CN116345163A - Coupling microstrip antenna unit, determining method and coupling antenna photoconductive detector - Google Patents

Coupling microstrip antenna unit, determining method and coupling antenna photoconductive detector Download PDF

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Publication number
CN116345163A
CN116345163A CN202310257310.0A CN202310257310A CN116345163A CN 116345163 A CN116345163 A CN 116345163A CN 202310257310 A CN202310257310 A CN 202310257310A CN 116345163 A CN116345163 A CN 116345163A
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antenna
groove
microstrip antenna
coupled
microstrip
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熊中刚
刘忠
刘泉澄
韩兴国
罗文军
李慧娴
罗素莲
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Guilin University of Aerospace Technology
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Guilin University of Aerospace Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/08—Radiating ends of two-conductor microwave transmission lines, e.g. of coaxial lines, of microstrip lines
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
    • G01R29/08—Measuring electromagnetic field characteristics
    • G01R29/0864—Measuring electromagnetic field characteristics characterised by constructional or functional features
    • G01R29/0878—Sensors; antennas; probes; detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
    • G01R29/08—Measuring electromagnetic field characteristics
    • G01R29/0864—Measuring electromagnetic field characteristics characterised by constructional or functional features
    • G01R29/0878—Sensors; antennas; probes; detectors
    • G01R29/0885—Sensors; antennas; probes; detectors using optical probes, e.g. electro-optical, luminescent, glow discharge, or optical interferometers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/225—Supports; Mounting means by structural association with other equipment or articles used in level-measurement devices, e.g. for level gauge measurement
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2283—Supports; Mounting means by structural association with other equipment or articles mounted in or on the surface of a semiconductor substrate as a chip-type antenna or integrated with other components into an IC package
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Waveguide Aerials (AREA)

Abstract

The invention discloses a coupling microstrip antenna unit, a determining method and a coupling antenna photoconductive detector, and relates to the technical field of terahertz, wherein the antenna unit mainly comprises: the antenna comprises an I-shaped antenna and two microstrip antennas with the same structural parameters; an opening is arranged at the center of the middle arm of the I-shaped antenna; the two microstrip antennas are symmetrically arranged on two sides of the middle arm respectively; the microstrip antenna comprises a plurality of groove structures, and an opening of each groove structure faces to the middle arm; the structural parameters of the microstrip antenna at least comprise the number of groove structures, the groove period, the groove width and the groove depth; through the resonance coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the center opening position of the I-shaped antenna, and the intensity of the THz wave localized electric field is enhanced, so that the detection sensitivity of the photoconductive detector of the coupling antenna is improved.

Description

Coupling microstrip antenna unit, determining method and coupling antenna photoconductive detector
Technical Field
The invention relates to the technical field of terahertz, in particular to a coupling microstrip antenna unit, a determining method and a coupling antenna photoconductive detector.
Background
Currently, in the visible and near infrared bands, researchers often use surface plasmons (SurfacePlasmonPolaritons, SPPs) to enhance the interaction of light with matter, enhancing the performance of photodetectors. SPPs are a surface-bound electromagnetic mode generated by collective oscillation of free electrons at the metal-dielectric interface at the same frequency as the incident light. The near-field enhancement can be realized by locally dividing the incident electromagnetic wave into sub-wavelength dimensions. In the TeraHertz (THz) band, metals are similar to ideal conductors (PECs), the coupling effect of electrons on the surface of metals and THz waves is weak, and SPPs are difficult to realize the local area of THz waves on the surface of metals. In 2004, the Pendry teaching of the university of imperial science in the united kingdom, proposed the concept of pseudo-surface plasmons (SproofSPPs, SSPPs), successfully applying SPPs to the THz band. He suggested that by making periodic hole structures on the metal surface, the plasma frequency of the metal can be equivalently reduced, so as to generate a surface electromagnetic mode similar to the optical frequency band SPPs in the THz band, and this surface electromagnetic mode is called pseudo surface plasmon mode. The transmission characteristics of the pseudo surface plasmon modes are closely related to the shape and geometric parameters of the structure, and the surface electromagnetic modes of different frequency bands can be realized by adjusting the structural parameters.
For the photoconductive detector of the I-shaped antenna (namely, the photoconductive detector with the simplex antenna unit), when the electromagnetic wave with the incident light frequency of 0.55THz perpendicularly enters the surface of the simplex antenna unit from the substrate end, the field enhancement effect is provided at the opening position of the I-shaped antenna, and when the electromagnetic wave with the incident light frequency of more than 0.8THz perpendicularly enters the surface of the simplex antenna unit from the substrate end, the field enhancement effect is weak at the opening position of the antenna, namely, the detection sensitivity of the photoconductive detector of the I-shaped antenna is not high for the electromagnetic wave with the incident light frequency of more than 0.8 THz.
Disclosure of Invention
The invention aims to provide a coupling microstrip type antenna unit, a determining method and a coupling antenna photoconductive detector, so as to achieve the purpose of improving the intensity of a THz wave local electric field and further improving the detection sensitivity of the coupling antenna photoconductive detector.
In order to achieve the above object, the present invention provides the following solutions:
in a first aspect, the present invention provides a coupled microstrip antenna element comprising:
a substrate;
the I-shaped antenna is arranged on the upper surface of the substrate; an opening is formed in the center of the middle arm of the I-shaped antenna;
two microstrip antennas with the same structural parameters are arranged on the upper surface of the substrate; the two microstrip antennas are symmetrically arranged on two sides of the middle arm respectively; the microstrip antenna comprises a plurality of groove structures, and an opening of each groove structure faces the middle arm; the structural parameters of the microstrip antenna at least comprise the number of groove structures, groove period, groove width and groove depth;
through the resonance coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the center opening position of the I-shaped antenna, and the local electric field intensity of the THz wave is enhanced.
Alternatively, when the groove period, the groove width, and the number of groove structures are unchanged, if the groove depth is reduced, the first order resonance frequency in the microstrip type antenna is shifted to a high frequency.
Optionally, a plurality of the groove structures are arranged side by side, and two adjacent groove structures share the same side wall.
Optionally, the substrate is a GaAs substrate.
Optionally, the thickness of the substrate is 20 μm.
Optionally, the groove period is the sum of the groove width and the groove sidewall width.
Optionally, the number of the groove structures is 3, and the groove period is 10 μm; the groove width was 5 μm.
In a second aspect, the present invention provides a method for determining a coupled microstrip antenna unit according to the first aspect, including:
constructing a dispersion relation of pseudo surface plasmons of the groove structure by using a mode expansion method and a continuity condition of an electromagnetic field, and analyzing a physical mechanism and dispersion characteristics of the pseudo surface plasmons of the groove structure according to the dispersion relation to obtain an analysis result; the groove structure is a two-dimensional structure or a three-dimensional structure;
determining the influence rule of a plurality of parameters in the groove structure on the pseudo-surface plasmon dispersion relation according to the analysis result and the geometric parameters of the groove structure; the geometric parameters comprise groove period, groove width and groove depth;
determining resonance characteristics of a microstrip antenna formed by a limited number of groove structures based on an influence rule;
determining the number of groove structures, the groove period, the groove width and the groove depth in the microstrip antenna based on resonance characteristics to obtain a final microstrip antenna;
and adding the microstrip antenna into the I-shaped antenna to obtain the coupled microstrip antenna unit.
In a third aspect, the present invention provides a photoconductive detector for a coupled antenna, including an electric field detector and a coupled microstrip antenna unit according to the first aspect; the electric field detector is placed at the position of the central opening of the I-shaped antenna and penetrates into the substrate.
Alternatively, the coupled antenna photoconductive detector is suitable for use in the 0.8-1.5THz range.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the incident THz wave can highly localize the incident energy at the resonance frequency at the center opening position of the I-shaped antenna through the resonance coupling effect of the coupling microstrip antenna unit, thereby improving the local electric field intensity of the THz wave and the detection sensitivity of the coupling antenna photoconductive detector.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a three-dimensional structure diagram of a coupled microstrip antenna unit according to an embodiment of the present invention;
fig. 2 is a schematic plan view of a coupled microstrip antenna unit according to an embodiment of the present invention;
fig. 3 is a graph showing a change of a local electric field amplitude enhancement value with an incident light frequency in a coupled microstrip antenna unit under the condition of different groove depths h according to an embodiment of the present invention;
FIG. 4 shows a frequency at the resonant frequency P according to an embodiment of the present invention 0 A local field distribution diagram of the coupled microstrip antenna unit in an XY plane; fig. 4 (a) shows an amplitude distribution diagram of the electric field; fig. 4 (b) is a graph showing the real part value of the Hz component of the magnetic field;
FIG. 5 shows the resonance frequency P according to the embodiment of the present invention 1 A local field distribution diagram of the coupled microstrip antenna unit in an XY plane; fig. 5 (a) shows an amplitude distribution diagram of the electric field; fig. 5 (b) is a graph showing the real part value of the Hz component of the magnetic field;
FIG. 6 shows a frequency at the resonant frequency P according to an embodiment of the present invention 2 A local field distribution diagram of the coupled microstrip antenna unit in an XY plane; fig. 6 (a) shows an amplitude distribution diagram of the electric field; fig. 6 (b) is a graph showing the real part value of the Hz component of the magnetic field;
FIG. 7 shows a frequency at the resonant frequency P according to an embodiment of the present invention 3 A local field distribution diagram of the coupled microstrip antenna unit in an XY plane; fig. 7 (a) shows an amplitude distribution diagram of the electric field; fig. 7 (b) is a graph showing the real value of the Hz component of the magnetic field;
FIG. 8 is a graph of comparing the time domain signals of photocurrents detected by the coupled antenna photoconductive detector and the I-shaped antenna photoconductive detector according to the embodiment of the present invention;
FIG. 9 is a graph of comparing signals of photocurrent frequency domains detected by the coupled antenna photoconductive detector and the I-shaped antenna photoconductive detector according to the embodiment of the present invention;
FIG. 10 is a graph showing comparison results of photocurrent frequency signals detected by a photoconductive detector of a coupled antenna under the condition of different groove depths h provided by the embodiment of the present invention;
fig. 11 is a graph showing a relationship between peak frequency of a high frequency portion of a photocurrent and corresponding detection bandwidth of the high frequency portion of the photocurrent and depth of a groove in a microstrip antenna in a photoconductive detector of a coupled antenna according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
As shown in fig. 1 and fig. 2, a coupled microstrip antenna unit provided in an embodiment of the present invention is characterized by comprising: the antenna comprises a substrate, an I-shaped antenna and two microstrip antennas with the same structural parameters.
The I-shaped antenna is arranged on the upper surface of the substrate; an opening is arranged at the center of the middle arm of the I-shaped antenna.
Two microstrip antennas with the same structural parameters are arranged on the upper surface of the substrate; the two microstrip antennas are symmetrically arranged on two sides of the middle arm respectively; the microstrip antenna comprises a plurality of groove structures; the groove structures are arranged side by side, two adjacent groove structures share the same side wall, and the opening of each groove structure faces to the middle arm; the structural parameters of the microstrip antenna at least comprise 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 denoted as h m The method comprises the steps of carrying out a first treatment on the surface of the The distance of the groove structure from the intermediate arm is denoted d. The groove period is the sum of the groove width and the groove side wall width.
THz waves polarized along the X direction vertically enter the surface of the antenna structure from the substrate end, and the incident THz waves are localized to the center opening position of the I-shaped antenna through the resonance coupling effect between the microstrip antenna and the I-shaped antenna, so that the local electric field intensity of the THz waves is enhanced.
When the groove period, the groove width and the number of groove structures are unchanged, if the groove depth is reduced, the first-order resonance frequency in the microstrip antenna moves to high frequency.
Further, the substrate is a GaAs substrate having a thickness of 20 μm.
Further, the number of the groove structures is 3, and the groove period is 10 μm; the groove width was 5 μm.
Further, for ease of analysis, the length of the middle arm of the I-shaped antenna is fixed at L m =120 μm, the central opening size is 10×10 μm.
The embodiment of the invention provides a coupling microstrip antenna unit designed by utilizing the resonance characteristic of a groove structure pseudo-surface plasmon, and the incident THz wave is highly localized at the center opening position of an I-shaped antenna, so that the intensity of a THz wave localized electric field is improved, and the detection sensitivity of a coupling antenna photoconductive detector is improved.
Example two
The embodiment of the invention provides a method for determining a coupled microstrip antenna unit, which comprises the following steps:
(1) Constructing a dispersion relation of pseudo surface plasmons of the groove structure by using a mode expansion method and a continuity condition of an electromagnetic field, and analyzing a physical mechanism and dispersion characteristics of the pseudo surface plasmons of the groove structure according to the dispersion relation to obtain an analysis result; the groove structure is a two-dimensional structure or a three-dimensional structure.
(2) Determining the influence rule of a plurality of parameters in the groove structure on the pseudo-surface plasmon dispersion relation according to the analysis result and the geometric parameters of the groove structure; the geometric parameters include groove period, groove width, and groove depth.
(3) Based on the rule of influence, the resonance characteristics of the microstrip antenna formed by the limited number of groove structures are determined.
(4) And determining the number of groove structures, the groove period, the groove width and the groove depth in the microstrip antenna based on the resonance characteristic to obtain the final microstrip antenna.
(5) And adding the microstrip antenna into the I-shaped antenna to obtain the coupled microstrip antenna unit.
The embodiment of the invention adds the determined microstrip antenna into the traditional terahertz I-shaped antenna, designs a coupling microstrip antenna unit and analyzes the resonance characteristic of the coupling microstrip antenna unit. Finally, a photoconductive detector with a coupling microstrip type antenna unit is designed, and the terahertz photoconductive antenna type single-band frequency selection detection performance with enhanced sensitivity in the high-frequency range of 0.8-1.5THz is realized.
Example III
The invention provides a coupling antenna photoconductive detector, which comprises an electric field detector and the coupling microstrip antenna unit in the first embodiment; wherein the electric field detector is placed at the center opening position of the I-shaped antenna and goes deep into the substrate (for example, 2 μm deep into the substrate layer). The coupled antenna photoconductive detector is suitable for the range of 0.8-1.5 THz.
The coupled microstrip antenna element shown in fig. 1 and 2 resembles a THz wave concentrator, and the incident THz wave can be localized to the center opening of the i-antenna by the resonant coupling action of the coupled microstrip antenna element.
The physical mechanism of the coupling microstrip antenna unit for enhancing the local electric field intensity of the THz wave is analyzed by a numerical simulation method. Wherein E is 0 Indicating the incident electric field when the microstrip type antenna element is not coupled. The depth of the groove is an important parameter affecting the resonance characteristics of the microstrip antenna and also affecting the field local performance of the THz wave in the coupled microstrip antenna unit. Fig. 3 shows the local electric field amplitude enhancement values in the coupled microstrip antenna element as a function of the frequency of the incident light for different groove depths h. At this time, the slot period p=10μm, the slot width w=0.5p, and the metal layer thickness (i.e. slot metal thickness) h in the microstrip antenna m =5 μm, inter-antenna distance d=5 μm.
As can be seen from fig. 3, for the simplex antenna unit, when an electromagnetic wave having an incident light frequency of 0.55THz is perpendicularly incident to the simplex antenna unit surface from the base end, the field enhancement effect at the opening position of the simplex antenna unit is weak when an electromagnetic wave having an incident light frequency of more than 0.8THz is perpendicularly incident to the simplex antenna unit surface from the base end, i.e., the detection sensitivity of the simplex antenna photoconductive detector is not high for an electromagnetic wave having an incident light frequency of more than 0.8 THz. When the microstrip antenna is introduced into the I-shaped antenna, the microstrip antenna has resonance characteristics, incident THz waves can be localized to the surface of the microstrip antenna through resonance effect, and then the incident THz waves are localized to the center opening position of the I-shaped antenna through near field coupling effect between the microstrip antenna and the I-shaped antenna, so that the local electric field intensity at the opening position of the I-shaped antenna is enhanced.
When the groove depth h=2.0p, 4 peaks, respectively labeled P, are obtained in the curve of the variation relationship of the local electric field amplitude enhancement value in the coupled microstrip antenna unit with the incident light frequency 0 ，P 1 ，P 2 And P 3 . When the groove depth is reduced, P 0 The resonance peak is almost unchanged, while P 1 -P 3 The resonance peak shifts to high frequencies. For the purpose ofUnderstanding the physical mechanism of the formation of the four resonance peaks, firstly setting the structural parameters of the microstrip antenna, when the groove period P=10μm, the groove width w=0.5P, the depth h=2.0P and the thickness h of the metal layer in the microstrip antenna m When=5 μm, the electric field distribution and the magnetic field distribution of the corresponding frequency points are given in fig. 4 to 7.
Fig. 4 (a) and (b) show the coupling microstrip antenna element at P, respectively 0 The frequency points correspond to the real part distribution of the electric field amplitude and the magnetic field Hz component. As can be seen from fig. 4, the magnetic field of the coupled microstrip antenna element is mainly localized on the middle arm of the i-antenna, and the electric field is mainly localized at the center opening of the i-antenna, then P 0 The frequency points correspond to the electric dipole resonances of the i-shaped antenna itself. Therefore, the resonance frequency point does not change with the structural parameter of the microstrip antenna.
Fig. 5 (a) and (b) show the coupling microstrip antenna element at P, respectively 1 The frequency points correspond to the real part distribution of the electric field amplitude and the magnetic field Hz component. As can be seen from the magnetic field distribution, at this frequency point the electric dipole mode (first order mode) of the microstrip antenna is excited, the first order modes of the two microstrip antennas forming an antisymmetric magnetic field distribution by near field coupling. Accordingly, the incident THz wave is localized at the center opening of the i-antenna by the near-field coupling of the mode, except for the localized in the microstrip antenna. Therefore, the electric field enhancement at this frequency point mainly comes from excitation of the first order mode in the microstrip antenna, and when the groove depth is reduced, the first order resonance frequency in the microstrip antenna shifts to high frequency, and thus, in the coupled microstrip antenna unit, the local field enhancement frequency also shifts to high frequency. This feature can be used to realize a THz photoconductive detector with a programmable detection peak frequency.
Compared with P 0 And P 1 Peak frequency point, P 2 And P 3 The electric field amplitude enhancement value of the frequency point is weak. Figures 6 and 7 show the coupling microstrip antenna element at P 2 And P 3 Electric field amplitude and magnetic field H corresponding to frequency points z The real part distribution of the components. From the magnetic field distribution, it can be seen that these two areThe frequency point is mainly from the excitation of the third order mode in the microstrip antenna. The coupling microstrip antenna units show different field local characteristics through interference effects among coupling modes. For example P 2 At the frequency point, the incident electric field is localized mainly in the microstrip antenna at the upper end, but at P 3 At the frequency point, the electric field of the upper microstrip antenna is weakened, and the incident electric field is mainly localized in the lower microstrip antenna. At these two frequency points, the electric field at the center opening of the i-shaped antenna is locally weaker and is not suitable for the application of a photoconductive detector. Thus, in the latter 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.
The following describes a simulation analysis of a photoconductive detector of a coupled antenna (i.e., a photoconductive detector with a coupled microstrip antenna element).
When a beam of laser with the wavelength of 800nm is vertically incident on the surface of the coupling microstrip antenna unit from the air end, since the energy of incident photons is larger than the band gap width in the semiconductor material (GaAs), electron-hole pairs are generated in the GaAs substrate, and form photocurrent under the action of incident THz waves, and the incident THz waves can be inverted by detecting the magnitude of the photocurrent. In the coupling antenna photoconductive detector, incident THz waves can be highly localized at the center opening position of the I-shaped antenna by the resonance coupling effect of the coupling microstrip antenna unit, so that the local electric field intensity of the THz waves is improved.
As the intensity of the THz wave local electric field increases, the magnitude of the photocurrent also increases. The sensitivity of the photoconductive detector can thus be enhanced at the resonance frequency of the coupled microstrip antenna element. The embodiment of the invention simulates the photoelectric response of the photoconductive detector of the coupled antenna by an FDTD Method (finish-Difference time-Domain Method). Fig. 8 shows comparison results of photocurrent time domain signals detected by the coupling antenna photoconductive detector and the i-type antenna photoconductive detector, and fig. 9 shows comparison results of photocurrent frequency signals detected by the coupling antenna photoconductive detector and the i-type antenna photoconductive detector. Wherein, the reality is thatThe line indicates the detection result of the coupled antenna photoconductive detector, and the broken line indicates the detection result of the i-shaped antenna photoconductive detector. The slot period P=10μm, the width w=0.5P, the slot depth h=1.5P, the antenna spacing d=5μm and the metal layer thickness h of the microstrip antenna in the coupling microstrip antenna unit m ＝5μm。
As can be seen from the simulation results of fig. 8 and 9, THz wave energy is stored in the coupled microstrip type antenna unit due to the resonance characteristics of the microstrip type antenna, and attenuated in the form of leakage. In the coupled microstrip antenna element, the THz wave local electric field has a longer relaxation time, and the length of the relaxation time is related to the resonance frequency value of the coupled microstrip antenna element, and the larger the resonance frequency value is, the longer the photon lifetime is, and the longer the relaxation time of the electric field attenuation is. Thus, the coupled antenna photoconductive detector has a longer relaxation time as seen in the time domain signal of the photocurrent. In the frequency domain signal of the photocurrent, the detection peak value of the photocurrent detected by the photoconductive detector of the I-shaped antenna is near 0.52THz, and in the high frequency part, the detection intensity of the photocurrent is sharply reduced, which is mainly that the enhancement of the local electric field intensity of THz wave in the I-shaped antenna is mainly near 0.52THz, and in the high frequency part, the enhancement amplitude of the local electric field intensity of THz wave is small, so that the detection capability of the photoconductive detector of the I-shaped antenna on high frequency electromagnetic waves (more than 0.8 THz) is limited. For a coupled antenna photoconductive detector, the photocurrent has a corresponding enhancement peak at a frequency of 1.17THz, in addition to an enhancement peak at a frequency of 0.52THz, with a bandwidth of 0.26THz. In contrast to the local electric field enhancement shown in fig. 6, the enhancement peak is mainly derived from the enhancement of the THz wave local electric field intensity caused by the resonant coupling effect of the coupled microstrip antenna element. Compared with the photoconductive detector of the simplex antenna unit, the detection intensity of the photoconductive detector of the coupling antenna is improved by 20 times at the frequency of 1.17THz, and the detection sensitivity of the photoconductive detector at the frequency is enhanced.
Fig. 10 shows the coupling pitch d=5 μm, the metal layer thickness h at the groove period p=10 μm, the width w=0.5P m Under the condition of=5 μm, under the condition of different groove depths h, the photoconductive detector of the coupling antenna detectsAnd comparing the measured photocurrent frequency signals.
When the depth h of the groove is increased from 0.7P to 2.0P, the detection peak value at the high frequency of the photocurrent detected by the photoconductive detector of the coupled antenna is moved from 1.46THz to 1.01THz, and the h value can be continuously increased to regulate the detection peak value to be near 0.8THz, so that the resonance frequency of the microstrip antenna is mainly moved to high frequency along with the increase of the depth of the groove.
Fig. 11 shows the peak frequency of the high frequency portion of the photocurrent and the corresponding detection bandwidth as a function of the depth of the notch in the microstrip antenna in a coupled antenna photoconductive detector. From the above-mentioned change curve, it can be seen that the peak frequency of the detector is linearly dependent on the change in groove depth. The detection bandwidth of the detector obtains a maximum value near the groove depth h=1.4p, and the detection bandwidth value gradually decreases away from the region. By the characteristics, the detection frequency and the bandwidth of the coupling antenna photoconductive detector can be designed by utilizing the groove depth, so that the photoconductive detector with the designable peak frequency and bandwidth is realized.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (10)

1. A coupled microstrip antenna element comprising:
a substrate;
the I-shaped antenna is arranged on the upper surface of the substrate; an opening is formed in the center of the middle arm of the I-shaped antenna;
two microstrip antennas with the same structural parameters are arranged on the upper surface of the substrate; the two microstrip antennas are symmetrically arranged on two sides of the middle arm respectively; the microstrip antenna comprises a plurality of groove structures, and an opening of each groove structure faces the middle arm; the structural parameters of the microstrip antenna at least comprise the number of groove structures, groove period, groove width and groove depth;
through the resonance coupling effect between the microstrip antenna and the I-shaped antenna, the incident THz wave is localized to the center opening position of the I-shaped antenna, and the local electric field intensity of the THz wave is enhanced.
2. The coupled microstrip antenna element according to claim 1, wherein when the slot period, the slot width and the number of slot structures are constant, the first order resonant frequency in the microstrip antenna shifts to a higher frequency if the slot depth is reduced.
3. The coupled microstrip antenna element of claim 1, wherein a plurality of said slot structures are disposed side-by-side and adjacent two of said slot structures share a common sidewall.
4. The coupled microstrip antenna element of claim 1, wherein said substrate is a GaAs substrate.
5. The coupled microstrip antenna element of claim 1, wherein said substrate has a thickness of 20 μm.
6. The coupled microstrip antenna element according to claim 1, wherein said slot period is the sum of slot width and slot sidewall width.
7. The coupled microstrip antenna element according to claim 1, wherein said number of slot structures is 3, and said slot period is 10 μm; the groove width was 5 μm.
8. A method of determining a coupled microstrip antenna element as claimed in any one of claims 1 to 7, comprising:
constructing a dispersion relation of pseudo surface plasmons of the groove structure by using a mode expansion method and a continuity condition of an electromagnetic field, and analyzing a physical mechanism and dispersion characteristics of the pseudo surface plasmons of the groove structure according to the dispersion relation to obtain an analysis result; the groove structure is a two-dimensional structure or a three-dimensional structure;
determining the influence rule of a plurality of parameters in the groove structure on the pseudo-surface plasmon dispersion relation according to the analysis result and the geometric parameters of the groove structure; the geometric parameters comprise groove period, groove width and groove depth;
determining resonance characteristics of a microstrip antenna formed by a limited number of groove structures based on an influence rule;
determining the number of groove structures, the groove period, the groove width and the groove depth in the microstrip antenna based on resonance characteristics to obtain a final microstrip antenna;
and adding the microstrip antenna into the I-shaped antenna to obtain the coupled microstrip antenna unit.
9. A coupled antenna photoconductive detector comprising an electric field detector and a coupled microstrip antenna element as claimed in any one of claims 1 to 7; the electric field detector is placed at the position of the central opening of the I-shaped antenna and penetrates into the substrate.
10. The coupled antenna photoconductive detector of claim 9, wherein the coupled antenna photoconductive detector is adapted for use in the range of 0.8-1.5 THz.
CN202310257310.0A 2023-03-17 2023-03-17 Coupling microstrip antenna unit, determining method and coupling antenna photoconductive detector Pending CN116345163A (en)

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