Coupled microstrip antenna unit, determination method and coupled antenna photoconductive detector

Abstract

This invention discloses a coupled microstrip antenna element, a determination method thereof, and a coupled antenna photoconductive detector, relating to the field of terahertz technology. The antenna element mainly comprises: an I-shaped antenna and two microstrip antennas with identical structural parameters; an opening is provided at the center of the middle arm of the I-shaped antenna; the two microstrip antennas are symmetrically placed on both sides of the middle arm; the microstrip antenna includes multiple groove structures, with the opening of each groove structure facing the middle arm; the structural parameters of the microstrip antenna include at least the number of groove structures, the groove period, the groove width, and the groove depth; through the resonant coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the central opening of the I-shaped antenna, enhancing the local electric field strength of the THz wave, thereby improving the detection sensitivity of the coupled antenna photoconductive detector.

Description

Technical Field

[0001] This invention relates to the field of terahertz technology, and in particular to a coupled microstrip antenna element, a method for determining it, and a coupled antenna photoconductive detector. Background Technology

[0002] Currently, in the visible and near-infrared bands, researchers often use surface plasmon polaritons (SPPs) to enhance the interaction between light and matter, thereby improving the performance of photodetectors. SPPs are surface-bound electromagnetic modes generated at the metal-dielectric interface by the collective oscillation of free electrons at the same frequency as the incident light. They can localize incident electromagnetic waves to the subwavelength scale, achieving near-field enhancement. However, in the terahertz (THz) band, metals are similar to perfect electric conductors (PECs), and the coupling between electrons on the metal surface and THz waves is weak, making it difficult for SPPs to achieve THz wave localization on metal surfaces. In 2004, Professor Pendry of Imperial College London proposed the concept of pseudo-surface plasmon polaritons (SSPPs), successfully applying SPPs to the THz band. He proposed that by creating periodic perforated structures on the metal surface, the plasma frequency of the metal can be effectively reduced, thereby generating surface electromagnetic modes in the THz band similar to optical surface plasmon polariton (SPPs). These surface electromagnetic modes are called pseudo-surface plasmon polariton modes. The transmission characteristics of pseudo-surface plasmon polariton modes are closely related to the shape and geometric parameters of the structure. By adjusting the structural parameters, surface electromagnetic modes in different frequency bands can be achieved.

[0003] For an I-type antenna photoconductive detector (i.e., a photoconductive detector with a simple I-type antenna element), when an electromagnetic wave with an incident light frequency of 0.55 THz is incident perpendicularly from the base end onto the surface of the simple I-type antenna element, there is a field enhancement effect at the opening position of the I-type antenna. When an electromagnetic wave with an incident light frequency greater than 0.8 THz is incident perpendicularly from the base end onto the surface of the simple I-type antenna element, the field enhancement effect at the opening position of the antenna is very weak. That is, for electromagnetic waves with an incident light frequency higher than 0.8 THz, the detection sensitivity of the I-type antenna photoconductive detector is not high. Summary of the Invention

[0004] The purpose of this invention is to provide a coupled microstrip antenna element, a determination method, and a coupled antenna photoconductive detector, so as to improve the local electric field strength of THz waves and thus improve the detection sensitivity of the coupled antenna photoconductive detector.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] In a first aspect, the present invention provides a coupled microstrip antenna element, comprising:

[0007] Base;

[0008] An I-shaped antenna is disposed on the upper surface of the substrate; an opening is provided at the center of the middle arm of the I-shaped antenna;

[0009] Two microstrip antennas with identical structural parameters are disposed on the upper surface of the substrate; the two microstrip antennas are symmetrically placed on both sides of the intermediate arm; each microstrip antenna includes multiple groove structures, and the opening of each groove structure faces the intermediate arm; the structural parameters of the microstrip antenna include at least the number of groove structures, the groove period, the groove width, and the groove depth.

[0010] Through the resonant coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the central opening of the I-shaped antenna, thereby enhancing the local electric field strength of the THz wave.

[0011] Optionally, when the groove period, the groove width, and the number of groove structures remain unchanged, if the groove depth decreases, the first-order resonant frequency in the microstrip antenna shifts to a higher frequency.

[0012] Optionally, multiple groove structures are arranged side by side, and two adjacent groove structures share the same sidewall.

[0013] Optionally, the substrate is a GaAs substrate.

[0014] Optionally, the thickness of the substrate is 20 μm.

[0015] Optionally, the groove period is the sum of the groove width and the groove sidewall width.

[0016] Optionally, the number of groove structures is three, the groove period is 10 μm, and the groove width is 5 μm.

[0017] In a second aspect, the present invention provides a method for determining the coupled microstrip antenna element as described in the first aspect, comprising:

[0018] The dispersion relation of pseudo-surface plasmons in a groove structure was constructed using the mode expansion method and the continuity condition of the electromagnetic field. Based on the dispersion relation, the physical mechanism and dispersion characteristics of the pseudo-surface plasmons in the groove structure were analyzed, and the analysis results were obtained. The groove structure is a two-dimensional or three-dimensional structure.

[0019] Based on the analysis results and the geometric parameters of the groove structure, the influence of several parameters in the groove structure on the pseudo-surface plasmon dispersion relation is determined; the geometric parameters include the groove period, groove width, and groove depth.

[0020] Based on the influence law, the resonance characteristics of a microstrip antenna composed of a finite number of groove structures are determined.

[0021] Based on the resonance characteristics, the number of groove structures, groove period, groove width, and groove depth in the microstrip antenna are determined to obtain the final microstrip antenna.

[0022] By adding a microstrip antenna to an I-shaped antenna, a coupled microstrip antenna element is obtained.

[0023] Thirdly, the present invention provides a coupled antenna photoconductive detector, including an electric field detector and the coupled microstrip antenna unit described in the first aspect; wherein the electric field detector is placed at the central opening of the I-shaped antenna and extends into the substrate.

[0024] Optionally, the coupled antenna photoconductive detector is suitable for the 0.8-1.5THz range.

[0025] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] The incident THz wave, through the resonant coupling effect of the coupled microstrip antenna element, can highly localize the incident energy at the resonant frequency at the central opening of the I-shaped antenna, thereby increasing the local electric field strength of the THz wave and thus improving the detection sensitivity of the coupled antenna photoconductive detector. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A three-dimensional structural diagram of a coupled microstrip antenna element provided in an embodiment of the present invention;

[0029] Figure 2 This is a planar schematic diagram of a coupled microstrip antenna element provided in an embodiment of the present invention;

[0030] Figure 3 This is a graph showing the relationship between the local electric field amplitude enhancement value in the coupled microstrip antenna element and the incident light frequency under different groove depths h, as provided in an embodiment of the present invention.

[0031] Figure 4 This is a local field distribution diagram of the coupled microstrip antenna element in the XY plane at the resonant frequency P0, provided by an embodiment of the present invention. Figure 4 (a) shows the amplitude distribution of the electric field. Figure 4 (b) shows the distribution of the real part of the Hz component of the magnetic field.

[0032] Figure 5 This is a local field distribution diagram of the coupled microstrip antenna element in the XY plane at the resonant frequency P1, provided by an embodiment of the present invention. Figure 5 (a) shows the amplitude distribution of the electric field. Figure 5 (b) shows the distribution of the real part of the Hz component of the magnetic field.

[0033] Figure 6 This is a local field distribution diagram of the coupled microstrip antenna element in the XY plane at the resonant frequency P2, provided by an embodiment of the present invention. Figure 6 (a) shows the amplitude distribution of the electric field. Figure 6 (b) shows the distribution of the real part of the Hz component of the magnetic field.

[0034] Figure 7 This is a local field distribution diagram of the coupled microstrip antenna element in the XY plane at the resonant frequency P3, provided by an embodiment of the present invention. Figure 7 (a) shows the amplitude distribution of the electric field. Figure 7 (b) shows the distribution of the real part of the Hz component of the magnetic field.

[0035] Figure 8 A comparison of the time-domain signals of photocurrent detected by a coupled antenna photoconductive detector and an I-type antenna photoconductive detector provided in an embodiment of the present invention;

[0036] Figure 9 A comparison of the photocurrent frequency domain signals detected by the coupled antenna photoconductive detector and the I-type antenna photoconductive detector provided in the embodiments of the present invention;

[0037] Figure 10 A comparison of photocurrent frequency signals detected by the photoconductive detector of the coupled antenna under different groove depths h, as provided in the embodiments of the present invention;

[0038] Figure 11 The graph shows the relationship between the peak frequency of the high-frequency portion of the photocurrent and the corresponding detection bandwidth in the coupled antenna photoconductive detector, as provided in the embodiments of the present invention, and the variation of the groove depth in the microstrip antenna. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1

[0042] like Figure 1 and Figure 2 As shown, the coupled microstrip antenna unit provided in this embodiment of the invention is characterized by comprising: a substrate, an I-shaped antenna, and two microstrip antennas having the same structural parameters.

[0043] An I-shaped antenna is disposed on the upper surface of the substrate; an opening is provided at the center of the middle arm of the I-shaped antenna.

[0044] Two microstrip antennas with identical structural parameters are disposed on the upper surface of the substrate; the two microstrip antennas are symmetrically placed on both sides of the intermediate arm; each microstrip antenna includes multiple groove structures; the multiple groove structures are arranged side by side, with adjacent groove structures sharing the same sidewall, and the opening of each groove structure facing the intermediate arm; the structural parameters of the microstrip antenna include at least the number of groove structures, the groove period P, the groove width w, and the groove depth h. The thickness of the metal layer is expressed as h. m The distance between the groove structure and the intermediate arm is represented by d. The groove period is the sum of the groove width and the width of the groove sidewall.

[0045] A THz wave polarized along the X direction is incident perpendicularly onto the surface of the antenna structure from the base end. Through the resonant coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the central opening of the I-shaped antenna, thereby enhancing the local electric field strength of the THz wave.

[0046] When the groove period, the groove width, and the number of groove structures remain unchanged, if the groove depth decreases, the first-order resonant frequency in the microstrip antenna will shift to a higher frequency.

[0047] Furthermore, the substrate is a GaAs substrate, and the thickness of the substrate is 20 μm.

[0048] Furthermore, the number of groove structures is 3, the groove period is 10μm, and the groove width is 5μm.

[0049] Furthermore, for ease of analysis, the length of the middle arm of the I-shaped antenna is fixed at L. m =120μm, with a central opening size of 10x10μm.

[0050] This invention proposes to design a coupled microstrip antenna unit by utilizing the resonance characteristics of the pseudo-surface plasmon polaritons in a groove structure. This unit localizes the incident THz wave height at the central opening of the I-shaped antenna, thereby increasing the local electric field strength of the THz wave and thus improving the detection sensitivity of the coupled antenna photoconductive detector.

[0051] Example 2

[0052] This invention provides a method for determining the coupled microstrip antenna element as described in Embodiment 1, comprising:

[0053] (1) The dispersion relation of pseudo-surface plasmons in the groove structure is constructed by using the mode expansion method and the continuity condition of the electromagnetic field. The physical mechanism and dispersion characteristics of pseudo-surface plasmons in the groove structure are analyzed based on the dispersion relation, and the analysis results are obtained. The groove structure is a two-dimensional structure or a three-dimensional structure.

[0054] (2) Based on the analysis results and the geometric parameters of the groove structure, determine the influence of several parameters in the groove structure on the pseudo-surface plasmon dispersion relation; the geometric parameters include the groove period, groove width and groove depth.

[0055] (3) Based on the influence law, the resonance characteristics of a microstrip antenna composed of a finite number of groove structures are determined.

[0056] (4) Based on the resonance characteristics, determine the number of groove structures, groove period, groove width and groove depth in the microstrip antenna to obtain the final microstrip antenna.

[0057] (5) Add the microstrip antenna to the I-type antenna to obtain a coupled microstrip antenna element.

[0058] This invention incorporates a defined microstrip antenna into a traditional terahertz antenna, designs a coupled microstrip antenna element, and analyzes its resonance characteristics. Finally, a photoconductive detector with the coupled microstrip antenna element is designed, achieving enhanced sensitivity terahertz photoconductive antenna-type single-band frequency-selective detection performance in the 0.8-1.5THz high-frequency range.

[0059] Example 3

[0060] This invention provides a coupled antenna photoconductive detector, comprising an electric field detector and the coupled microstrip antenna unit described in Embodiment 1; wherein the electric field detector is placed at the central opening of the I-shaped antenna and extends into the substrate (e.g., 2 μm into the substrate layer). The coupled antenna photoconductive detector is suitable for the 0.8-1.5 THz range.

[0061] Figure 1 and Figure 2 The coupled microstrip antenna element shown is similar to a THz wave concentrator. Through the resonant coupling effect of the coupled microstrip antenna element, the incident THz wave can be localized to the central opening position of the I-shaped antenna.

[0062] The physical mechanism by which coupled microstrip antenna elements enhance the local electric field intensity of THz waves is analyzed below using numerical simulation. Here, E0 represents the incident electric field without coupled microstrip antenna elements. The groove depth is a crucial parameter affecting the resonant characteristics of the microstrip antenna and also a significant parameter influencing the field localization performance of THz waves within coupled microstrip antenna elements. Figure 3 The relationship between the local electric field amplitude enhancement and the incident light frequency in a coupled microstrip antenna element is presented for different groove depths h. In this case, the groove period P = 10 μm, the groove width w = 0.5P, and the metal layer thickness (i.e., the groove metal thickness) h in the microstrip antenna is given. m =5μm, the distance between antennas d =5μm.

[0063] from Figure 3 It can be seen that for a simple I-shaped antenna element, when an electromagnetic wave with an incident light frequency of 0.55 THz is incident perpendicularly from the base end onto the surface of the simple I-shaped antenna element, there is a field enhancement effect at the opening position of the antenna. When an electromagnetic wave with an incident light frequency greater than 0.8 THz is incident perpendicularly from the base end onto the surface of the simple I-shaped antenna element, the field enhancement effect at the opening position is very weak. That is, for electromagnetic waves with incident light frequencies higher than 0.8 THz, the detection sensitivity of the photoconductive detector of the I-shaped antenna is not high. However, when a microstrip antenna is introduced into the I-shaped antenna, due to the resonant characteristics of the microstrip antenna itself, the incident THz wave can be localized to the surface of the microstrip antenna through the resonance effect. Then, through the near-field coupling between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the central opening position of the I-shaped antenna, thereby enhancing the local electric field strength at the opening position of the I-shaped antenna.

[0064] When the groove depth h = 2.0P, the curve showing the increase in local electric field amplitude in the coupled microstrip antenna element as a function of incident light frequency reveals four peaks, labeled P0, P1, P2, and P3. As the groove depth decreases, the P0 resonant peak remains almost unchanged, while the P1-P3 resonant peaks shift to higher frequencies. To understand the physical mechanism behind the formation of these four resonant peaks, the structural parameters of the microstrip antenna are first set as follows: groove period P = 10 μm, groove width w = 0.5P, depth h = 2.0P, and metal layer thickness h... m When μm = 5 μm, the electric field distribution and magnetic field distribution at the corresponding frequency point are as follows: Figures 4 to 7 The information is provided in the text.

[0065] Figure 4 (a) and (b) in the figure respectively show the real distribution of the electric field amplitude and the Hz component of the magnetic field of the coupled microstrip antenna element at the P0 frequency point. Figure 4 As can be seen, the magnetic field of the coupled microstrip antenna element is mainly localized on the middle arm of the I-shaped antenna, while the electric field is mainly localized at the central opening of the I-shaped antenna. Therefore, the P0 frequency point corresponds to the electric dipole resonance of the I-shaped antenna itself. Thus, this resonance frequency point does not change with the structural parameters of the microstrip antenna.

[0066] Figure 5 Figures (a) and (b) show the real distribution of the electric field amplitude and the Hz component of the magnetic field of the coupled microstrip antenna element at frequency P1, respectively. The magnetic field distribution shows that the electric dipole mode (first-order mode) of the microstrip antenna is excited at this frequency, and the first-order modes in the two microstrip antennas form an antisymmetric magnetic field distribution through near-field coupling. Correspondingly, the incident THz wave, in addition to being localized in the microstrip antenna, is also localized at the central opening of the I-shaped antenna through near-field coupling of the modes. Therefore, the electric field enhancement at this frequency mainly comes from the excitation of the first-order mode in the microstrip antenna. As the groove depth decreases, the first-order resonant frequency in the microstrip antenna shifts to higher frequencies; consequently, the localized field enhancement frequency in the coupled microstrip antenna element also shifts to higher frequencies. This characteristic can be used to realize a THz photoconductive detector with a configurable peak frequency.

[0067] Compared to the peak frequencies P0 and P1, the electric field amplitude enhancement at frequencies P2 and P3 is weaker. Figure 6 and Figure 7 The electric field amplitude and magnetic field H of the coupled microstrip antenna element at frequencies P2 and P3 are given respectively. zThe real component distribution. The magnetic field distribution shows that these two frequency points mainly originate from the excitation of the third-order mode in the microstrip antenna. Through the interference effect between coupled modes, the coupled microstrip antenna elements exhibit different field localization characteristics. For example, at frequency P2, the incident electric field is mainly localized in the upper microstrip antenna, while at frequency P3, the electric field of the upper microstrip antenna weakens, and the incident electric field is mainly localized in the lower microstrip antenna. At these two frequency points, the electric field localization at the center opening of the I-shaped antenna is relatively weak, making it unsuitable for photoconductive detector applications. Therefore, in subsequent photoconductive detector applications, the resonance of the first-order mode of the microstrip antenna is mainly utilized to enhance the performance of the photoconductive detector.

[0068] The following is a simulation analysis of the coupled antenna photoconductive detector (i.e., a photoconductive detector with coupled microstrip antenna elements).

[0069] When an 800nm ​​laser beam is incident perpendicularly onto the surface of a coupled microstrip antenna element from the air end, electron-hole pairs are generated in the GaAs substrate because the energy of the incident photons is greater than the bandgap width in the semiconductor material (GaAs). These electron-hole pairs, under the influence of the incident THz wave, form a photocurrent. The magnitude of the photocurrent can be detected to infer the incident THz wave. In the coupled antenna photoconductive detector, the incident THz wave, through the resonant coupling effect of the coupled microstrip antenna element, can highly localize the incident energy at the resonant frequency to the central opening of the I-shaped antenna, thereby increasing the local electric field strength of the THz wave.

[0070] As the local electric field intensity of the THz wave increases, the amplitude of the photocurrent also increases. Therefore, the sensitivity of the photoconductive detector can be enhanced at the resonant frequency of the coupled microstrip antenna element. This invention uses the FDTD (Finite-Difference Time-Domain Method) to simulate the photoelectric response of the coupled antenna photoconductive detector. Figure 8 The comparison results of the photocurrent time-domain signals detected by the coupled antenna photoconductive detector and the I-type antenna photoconductive detector are presented. Figure 9 Comparison of photocurrent frequency signals detected by the coupled antenna photoconductive detector and the I-shaped antenna photoconductive detector is presented. Solid lines represent the detection results of the coupled antenna photoconductive detector, and dashed lines represent the detection results of the I-shaped antenna photoconductive detector. The microstrip antenna in the coupled microstrip antenna element has a groove period P = 10 μm, a width w = 0.5P, a groove depth h = 1.5P, an antenna spacing d = 5 μm, and a metal layer thickness h. m =5μm.

[0071] from Figure 8 and Figure 9Simulation results show that, due to the resonant characteristics of the microstrip antenna, THz wave energy is stored in the coupled microstrip antenna element and attenuates in the form of leakage. Within the coupled microstrip antenna element, the local electric field of the THz wave has a relatively long relaxation time. This time length is related to the resonant frequency of the coupled microstrip antenna element; the higher the resonant frequency, the longer the photon lifetime and the longer the relaxation time of the electric field attenuation. Therefore, in the time domain of the photocurrent signal, the coupled antenna photoconductive detector has a longer relaxation time. In the frequency domain of the photocurrent signal, the peak detection value of the photocurrent detected by the I-type antenna photoconductive detector is around 0.52 THz. In the high-frequency part, the photocurrent detection intensity decreases sharply. This is mainly because the enhancement of the local electric field intensity of the THz wave in the I-type antenna is mainly around 0.52 THz; in the high-frequency part, the enhancement amplitude of the local electric field intensity of the THz wave is very small. Therefore, the I-type antenna photoconductive detector has limited detection capability for high-frequency electromagnetic waves (greater than 0.8 THz). For the coupled antenna photoconductive detector, the photocurrent exhibits an enhanced peak at 0.52 THz and also a corresponding enhanced peak at 1.17 THz, with a bandwidth of 0.26 THz at this enhanced frequency. (Comparison) Figure 6 Regarding the local electric field enhancement shown, the peak enhancement mainly originates from the enhanced local electric field intensity of the THz wave caused by the resonant coupling effect of the coupled microstrip antenna element. Compared to the photoconductive detector with a simple I-shaped antenna element, the detection intensity of the coupled antenna photoconductive detector is increased by 20 times at the 1.17THz frequency, thus enhancing the detection sensitivity of the photoconductive detector at this frequency.

[0072] Figure 10 The parameters given are: groove period P = 10 μm, width w = 0.5P, coupling spacing d = 5 μm, and metal layer thickness h. m Comparison of photocurrent frequency signals detected by the photoconductive detector of the coupled antenna under different groove depths h when the groove depth is 5μm.

[0073] When the groove depth h increases from 0.7P to 2.0P, the peak value of the photocurrent detected by the photoconductive detector of the coupled antenna at high frequency moves from 1.46THz to 1.01THz, and the peak value can be further increased by h to adjust the detection peak value to around 0.8THz. It can be seen that this is mainly due to the resonant frequency of the microstrip antenna itself shifting to higher frequencies as the groove depth increases.

[0074] Figure 11The relationship between the peak frequency of the high-frequency component of the photocurrent and the corresponding detection bandwidth in a coupled antenna photoconductive detector, and the groove depth in the microstrip antenna, is presented. The curves show a linear relationship between the detector's peak frequency and the groove depth. The detector's bandwidth reaches a maximum near a groove depth h = 1.4P, and gradually decreases further away from this region. Based on this characteristic, the detection frequency and bandwidth of the coupled antenna photoconductive detector can be designed using the groove depth, thus enabling the realization of a photoconductive detector with designable peak frequency and bandwidth.

[0075] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of the invention; furthermore, those skilled in the art will recognize that, based on the ideas of the invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. A coupled microstrip antenna element, characterized in that, include: Base; An I-shaped antenna is disposed on the upper surface of the substrate; An opening is provided at the center of the middle arm of the I-shaped antenna; Two microstrip antennas with identical structural parameters are disposed on the upper surface of the substrate; The two microstrip antennas are symmetrically placed on both sides of the intermediate arm; the microstrip antenna includes multiple groove structures, and the opening of each groove structure faces the intermediate arm; the structural parameters of the microstrip antenna include at least the number of groove structures, the groove period, the groove width, and the groove depth. Through the resonant coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the central opening of the I-shaped antenna, thereby enhancing the local electric field strength of the THz wave.

2. The coupled microstrip antenna element according to claim 1, characterized in that, When the groove period, the groove width, and the number of groove structures remain unchanged, if the groove depth decreases, the first-order resonant frequency in the microstrip antenna will shift to a higher frequency.

3. The coupled microstrip antenna element according to claim 1, characterized in that, Multiple groove structures are arranged side by side, and two adjacent groove structures share the same sidewall.

4. A coupled microstrip antenna element according to claim 1, characterized in that, The substrate is a GaAs substrate.

5. A coupled microstrip antenna element according to claim 1, characterized in that, The thickness of the substrate is 20 μm.

6. A coupled microstrip antenna element according to claim 1, characterized in that, The groove period is the sum of the groove width and the groove sidewall width.

7. A coupled microstrip antenna element according to claim 1, characterized in that, The number of groove structures is 3, the groove period is 10μm, and the groove width is 5μm.

8. A method for determining a coupled microstrip antenna element according to any one of claims 1-7, characterized in that, include: The dispersion relation of pseudo-surface plasmons in a groove structure was constructed using the mode expansion method and the continuity condition of the electromagnetic field. Based on the dispersion relation, the physical mechanism and dispersion characteristics of the pseudo-surface plasmons in the groove structure were analyzed, and the analysis results were obtained. The groove structure is a two-dimensional or three-dimensional structure. Based on the analysis results and the geometric parameters of the groove structure, the influence of several parameters in the groove structure on the pseudo-surface plasmon dispersion relation is determined; the geometric parameters include the groove period, groove width, and groove depth. Based on the influence law, the resonance characteristics of a microstrip antenna composed of a finite number of groove structures are determined. Based on the resonance characteristics, the number of groove structures, groove period, groove width, and groove depth in the microstrip antenna are determined to obtain the final microstrip antenna. By adding a microstrip antenna to an I-shaped antenna, a coupled microstrip antenna element is obtained.

9. A coupled antenna photoconductive detector, characterized in that, It includes an electric field detector and a coupled microstrip antenna element as described in any one of claims 1-7; wherein the electric field detector is placed at the central opening of the I-shaped antenna and extends into the substrate.

10. A coupled antenna photoconductive detector according to claim 9, characterized in that, The coupled antenna photoconductive detector is suitable for the 0.8-1.5THz range.

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