Terahertz radiation source system of air plasma antenna

Abstract

The invention belongs to the technical field of optics, and particularly relates to a terahertz radiation source system of an air plasma antenna, which comprises a laser, an air plasma generation unit, a terahertz radiation generation unit, a terahertz waveguide and transmission system, a detection analysis unit and a control synchronization system, the laser device is a high-power femtosecond laser device and is used for generating ultra-short pulse laser, the pulses can excite plasma in the air, and the problem that a traditional photoconductive antenna terahertz source is low in terahertz radiation intensity due to limitation of a material damage threshold value is solved; the bandwidth of terahertz radiation can be regulated and controlled by adjusting the distance between the plasma antennas, and the interval time of switching on the plasma antennas can be controlled by controlling the delay time of the third beam of laser, so that the regulation and control of the terahertz wave intensity are realized.

Description

Technical Field

[0001] The present invention relates to the field of optical technologies, and particularly to a terahertz radiation source system of an air plasma antenna. Background Art

[0002] Terahertz waves (0.1 - 10 THz) are located between the microwave and infrared regions in the electromagnetic spectrum, and have many advantages such as low single - photon energy, strong penetrability to non - polar substances, fingerprint characteristics, and broadband properties, and have important application prospects in fields such as biomedicine, security inspection, and communication. The main reason restricting the development of terahertz technology is that currently, a terahertz radiation source with a sufficiently large terahertz power cannot be provided. If the terahertz radiation intensity and power can be increased, then a higher terahertz radiation intensity and power can be used to offset the losses and absorption during terahertz transmission. Therefore, how to effectively increase the terahertz radiation intensity and power has always been a current research hotspot.

[0003] Currently, the methods for generating terahertz waves mainly include those based on free - electron lasers, optical rectification, the interaction between lasers and plasmas, and photoconductive antennas, etc. Free - electron lasers can generate ultra - strong terahertz waves (peak power above kW), but their equipment is large in volume and expensive in cost, making it difficult to promote. Moreover, the conversion efficiency of such terahertz sources is low, and a large amount of energy will be wasted. Terahertz sources based on nonlinear crystal optical rectification have relatively high stability and conversion efficiency, but there are problems such as phonon absorption and damage thresholds in the crystals, and the absolute intensity of terahertz waves is also limited. The broadband terahertz wave radiation scheme based on the interaction between femtosecond lasers and gas plasmas can generate stronger terahertz waves using stronger pump lasers because there is no limitation on the damage threshold. The terahertz intensity generated by femtosecond two - color field excitation in the gas plasma scheme can reach several μJ. However, due to the low density of the gas, the number of molecules provided for interaction with the laser is limited, so its conversion efficiency is low, and when the pump laser energy increases to a certain value, the output energy of the terahertz wave no longer increases accordingly. Photoconductive antennas are the most widely used type of terahertz radiation source currently. They have a relatively high efficiency in generating terahertz waves, and low - power pump light can obtain terahertz waves with high peak power through photoconductive antennas.

[0004] However, the structure of a general photoconductive antenna is fixed, so it cannot be adjusted. Moreover, photoconductive antennas are affected by the carrier lifetime, mobility, and threshold voltage of the material, especially the limitation of the laser intensity damage threshold, resulting in a relatively low absolute power.

[0005] Therefore, a terahertz radiation source system of an air plasma antenna is proposed to solve the above - mentioned problems. Summary of the Invention

[0006] The object of the present invention is to provide a terahertz radiation source system for an air plasma antenna to solve the problems raised in the above-mentioned background art.

[0007] To achieve the above object, the present invention provides the following technical solution: A terahertz radiation source system for an air plasma antenna, which includes a laser, an air plasma generation unit, a terahertz radiation generation unit, a terahertz waveguide and transmission system, a detection and analysis unit, and a control and synchronization system;

[0008] The laser is a high-power femtosecond laser, which is used to generate ultrashort pulse lasers. These pulses can excite plasma in the air. The femtosecond laser can provide extremely high peak power, which is crucial for forming stable and controllable plasma in the air;

[0009] The air plasma generation unit includes a focusing optical system and a plasma control mechanism;

[0010] The terahertz radiation generation unit includes a nonlinear effect and an enhancement mechanism;

[0011] The terahertz waveguide and transmission system includes waveguide design and transmission medium selection;

[0012] The detection and analysis unit includes a terahertz detector and data analysis equipment;

[0013] The control and synchronization system includes a synchronization controller and a feedback control system.

[0014] Preferably, the focusing optical system focuses the femtosecond laser beam on a specific point in the air to generate a local high-intensity electric field, thereby triggering the ionization of gas molecules in the air to form a plasma channel.

[0015] Preferably, the plasma control mechanism precisely controls the formation position, size, and duration of the plasma by adjusting laser parameters such as pulse energy, repetition frequency, and pulse width.

[0016] Preferably, the nonlinear effect is that when a femtosecond laser pulse passes through the air plasma, due to the presence of a strong electric field, various nonlinear optical effects will occur, such as four-wave mixing and difference-frequency generation. These effects generate terahertz waves; the enhancement mechanism uses a specially designed structure or material to enhance the nonlinear interaction in order to improve the terahertz radiation efficiency, such as using metal nanostructures or other metamaterials.

[0017] Preferably, the waveguide design is used to guide the generated terahertz wave from the generation point to the application point, reducing losses and maintaining signal quality; the transmission medium selection is to select a suitable transmission medium according to the specific application scenario, such as air, plastic optical fiber, or other low-loss materials.

[0018] Preferably, the terahertz detector is used to detect and measure the intensity of the generated terahertz radiation and its spectral characteristics. Common detector types include Schottky diode detectors, pyroelectric detectors, and photoconductive antennas. The data analysis device processes and analyzes the detected data to extract useful information such as spectral distribution and phase information.

[0019] Preferably, the synchronization controller ensures precise synchronization between various components, especially the time synchronization between the generation of laser pulses and the detection of terahertz waves. The feedback control system monitors the operating state of the system in real time and adjusts parameters as needed to optimize performance.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The present invention overcomes the problem that the terahertz radiation intensity of traditional photoconductive antenna terahertz sources is relatively low due to the limitation of the material damage threshold. The bandwidth of terahertz radiation can be regulated by adjusting the spacing between plasma antennas, and the interval time for turning on the plasma antennas can be controlled by controlling the delay time of the third laser beam, thereby realizing the regulation of the terahertz wave intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of an embodiment of the present system.

[0023] In the figure: femtosecond laser amplifier 1; first plane mirror 2; first beam splitter 3; second plane mirror 4; third plane mirror 5; fourth plane mirror 6; fifth plane mirror 7; sixth plane mirror 8; cylindrical lens 9; seventh plane mirror 10; eighth plane mirror 11; ninth plane mirror 12; first focusing lens 13; tenth plane mirror 14; eleventh plane mirror 15; second focusing lens 16; DC high-voltage electrode 17; first off-axis parabolic mirror 18; planar reflective gold mirror 19; high-resistivity silicon wafer 20; second off-axis parabolic mirror 21; detector 22; second plane mirror 23; second beam splitter 24. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0026] Embodiment:

[0027] Please refer to Figure 1 , the present invention provides a technical solution:

[0028] A terahertz radiation source system of an air plasma antenna, the terahertz radiation source system of the air plasma antenna includes a laser, an air plasma generation unit, a terahertz radiation generation unit, a terahertz waveguide and transmission system, a detection and analysis unit, and a control and synchronization system;

[0029] The laser is a high-power femtosecond laser, which is used to generate ultrashort pulse laser. These pulses can excite plasma in the air. The femtosecond laser can provide extremely high peak power, which is crucial for forming a stable and controllable plasma in the air;

[0030] The air plasma generation unit includes a focusing optical system and a plasma control mechanism;

[0031] The terahertz radiation generation unit includes a nonlinear effect and an enhancement mechanism;

[0032] The terahertz waveguide and transmission system includes waveguide design and transmission medium selection;

[0033] The detection and analysis unit includes a terahertz detector and data analysis equipment;

[0034] The control and synchronization system includes a synchronization controller and a feedback control system.

[0035] The focusing optical system focuses the femtosecond laser beam onto a specific point in the air to generate a local high-intensity electric field, thereby triggering the ionization of gas molecules in the air and forming a plasma channel.

[0036] The plasma control mechanism precisely controls the formation position, size, and duration of the plasma by adjusting laser parameters such as pulse energy, repetition frequency, and pulse width.

[0037] The non - linear effect is that when femtosecond laser pulses pass through air plasma, due to the presence of a strong electric field, various non - linear optical effects occur, such as four - wave mixing and difference - frequency generation. These effects generate terahertz waves. The enhancement mechanism uses specially designed structures or materials to enhance the non - linear interaction in order to improve the terahertz radiation efficiency, such as using metal nanostructures or other metamaterials.

[0038] The waveguide is designed to guide the generated terahertz waves from the generation point to the application point, reducing losses and maintaining signal quality. The transmission medium is selected according to the specific application scenario, such as air, plastic optical fiber or other low - loss materials.

[0039] The terahertz detector is used to detect and measure the intensity and spectral characteristics of the generated terahertz radiation. Common detector types include Schottky diode detectors, pyroelectric detectors, and photoconductive antennas. The data analysis device processes and analyzes the detected data to extract useful information, such as spectral distribution and phase information.

[0040] The synchronization controller ensures precise synchronization between various components, especially the time synchronization between the generation of laser pulses and the detection of terahertz waves. The feedback control system monitors the operating state of the system in real - time and adjusts parameters as needed to optimize performance.

[0041] The specific working principle of the terahertz radiation source system of this air plasma antenna is as follows:

[0042] Step 1: The system first uses a high - power femtosecond laser to generate ultrashort pulses (usually in the femtosecond level, i.e., 10^ - 15 seconds). Such ultrashort pulses have extremely high peak power and can trigger strong non - linear optical effects in air.

[0043] Step 2: The femtosecond laser pulses are focused onto a very small point in air through a focusing optical system (such as a lens or a mirror). Due to the high - intensity electric field of the laser, gas molecules in the air (mainly nitrogen and oxygen) are ionized, forming a local plasma channel. Plasma is an ionized gas composed of free electrons and positive ions. Its existence greatly changes the optical properties of the local medium, enabling it to support the propagation of strong electromagnetic waves and non - linear interactions.

[0044] Step 3: When femtosecond laser pulses pass through air plasma, various non - linear optical effects occur. The most important ones are four - wave mixing and difference - frequency generation. Two or more high - frequency laser pulses interact in the plasma to generate new low - frequency photons. These newly generated photons can fall within the terahertz band. If two laser pulses with different frequencies pass through the plasma region simultaneously, the frequency difference between them can generate a new lower - frequency photon, which may also be a terahertz wave.

[0045] Step 4: Enhance the nonlinear interaction by optimizing laser parameters (such as pulse energy, repetition frequency, pulse width, etc.) and introducing specially designed structures (such as metal nanoparticles or other metamaterials). By adjusting the parameters of the laser pulse, the density and distribution of the plasma can be controlled, thereby affecting the intensity and direction of the terahertz wave;

[0046] Step 5: The generated terahertz wave needs to be transmitted through a specific waveguide structure to reduce losses and maintain signal quality; According to specific application requirements, a complex transmission path may need to be designed to ensure that the terahertz wave can accurately reach the target position;

[0047] Step 6: The generated terahertz wave is detected by a specially designed detector. The detected data is processed and analyzed to extract useful spectral information, phase information, etc. for further research or practical applications;

[0048] Step 7: Precise synchronization is required between the components of the entire system, especially the time synchronization between the generation of the laser pulse and the detection of the terahertz wave. The operating state of the system is monitored in real time, and parameters are adjusted as needed to optimize performance, such as automatically adjusting the laser power or pulse width.

[0049] As Figure 1 shown, a laser beam is emitted by the femtosecond laser amplifier 1, reflected by the first plane mirror 2 and the second plane mirror 23, and then the laser beam is split into a laser beam and a first laser beam by the first beam splitter 3. The laser beam is further split into a second laser beam and a third laser beam by the second beam splitter 24;

[0050] The first laser beam passes through the second plane mirror 4, the third plane mirror 5, the fourth plane mirror 6, the fifth plane mirror 7, the sixth plane mirror 8, and finally through the cylindrical lens 9. The second laser beam passes through the seventh plane mirror 10, the eighth plane mirror 11, the ninth plane mirror 12, and the first focusing lens 13;

[0051] The third laser beam passes through the tenth plane mirror 14, the eleventh plane mirror 15, and the second focusing lens 16;

[0052] The first laser beam, the second laser beam, and the third laser beam pass through the DC high-voltage electrode 17 and then pass through the first off-axis parabolic mirror 18, the plane reflective gold mirror 19, the high-resistivity silicon wafer 20, the second off-axis parabolic mirror 21, and finally converge on the detector 22 for detection.

[0053] A focusing lens is set in this system to focus the laser beam: by focusing the femtosecond laser pulse onto a small spot (usually at the micron or sub-micron level), the light intensity at that spot is significantly increased, reaching an energy density sufficient to initiate air ionization, ensuring that the laser energy is concentrated at a specific spatial position, thereby achieving precise control over the plasma generation position;

[0054] Enhance the nonlinear optical effect: when the femtosecond laser pulse is focused into the air, the high-intensity electric field generated will trigger various nonlinear optical effects, such as four-wave mixing and difference-frequency generation. These effects can generate terahertz waves. The focusing lens can provide the optimal light intensity distribution, making the nonlinear interaction more efficient, thereby improving the generation efficiency of terahertz waves;

[0055] Form a stable plasma channel: the high-intensity electric field at the focal point can ionize the gas molecules in the air (mainly nitrogen and oxygen), forming a local plasma channel. By adjusting the position and parameters of the focusing lens, the formation position, size, and duration of the plasma can be controlled, thereby obtaining a more stable and controllable plasma channel.

[0056] The function of setting a high-resistivity silicon wafer in this system:

[0057] As a terahertz wave transmission medium: the high-resistivity silicon wafer has a low terahertz wave absorption coefficient, which can effectively reduce the energy loss of terahertz waves during transmission. The high-resistivity silicon material has a high transparency to terahertz waves, making it an ideal transmission medium;

[0058] Waveguide structure: the high-resistivity silicon wafer can be processed into a specific waveguide structure (such as a strip waveguide, ridge waveguide, etc.) to guide and control the propagation path of terahertz waves. By designing an appropriate waveguide structure, efficient coupling and transmission of terahertz waves between different components can be achieved;

[0059] Used to generate terahertz waves: the high-resistivity silicon wafer can generate optical rectification under the action of a strong laser field, thereby generating terahertz waves. This effect utilizes the nonlinear optical properties of the material to convert the femtosecond laser pulse into a broadband terahertz wave. The high-resistivity silicon material can also be used in nonlinear optical processes such as difference-frequency generation and four-wave mixing, further enriching the generation mechanism of terahertz waves.

[0060] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes within the meaning and scope of the equivalent elements of the claims in the present invention, and any reference signs in the claims should not be regarded as limiting the claims involved.

[0061] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A terahertz radiation source system for an air plasma antenna, characterized in that: The terahertz radiation source system of the air plasma antenna includes a laser, an air plasma generating unit, a terahertz radiation generating unit, a terahertz waveguide and transmission system, a detection and analysis unit, and a control and synchronization system; The laser is a high-power femtosecond laser used to generate ultrashort pulse lasers that can excite plasma in the air. Femtosecond lasers can provide extremely high peak power, which is essential for forming stable and controllable plasma in the air. The air plasma generating unit includes a focusing optical system and a plasma control mechanism; The terahertz radiation generating unit includes nonlinear effects and enhancement mechanisms; The terahertz waveguide and transmission system includes waveguide design and transmission medium selection; The detection and analysis unit includes a terahertz detector and a data analysis device; The control synchronization system includes a synchronization controller and a feedback control system.

2. The terahertz radiation source system of an air plasma antenna according to claim 1, characterized in that: The focusing optical system focuses the femtosecond laser beam onto a specific point in the air to generate a local high-intensity electric field, thereby inducing ionization of gas molecules in the air to form a plasma channel.

3. The terahertz radiation source system of an air plasma antenna according to claim 1, characterized in that: The plasma control mechanism precisely controls the formation position, size and duration of plasma by adjusting laser parameters such as pulse energy, repetition frequency and pulse width.

4. The terahertz radiation source system of an air plasma antenna according to claim 1, characterized in that: The nonlinear effect is that when a femtosecond laser pulse passes through air plasma, due to the existence of a strong electric field, a variety of nonlinear optical effects will occur, such as four-wave mixing and difference frequency generation, which produce terahertz waves; in order to improve the efficiency of terahertz radiation, the enhancement mechanism will use specially designed structures or materials to enhance nonlinear interactions, such as using metal nanostructures or other metamaterials.

5. The terahertz radiation source system of an air plasma antenna according to claim 1, characterized in that: The waveguide is designed to guide the generated terahertz wave from the generation point to the application point, reducing loss and maintaining signal quality; the transmission medium selection is to select a suitable transmission medium according to the specific application scenario, such as air, plastic optical fiber or other low-loss materials.

6. The terahertz radiation source system of an air plasma antenna according to claim 1, characterized in that: The terahertz detector is used to detect and measure the intensity of the generated terahertz radiation and its spectral characteristics. Common detector types include Schottky diode detectors, pyroelectric detectors, and photoconductive antennas. The data analysis equipment processes and analyzes the detected data to extract useful information, such as spectrum distribution and phase information.

7. The terahertz radiation source system of an air plasma antenna according to claim 1, characterized in that: The synchronization controller ensures accurate synchronization between various components, especially the time synchronization between the generation of laser pulses and the detection of terahertz waves; the feedback control system monitors the system operation status in real time and adjusts parameters as needed to optimize performance.

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