An apparatus for simultaneously generating terahertz waves and tunable laser light

Abstract

The application provides a device for simultaneously generating terahertz waves and tunable laser, comprising a first pump source and a second pump source, a first APPLN crystal, a second APPLN crystal, a beam combiner, a phase delay system and a fifth mirror for changing an optical path, a first parabolic mirror and a second parabolic mirror; through cascade optical difference frequency action, terahertz waves and tunable laser can be generated simultaneously, and the energy of each cascade light in the cascade light can be gathered at a mid-infrared frequency.

Description

Technical Field

[0001] This invention belongs to the field of mid-infrared laser technology, specifically relating to a device that simultaneously generates terahertz waves and tunable lasers. Background Technology

[0002] Mid-infrared lasers in the 3–5 μm band are located in the atmospheric window region, the region of concentrated thermal radiation energy from high-temperature objects, and the region of strong absorption by water molecules, making them crucial for applications in remote sensing, optoelectronic countermeasures, and medical diagnosis. Compared to ordinary single-peak mid-infrared lasers with fixed wavelengths, multi-peak, broadband, and wide-tunable mid-infrared lasers have more important applications in certain special situations, such as terahertz generation, CARS spectrothermal measurement, coherent pulse synthesis, quantum optics, and simultaneous detection of multi-component gases. Therefore, spectral modulation technology for mid-infrared laser sources has always been a research hotspot in the field of nonlinear frequency conversion. Mid-infrared lasers are mainly used in the following areas:

[0003] (1) Spectral analysis

[0004] The mid-infrared 3-5 μm band is known as the "fingerprint spectrum" of molecules. This band has numerous and complex peaks, covering the absorption lines of most molecules. Gases such as methane, ethane, propane, hydrogen chloride, hydrogen sulfide, hydrogen fluoride, and water vapor can be detected using the mid-infrared band. Therefore, lasers in this band can be used to detect a wider range of atmospheric components, air pollution, biochemical agents, and the distribution of ozone and water vapor.

[0005] (2) Medical diagnosis

[0006] The mid-infrared band contains the absorption peak of water. When irradiating biological tissue, the water molecules inside the tissue rapidly absorb the laser energy, instantly reach the vaporization temperature and decompose under heat. The vaporization of the biological tissue takes away most of the heat, thus reducing the photochemical dissociation and ablation effect on the surrounding tissue. This allows for high-precision ablation of the diseased tissue and greatly reduces the risk of mutation.

[0007] (3) Optoelectronic countermeasures

[0008] In today's rapidly developing technological world, mastering precision strike and counter-precision strike technologies has become crucial for victory in warfare. Utilizing lasers to rapidly and accurately locate and guide enemy optoelectronic equipment or dangerous targets for destruction offers advantages such as high stealth, offensive capability, and high precision. In particular, fourth-generation infrared-guided missiles, developed using imaging, staring, and multi-band composite guidance technologies, possess significant advantages in guidance sensitivity and anti-jamming capabilities, enabling them to attack targets at greater distances with greater precision.

[0009] Optical parametric oscillators (OPOs) based on crystal nonlinear frequency conversion technology possess numerous advantages, including wide tuning range, high conversion efficiency, good beam quality, compact and flexible structure, and high spectral selectivity. They are currently one of the important means to achieve mid-infrared laser output, gaining favor in the industry and becoming a research hotspot. However, due to the resonant cavity structure used in OPOs, there are threshold limitations, and for gas detection, their single-frequency control needs improvement. In recent years, mid-infrared light sources based on difference frequency generation have received widespread attention due to their excellent characteristics such as simple structure, convenient tuning, room temperature operation, and no threshold limitations. With the application of quasi-phase matching (QPM) technology and various novel periodically polarized nonlinear crystals, mid-infrared DFG light sources have developed rapidly and have become the mainstream light source for current gas spectral detection. Summary of the Invention

[0010] This invention provides a device for simultaneously generating terahertz waves and tunable lasers. By using cascaded optical difference frequency generation, tunable lasers can be generated at the same time as terahertz waves, and the energy of each cascaded beam can be concentrated at the mid-infrared frequency.

[0011] The object of the present invention is achieved in the following manner: an apparatus for simultaneously generating terahertz waves and tunable lasers, comprising a first pump source and a second pump source, a first APPLN crystal, a second APPLN crystal, a beam combiner, a phase delay system, and a fifth mirror for changing the optical path, a first parabolic mirror, and a second parabolic mirror.

[0012] The first pump light emitted from the first pump source enters the beam combiner; the second pump light emitted from the second pump source enters the beam combiner after passing through the phase delay system and the fifth reflector; the first pump light and the second pump light are combined into a first mixed light in the beam combiner; the first mixed light is directly or after passing through the telescope system and then incident into the first APPLN crystal; the first pump light and the second pump light in the first mixed light generate a second mixed light in the first APPLN crystal through cascaded optical difference frequency effect; the terahertz wave in the second mixed light is reflected out after passing through the first parabolic mirror; the multi-stage cascaded light in the second mixed light is transmitted after passing through the first parabolic mirror and then incident into the second APPLN crystal, where it is cascaded optical difference frequency to obtain a third mixed light; the third mixed light is split into mid-infrared laser and a fourth mixed light by the second parabolic mirror, reflected by the second parabolic mirror to obtain the fourth mixed light, and transmitted by the second parabolic mirror to obtain infrared laser;

[0013] The frequency difference between the first and second pump lights is 0.5-2 THz; the plane of beam propagation is the plane defined by the X and Y axes, and the Z axis is perpendicular to the plane of beam propagation; the initial propagation directions of the first pump light emitted from the first pump source and the second pump light emitted from the second pump source are both positive X-axis; the propagation directions of the first mixer light, the second mixer light, the multi-stage mixed light, the third mixer light, and the mid-infrared laser are all positive X-axis; the propagation directions of the terahertz wave and the fourth mixer light are positive Y-axis; the polarization directions of the first and second pump lights are both Z-axis.

[0014] The phase delay system consists of a first mirror, a second mirror, a third mirror, and a fourth mirror. The second pump light emitted from the second pump source passes sequentially through the phase delay system consisting of the first mirror, the second mirror, the third mirror, and the fourth mirror, and then enters the beam combiner after the optical path is changed by the fifth mirror.

[0015] The first, second, third, fourth, and fifth reflecting mirrors are all plane mirrors; the first, second, third, fourth, and fifth reflecting mirrors totally reflect the second pump light; the first parabolic mirror has high transmission for multi-stage beams and totally reflects terahertz waves; the second parabolic mirror has high transmission for mid-infrared lasers and totally reflects the fourth mixing light.

[0016] The first parabolic mirror has a transmittance of 99.9% for multi-stage beams, and the second parabolic mirror has a transmittance of 99.9% for mid-infrared laser 22.

[0017] Both the first and second APPLN crystals are cuboids, rectangular in the XY plane, with their length direction aligned with the positive X-axis and their optical axis along the Z-axis. Both are aperiodic polarized crystals. The aperiodic polarization distribution of the first APPLN crystal exhibits a phase mismatch of zero along its length from the first redshift to the nth redshift, where the nth redshift is any order greater than the first order and less than {(frequency of the first pump light - 60 THz) / frequency of the terahertz wave}. The aperiodic polarization distribution of the second APPLN crystal exhibits a phase mismatch of zero along its length from the mth redshift to the kth redshift, where the kth redshift is any order greater than the mth order and less than {(frequency of the first pump light - 60 THz) / frequency of the terahertz wave}. The mth difference frequency contains two beams of difference frequency light: the cascade light with the highest energy among the multi-stage cascaded beams and its adjacent cascade light with a lower frequency.

[0018] The multi-stage beam is a mixed light that combines multiple cascaded beams of different frequencies, and these beams propagate collinearly. The frequency difference between adjacent stages in the multi-stage beam is equal to the frequency difference between the first pump light and the second pump light.

[0019] The fourth mixing light includes the first mixing light and the anti-stokes light.

[0020] Compared to existing technologies, this invention provides a device for simultaneously generating terahertz waves and tunable lasers based on nonlinear optical frequency conversion technology. By changing the crystal length and aperiodic polarization distribution of the first APPLN crystal, a second mixing light composed of terahertz waves of varying intensities and multi-stage beams with different energy distributions is obtained. Correspondingly, changing the crystal length of the second APPLN crystal yields the tunable laser. Compared to existing devices for generating mid-infrared lasers, by setting the polarization periods of the first and second APPLN crystals, the energy of each stage of beams can be concentrated into a mid-infrared laser, resulting in high optical conversion efficiency. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structural principle of the present invention.

[0022] Figure 2(a) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2 The energy intensity distribution of multi-stage ionization 17 when the length of the first APPLN crystal is 5 mm.

[0023] Figure 2(b) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2 The energy intensity distribution of infrared laser 22 when the length of the first APPLN crystal is 5 mm and the length of the second APPLN crystal is 67.9 mm.

[0024] Figure 2(c) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2 The polarization period distribution diagram of the first APPLN crystal when the length of the first APPLN crystal is 5 mm.

[0025] Figure 3(a) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2 The energy intensity distribution of multi-stage ionized light 17 when the length of the first APPLN crystal is 5.5 mm.

[0026] Figure 3(b) shows the power densities of the two pump sources at 300 MW / cm². 2 The energy intensity distribution of infrared laser 22 when the length of the first APPLN crystal is 5.5 mm and the length of the second APPLN crystal is 46.8 mm.

[0027] Figure 3(c) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2The polarization period distribution diagram of the first APPLN crystal when the length of the first APPLN crystal is 5.5 mm.

[0028] Figure 4(a) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2 The energy intensity distribution of multi-stage ionization 17 when the length of the first APPLN crystal is 6 mm.

[0029] Figure 4(b) shows the power densities of the two pump sources, each 300 MW / cm². 2 The energy intensity distribution of infrared laser 22 when the length of the first APPLN crystal is 6 mm and the length of the second APPLN crystal is 43.1 mm.

[0030] Figure 4(c) shows the situation when the power densities of the two pump sources are 300 MW / cm². 2 The polarization period distribution diagram of the first APPLN crystal when the length of the first APPLN crystal is 6 mm.

[0031] Figure 5 This is an intensity diagram of the generated terahertz wave 16. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. It should be understood that the preferred embodiments described herein are only for illustration and explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the following content of the present invention. In this invention, unless otherwise expressly specified and limited, the technical terms used in this application should have the ordinary meaning understood by those skilled in the art.

[0033] As attached Figure 1 As shown, a device for simultaneously generating terahertz waves and tunable lasers includes a first pump source 1 and a second pump source 3, a first APPLN crystal 13, a second APPLN crystal 18, a beam combiner 10, a telescope system 12, a phase delay system, a fifth reflector 9 for changing the optical path, a first parabolic mirror 15, and a second parabolic mirror 20.

[0034] The first pump light 2 emitted from the first pump source 1 enters the beam combiner 10; the second pump light 4 emitted from the second pump source 3 enters the beam combiner 10 after passing through the phase delay system and the fifth reflector 9; the first pump light 2 and the second pump light 4 are combined into a first mixed light 11 in the beam combiner 10; the first mixed light 11 is incident on the first APPLN crystal 13 directly or after passing through the telescope system 12, and the first pump light 2 and the second pump light 4 in the first mixed light 11 generate a cascaded optical difference frequency effect in the first APPLN crystal 13. The second mixing light 14; the terahertz wave 16 in the second mixing light 14 is reflected after passing through the first parabolic mirror 15, and the multi-stage cascaded light 17 in the second mixing light 14 is transmitted after passing through the first parabolic mirror 15, and then incident into the second APPLN crystal 18. After cascading optical difference frequency, the third mixing light 19 is obtained. The third mixing light 19 is split into mid-infrared laser 22 and fourth mixing light 21 by the second parabolic mirror 20. After being reflected by the second parabolic mirror 20, the fourth mixing light 21 is obtained. After being transmitted by the second parabolic mirror 20, the infrared laser 22 is obtained.

[0035] The frequency difference between the first pump light 2 and the second pump light 4 can be 0.5-2 THz.

[0036] Specifically, in this embodiment, the frequency difference between the first pump light 2 and the second pump light 4 is 0.5 THz; the plane of beam propagation is the plane defined by the X-axis and Y-axis, with the Z-axis perpendicular to the plane of beam propagation. The initial propagation directions of the first pump light 2 emitted from the first pump source 1 and the second pump light 4 emitted from the second pump source 3 are both positive X-axis. The propagation directions of the first mixer light 11, the second mixer light 14, the multi-stage mixed light 17, the third mixer light 19, and the mid-infrared laser 22 are all positive X-axis, while the propagation directions of the terahertz wave 16 and the fourth mixer light 21 are positive Y-axis. The polarization directions of the first pump light 2 and the second pump light 4 are both Z-axis. The frequency difference between adjacent stages in the multi-stage mixed light 17 is equal to the frequency difference between the first pump light 2 and the second pump light 4.

[0037] The purpose of passing a pump light through a phase delay system is to synchronize the phases of two pump lights.

[0038] The phase delay system consists of a first reflector 5, a second reflector 6, a third reflector 7, and a fourth reflector 8. The second pump light 4 emitted from the second pump source 3 passes through the phase delay system composed of the first reflector 5, the second reflector 6, the third reflector 7, and the fourth reflector 8, and then enters the beam combiner 10 after its optical path is changed by the fifth reflector 9. The pump light does not change its propagation direction when passing through the phase delay system, and the pump light can pass through more than one phase delay system.

[0039] In this embodiment, the first pump source 1 is a Yb:YAG pulsed laser, and the frequency of the first pump light 2 is 291.26 THz. The second pump source 3 is a Yb:YAG pulsed laser, and the frequency of the second pump light 4 is 290.76 THz. The pump power density of both pump lights is 500 MW / cm². 2 The repetition frequency was 10 Hz, the beam diameter was 1 mm, and the polarization direction was Z-axis.

[0040] The first reflector 5, the second reflector 6, the third reflector 7, the fourth reflector 8, and the fifth reflector 9 are all plane mirrors; the first reflector 5, the second reflector 6, the third reflector 7, the fourth reflector 8, and the fifth reflector 9 totally reflect the second pump light 4; the first parabolic mirror 15 has high transmission to the multi-stage beam 17 and totally reflects the terahertz wave 16; the second parabolic mirror 20 has high transmission to the mid-infrared laser 22 and totally reflects the fourth mixing beam 21.

[0041] Specifically, in this embodiment, the first reflecting mirror 5, the second reflecting mirror 6, the third reflecting mirror 7, the fourth reflecting mirror 8, and the fifth reflecting mirror 9 are all plane mirrors; the first reflecting mirror 5, the second reflecting mirror 6, the third reflecting mirror 7, the fourth reflecting mirror 8, and the fifth reflecting mirror 9 exhibit total internal reflection of the second pump light 4. The first parabolic mirror 15 exhibits high transmission of the multi-stage beam 17 with a transmittance of 99.9%, and exhibits total internal reflection of the terahertz wave 16. The second parabolic mirror 20 exhibits high transmission of the mid-infrared laser 22 with a transmittance of 99.9%, and exhibits total internal reflection of the fourth mixing beam 21.

[0042] Both the first APPLN crystal 13 and the second APPLN crystal 18 are cuboids, rectangular in the XY plane, with their length direction aligned with the positive X-axis and their optical axis along the Z-axis. Both are aperiodic polarized crystals. The aperiodic polarization distribution of the first APPLN crystal 13, along its length, exhibits a phase mismatch that gradually decreases from the first to the nth redshift, where the nth redshift is any order greater than the first order but less than {(frequency of the first pump light - 60 THz) / frequency of the terahertz wave}. The aperiodic polarization distribution of the second APPLN crystal 18, along its length... The phase mismatch in length from the m-th order redshift to the k-th order redshift gradually equals 0. The k-th order is any order within the range greater than the m-th order and less than {(frequency of the first pump light - 60 THz) / frequency of the terahertz wave}. The m-th order difference frequency includes two beams of difference frequency light: the cascade light with the highest energy in the multi-stage cascade light 17 and its adjacent cascade light with a lower frequency. Here, "lower frequency" refers to the adjacent cascade light, because for any cascade light, there are two adjacent cascade lights, one with a higher frequency and one with a lower frequency. Therefore, once the cascade light with the highest energy is determined, the adjacent light with the lower frequency is simultaneously determined. Redshift refers to the phenomenon where the frequency decreases and the wavelength increases.

[0043] In this embodiment, both the first APPLN crystal 13 and the APPLN-3 crystal 18 are aperiodic polarized crystals, both with a cuboid shape, which is rectangular in the XY plane, and the optical axis of both crystals is along the Z-axis. The first APPLN crystal 13 has a dimension of 5mm × 2mm on the Y×Z axis, and the length direction of the crystal is consistent with the positive X-axis. The second APPLN crystal 18 has a dimension of 5mm × 2mm on the Y×Z axis, and the length direction of the crystal is consistent with the positive X-axis.

[0044] In this embodiment, by changing the crystal length and aperiodic polarization distribution of the first APPLN crystal 13, a second mixing light 14 is formed by terahertz waves 16 of different intensities and multi-order combined light 17 with different energy distributions. Correspondingly, by changing the crystal length of the second APPLN crystal 18, a tunable laser is obtained.

[0045] In this embodiment, the purpose of using the telescope system is to reduce the beam to 0.5 mm. The purpose of beam reduction is to allow the pump light to pass completely through the subsequent device. When beam reduction is not required, the telescope system can be omitted.

[0046] In this embodiment, the crystal length direction is along the positive X-axis:

[0047] (1) When the length of the first APPLN crystal 13 on the X-axis is set to 5 mm, the polarization period, as shown in Figure 2(c), decreases from 237.14 μm to 236.15 μm. That is, the phase mismatch of the non-periodic polarization distribution of the first APPLN crystal 13 along the crystal length from the first redshift to the 50th redshift is gradually equal to 0. The energy distribution of the multi-order coupled light 17 generated at this time is shown in Figure 2(a), and the energy distribution of the generated terahertz wave 16 is shown in Figure 2(a). Figure 5 The value shown is 18.24 MW / cm². 2 When the length of the second APPLN crystal 18 on the X-axis is set to 67.9 mm, the generated mid-infrared laser 22 is shown in Figure 2(b). At this time, the energy is concentrated at 285.76 THz, that is, the phase mismatch of the non-periodic polarization distribution of the second APPLN crystal 18 along the crystal length from the 11th redshift to the 112th redshift is equal to 0 step by step.

[0048] (2) When the length of the first APPLN crystal 13 on the X-axis is set to 5.5 mm, the polarization period, as shown in Figure 3(c), decreases from 237.14 μm to 236.07 μm. That is, the phase mismatch of the non-periodic polarization distribution of the first APPLN crystal 13 along the crystal length from the first redshift to the 55th redshift is gradually equal to 0. The energy distribution of the multi-order coupled light 17 generated at this time is shown in Figure 3(a), and the energy distribution of the generated terahertz wave 16 is shown in Figure 3(a). Figure 5 The value shown is 21.34 MW / cm². 2 When the length of the second APPLN crystal 18 on the X-axis is set to 46.8 mm, the generated mid-infrared laser 22 is shown in Figure 3(b). At this time, the energy is concentrated at 282.26 THz, that is, the phase mismatch of the non-periodic polarization distribution of the second APPLN crystal 18 along the crystal length from the 19th redshift to the 120th redshift is equal to 0 step by step.

[0049] (3) When the length of the first APPLN crystal 13 on the X-axis is set to 6 mm, the polarization period, as shown in Figure 4(c), decreases from 237.14 μm to 235.97 μm. That is, the phase mismatch of the non-periodic polarization distribution of the first APPLN crystal 13 along the crystal length from the 1st redshift to the 60th redshift is successively equal to 0. The energy distribution of the multi-order coupled light 17 generated at this time is shown in Figure 4(a), and the energy distribution of the generated terahertz wave 16 is shown in Figure 4(a). Figure 5 The value shown is 26.45 MW / cm². 2 When the length of the second APPLN crystal 18 on the X-axis is set to 43.1 mm, the generated mid-infrared laser 22 is shown in Figure 4(b). At this time, the energy is concentrated at 280.26 THz, that is, the phase mismatch of the non-periodic polarization distribution of the second APPLN crystal 18 along the crystal length from the 24th redshift to the 125th redshift is equal to 0 step by step.

[0050] The embodiments described above are merely examples and illustrations of the technical solutions of the present invention, intended to facilitate understanding of the technical solutions of this application by those skilled in the art, and are not all implementation methods. The scope of protection of the present invention is not limited thereto. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. The basic idea of ​​the present invention lies in the above basic solution. For those skilled in the art and any person skilled in the art, designing various modified models, formulas, and parameters based on the teachings of the present invention does not require creative effort without departing from the overall concept of the invention and the spirit of the principles of the present invention. Changes, modifications, substitutions, equivalent substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A device for simultaneously generating terahertz waves and tunable lasers, characterized in that: It includes a first pump source (1) and a second pump source (3), a first APPLN crystal (13), a second APPLN crystal (18), a beam combiner (10), a phase delay system, and a fifth mirror (9) for changing the optical path, a first parabolic mirror (15), and a second parabolic mirror (20). The first pump light (2) emitted from the first pump source (1) enters the beam combiner (10); the second pump light (4) emitted from the second pump source (3) enters the beam combiner (10) after passing through the phase delay system and the fifth reflector (9); the first pump light (2) and the second pump light (4) are combined into a first mixed light (11) in the beam combiner (10); the first mixed light (11) is directly or after passing through the telescope system (12) and then incident into the first APPLN crystal (13), where the first pump light (2) and the second pump light (4) in the first mixed light (11) generate a cascaded optical difference frequency effect in the first APPLN crystal (13). The second mixing light (14); the terahertz wave (16) in the second mixing light (14) is reflected and emitted after passing through the first parabolic mirror (15). The multi-stage cascaded light (17) in the second mixing light (14) is transmitted after passing through the first parabolic mirror (15) and then incident into the second APPLN crystal (18). After cascading optical difference frequency, the third mixing light (19) is obtained. The third mixing light (19) is divided into mid-infrared laser (22) and fourth mixing light (21) by the second parabolic mirror (20). After being reflected by the second parabolic mirror (20), the fourth mixing light (21) is obtained. After being transmitted by the second parabolic mirror (20), the infrared laser (22) is obtained. The frequency difference between the first pump light (2) and the second pump light (4) is 0.5-2 THz; the plane of beam propagation is the plane determined by the X-axis and Y-axis, and the Z-axis is perpendicular to the plane of beam propagation; the initial propagation directions of the first pump light (2) emitted from the first pump source (1) and the second pump light (4) emitted from the second pump source (3) are both positive X-axis; the propagation directions of the first mixing light (11), the second mixing light (14), the multi-stage mixed light (17), the third mixing light (19) and the mid-infrared laser (22) are all positive X-axis; the propagation directions of the terahertz wave (16) and the fourth mixing light (21) are positive Y-axis; the polarization directions of the first pump light (2) and the second pump light (4) are both Z-axis.

2. The device for simultaneously generating terahertz waves and tunable lasers according to claim 1, characterized in that: The phase delay system consists of a first mirror (5), a second mirror (6), a third mirror (7) and a fourth mirror (8). The second pump light (4) emitted from the second pump source (3) passes through the phase delay system consisting of the first mirror (5), the second mirror (6), the third mirror (7) and the fourth mirror (8) in sequence, and then enters the beam combiner (10) after the optical path is changed by the fifth mirror (9).

3. The apparatus for simultaneously generating terahertz waves and tunable lasers according to claim 2, characterized in that: The first reflector (5), the second reflector (6), the third reflector (7), the fourth reflector (8), and the fifth reflector (9) are all plane mirrors; the first reflector (5), the second reflector (6), the third reflector (7), the fourth reflector (8), and the fifth reflector (9) are totally internally reflected by the second pump light (4); the first parabolic mirror (15) has high transmission to the multi-stage beam (17) and totally internally reflects the terahertz wave (16); the second parabolic mirror (20) has high transmission to the mid-infrared laser (22) and totally internally reflects the fourth mixing beam (21).

4. The apparatus for simultaneously generating terahertz waves and tunable lasers according to claim 1, characterized in that: The first parabolic mirror (15) has a transmittance of 99.9% for the multi-stage beam (17), and the second parabolic mirror (20) has a transmittance of 99.9% for the mid-infrared laser 22.

5. The apparatus for simultaneously generating terahertz waves and tunable lasers according to claim 1, characterized in that: Both the first APPLN crystal (13) and the second APPLN crystal (18) are cuboids, which are rectangular in the XY plane. The length direction of the crystal is consistent with the positive X-axis, and the optical axis of the crystal is along the Z-axis. Both the first APPLN crystal (13) and the second APPLN crystal (18) are aperiodic polarized crystals. The phase mismatch of the aperiodic polarization distribution of the first APPLN crystal (13) along the length of the crystal from the first redshift to the nth redshift is equal to 0 step by step. The nth redshift is any one of the following orders, which is greater than the first order and less than the order {(frequency of the first pump light - 60THz) / frequency of the terahertz wave}. The phase mismatch of the aperiodic polarization distribution of the second APPLN crystal (18) along the length of the crystal from the mth redshift to the kth redshift is equal to 0 step by step. The kth redshift is any one of the following orders, which is greater than the mth order and less than the order {(frequency of the first pump light - 60THz) / frequency of the terahertz wave}. The m-th difference frequency contains two difference frequency beams: the cascade beam with the highest energy in the multi-stage cascade beam (14) and the cascade beam with a lower frequency adjacent to it.

6. The apparatus for simultaneously generating terahertz waves and tunable lasers according to claim 1, characterized in that: The multi-stage beam (17) is a mixed beam of multiple cascaded beams, which propagate in a collinear manner; the frequency difference between adjacent beams in the multi-stage beam (17) is equal to the frequency difference between the first pump beam (2) and the second pump beam (4).

7. The apparatus for simultaneously generating terahertz waves and tunable lasers according to claim 1, characterized in that: The fourth mixing light (21) includes the first mixing light (11) and the anti-stokes light.

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