Apparatus and method for generating high power broadband terahertz radiation using sulfur-doped gallium selenide crystal

Abstract

The application relates to a device and a method for generating high-power broadband terahertz radiation by utilizing sulfur-doped gallium selenide crystals, which comprises a femtosecond laser, a beam splitter, a first reflector, a second reflector, an optical delay line, a mechanical chopper, a BBO frequency-doubling crystal, a sulfur-doped gallium selenide crystal, a terahertz horizontal polarizer, a zinc telluride crystal, a 1 / 4 wave plate, a Wollaston prism, a balanced detector and a lock-in amplifier, the first reflector and the second reflector are respectively arranged on two light paths split by the beam splitter, the mechanical chopper, the BBO frequency-doubling crystal, the sulfur-doped gallium selenide crystal, the terahertz horizontal polarizer, the zinc telluride crystal, the 1 / 4 wave plate, the Wollaston prism, the balanced detector and the lock-in amplifier are sequentially arranged along the light path, and the optical delay line is further arranged between the first reflector and the zinc telluride crystal. Compared with the prior art, the application has the characteristics of simple device, easy operation, operation at room temperature, high terahertz radiation power and wide frequency band.

Description

Technical Field

[0001] This invention belongs to the field of terahertz radiation technology and relates to an apparatus and method for generating high-power broadband terahertz radiation using sulfur-doped gallium selenide crystals. Background Technology

[0002] Terahertz waves have broad application prospects in non-destructive testing, secure communication, condensed matter physics, and other fields. Terahertz time-domain spectroscopy, due to its ability to simultaneously acquire waveform and phase information of terahertz waves and provide very high signal-to-noise ratios and ultra-high time resolution, has become a research hotspot in terahertz-related technologies. Terahertz radiation sources, as a core component of terahertz time-domain spectroscopy, are crucial for accurately acquiring the rich spectral information of matter across the entire terahertz band. However, current technologies still cannot meet the demand for high-power, high-conversion-efficiency terahertz radiation sources.

[0003] Currently, there are many methods for generating broadband terahertz radiation, such as optical rectification technology based on lithium niobate crystal wavefront tilting, optical rectification methods based on organic crystals, and large-aperture photoconductive antennas enhanced by surface plasmon resonance. Among these, optical rectification technology based on lithium niobate crystal wavefront tilting can generate high-power terahertz radiation and is the main means of generating terahertz waves in the laboratory. However, the experimental optical path is complex to build and requires high precision in phase matching, making it difficult to meet practical needs. Moreover, lithium niobate crystals have a strong absorption effect on terahertz radiation, making it difficult to effectively improve the utilization efficiency of terahertz radiation. On the other hand, terahertz radiation sources based on organic crystal optical rectification and photoconductive antennas are limited by the complexity of the system, resulting in relatively limited stability of the output terahertz waves. Therefore, finding new material systems and physical structure designs for radiation sources is a very important research direction in the field of terahertz radiation.

[0004] Gallium selenide crystals have a large second-order nonlinear optical coefficient (d 22 Gallium selenide (GLS) exhibits a high absorption coefficient (λ = 54 pm / V) and a wide transmission range (0.62-20 μm), along with significant birefringence (0.35 at λ = 1064 nm). This allows it to meet phase-matching conditions across a broad wavelength range (mid-infrared, terahertz, and millimeter waves). Furthermore, among known inorganic nonlinear crystals, it possesses the lowest absorption coefficient in the terahertz band, making it highly suitable for generating high-power, wide-bandwidth terahertz waves. However, gallium selenide's poor mechanical properties, making it difficult to cut and polish in arbitrary directions, limit its practical application in terahertz radiation sources. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and method for generating high-power broadband terahertz radiation using sulfur-doped gallium selenide crystals.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention specifically relates to the generation of high-power broadband terahertz radiation using a 2.5mass% sulfur-doped gallium selenide crystal through an oo-o phase-matched nonlinear optical rectification effect. Compared to intrinsic gallium selenide crystals, sulfur-doped gallium selenide crystals exhibit significantly improved mechanical and optical properties, which is beneficial for the generation and detection of broadband, high-power terahertz waves. Furthermore, the conversion efficiency, radiation power, and bandwidth of the terahertz pulse can be optimized by changing the crystal azimuth angle and adjusting the excitation light power.

[0008] One of the technical solutions of the present invention provides a device for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal, comprising a femtosecond laser, a beam splitter, a first mirror, a second mirror, an optical delay line, a mechanical chopper, a BBO frequency doubling crystal, a sulfur-doped gallium selenide crystal, a terahertz horizontal polarizer, a zinc telluride crystal, a quarter-wave plate, a Wollaston prism, a balanced detector, and a lock-in amplifier. The first mirror and the second mirror are respectively located on the two optical paths split by the beam splitter. The mechanical chopper, the sulfur-doped gallium selenide crystal, the terahertz horizontal polarizer, the zinc telluride crystal, the quarter-wave plate, the Wollaston prism, the balanced detector, and the lock-in amplifier are sequentially arranged behind the second mirror along the optical path. An optical delay line is also provided along the optical path between the first mirror and the zinc telluride crystal.

[0009] Furthermore, the sulfur doping concentration in the sulfur-doped gallium selenide crystal is 2.5 mass%.

[0010] Furthermore, the azimuth angles of the sulfur-doped gallium selenide crystal are 0°, 120°, and 240°.

[0011] Furthermore, of the two beams split by the beam splitter, the stronger beam is used as the excitation light and incident on the second reflector, while the weaker beam is used as the probe light and incident on the optical delay line.

[0012] Furthermore, the optical delay line consists of two symmetrically arranged reflective mirrors tilted at 45°.

[0013] The second technical solution of the present invention provides a method for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal, which is based on the device described above, and the method includes the following steps:

[0014] (1) The femtosecond laser emitted by the femtosecond laser is irradiated onto the beam splitter, and the femtosecond laser is split into two beams: reflected light and transmitted light.

[0015] (2) The reflected light is used as the excitation light. After passing through the second mirror and the mechanical chopper, the excitation light is frequency doubled to 400nm by the BBO frequency doubling crystal and then incident vertically on the sulfur-doped gallium selenide crystal. Terahertz radiation wave is generated through the optical rectification effect. At the same time, the mechanical chopper outputs a reference signal to the lock-in amplifier. The obtained terahertz radiation wave is focused on the zinc telluride crystal by the terahertz horizontal polarizer, thereby changing the refractive index ellipsoid of the electro-optic crystal.

[0016] (3) The transmitted light is used as the probe light. After passing through the first reflecting mirror and the optical delay line, it propagates collinearly with the terahertz radiation wave inside the zinc telluride crystal. A quarter-wave plate placed behind the zinc telluride crystal introduces a 90° phase difference in the polarization direction of the probe light, so that the electro-optic sampling system composed of the zinc telluride crystal, the quarter-wave plate, the Wollaston prism, and the balanced detector works in the linear region. Then, the Wollaston prism converts the phase delay of the probe light into intensity modulation of two linearly polarized beams with mutually orthogonal polarization directions. The balanced detector converts the intensity difference of the two beams into a current difference, thereby detecting the time-domain spectrum of the terahertz electric field as a function of time. In addition, the differential signal output by the balanced detector is amplified by the lock-in amplifier, and the information of the amplitude and phase of the terahertz electric field is obtained by using the lock-in detection technology.

[0017] Furthermore, the excitation light and the probe light have the same initial phase.

[0018] Furthermore, oo-o phase matching is used in the optical rectification process.

[0019] Furthermore, the excitation light power is within the linear range of terahertz generation.

[0020] Furthermore, the femtosecond laser is a laser pulse with a center wavelength of 800nm, a repetition frequency of 1kHz, and a pulse width of 120fs.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) Sulfur doping not only significantly increases the hardness of the crystal, enabling it to be cut and polished according to any crystal axis direction selected by the phase matching condition, but also changes the optical properties of gallium selenide crystals. Both the refractive index and the absorption coefficient are altered in the terahertz band, which is beneficial for the generation and detection of broadband high-power terahertz waves.

[0023] 2) Sulfur-doped gallium selenide crystals can optimize the conversion efficiency, radiation power, and bandwidth of terahertz pulses by changing the crystal azimuth angle and adjusting the excitation power. Furthermore, compared to intrinsic gallium selenide crystals, sulfur-doped gallium selenide crystals exhibit a reduced two-photon absorption coefficient, thereby increasing the saturation of terahertz radiation.

[0024] 3) Add a BBO frequency doubling crystal to the excitation light path to double the excitation light with a center wavelength of 800nm ​​to 400nm, thereby reducing GaSe absorption of the excitation light and improving THz radiation efficiency. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the device of the present invention;

[0026] Figure 2 The graph shows the relationship between the absorption coefficient of sulfur-doped gallium selenide crystal and intrinsic gallium selenide crystal as a function of terahertz frequency.

[0027] Figure 3 The graph shows the relationship between the peak value of the terahertz pulse emitted by sulfur-doped gallium selenide crystal and intrinsic gallium selenide crystal and the azimuth angle.

[0028] Figure 4 The graph shows the relationship between the peak value of the terahertz pulse emitted by sulfur-doped gallium selenide crystal and intrinsic gallium selenide crystal and the excitation light power.

[0029] Explanation of markings in the diagram:

[0030] 1-Femtosecond laser, 2-Beam splitter, 3-First reflector, 4-Optical delay line, 5-Second reflector, 6-Mechanical chopper, 7-BBO frequency doubling crystal, 8-Sulfur-doped gallium selenide crystal, 9-Terahertz horizontal polarizer, 10-Zinc telluride crystal, 11-1 / 4 wave plate, 12-Wollaston prism, 13-Balanced detector, 14-Electro-optic sampling system, 15-Lock-in amplifier. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0032] In the following embodiments or examples, the intrinsic GaSe crystal and the sulfur-doped 2.5mass% gallium selenide crystal used were obtained by growing using a modified vertical Bridgman method. Specifically, the following steps were performed: First, stoichiometric amounts of gallium and selenium, along with the required amount of sulfur for doping, were weighed and remelted separately in a vacuum quartz ampoule to obtain a sulfur-doped gallium selenide polycrystalline material. The gallium selenide polycrystalline material was then sealed in a quartz ampoule that had been annealed at 1140K for 4 hours under vacuum. A rotating system was used to uniformly melt the gallium selenide polycrystalline material in a high-temperature region at 1265K. The quartz ampoule was then moved axially at a rate of 0.4 mm / h, sequentially passing through a gradient region and a low-temperature region at 1135K, finally cooling to precipitate a single-crystal gallium selenide crystal. Both samples were ε-type, z-axis tangential, uncoated, and unpolished, with thicknesses of 0.55 mm and 0.59 mm, respectively, and lateral dimensions of 1.5 x 1.5 cm. 2 The entire experiment was conducted in a room temperature environment filled with N2 and with a humidity of 3.8%.

[0033] Unless otherwise specified, all other functional components or structures are conventional components or structures used in the field to achieve the corresponding functions.

[0034] To enhance terahertz radiation intensity, emit high-power broadband terahertz pulses, and increase the saturation of terahertz radiation, this invention provides a device for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal (8). The structure of this device can be found in [reference needed]. Figure 1 As shown, the system includes a femtosecond laser 1, a beam splitter 2, a first reflector 3, a second reflector 5, an optical delay line 4, a mechanical chopper 6, a BBO frequency doubling crystal 7, a sulfur-doped gallium selenide crystal 8, a terahertz horizontal polarizer 9, a zinc telluride crystal 10, a quarter-wave plate 11, a Wollaston prism 12, a balanced detector 13, and a lock-in amplifier 15. The first reflector 3 and the second reflector 5 are respectively located on the two optical paths split by the beam splitter 2. The mechanical chopper 6, the BBO frequency doubling crystal 7, the sulfur-doped gallium selenide crystal 8, the terahertz horizontal polarizer 9, the zinc telluride crystal 10, the quarter-wave plate 11, the Wollaston prism 12, the balanced detector 13, and the lock-in amplifier 15 are sequentially arranged behind the second reflector 5 along the optical path. An optical delay line 4 is also provided along the optical path between the first reflector 3 and the zinc telluride crystal 10.

[0035] In some specific embodiments, the sulfur doping concentration in the sulfur-doped gallium selenide crystal 8 is 2.5 mass.

[0036] In some specific embodiments, the azimuth angle of the sulfur-doped gallium selenide crystal 8 is 0°, 120°, and 240°.

[0037] In some specific embodiments, of the two beams of light split by the beam splitter 2, the stronger beam is used as excitation light and incident on the second reflector 5, while the weaker beam is used as probe light and incident on the optical delay line 4.

[0038] In some specific embodiments, the optical delay line 4 consists of two symmetrically arranged reflective mirrors tilted at 45°.

[0039] In addition, the present invention also provides a method for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal 8, which is based on the apparatus described above, and the method includes the following steps:

[0040] (1) The horizontally polarized femtosecond laser emitted by the femtosecond laser 1 is irradiated onto the beam splitter 2, and the femtosecond laser is split into two beams, reflected light and transmitted light, by the beam splitter 2.

[0041] (2) The reflected light is used as the excitation light and passes through the second reflecting mirror 5 and the mechanical chopper 6. After passing through the BBO frequency doubling crystal 7, the wavelength is doubled to 400nm and then incident vertically on the sulfur-doped gallium selenide crystal 8. Terahertz radiation wave is generated through the optical rectification effect. At the same time, the mechanical chopper 6 outputs a reference signal to the lock-in amplifier 15. The obtained terahertz radiation wave is focused on the zinc telluride crystal 10 through the terahertz horizontal polarizer 9, thereby changing the refractive index ellipsoid of the electro-optic crystal.

[0042] (3) The transmitted light is used as the probe light. After passing through the first reflecting mirror 3 and the optical delay line 4, it propagates collinearly with the terahertz radiation wave inside the zinc telluride crystal 10. The quarter-wave plate placed behind the zinc telluride crystal 10 introduces a 90° phase difference in the polarization direction of the probe light, so that the electro-optic sampling system 14 composed of the zinc telluride crystal 10, the quarter-wave plate 11, the Wollaston prism 12 and the balanced detector 13 works in the linear region. Then, the Wollaston prism 12 converts the phase delay of the probe light into intensity modulation of two linearly polarized beams with mutually orthogonal polarization directions. The balanced detector 13 converts the intensity difference of the two beams into a current difference, thereby detecting the time-domain spectrum of the terahertz electric field as a function of time. In addition, the differential signal output by the balanced detector 13 is input to the lock-in amplifier 15 for amplification, and the information of the amplitude and phase of the terahertz electric field is obtained by using the lock-in detection technology.

[0043] In some specific implementations, the excitation light and the probe light have the same initial phase.

[0044] In some specific implementations, oo-o phase matching is used in the optical rectification process.

[0045] In some specific implementations, the excitation power is within the linear range of terahertz generation.

[0046] In some specific implementations, the femtosecond laser is a laser pulse with a center wavelength of 800 nm, a repetition frequency of 1 kHz, and a pulse width of 120 fs.

[0047] Each of the above implementation methods can be implemented individually, or in any combination of two or more.

[0048] The above implementation methods will be described in more detail below with reference to specific embodiments.

[0049] Example 1:

[0050] like Figure 1 As shown, the device for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal provided in this embodiment includes a femtosecond laser 1, a beam splitter 2, a first reflector 3, an optical delay line composed of two reflectors 4, a second reflector 5, a mechanical chopper 6, a BBO frequency doubling crystal 7, a sulfur-doped gallium selenide crystal 8, a terahertz horizontal polarizer 9, a zinc telluride crystal 10, a quarter-wave plate 11, a Wollaston prism 12, a balanced detector 13, a lock-in amplifier 15, etc., wherein the electro-optic sampling system 14 is composed of the zinc telluride crystal 10, the quarter-wave plate 11, the Wollaston prism 12, and the balanced detector 13.

[0051] Based on the above-described apparatus, this embodiment also provides a method for generating broadband high-power terahertz radiation using a sulfur-doped gallium selenide crystal, the specific steps of which are as follows:

[0052] The femtosecond laser 1 is activated to generate a laser pulse with a center wavelength of 800 nm, a repetition frequency of 1 kHz, and a pulse width of 120 fs. The laser pulse is split into two beams by the beam splitter 2: the reflected beam is the excitation beam, and the transmitted beam is the probe beam. The excitation beam and the probe beam have the same initial phase, and their average powers are 45 mW and 5 mW, respectively.

[0053] The excitation light, after passing through the second reflector 5 and the mechanical chopper 6, is frequency-doubled to 400nm by the BBO frequency-doubling crystal 7 and then perpendicularly incident into the natural solution of the sulfur-doped gallium selenide crystal 8. In this embodiment, the sulfur-doped gallium selenide crystal 8 is a gallium selenide crystal with 2.5 mass% sulfur doping. Terahertz radiation is generated through the optical rectification effect, while the mechanical chopper 6 outputs a reference signal to the lock-in amplifier 15. The terahertz wave is focused onto the zinc telluride crystal 10 by the terahertz horizontal polarizer 9, thereby changing the refractive index ellipsoid of the electro-optic crystal. The probe light, passing through the first reflector 3 and the optical delay line 4 composed of two reflectors, propagates collinearly with the terahertz radiation inside the zinc telluride crystal 10. In this embodiment, an oo-o phase matching method is used in the optical rectification process.

[0054] A quarter-wave plate 11 is placed behind the zinc telluride crystal 10 to introduce a 90° phase difference in the polarization direction of the probe light, enabling the electro-optic sampling system 14 to operate in the linear region. A Wollaston prism 12 converts the phase delay of the probe light into intensity modulation of two linearly polarized beams with mutually orthogonal polarization directions. A balanced detector 13 converts the intensity difference between these two beams into a current difference, thereby detecting the time-domain spectrum of the terahertz electric field. An optical delay line 4 can be used to change the time delay of the terahertz pulse and the probe pulse; scanning this time delay yields the time-domain waveform of the terahertz electric field. The differential signal output from the balanced detector 13 is amplified by a lock-in amplifier 15, and information on the amplitude and phase of the terahertz electric field is obtained using lock-in detection technology.

[0055] Figure 2 The graph shows the relationship between the absorption coefficient of sulfur-doped gallium selenide (GLS) crystal and intrinsic GLS crystal as a function of terahertz frequency. In this embodiment, by doping the GLS crystal with sulfur at a concentration of 2.5 mass%, the absorption coefficient of the GLS crystal is altered, thereby reducing its absorption of terahertz waves. Figure 2 As shown, the absorption coefficient of sulfur-doped 2.5mass% gallium selenide crystal is significantly lower than that of intrinsic gallium selenide crystal at most frequency points, which can effectively reduce the power loss caused by crystal absorption and increase the power of terahertz radiation.

[0056] Figure 3 This diagram shows the relationship between the peak value of terahertz pulses emitted by sulfur-doped gallium selenide (GaSe) crystals and intrinsic GaSe crystals as a function of azimuth angle. In this embodiment, higher output power terahertz pulses are obtained by adjusting the azimuth angle of the sulfur-doped GaSe crystal. Figure 3 As shown, under an excitation power of 45 mW, the peak value of the terahertz pulse radiated from a sulfur-doped 2.5 mass% gallium selenide crystal varies with the azimuth angle. Periodic changes, with a cycle of approximately 120. 0 The maximum terahertz pulse peak value radiated by this crystal increased by 28.3% compared to the maximum terahertz pulse peak value radiated by the intrinsic gallium selenide crystal. Furthermore, it was determined that the maximum terahertz pulse power could be obtained at azimuth angles of 0°, 120°, and 240° in this experiment. This is because changes in the azimuth angle of the nonlinear crystal lead to alterations in the crystal's effective nonlinear coefficient and optical properties in the terahertz band, thereby affecting the output power and conversion efficiency of the terahertz pulse.

[0057] Figure 4 The graph shows the relationship between the peak value of the terahertz pulse emitted by sulfur-doped gallium selenide (GaSe) crystal and intrinsic GaSe crystal as a function of excitation light power. This invention, by adjusting the excitation light power within a certain range, determined that sulfur-doped GaSe crystal can suppress two-photon absorption of 800nm ​​light, thereby improving the saturation of the output terahertz wave. Figure 4As shown, the peak terahertz waves emitted by both intrinsic gallium selenide (LSS) and sulfur-doped LLS crystals are directly proportional to the excitation power when the excitation power is below 110 mW. With further increases in excitation power, the peak terahertz wave of intrinsic LLS remains essentially unchanged, reaching saturation, while the peak terahertz wave of the 2.5 mass% sulfur-doped LLS crystal shows a significant increase, not reaching saturation. This indicates that under high-power excitation light, the 2.5 mass% sulfur-doped LLS crystal reduces the two-photon absorption coefficient, thereby decreasing the excitation power loss due to crystal absorption and increasing the saturation of terahertz radiation.

[0058] Comparative Example 1:

[0059] Compared to Example 1, most aspects are the same, except that the BBO frequency-doubling crystal is omitted. For excitation light with a center wavelength of 800 nm that has not undergone frequency doubling, the gallium selenide crystal experiences increased pump energy loss due to two-photon absorption, resulting in a decrease in the radiation efficiency of the terahertz pulse.

[0060] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for generating high-power broadband terahertz radiation using sulfur-doped gallium selenide crystals, characterized in that, The apparatus used in this method includes a femtosecond laser, a beam splitter, a first mirror, a second mirror, an optical delay line, a mechanical chopper, a BBO frequency doubling crystal, a gallium selenide sulfur-doped crystal, a terahertz horizontal polarizer, a zinc telluride crystal, a quarter-wave plate, a Wollaston prism, a balanced detector, and a lock-in amplifier. The first mirror and the second mirror are respectively located on the two optical paths split by the beam splitter. The mechanical chopper, BBO frequency doubling crystal, gallium selenide sulfur-doped crystal, terahertz horizontal polarizer, zinc telluride crystal, quarter-wave plate, Wollaston prism, balanced detector, and lock-in amplifier are sequentially arranged behind the second mirror along the optical path. An optical delay line is also provided along the optical path between the first mirror and the zinc telluride crystal. The method includes the following steps: (1) The femtosecond laser emitted by the femtosecond laser is irradiated onto the beam splitter, and the femtosecond laser is split into two beams: reflected light and transmitted light. (2) The reflected light is used as the excitation light and passes through the second mirror and the mechanical chopper. The wavelength is doubled to 400 nm by the BBO frequency doubling crystal and then incident vertically on the sulfur-doped gallium selenide crystal. Terahertz radiation wave is generated through the optical rectification effect. At the same time, the mechanical chopper outputs the reference signal to the lock-in amplifier. The obtained terahertz radiation wave is focused on the zinc telluride crystal by the terahertz horizontal polarizer, thereby changing the refractive index ellipsoid of the electro-optic crystal. (3) The transmitted light is used as the probe light. After passing through the first reflector and the optical delay line, it propagates collinearly with the terahertz radiation wave inside the zinc telluride crystal. The quarter wave plate placed behind the zinc telluride crystal introduces a 90° phase difference in the polarization direction of the probe light, so that the electro-optic sampling system composed of the zinc telluride crystal, the quarter wave plate, the Wollaston prism and the balanced detector works in the linear region. Then, the Wollaston prism converts the phase delay of the probe light into intensity modulation of two linearly polarized beams with mutually orthogonal polarization directions. The balanced detector converts the intensity difference of the two beams into a current difference, thereby detecting the time-domain spectrum of the terahertz electric field as a function of time. In addition, the differential signal output by the balanced detector is amplified by the lock-in amplifier, and the information of the amplitude and phase of the terahertz electric field is obtained by using the lock-in detection technology. The excitation light and the probe light have the same initial phase; OO-O phase matching is used in the optical rectification process; The excitation power is within the linear range of terahertz generation; Femtosecond lasers are laser pulses with a center wavelength of 800 nm, a repetition frequency of 1 kHz, and a pulse width of 120 fs.

2. The method for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal according to claim 1, characterized in that, The sulfur doping concentration in the sulfur-doped gallium selenide crystal is 2.5 mass.

3. The method for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal according to claim 1, characterized in that, The azimuth angles of the sulfur-doped gallium selenide crystal are 0°, 120°, and 240°.

4. The method for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal according to claim 1, characterized in that, Of the two beams of light split by the beam splitter, the stronger beam is used as the excitation light and incident on the second reflector, while the weaker beam is used as the probe light and incident on the optical delay line.

5. The method for generating high-power broadband terahertz radiation using a sulfur-doped gallium selenide crystal according to claim 1, characterized in that, The optical delay line consists of two symmetrically arranged reflective mirrors tilted at 45°.

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