Microwave detection method applied to passive pulsed electric field

Abstract

The invention provides a microwave detection method applied to a passive pulsed electric field, which is used for detecting microwave parameters when strong laser interacts with plasma, and comprises the following steps: a passive pulsed electric field probe is arranged in a preset range around a laser target spot, and the passive pulsed electric field probe is a prefabricated terahertz photoconductive antenna; and microwave parameters are detected through the electric field probe when the intense laser interacts with the plasma. The terahertz photoconductive antenna is used as a probe for detection, detection of ultra-wide spectrum strong field microwaves can be realized, measurement of microwave parameters generated by the action of strong laser and plasma can be realized without a plurality of detectors, and the operation is simple; in addition, the size of the electric field probe in the scheme is in a millimeter order, extra power supply is not needed, and interference to a detected signal is avoided. And the adopted terahertz photoconductive antenna has the characteristics of small size, small volume and strong anti-interference capability, and is beneficial to measurement in a narrow space.

Description

Technical Field

[0001] This invention relates to the field of electromagnetics, specifically to electromagnetic field detection technology, and more specifically, to a microwave detection method applied to passive pulsed electric fields. Background Technology

[0002] The interaction between high-power lasers and plasma can achieve extremely high energy densities per unit time and space, generating a series of extreme physical conditions previously only found in nuclear explosions or celestial bodies, accompanied by a large number of high-energy particles, bright gamma rays and X-rays, ultra-strong terahertz radiation, and microwave radiation. The microwaves generated by the interaction of high-power lasers and plasma are ultra-wideband (UWB) radiation with center frequencies ranging from several GHz to tens of GHz and pulse widths on the order of hundreds of picoseconds to hundreds of nanoseconds. Their radiated electric fields can reach the order of MV / m, and the estimated instantaneous radiated power can reach the order of GW. Diagnosing the microwave radiation generated by the interaction of high-power lasers and plasma under such extreme physical conditions is an important research area with significant implications for the development of the electromagnetic field.

[0003] In existing technologies, microwave diagnostics are mainly implemented by drawing on work done on the measurement of electric fields from nuclear explosion electromagnetic pulses. The main methods are twofold: electric field detectors based on differential measurements and fiber optic transmission electric field detectors based on raw signal measurements. These two types of electric field detectors are relatively mature in development and have been applied to the measurement of microwave parameters generated by the interaction of high-intensity lasers and plasmas. However, both of these existing detectors have certain shortcomings. First, the electromagnetic pulse fields matched to these detectors are primarily designed to be compatible with nuclear electromagnetic pulses, based on the standards specified in IEC 6100-2-9: a peak electric field value of 50 kV / m, a leading edge of 2.5 ns, and a full width at half maximum (FWHM) of 23 ns. However, the microwave radiation conditions under the influence of strong lasers and plasmas have larger peak electric fields (MV / m), steeper leading edges, and wider spectral widths. Therefore, in practical applications, using differential measurement-based electric field detectors and fiber optic transmission electric field detectors based on raw signal measurements for microwave detection often requires multiple detectors to cover different frequency ranges, making operation difficult and accuracy dependent on human experience. This is especially true for detecting the high-frequency portion of the electric field above 10 GHz, where achieving full spectrum coverage is challenging. Second, differential measurement-based electric field detectors rely on cable transmission, resulting in relatively poor anti-interference capabilities and unsuitability for long-distance electric field signal transmission. Fiber optic transmission electric field detectors based on raw signal measurements are active detectors, requiring power to the front end, making them unsuitable for the vacuum environment of strong lasers and plasmas. In addition, both types of detectors contain a lot of metal components and have large antennas, generally larger than 10cm*10cm. This not only easily interferes with the measured signal, but also limits or even renders them unsuitable for electric field measurements in confined spaces.

[0004] It should be noted that the background information presented here is only for illustrating relevant information about the present invention to aid in understanding the technical solutions of the present invention, and does not imply that the relevant information is necessarily prior art. In the absence of evidence indicating that the relevant information was disclosed before the filing date of this invention, the relevant information should not be considered prior art. Summary of the Invention

[0005] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a microwave detection method for passive pulsed electric fields.

[0006] The present invention discloses a microwave detection method for passive pulsed electric fields, used to detect microwave parameters when a strong laser interacts with plasma. The method includes: setting a passive pulsed electric field probe within a preset range around a laser target, wherein the passive pulsed electric field probe is a prefabricated terahertz photoconductive antenna; and detecting microwave parameters through the electric field probe when a strong laser interacts with plasma.

[0007] Preferably, the preset range is the range outside the laser incident path and laser exit path within a sphere with the target point as the center and a radius of 10cm.

[0008] Preferably, the passive pulsed electric field probe includes: a substrate made of low-temperature gallium arsenide; and a dipole antenna consisting of two symmetrically spaced wires disposed on the surface of the substrate.

[0009] Preferably, the low-temperature gallium arsenide is gallium arsenide grown at a temperature of 200-300°C and annealed at a temperature of 350-550°C.

[0010] Preferably, the substrate is a square substrate.

[0011] Preferably, the dimension of each side of the substrate is less than or equal to 1 cm.

[0012] Preferably, the substrate is a 5mm*5mm square substrate.

[0013] Preferably, a gap of a preset width is provided between the two conductors of the dipole antenna.

[0014] Preferably, the preset width between the two conductors of the dipole antenna is determined according to the terahertz intensity.

[0015] Preferably, each wire of the dipole antenna is a layer of gold plated on the substrate.

[0016] Compared with existing technologies, the advantages of this invention are as follows: This invention uses a terahertz photoconductive antenna as a probe for detection. The substrate material of the probe, low-temperature gallium arsenide, possesses characteristics such as high carrier mobility, rapid charge trapping, high dark resistance, and a large threshold breakdown voltage, enabling the detection of ultra-wideband strong-field microwaves. It can measure microwave parameters generated by the interaction of strong lasers and plasma without requiring multiple detectors, simplifying operation. Furthermore, the electric field probe in this invention is on the order of millimeters in size, requires no additional power supply, and does not interfere with the measured signal. The terahertz photoconductive antenna used has the characteristics of small size, compact volume, and strong anti-interference capability, which is beneficial for measurements in confined spaces. Attached Figure Description

[0017] The embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

[0018] Figure 1 This is a schematic diagram of the probe installation position in a microwave detection method for passive pulsed electric fields according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the probe structure in a microwave detection method for passive pulsed electric fields according to an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram comparing the results of microwave signal detection using the present invention's solution according to an embodiment of the invention with those obtained using a calibrated probe. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0022] As mentioned in the background section, both existing detectors have certain shortcomings. First, the electromagnetic pulse fields matched to these detectors are mainly designed to be compatible with nuclear electromagnetic pulses, based on the standards specified in IEC 6100-2-9, which define an electric field peak value of 50 kV / m, a leading edge of 2.5 ns, and a full width at half maximum (FWHM) of 23 ns. However, under microwave radiation conditions caused by strong lasers and plasmas, the electric field peak value is larger (MV / m), the leading edge is steeper, and the spectral width is wider. Therefore, in practical applications, if electric field detectors based on differential measurements and fiber optic transmission electric field detectors based on raw signal measurements are used to achieve microwave detection, multiple detectors are often required to cover different frequency ranges, making operation difficult and accuracy dependent on human experience. Second, electric field detectors based on differential measurements rely on cable transmission, resulting in relatively poor anti-interference capabilities and making them unsuitable for long-distance electric field signal transmission. On the other hand, fiber optic transmission electric field detectors based on raw signal measurements are active detectors, requiring power to the front end, and are not suitable for vacuum environments caused by strong lasers and plasmas. Furthermore, both types of detectors mentioned above contain a significant amount of metal and have large antennas, typically exceeding 10cm x 10cm. This not only easily interferes with the measured signal but also limits or renders them unsuitable for electric field measurements in confined spaces. Therefore, this invention proposes a microwave detection scheme with a smaller probe size and volume, and stronger anti-interference capabilities.

[0023] According to one embodiment of the present invention, a novel microwave detection scheme for passive pulse electric fields is proposed. In summary, the microwave detection scheme of the present invention uses a terahertz photoconductive antenna as a probe to detect microwave parameters, resulting in a small probe size, compact volume, and stronger anti-interference capability. Simply put, a prefabricated terahertz photoconductive antenna is set within a predetermined range around the laser target as a passive pulse electric field probe to detect microwave parameters during the interaction of a strong laser and plasma.

[0024] According to one embodiment of the present invention, the preset range of the electric field probe is: the range outside the laser incident path and the laser exit path in a sphere with the target point as the center and a radius of 10 cm.

[0025] According to one embodiment of the present invention, the passive pulsed electric field probe includes: a substrate made of low-temperature gallium arsenide; and a dipole antenna consisting of two symmetrically spaced wires disposed on the surface of the substrate. The low-temperature gallium arsenide is gallium arsenide grown at a temperature of 200-300°C and annealed at a temperature of 350-550°C. The substrate is a square substrate.

[0026] Since high-powered laser ablation is performed in a vacuum, the point of impact is very small. Existing detection devices are typically large and prone to interference. This invention addresses this by designing the dimensions of each side of the substrate to be less than or equal to 1 cm, with a preferred substrate being a 5mm x 5mm square substrate. Furthermore, a predetermined gap of width is provided between the two conductors of the dipole antenna. This predetermined width is determined based on the terahertz frequency; the higher the terahertz frequency, the narrower the gap. Each conductor of the dipole antenna is a layer of gold plated onto the substrate.

[0027] To provide a more intuitive understanding of the present invention, it will be further described below with reference to the accompanying drawings.

[0028] like Figure 1 As shown, in the solution of this invention, microwave parameters are detected by setting a terahertz photoconductive antenna in the probe area around the target point, wherein... Figure 1 The red light indicates the laser's incident direction, and the pink light indicates its exit direction. The probe should avoid these two light paths and can be positioned anywhere within a sphere with a radius of 10cm and the target point as its center. Because it uses a terahertz photoconductive antenna, its size and volume are smaller than those of existing electric field probes, and it will not interfere with the measured signal.

[0029] In this invention, the electric field probe is a terahertz photoconductive antenna, such as... Figure 2 As shown, the probe consists of a substrate 1 and a dipole antenna. The substrate is made of low-temperature gallium arsenide, and the dipole antenna consists of two symmetrically spaced wires 2 and 3 arranged on the surface of the substrate. It should be noted that the low-temperature gallium arsenide is gallium arsenide grown at a temperature of 200-300℃ and annealed at a temperature of 350-550℃. Wires 2 and 3 are gold-plated on the substrate. Because the antennas in this invention are gold-plated on the substrate, their size and volume are much smaller than other antenna structures, which can significantly reduce the probe volume and meet the measurement requirements in confined spaces.

[0030] As is well known, the microwave radiation environment of strong laser and plasma interaction is characterized by strong field strength, short duration, and high instantaneous power, which places high demands on the electric field probe. The terahertz photoconductive probe used in this invention has the characteristics of high carrier mobility, fast charge capture, high dark resistance and high threshold breakdown voltage, which is well adapted to the microwave radiation environment of strong laser and plasma interaction.

[0031] Furthermore, in this invention, the substrate is designed as a square substrate to facilitate antenna deposition. According to one embodiment of the invention, the dimension of each side of the substrate is less than or equal to 5cm. Preferably, the substrate is a square substrate less than or equal to 1cm*1cm (e.g., 5mm*5mm).

[0032] According to one embodiment of the present invention, a gap of a predetermined width is provided between conductor 2 and conductor 3. The predetermined width between the two conductors is determined based on the terahertz frequency. The higher the terahertz frequency, the smaller the gap between the conductors.

[0033] To verify the effectiveness of the present invention, the present invention's method and a calibrated high-sensitivity progressive conical electric field probe (model: SHET-3CM, center frequency 1GHz, black line) were used to detect and compare the strong electromagnetic pulse signals generated by laser target shooting. The results are as follows: Figure 3 As shown, the red line represents the detection results of the present invention, and the black line represents the detection results of the calibrated high-sensitivity progressive conical electric field probe. It can be seen that in the first half-cycle, the signals detected by the two detectors are almost identical, thus proving that the terahertz photoconductive antenna scheme of the present invention has excellent pulse detection capability. In particular, in the second half-cycle, the terahertz photoconductive antenna in the present invention still maintains extremely high detection accuracy, while the progressive conical antenna signal exhibits obvious expansion. This indicates that the spectral width of the strong electric field pulse generated by laser target ablation has exceeded the response range of the conical antenna, causing distortion of the progressive conical antenna signal.

[0034] Compared with existing technologies, the advantages of this invention are as follows: This invention uses a terahertz photoconductive antenna as a probe for detection. The substrate material of the probe, low-temperature gallium arsenide, possesses characteristics such as high carrier mobility, rapid charge trapping, high dark resistance, and a large threshold breakdown voltage, enabling the detection of ultra-wideband strong-field microwaves with terahertz intensity. It can measure microwave parameters generated by the interaction of strong lasers and plasma without requiring multiple detectors, simplifying operation. Furthermore, the electric field probe in this invention is on the order of millimeters in size, requires no additional power supply, and does not interfere with the measured signal. The terahertz photoconductive antenna used has the characteristics of small size, compact volume, and strong anti-interference capability, which is beneficial for measurements in confined spaces.

[0035] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A microwave detection method for passive pulsed electric fields, used to detect microwave parameters during the interaction of a strong laser and plasma, characterized in that, The method includes: A passive pulse electric field probe is set within a preset range around the laser target point. The passive pulse electric field probe is a prefabricated terahertz photoconductive antenna. Microwave parameters are detected using an electric field probe when a strong laser interacts with plasma.

2. The microwave detection method for passive pulsed electric fields according to claim 1, characterized in that, The preset range is defined as the area outside the laser incident path and laser exit path within a sphere with the target point as the center and a radius of 10cm.

3. The microwave detection method for passive pulsed electric fields according to claim 1, characterized in that, The passive pulsed electric field probe includes: The substrate is made of low-temperature gallium arsenide; A dipole antenna, which consists of two symmetrically spaced wires arranged on the surface of the substrate.

4. The microwave detection method for passive pulsed electric fields according to claim 3, characterized in that, The low-temperature gallium arsenide is gallium arsenide produced at a growth temperature of 200-300℃ and an annealing temperature of 350-550℃.

5. The microwave detection method for passive pulsed electric fields according to claim 4, characterized in that, The substrate is a square substrate.

6. The microwave detection method for passive pulsed electric fields according to claim 5, characterized in that, The dimension of each side of the substrate is less than or equal to 1 cm.

7. The passive pulsed electric field probe according to claim 6, characterized in that, The substrate is a 5mm*5mm square substrate.

8. The microwave detection method for passive pulsed electric fields according to claim 7, characterized in that, A gap of a preset width is provided between the two conductors of a dipole antenna.

9. The microwave detection method for passive pulsed electric fields according to claim 8, characterized in that, The preset width between the two conductors of the dipole antenna is determined according to the terahertz frequency.

10. The microwave detection method for passive pulsed electric fields according to claim 9, characterized in that, Each wire of the dipole antenna is a layer of gold plated on the substrate.

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