angle are crucial because, in some situations, incident waves are obliquely incident on the device. Therefore, the absorption performance of the extended log-spiral antenna structure 100a under different EM environments (i.e., TE and TM modes) is tested for normal and oblique incidence. See Figures 10A, 10B, 10C, and 10D. Figure 10A shows the absorption spectrum of the extended log-spiral antenna structure 100a of Figure 2A at different incident angles θ ranging from 0° to 75° for the TE mode. Figure 10B shows the absorption spectrum of the extended log-spiral antenna structure 100a of Figure 2A at different incident angles θ ranging from 0° to 75° for the TM mode. Figure 10C shows the absorption spectrum of the extended log-spiral antenna structure of Figure 2A at different polarization angles φ ranging from 0° to 90° for the TE mode. FIG. 10D shows the curve plot of the absorption spectrum of the extended logarithmic spiral antenna structure 100a of FIG. 2A at different polarization angles φ ranging from 0° to 90° for the TM mode.

[0072] In Figures 10A and 10B, high absorption is maintained when the incident angle θ increases to 45°. Under the TE mode, the spectral bandwidth reaches 95.6 THz with an absorption higher than 85.76% in the frequency range from 4.5 THz to 100 THz. In the TE mode, the average absorption is up to 86.1% in the operating frequency band. In the TM mode, the average absorption reaches 89.45% in the same frequency range. It can be observed that a broadband absorption window is maintained up to 45° for both the TE and TM modes. The incident angle insensitivity of the extended log-spiral antenna structure 100a is attributed to the structural asymmetry of the hybrid log-spiral structure. In addition, to demonstrate the polarization-independent and wide-angle characteristics of the extended log-spiral antenna structure 100a, the effects of different polarization angles φ of the incident wave on the absorption spectrum are shown in Figures 10C and 10D. This figure shows that the simulated absorption spectra for the TE and TM modes are polarization insensitive over the polarization angle φ ranging from 0° to 90°. From this, it can be concluded that at φ = 90°, the TE mode becomes the TM mode, and vice versa. Based on the above numerical results, it is clear that the extended logarithmic spiral antenna structure 100a can achieve ideal IR absorption in a complex EM environment, is polarization-independent under both normal and oblique incidence of plane waves, and maintains absorption performance for both the TE and TM modes within the operating frequency band.

[0073] Far-field directivity and gain testing

[0074] EM radiation pattern refers to the directional (angular) dependence of the intensity of EM waves from an antenna. It is defined as a mathematical function or graphical representation of the far-field radiation characteristics of an antenna as a function of the direction of departure of the EM waves. Return loss (S11) is an important parameter in any EM antenna. However, there are other parameters such as directivity, gain, and beamwidth, which play a major role and describe the performance of an antenna.

[0075] Please refer to Figures 11A and 11B. Figure 11A shows a three-dimensional (3D) schematic diagram of the far-field directivity of the extended log-spiral antenna structure 100 of Figure 1A at 65.75 THz. Figure 11B shows a polar plot of the far-field directivity of the extended log-spiral antenna structure 100 of Figure 1A at 67.75 THz. As shown in Figures 11A and 11B, it is observed that the peak directivity D1 of the extended log-spiral antenna structure 100 in Figure 11A can reach a value of 8.309 dBi at 65.75 THz, which is given by the 3D and polar plots derived from the far-field radiation pattern. The directivity in other directions is relatively lower than that value in the peak direction. The half-power beamwidth of the extended log-spiral antenna structure 100 reaches 57.3 degrees, and the maximum EM energy obtained by the antenna over this range.

[0076] Please refer to Figures 12A and 12B. Figure 12A shows a three-dimensional schematic diagram of the far-field directivity of the extended log-spiral antenna structure 100a of Figure 2A at 65.75 THz. Figure 12B shows a polar plot of the far-field directivity of the extended log-spiral antenna structure 100a of Figure 2A at 67.75 THz. As shown in Figures 12A and 12B, it is observed that the peak directivity D2 of the extended log-spiral antenna structure 100a of Figure 12A can reach a value of 6.678 dBi at 65.75 THz. The full-power beam width of the extended log-spiral antenna structure 100a reaches 59.2 degrees. Therefore, the extended log-spiral antenna structure 100a efficiently absorbs EM energy from different directions, indicating that the antenna is omnidirectional. This omnidirectional property of the extended logarithmic spiral antenna structure 100a is due to the geometric asymmetry and the groove-like asymmetric structure (ie, the first pattern of the first conductive layer 200a and the second pattern of the dielectric layer 300a).

[0077] Another parameter that indicates how efficiently an antenna converts received EM signals into electrical energy is known as antenna gain. It is a measure of how concentrated the radiated / received power is in a particular direction. Generally, antenna gain is closely related to the antenna's directivity, but it is also a measure that takes into account the antenna's efficiency.

[0078] Please refer to Figures 13A, 13B, 14A, and 14B. Figure 13A shows a three-dimensional schematic diagram of the far-field gain of the extended log-spiral antenna structure 100 of Figure 1A at 65.75 THz. Figure 13B shows a polar plot of the far-field gain of the extended log-spiral antenna structure 100 of Figure 1A at 67.75 THz. Figure 14A shows a three-dimensional schematic diagram of the far-field gain of the extended log-spiral antenna structure 100a of Figure 2A at 65.75 THz. Figure 14B shows a polar plot of the far-field gain of the extended log-spiral antenna structure 100a of Figure 2A at 67.75 THz. As shown in Figures 13A, 13B, 14A, and 14B, the far-field gain G1 of the extended log-spiral antenna structure 100 (Figure 13A) and the far-field gain G2 of the extended log-spiral antenna structure 100a (Figure 14A) are 3.573 dB and 3.55 dB, respectively, at an operating frequency of 65.75 THz. The polar plots clearly show that the extended log-spiral antenna structure 100a has a lower gain than the extended log-spiral antenna structure 100. The lower gain of the extended log-spiral antenna structure 100a limits its practical application to distant energy sources. Therefore, to maximize received power, the distance between the antenna and the EM power source should not be too far. Due to the lower gain, the extended log-spiral antenna structure 100a is more omnidirectional and can receive energy from all directions.

[0079] In summary, the present disclosure has the following advantages. First, the disclosed extended log-spiral antenna structure achieves broadband response in the IR region by using a planar gradient log-spiral antenna with a metal-insulator-metal (MIM) configuration. Second, the hybrid log-spiral structure achieves an average ultra-broadband absorption of 88.5% in the frequency range of 4.5 to 100 THz. Third, the grooved asymmetric structure (i.e., both the first conductive layer and the dielectric layer have a patterned hybrid log-spiral structure) makes the extended log-spiral antenna structure insensitive to polarization angle (0° to 90°) and incidence angle (0° to 45°) for both TE mode and TM mode, enabling it to collect EM radiation from multiple directions.

[0080] Although the present disclosure has been described in considerable detail with reference to specific embodiments thereof, other embodiments are possible, and therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.

[0081] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.

Claims

1. a first conductive layer, a first spiral arm having a first initial radius; and a first conductive layer comprising: a plurality of second spiral arms disposed around and connected to the first spiral arm, each of the second spiral arms comprising a second initial radius; a dielectric layer having a top surface and a bottom surface, the top surface connected to the first conductive layer; a second conductive layer connected to the lower surface, The extended logarithmic spiral antenna structure, wherein the second initial radii of the second spiral arms are different from each other and different from the first initial radii.

2. The first spiral arm further comprises a first inner curve radius, a first outer curve radius, a flare rate, an angular position and a phase shift between two consecutive curves of the first spiral arm, and the ... [Equation 1] is satisfied, where r ０ is the first initial radius, and r １ is the first inside curve radius, and r ２ 2. The extended logarithmic spiral antenna structure of claim 1, wherein α is the first outer curve radius, α is the flare rate, φ is the angular position that varies from 0 to 3π, and δ is the phase shift.

3. 3. The extended logarithmic spiral antenna structure of claim 2, wherein the flare rate and angular position of each of said second spiral arms is the same as the flare rate and angular position of said first spiral arm.

4. 2. The extended logarithmic spiral antenna structure of claim 1, wherein both the dielectric layer and the second conductive layer are continuous layers, the first conductive layer being laminated to the top surface of the dielectric layer, and the bottom surface of the dielectric layer being laminated to the second conductive layer.

5. the first conductive layer is made of a lossy metal, the dielectric layer is made of a highly insulating material, and the second conductive layer is made of another lossy metal; 2. The extended logarithmic spiral antenna structure of claim 1, wherein the lossy metal is nickel (Ni), the highly insulating material is SU-8, having a dielectric constant of 2.8, and the other lossy metal is gold (Au).

6. The thickness of the first conductive layer is Z １ and the thickness of the dielectric layer is Z ２ and the thickness of the second conductive layer is Z ３ and the following conditions: Z １ =Z ３ <Z ２ 2. The extended logarithmic spiral antenna structure of claim 1, wherein:

7. 7. The extended logarithmic spiral antenna structure of claim 6, wherein the thickness of the first conductive layer is greater than a skin depth of the first conductive layer, the thickness of the dielectric layer is greater than a penetration depth of the dielectric layer, and the thickness of the second conductive layer is greater than a skin depth of the second conductive layer.

8. 10. An electromagnetic energy absorber comprising a nanoantenna comprising at least one extended logarithmic spiral antenna structure according to claim 1, wherein the nanoantenna is configured to absorb incident radiation, the incident radiation having a frequency f, and the following condition: 4.5THz<f≦100THz An electromagnetic wave energy absorber that satisfies the above requirements.

9. The incident radiation is incident on the nanoantenna in a normal direction, and the nanoantenna has an average absorptance corresponding to the incident radiation, the average absorptance being AA, and the following condition is satisfied: 88.5%≦AA 9. The electromagnetic wave energy absorber according to claim 8, wherein the following is satisfied.

10. a first conductive layer having a first pattern, a first spiral arm having a first initial radius; and a first conductive layer comprising: a plurality of second spiral arms disposed around and connected to the first spiral arm, each of the second spiral arms having a second initial radius; a dielectric layer connected to the first conductive layer and having a second pattern, the second pattern being identical to the first pattern; and a second conductive layer connected to the dielectric layer, the dielectric layer being disposed between the first conductive layer and the second conductive layer, wherein the second initial radii of the second spiral arms are different from each other and different from the first initial radii.

11. The first spiral arm further comprises a first inner curve radius, a first outer curve radius, a flare rate, an angular position and a phase shift between two consecutive curves of the first spiral arm, and the ... [Equation 2] is satisfied, where r ０ is the first initial radius, and r １ is the first inside curve radius, and r ２ 11. The extended logarithmic spiral antenna structure of claim 10, wherein α is the first outer curve radius, α is the flare rate, φ is the angular position that varies from 0 to 3π, and δ is the phase shift.

12. 12. The extended log-spiral antenna structure of claim 11, wherein the flare rate and angular position of each of the second spiral arms is the same as the flare rate and angular position of the first spiral arm.

13. 11. The extended logarithmic spiral antenna structure of claim 10, wherein the second conductive layer is a continuous layer having a surface, the first conductive layer is laminated to the dielectric layer, the first pattern is aligned with the second pattern, and the dielectric layer is laminated to the surface of the second conductive layer.

14. the first conductive layer is made of a lossy metal, the dielectric layer is made of a highly insulating material, and the second conductive layer is made of another lossy metal; 11. The extended logarithmic spiral antenna structure of claim 10, wherein the lossy metal is nickel (Ni), the highly insulating material is SU-8, having a dielectric constant of 2.8, and the other lossy metal is gold (Au).

15. The thickness of the first conductive layer is Z １ and the thickness of the dielectric layer is Z ２ and the thickness of the second conductive layer is Z ３ and the following conditions: Z １ =Z ３ <Z ２ 11. The extended logarithmic spiral antenna structure of claim 10, wherein:

16. 16. The extended logarithmic spiral antenna structure of claim 15, wherein the thickness of the first conductive layer is greater than a skin depth of the first conductive layer, the thickness of the dielectric layer is greater than a penetration depth of the dielectric layer, and the thickness of the second conductive layer is greater than a skin depth of the second conductive layer.

17. 11. An electromagnetic energy absorber comprising a nanoantenna comprising at least one extended logarithmic spiral antenna structure according to claim 10, wherein the nanoantenna is configured to absorb incident radiation, the incident radiation having a frequency f, and the following condition: 4.5THz<f≦100THz An electromagnetic wave energy absorber that satisfies the above requirements.

18. The incident radiation is incident on the nanoantenna in a normal direction, and the nanoantenna has an average absorptance corresponding to the incident radiation, the average absorptance being AA, and the following condition is satisfied: 88.5%≦AA 18. The electromagnetic wave energy absorber according to claim 17, wherein the following is satisfied.

19. 1. A photoconductive antenna configured to replace one of a spiral antenna and a bowtie antenna, the photoconductive antenna comprising: the first conductive layer of the extended logarithmic spiral antenna structure of claim 10; a light-absorbing semiconductor layer connected to the first conductive layer, the structure of the light-absorbing semiconductor layer being the same as the structure of the dielectric layer of the extended logarithmic spiral antenna structure of claim 10; 11. The extended logarithmic spiral antenna structure of claim 10, connected to the light-absorbing semiconductor layer. the second conductive layer, wherein the light-absorbing semiconductor layer is disposed between the first conductive layer and the second conductive layer; A photoconductive antenna comprising:

20. 11. An array antenna comprising a plurality of extended log-spiral antenna structures according to claim 10, An array antenna, wherein the first conductive layers of the extended logarithmic spiral antenna structure are spaced apart, the dielectric layers of the extended logarithmic spiral antenna structure are spaced apart, and the second conductive layers of the extended logarithmic spiral antenna structure are connected to each other or integrally formed.

21. 21. The array antenna of claim 20, wherein a slot is disposed between each two of the extended logarithmic spiral antenna structures, the slot having a width, a plurality of the slots being connected to each other in a lattice pattern, and the width of each of the slots being the same.

22. 1. A rectenna for use in a communications or energy harvesting device, the rectenna comprising: an extended logarithmic spiral antenna structure according to claim 10 for receiving radio frequency signals or radiation; a rectification module electrically connected to the extended log-spiral antenna structure for converting the radio frequency signal or the radiation from alternating current to direct current.

23. a first conductive layer having a first pattern and adapted to receive thermal radiation, the first conductive layer comprising: a first spiral arm having a first initial radius; and disposed around the first spiral arm; a plurality of second spiral arms connected to the first spiral arm, each of the second spiral arms having a second initial radius; a dielectric layer connected to the first conductive layer and having a second pattern, the second pattern being identical to the first pattern; a second conductive layer connected to the dielectric layer, the dielectric layer being disposed between the first conductive layer and the second conductive layer; and a contact electrode disposed through the dielectric layer and electrically connected between the first conductive layer and the second conductive layer; a coaxial cable electrically connected to the contact electrodes and converting the thermal radiation into direct current according to the Seebeck effect, A thermoelectric energy harvester, wherein the second initial radii of the second spiral arms are different from each other and different from the first initial radii.

24. 24. The thermoelectric energy harvester of claim 23, wherein the first conductive layer is made of a P-type semiconductor and the second conductive layer is made of an N-type semiconductor.

25. 24. The thermoelectric energy harvester of claim 23, wherein the first conductive layer is made of nickel (Ni) or one of a plurality of P-type conductive materials, and the second conductive layer is made of gold (Au) or one of a plurality of N-type conductive materials.

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