A terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium

Abstract

The present invention relates to a terahertz radiation system with adjustable spatial matching between laser filamentation and a liquid medium, belonging to the field of terahertz technology. The present invention includes an excitation module for providing a pulsed laser that can achieve breakdown of the liquid medium under the focusing action of a focusing device, and the pulse energy, pulse width, focusing energy, phase, and polarization are adjustable within a certain range, a medium module for providing a circulating liquid medium with adjustable shape, size, position, and flow rate, and a monitoring module for monitoring the spatial matching condition of the focusing region. Guided by the observation of the monitoring module, the present invention realizes the optimal spatial matching between the laser focusing region and the liquid medium through the collaborative work of the excitation module and the medium module, reduces the absorption of terahertz radiation by the medium on the premise of sufficient interaction between the laser and the medium, and significantly improves the terahertz excitation efficiency.

Description

Technical Field

[0001] The present invention relates to a terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium, and belongs to the field of terahertz technology. Background Technique

[0002] The terahertz band has unique characteristics such as transience, broadband, coherence, and low energy, making it widely used in ultrafast spectroscopy, biomedical diagnosis, non-destructive detection, tomography, electron acceleration, etc. In addition, terahertz can also detect low-energy excitation processes such as lattice vibrations, molecular rotations, and internal excitations of bound electron-hole pairs. A high-power and high-efficiency terahertz source is a decisive factor for the practical application of terahertz time-domain spectroscopy technology, terahertz imaging technology, terahertz radar, and communication. How to generate a terahertz radiation source with high power, high energy and stable operation at room temperature is an urgent practical problem to be solved in the field of terahertz technology.

[0003] The generation of electromagnetic waves follows basic theoretical laws. Generally, in the electrical frequency band, it follows Maxwell's equations, and the emission method originates from the classical motion of charges, and the typical wave source is an antenna. In the optical frequency band, it follows Schrödinger's equation, and the emission method is quantum transition, and the typical wave source is a laser. Since the frequency of terahertz waves is between the electrical and optical frequency bands, the frequency can be extended to the high frequency by electrical means or to the low frequency by optical means. However, the results of such radiation methods are often not ideal. For example, when the frequency of the electromagnetic wave generated by the electrical method reaches the terahertz band, the influence of some effects that can be ignored at low frequencies (such as stray capacitance effects, etc.) becomes more and more significant; when the frequency of the electromagnetic wave generated by the optical method is reduced to the terahertz band, it is severely affected by the thermal relaxation effect.

[0004] Due to the limitations of electrical and optical methods, ultrafast optoelectronics technology emerged in the 1990s. Its covered frequency extends from 1 THz to both ends, well covering the terahertz frequency range. The generation of terahertz radiation by ultrafast optoelectronics technology is based on a basic principle, that is, the frequency range of an electromagnetic pulse with a pulse width close to 1 ps will reach the terahertz band. Therefore, a laser with a pulse width in the femtosecond order becomes an essential pump source for optoelectronic terahertz radiation. Typical femtosecond laser-based terahertz sources include photoconductivity and optical rectification. However, photoconductivity is prone to saturation when the optical flux is not large, and optical rectification requires satisfying the phase matching condition. Moreover, they are all terahertz sources based on solid media, and irreversible damage to the medium will occur when the laser is too strong. To avoid these limiting factors, terahertz can be generated by the method of femtosecond laser-induced air plasma. The terahertz wave generated by this method has a strong electric field and a wide spectrum, and has good application prospects.

[0005] Optimizing an air plasma terahertz source can be achieved by replacing the gas medium with a liquid. First, liquid molecules have a high density and a low ionization potential, and more carriers can be generated per unit volume under the same laser conditions. Second, liquids have good self-healing properties and can quickly recover after breakdown, increasing the laser intensity and repetition frequency that the medium can withstand. These advantages make liquid media a promising terahertz radiation source.

[0006] Liquid media also have drawbacks, namely the strong absorption of liquid media in the terahertz band. Therefore, when developing a terahertz liquid source based on femtosecond lasers, two factors need to be weighed. First, the liquid medium and the laser filament need to be in full contact to generate strong enough terahertz radiation. Second, except for the laser focus area, there should be as little liquid medium as possible to avoid significant absorption. Current technologies use ultra-thin low-dimensional liquid medium structures such as liquid lines and liquid films to mitigate medium absorption. At this time, the spatial matching between the laser filament and the liquid medium is particularly important. If the overlapping area between the two is too small, it will affect the full interaction between the medium and the laser, seriously affecting the improvement of terahertz emission efficiency. At the same time, the size and position of the laser filament are regulated by the excitation conditions, and the liquid media generated by current technologies cannot change with the changes in the filament situation. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a terahertz radiation system with adjustable spatial matching between a laser filament and a liquid medium, which can achieve the best interaction effect between the laser and the liquid medium through the collaborative work of an excitation module and a medium module, effectively avoiding the excessive absorption of terahertz radiation by the liquid medium and the insufficient interaction caused by too small a medium size, thereby significantly improving the terahertz radiation power.

[0008] The technical solution of the present invention is: a terahertz radiation system with adjustable spatial matching between a laser filament and a liquid medium, comprising:

[0009] An excitation module for providing pulsed laser light that can achieve breakdown of the liquid medium under the focusing action of a focusing device, and the pulse energy, pulse width, focusing energy, phase, and polarization are adjustable within a certain range.

[0010] A medium module for providing a circulating liquid medium with adjustable shape, size, position, and flow rate.

[0011] A monitoring module for monitoring the spatial matching situation in the focusing area.

[0012] The excitation module includes:

[0013] A laser for providing laser pulses with continuously adjustable pulse energy and pulse width. The pulse width of the pulsed laser is on the femtosecond scale because the action time of the pulse on the medium is on the picosecond scale from the moment the pulse enters the focusing region until it leaves the focusing region, so that electromagnetic pulses with a spectral range up to the terahertz band can be obtained. Adjustable pulse duration can also achieve the control of the filament shape, especially for the filament length.

[0014] An optical focusing device for focusing laser energy by means of transmission or reflection. The focusing effect can, on the one hand, enhance the energy of the laser coupled to the medium, and on the other hand, achieve spatial alignment with respect to the liquid medium.

[0015] A harmonic generation device placed in the fundamental light path to generate the second harmonic. The superposition of the second harmonic and the fundamental wave will enhance the asymmetry of the fundamental wave laser electric field and enhance the excitation effect.

[0016] An optical path adjustment device for adjusting the parameters of the laser, including energy, polarization, and phase.

[0017] The laser pulses provided by the laser have a pulse duration on the femtosecond scale and can achieve the breakdown of the liquid medium under the focusing action of the focusing device.

[0018] The optical path adjustment device includes:

[0019] An energy adjustment device for adjusting the pulse energy.

[0020] A polarization adjustment device for adjusting the relative polarization of the fundamental wave and the harmonic wave.

[0021] A phase adjustment device for adjusting the relative phase of the fundamental wave and the harmonic wave.

[0022] The medium module includes:

[0023] A liquid circulation system for forming a liquid circulation with adjustable flow rate.

[0024] An adjustable nozzle for forming a flowing liquid film with adjustable shape and size.

[0025] A liquid recovery device for recovering the medium after interaction with the laser to form a complete liquid circulation.

[0026] A three-dimensional translation stage for adjusting the position of the liquid medium.

[0027] The liquid circulation system includes a water pump, a control valve, a flow meter, and necessary pipelines to form a complete water cycle. The cooperation of the water pump and the control valve can form a liquid circulation with adjustable flow rate in the pipeline to achieve the adjustment of the liquid flow velocity. High-flow-rate liquid can withstand higher laser intensity and laser repetition frequency to generate stronger terahertz radiation. Recycling the liquid medium reduces the total amount of medium participating in excitation and lowers the cost. The flow meter is used to monitor the liquid flow rate.

[0028] The adjustable nozzle includes a flexible part and a rigid part.

[0029] The rigid part refers to the other parts of the adjustable nozzle except the flexible part.

[0030] The flexible part is made of flexible material, and the rigid part is made of rigid material.

[0031] The flexible part is a hollow integral body including water inlet Ⅰ and water outlet Ⅰ.

[0032] The rigid part includes an adjustment bracket, an adjusting nut, and a central adjustment bracket.

[0033] The central adjustment bracket includes a double-column structure and a single-column part. The double-column structure is embedded in the flexible part to ensure that the flexible material does not produce other longitudinal deformations when pressed, so as to ensure the flatness of the liquid film surface. The single-column part is provided with threads, and the adjusting nut is installed on the single-column part. Rotating the adjusting nut can adjust its position on the single column, and transmit the pressure brought by the position change of the adjusting nut to the flexible part through the adjustment bracket, so that the flexible part makes a shape change matching the position of the nut. The deformation of the flexible part directly results in the change of the shape of the water outlet of the adjustable nozzle, thereby obtaining a liquid medium with adjustable shape and size.

[0034] The liquid recovery device includes a water inlet Ⅱ, a thin anti-splash layer, a thick anti-splash layer, a filter screen, a filter layer, and a water outlet Ⅱ.

[0035] The main structure of the liquid recovery device is a cavity. The upper end of the cavity is provided with a "V"-shaped water inlet Ⅱ, and the bottom end of the cavity is provided with a "V"-shaped water outlet Ⅱ. A thin anti-splash layer is provided on the outer surface of the water inlet Ⅱ, a filter layer is provided on the water outlet Ⅱ, a filter screen is installed on the filter layer, and a thick anti-splash layer is installed on the filter screen. The thick anti-splash layer, the filter screen, and the filter layer are located inside the cavity.

[0036] The "V"-shaped water inlet II and water outlet II facilitate the cyclic flow of liquid under the action of gravity. The "V"-shaped water inlet II and water outlet II facilitate the cyclic flow of liquid under the action of gravity. On the one hand, the water inlet II allows the liquid film ejected by the adjustable nozzle to pass through and isolates the splashing generated during the liquid recovery process within the recovery cavity; on the other hand, the anti-splash layer can reduce liquid splashing. The combination of these two points can alleviate the technical problem of terahertz absorption by the splashing medium. The lower filter layer and filter mesh can filter impurities in the liquid cycle to ensure the quality of the liquid film.

[0037] The adjustable nozzle and the liquid recovery device are fixed on a three-dimensional translation stage, and the shapes of the water inlet II of the liquid recovery device and the water outlet I of the adjustable nozzle are the same and are vertically aligned when not under pressure.

[0038] The monitoring module can image the vicinity of the interaction between the laser and the liquid medium to monitor the shape of the laser filament, the shape of the liquid film, and their relative positions.

[0039] To achieve the spatial matching of the laser filament and the liquid medium, it is necessary to observe the focusing area. However, the brightness of the laser focusing area is extremely high, and long-term observation is harmful to the human eye. Therefore, a monitoring module that can accurately image, such as an industrial camera, is used for observation, which can also obtain higher measurement accuracy.

[0040] The beneficial effects of the present invention are:

[0041] Guided by the observation of the monitoring module, the present invention realizes the optimal spatial matching between the laser focusing area and the liquid medium through the collaborative work of the excitation module and the medium module, reduces the absorption of terahertz radiation by the medium on the premise of sufficient interaction between the laser and the medium, and significantly improves the terahertz excitation efficiency.

[0042] The liquid recovery device of the present invention reduces the absorption of terahertz radiation caused by liquid splashing.

[0043] The recycling of the liquid medium in the present invention can reduce costs; pressurizing the medium fluid can enhance its ability to withstand laser energy and repetition frequency, providing a basic condition for enhancing terahertz radiation through the improvement of pump source energy.

[0044] The imaging observation method using the monitoring module in the present invention is safer and more reliable. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. By referring to the drawings, the features and advantages of the present invention will be more clearly understood. The drawings are schematic and should not be construed as limiting the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is a schematic diagram of the device structure principle of the present invention;

[0047] Figure 2 It is a schematic diagram of the excitation module structure of the present invention;

[0048] Figure 3 It is a three-dimensional view of the adjustable nozzle of the present invention;

[0049] Figure 4 It is a sectional view of the liquid recovery device of the present invention;

[0050] Figure 5 It is the imaging effect diagram of the monitoring module of the present invention (laser filamentation, flowing liquid film and their spatial matching respectively).

[0051] In the figure: 1 - laser, 2 - energy adjustment device, 3 - optical focusing device, 4 - harmonic generation device, 5 - polarization adjustment device, 6 - phase adjustment device, 7 - water inlet Ⅰ, 8 - flexible part, 9 - adjustment bracket, 10 - adjusting nut, 11 - center adjustment bracket, 12 - water outlet Ⅰ, 13 - water inlet Ⅱ, 14 - thin anti-splash layer, 15 - thick anti-splash layer, 16 - filter screen, 17 - filter layer, 18 - water outlet Ⅱ. Specific embodiments

[0052] In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0053] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0054] As Figure 1 shown, a terahertz radiation system with adjustable spatial matching of laser filamentation and liquid medium includes:

[0055] An excitation module for providing pulsed laser that can achieve breakdown of liquid medium under the focusing action of a focusing device, and the pulsed energy, pulse width, focusing energy, phase, and polarization are adjustable within a certain range.

[0056] The excitation module includes:

[0057] A laser 1 for providing laser pulses with continuously adjustable pulse energy and pulse width, and the pulse width of the pulsed laser is of femtosecond order.

[0058] An optical focusing device 3 for focusing laser energy by means of transmission or reflection.

[0059] A harmonic generation device 4 for generating second harmonics.

[0060] An optical path adjustment device for adjusting parameters of the laser, including energy, polarization, and phase.

[0061] The optical path adjustment device includes:

[0062] An energy adjustment device 2 for adjusting the pulse energy.

[0063] A polarization adjustment device 5 for adjusting the relative polarization of the fundamental wave and the harmonic wave.

[0064] A phase adjustment device 6 for adjusting the relative phase of the fundamental wave and the harmonic wave.

[0065] As Figure 2 shown, a laser 1 generates laser pulses with a pulse width of 100 - 500 fs, an energy of 1.5 - 3 mJ, and a central wavelength of 800 nm. The laser pulses are first intensity - regulated by the energy adjustment device and then focused into a flowing liquid medium by the optical focusing device. During the focusing process, the second harmonics are generated by the harmonic generation device through nonlinear effects. Thereafter, the laser pulses in the optical path are composed of the superposition of the 800 - nm fundamental wave and the 400 - nm harmonic wave. Subsequently, a zero - order dual - wavelength waveplate is rotated to adjust the relative polarization of the fundamental wave and the harmonic wave, and a dual - optical - wedge compensator is rotated to adjust the relative phase of the fundamental wave and the harmonic wave. In this way, a laser filament with adjustable energy, size, polarization, and phase is obtained.

[0066] In this embodiment, the laser 1 is a RA1K100 - 3 type regenerative amplifier based on CPA technology (single - pulse energy 3 mJ, repetition frequency 1 kHz, pulse width 100 fs, energy stability <0.5%, beam diameter 7 mm (1 / e2), contrast pre - pulse >10^4:1, post - pulse >100:1, spatial mode TEM00, polarization direction horizontal). The optical focusing device 3 is a quartz plano - convex lens (GCL - 010814: Ø1 inch, f = 100.0 mm). The harmonic generation device 4 is a barium metaborate crystal (800 nm, 100 µm thick, 25.4 mm outer frame). The energy adjustment device 2 is a circular adjustable attenuator (GCO - 0704M: Ø50 mm, optical density: 0 - 3.0). The polarization adjustment device 5 is a zero - order dual - wavelength waveplate (WPD03 - H800 - F400 - SP: λ / 2@800 nm+λ@400 nm, thickness 45 µm, diameter 15 mm). The phase adjustment device 6 is a dual - optical - wedge compensator (GCO - 030211M: optical - wedge diameter 25.4 mm, wedge angle ±2°, clear aperture 24 mm, center height 25 mm).

[0067] A medium module is used to provide a circulating liquid medium with adjustable shape, size, position and flow rate.

[0068] As Figure 1 shown, the medium module includes:

[0069] A liquid circulation system is used to form a liquid circulation with adjustable flow rate.

[0070] An adjustable nozzle is used to form a flowing liquid film with adjustable shape and size.

[0071] A liquid recovery device is used to recover the medium after interaction with the laser to constitute a complete liquid circulation.

[0072] A three-dimensional translation stage is used to adjust the position of the liquid medium.

[0073] The liquid circulation system includes: a water pump, a control valve, a flow meter and necessary pipelines.

[0074] The cooperation between the water pump and the control valve can form a liquid circulation with adjustable flow rate in the pipeline.

[0075] The flow meter is used to monitor the liquid flow rate.

[0076] As Figure 3 shown, the adjustable nozzle includes: a flexible part 8 and a rigid part.

[0077] The rigid part refers to other parts of the adjustable nozzle except the flexible part 8.

[0078] The flexible part 8 is made of a flexible material, and the rigid part is made of a rigid material.

[0079] The flexible part 8 is a hollow integral body including a water inlet Ⅰ7 and a water outlet Ⅰ12.

[0080] The rigid part includes an adjustment bracket 9, an adjusting nut 10, and a center adjustment bracket 11.

[0081] The center adjustment bracket 11 includes a double-column structure and a single-column part. The double-column structure is embedded in the flexible part 8. The single-column part is provided with threads, and the adjusting nut 10 is installed on the single-column part. Rotating the adjusting nut 10 can adjust its position on the single column, and transmit the pressure brought by the position change of the adjusting nut 10 to the flexible part 8 through the adjustment bracket 9, so that the flexible part 8 makes a shape change matching the position of the nut, thereby obtaining a liquid medium with adjustable shape and size.

[0082] As Figure 4 shown, the liquid recovery device includes: a water inlet Ⅱ13, a thin anti-splash layer 14, a thick anti-splash layer 15, a filter screen 16, a filter layer 17 and a water outlet Ⅱ18.

[0083] The main structure of the liquid recovery device is a cavity. At the upper end of the cavity, there is a "V"-shaped water inlet II 13, and at the bottom end of the cavity, there is a "V"-shaped water outlet II 18. A thin anti-splash layer 14 is provided on the outer surface of the water inlet II 13, and a filter layer 17 is provided on the water outlet II 18. A filter screen 16 is installed on the filter layer 17, and a thick anti-splash layer 15 is installed on the filter screen 16. The thick anti-splash layer 15, the filter screen 16, and the filter layer 17 are located inside the cavity.

[0084] The adjustable nozzle and the liquid recovery device are fixed to a three-dimensional translation stage. The shapes of the water inlet II 13 of the liquid recovery device and the water outlet I 12 of the adjustable nozzle are the same and are vertically aligned when not under pressure.

[0085] During operation, first, a liquid medium in a water tank is pumped into a pipeline by a water pump, passes through a flow meter, and is then ejected through the adjustable nozzle. After interacting with the laser component, the liquid medium enters the pipeline again through the liquid recovery device and returns to the water tank. At the same time, according to the reading of the flow meter, the control valve is adjusted to adjust the liquid flow by adjusting the pressure in the closed pipeline. The adjustable nut is rotated to change its fixed position to control the shape and size of the ejected liquid medium. In this way, a liquid medium with adjustable flow rate, shape, and size is obtained.

[0086] In this embodiment, an industrial small water pump with a head of 5 meters is selected as the water pump. The pressure gauge uses a TXY816E explosion-proof pressure transmitter, the pressure is set to 20 KPa, and the accuracy is ±0.5% FS. The rigid part of the adjustable nozzle is made of aluminum alloy, and the flexible part is made of waterproof foamed silica gel (density 0.55 - 0.9 g / cm3, tear strength 55 Kn / m, pressure strength 30 Mpa). The length of the adjustable nozzle without pressure is 15 mm, and the maximum length change of 15 mm can be generated after applying pressure through the nut to realize the change of the liquid film width in the range of 35 - 50 mm. The metal column structure is made of aluminum alloy. In the liquid recovery device, the rigid cavity is made of aluminum alloy, the anti-splash material is made of absorbent sponge, and the filter part uses a metal filter screen and activated carbon.

[0087] The monitoring module is used to monitor the spatial matching situation of the focusing area.

[0088] The monitoring module can image the vicinity of the interaction between the laser and the liquid medium to monitor the shape of the laser filament, the shape of the liquid film, and their relative positions.

[0089] First, the position information of the laser filament and the liquid medium is obtained from the imaging pictures of the software part of the monitoring module. According to this information, the optical three-dimensional translation stage is adjusted to enable the adjustable nozzle and the liquid recovery device to have three degrees of freedom of change in space. The translation stage, the adjustable nozzle, the control valve, and the optical elements of the excitation module are adjusted to achieve the best position matching between the laser filament and the liquid medium.

[0090] As Figure 5 shown, the monitoring module selects the MER-301-125U3M / C-L industrial camera based on a CMOS sensor (1 / 1.8", Global Shutter Sony IMX252 CMOS) (resolution 2048(H) × 1536(V), frame rate 125fps, pixel size 3.45 μm × 3.45 μm). The optical translation stage adopts an optically high-precision three-dimensional translation stage (XY-axis travel -6.5~﹢6.5mm, accuracy ±0.02mm, Z-axis travel -5~﹢5mm, accuracy ±0.02mm).

[0091] The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium, characterized in that, Comprising: An excitation module for providing a pulsed laser capable of achieving breakdown of a liquid medium under the focusing action of a focusing device, and the pulse energy, pulse width, focusing energy, phase, and polarization are adjustable within a certain range; A medium module for providing a circulating flowing liquid medium with adjustable shape, size, position, and flow rate; A monitoring module for monitoring the spatial matching condition of the focusing region; The excitation module includes: A laser (1) for providing laser pulses with continuously adjustable pulse energy and pulse width; For providing laser pulses with continuously adjustable pulse energy and pulse width, and the pulse width of the pulsed laser is in the femtosecond order of magnitude; An optical focusing device (3) for focusing laser energy by means of transmission or reflection; A harmonic generation device (4) for generating second harmonics; An optical path adjustment device for adjusting parameters of the laser, including energy, polarization, and phase; The optical path adjustment device includes: An energy adjustment device (2) for adjusting the pulse energy; A polarization adjustment device (5) for adjusting the relative polarization of the fundamental wave and the harmonic wave; A phase adjustment device (6) for adjusting the relative phase of the fundamental wave and the harmonic wave; The medium module includes: A liquid circulation system for forming a liquid circulation with adjustable flow rate; An adjustable nozzle for forming a flowing liquid film with adjustable shape and size; A liquid recovery device for recovering the medium after interaction with the laser to form a complete liquid circulation; A three-dimensional translation stage for adjusting the position of the liquid medium; The liquid recovery device includes: a water inlet II (13), a thin splash-proof layer (14), a thick splash-proof layer (15), a filter screen (16), a filter layer (17), and a water outlet II (18); The main structure of the liquid recovery device is a cavity. The upper end of the cavity is provided with a "V"-shaped water inlet II (13), and the bottom end of the cavity is provided with a "V"-shaped water outlet II (18). A thin splash-proof layer (14) is provided on the outer surface of the water inlet II (13), a filter layer (17) is provided on the water outlet II (18), a filter screen (16) is installed on the filter layer (17), and a thick splash-proof layer (15) is installed on the filter screen (16). The thick splash-proof layer (15), the filter screen (16), and the filter layer (17) are located inside the cavity; The monitoring module can image the vicinity of the interaction between the laser and the liquid medium to monitor the shape of the laser filament, the shape of the liquid film, and their relative positions.

2. The terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium according to claim 1, characterized in that: The laser pulses provided by the laser (1) have a pulse duration in the femtosecond order of magnitude and can achieve breakdown of the liquid medium under the focusing action of the focusing device.

3. The terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium according to claim 1, characterized in that, The liquid circulation system includes: a water pump, a control valve, a flow meter, and necessary pipelines; The cooperation of the water pump and the control valve can form a liquid circulation with adjustable flow rate in the pipeline; The flow meter is used to monitor the liquid flow rate.

4. The terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium according to claim 1, characterized in that, The adjustable nozzle includes: a flexible part (8) and a rigid part; The rigid part refers to other parts of the adjustable nozzle except the flexible part (8); The flexible part (8) is a hollow integral body including a water inlet I (7) and a water outlet I (12); The rigid part includes an adjustment bracket (9), an adjusting nut (10), and a center adjustment bracket (11); The central adjustment bracket (11) includes a double-column structure and a single-column part. The double-column structure is embedded in the flexible part (8), and the single-column part is provided with threads. The adjusting nut (10) is installed on the single-column part. The adjusting nut (10) can adjust its position on the single column, and the pressure caused by the position change of the adjusting nut (10) is transmitted to the flexible part (8) through the adjusting bracket (9), so that the flexible part (8) makes a shape change matching the position of the nut.

5. The terahertz radiation system with adjustable spatial matching between laser filamentation and liquid medium according to claim 3, characterized in that: The adjustable nozzle and the liquid recovery device are fixed on the three-dimensional translation stage. The shape of the water inlet II (13) of the liquid recovery device and the water outlet I (12) of the adjustable nozzle is the same and they are vertically aligned when not under pressure.

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