Optical pumping terahertz laser pumping source structure

Abstract

The application belongs to the technical field of gas lasers, and specifically discloses a kind of optical pumping terahertz laser pumping source structures, including support frame and along the length direction of support frame sequentially arranged tuning mechanism, first Brewster window, laser tube, second Brewster window, light emitting barrel, the laser tube has coaxial sleeve set inner tube body and outer tube body, and cooling cavity is formed between the inner tube body and outer tube body.The application provides a kind of optical pumping terahertz laser pumping source structures, through support frame as rigid matrix guarantee the relative position accuracy of each optical element, utilize screw step structure drive diffraction grating sleeve to realize accurate frequency selection, and pass through the double-layer sleeve sandwich cooling structure of laser tube to guarantee discharge stability, each functional component is coaxially arranged along the same axis, realizes the high stability of pumping laser, narrow line width and wavelength adjustable output;At the same time, through cooling cavity setting, realize the uniform heat dissipation of discharge chamber.

Description

Technical Field

[0001] This invention relates to the field of gas laser technology, and in particular to a pump source structure for an optically pumped terahertz laser. Background Technology

[0002] Terahertz lasers, with their low photon energy, excellent penetration, and lack of ionizing damage, possess irreplaceable application value in fields such as spectral detection, non-destructive testing, biomedical imaging, security inspection, and space remote sensing. Optically pumped terahertz continuous-wave lasers, due to their strong output stability, high output power, and suitable output frequency band, are currently the core light source in polarization interferometer systems for fusion plasma diagnostics, holding an irreplaceable and crucial position. The pump source for optically pumped terahertz lasers typically uses a carbon dioxide laser, and the wavelength stability, output power stability, and cavity length stability of the output laser directly determine the operating efficiency and beam quality of the optically pumped terahertz gas laser.

[0003] Currently, commercially available and laboratory-developed carbon dioxide pumped lasers generally employ a common carbon steel frame, glass laser tube, and simple resonant cavity structure. Under long-term continuous operation, this reveals several technical shortcomings: First, the aluminum / steel support components expand and contract with temperature rise, causing optical path deviation, power drift, increased spectrogram noise, and poor pump compatibility. Second, manual angle adjustment accuracy is low, single-line frequency selection in the 9-11 micrometer band is difficult, and it is hard to match the absorption peaks of various terahertz media. Third, the optical area lacks dust protection, increasing optical loss due to dust, resulting in poor flange sealing reliability, working gas leakage, and shortened continuous operating life. Fourth, the rigid coupling mirror cannot rely on piezoelectric ceramics to compensate for cavity length thermal drift in real time, leading to poor beam stability. More importantly, traditional carbon dioxide lasers have relatively wide output spectral linewidths and are mostly pulsed outputs. Existing CO2 lasers with continuous output on the market can only output efficiently around the commonly used spectral lines in industrial fields (such as wavelengths of 9.3 micrometers and 10.6 micrometers). They cannot be frequency tuned and have a wide linewidth, resulting in multi-frequency output of the pumped terahertz laser, which cannot meet the application requirements of optically pumped terahertz lasers in interferometric measurements.

[0004] Existing pump source structures are limited by frame material, tuning mechanism, heat dissipation design, sealing protection, and cavity length control design. They suffer from poor single-spectral line output controllability, weak long-term working stability, and low environmental temperature adaptability, which restricts the engineering development of optically pumped terahertz lasers towards high stability, narrow linewidth, and customizable pump wavelength. Therefore, a new structure is urgently needed to solve the above-mentioned defects.

[0005] In summary, existing carbon dioxide pump source lasers suffer from problems such as easy optical path deviation, low grating frequency selection accuracy, poor device heat dissipation, inability to dynamically compensate for cavity length, and insufficient dustproof vacuum performance. Summary of the Invention

[0006] This invention provides a pump source structure for an optically pumped terahertz laser, which can solve the problems of easy optical path deviation, low grating frequency selection accuracy, poor heat dissipation, inability to dynamically compensate cavity length, and insufficient dustproof vacuum performance in existing carbon dioxide pump source lasers.

[0007] A pump source structure for an optically pumped terahertz laser includes a support frame and a tuning mechanism, a first Brewster window, a laser tube, a second Brewster window, and a light-emitting tube arranged sequentially along the length of the support frame. The laser tube has an inner tube body and an outer tube body that are coaxially sleeved together, and a cooling cavity is formed between the inner tube body and the outer tube body. The tuning mechanism includes a lead screw stepping structure and a diffraction grating sleeve. A diffraction grating is provided inside the diffraction grating sleeve. The lead screw stepping structure is used to drive the diffraction grating sleeve to rotate around a first direction to adjust the deflection angle of the diffraction grating. The first direction is perpendicular to the length direction of the support frame. The optical path exit of the diffraction grating sleeve, the optical center of the first Brewster window, the cavity center of the laser tube, the optical center of the second Brewster window, and the optical path entrance of the light exit tube are all located on the same axis.

[0008] Furthermore, the support frame includes several fixed baffles and several connecting rods; Multiple fixed baffles are arranged in sequence and are connected in series by several connecting rods. Each of the multiple fixed baffles has a light-transmitting hole for the light beam to pass through.

[0009] Furthermore, the connecting rod is made of Invar steel.

[0010] Furthermore, the cooling cavity has a water-cooled inlet and a water-cooled outlet, which are respectively used to connect to the water supply end and the water return end of an external cooling water source to form a series cooling circuit.

[0011] Furthermore, a cathode electrode structure is provided on the outer tube of the laser tube near the water-cooling inlet, and an anode electrode structure is provided on the outer tube of the laser tube near the water-cooling outlet. A closed cavity is formed between the first Brewster window, the inner tube of the laser tube, and the second Brewster window. The closed cavity is used to fill the gain gas after evacuation. The cathode electrode structure and the anode electrode structure are used to form a glow discharge in the closed cavity after energization, so as to excite the gain gas to generate energy level transitions and output laser light.

[0012] Furthermore, both the lead screw stepping structure and the diffraction grating sleeve are mounted on the support frame, and the lead screw stepping structure and the diffraction grating sleeve are connected by a lever transmission. The fulcrum of the lever is hinged to the support frame, the output end of the lead screw stepping structure is hinged to the short arm end of the lever, and the long arm end of the lever is connected to the outer wall of the diffraction grating sleeve.

[0013] Furthermore, the diffraction grating sleeve is also provided with water-cooling pipes, and a water chiller is connected to the outside of the water-cooling pipes; The water-cooling pipeline is used to circulate water to cool the diffraction grating inside the diffraction grating sleeve.

[0014] Furthermore, dustproof covers are provided at both ends of the support frame near the positions of the first Brewster window and the second Brewster window, respectively.

[0015] Furthermore, an annular piezoelectric ceramic is provided on the side of the light-emitting tube near the second Brewster window, and a coupling mirror flange structure is provided on the side of the annular piezoelectric ceramic away from the light-emitting tube. The coupling mirror flange structure contains a coupling mirror; The ring-shaped piezoelectric ceramic expands under electrical current, thereby adjusting the length of the resonant cavity.

[0016] Furthermore, the side wall of the light-emitting tube is provided with a lead wire routing port, through which the driving cable of the annular piezoelectric ceramic is led out to the outside of the light-emitting tube.

[0017] This invention provides a pump source structure for an optically pumped terahertz laser, which, compared to existing technologies, has, but is not limited to, the following beneficial effects: In the pump source structure of this optically pumped terahertz laser, the support frame serves as the rigid support base for the entire machine, supporting and fixing the aforementioned functional components. The tuning mechanism is located at the upstream end of the optical path, used for selecting and tuning the laser wavelength. The first and second Brewster windows are respectively located at both ends of the laser tube, serving as transmission windows for the laser resonant cavity. Simultaneously, the Brewster angle incident characteristic is utilized to reduce reflection loss, achieving linearly polarized light output. The laser tube serves as the gain medium carrier and the region where laser oscillation occurs. The output tube is located at the downstream end of the optical path, used to couple the frequency-selected laser beam to the subsequent terahertz laser. The laser tube has an inner tube and an outer tube coaxially nested within it. The inner tube is coaxially positioned inside the outer tube, and the inner wall of the inner tube encloses a discharge chamber to accommodate the gain gas and generate glow discharge. A cooling cavity is formed between the outer wall of the inner tube and the inner wall of the outer tube. This cooling cavity is an annular sandwich structure that extends along the axial direction of the laser tube and is used to accommodate the circulating cooling medium (such as cooling water) to achieve uniform heat dissipation from the discharge chamber. Through this double-layered tube structure, the cooling medium can wrap around the inner tube as it circulates within the sandwich, continuously carrying away the Joule heat generated by the discharge and the radiative heat from the cavity. This effectively controls the uniformity of the temperature field in the discharge region and avoids thermally induced changes in refractive index and optical path disturbances.

[0018] A lead screw stepping structure is used to drive the diffraction grating sleeve to rotate around a first direction to adjust the deflection angle of the diffraction grating, wherein the first direction is perpendicular to the length direction of the support frame. Specifically, the lead screw stepping structure drives the diffraction grating sleeve to rotate around this first direction, thereby changing the angle between the diffraction grating blaze surface and the incident light, achieving frequency-selective output of laser light of different wavelengths. Through the precise micro-feeding of the lead screw stepping structure, accurate adjustment of the diffraction grating angle can be achieved, resulting in high angular resolution.

[0019] This invention provides a pump source structure for an optically pumped terahertz laser. A support frame serves as a rigid substrate to ensure the relative positional accuracy of each optical element. A lead screw stepping structure drives a diffraction grating sleeve to achieve precise frequency selection. A double-layer sleeve cooling structure of the laser tube ensures discharge stability. All functional components are coaxially arranged along the same axis, achieving high stability, narrow linewidth, and wavelength-tunable output of the pump laser. Simultaneously, a cooling cavity is provided to achieve uniform heat dissipation of the discharge chamber. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 A partial structural schematic diagram of a pump source structure for an optically pumped terahertz laser provided by the present invention; Figure 2 This invention provides a partial front view of the pump source structure of an optically pumped terahertz laser. Figure 3 A schematic diagram of the pump source structure for an optically pumped terahertz laser provided by the present invention; Figure 4 A front view of the pump source structure of an optically pumped terahertz laser provided by the present invention; Figure 5 A schematic diagram of the light-emitting tube of a pump source structure for an optically pumped terahertz laser provided by the present invention; Figure 6 A schematic diagram of the light-emitting tube of a pump source structure for an optically pumped terahertz laser provided by the present invention; Figure 7 This invention provides a front view of the light-emitting tube of a pump source structure for an optically pumped terahertz laser. Figure 8 A schematic diagram of the installation structure of the diffraction grating sleeve and the fixed baffle of the pump source structure of an optically pumped terahertz laser provided by the present invention; Figure 9This invention provides a schematic diagram of the connection structure between the diffraction grating sleeve and the lead screw stepping structure of a pump source structure for an optically pumped terahertz laser.

[0021] Explanation of reference numerals in the attached figures: 1. Exhaust port; 2. Laser tube; 3. Cathode electrode structure; 4. Anode electrode structure; 5. Connecting rod; 6. First Brewster window; 7. Lead screw stepping structure; 8. Lever; 9. Diffraction grating sleeve; 10. Fixed baffle; 11. Light output tube; 12. Dustproof cover; 13. Coupler mirror; 14. Coupler mirror flange structure; 15. Annular piezoelectric ceramic; 16. Lead wire routing port; 17. Second Brewster window. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, specific embodiments of this application are described clearly and completely below with reference to the accompanying drawings. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the specification of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," "comprise," etc., in the specification, claims, and accompanying drawings of this application are open-ended terms, indicating that a method comprises one or more steps, or an apparatus comprises one or more elements, but do not exclude the inclusion of other steps or elements. The terms "first," "second," etc., in the specification, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or primary / secondary relationship. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, C and / or B can represent: C existing alone, C and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0027] like Figures 1 to 9 As shown, an embodiment of the present invention provides a pump source structure for an optically pumped terahertz laser, including a support frame and a tuning mechanism, a first Brewster window 6, a laser tube 2, a second Brewster window 17, and a light-emitting tube 11 arranged sequentially along the length of the support frame. The laser tube 2 has an inner tube body and an outer tube body coaxially sleeved together, and a cooling cavity is formed between the inner tube body and the outer tube body. The tuning mechanism includes a lead screw stepping structure 7 and a diffraction grating sleeve 9. A diffraction grating is provided inside the diffraction grating sleeve 9. The lead screw stepping structure 7 is used to drive the diffraction grating sleeve 9 to rotate around a first direction to adjust the deflection angle of the diffraction grating. The first direction is perpendicular to the length direction of the support frame. The optical path exit of the diffraction grating sleeve 9, the optical center of the first Brewster window 6, the cavity center of the laser tube 2, the optical center of the second Brewster window 17, and the optical path entrance of the light-emitting tube 11 are all located on the same axis.

[0028] Specifically, the support frame serves as the rigid support base for the entire device, used to support and fix the aforementioned functional components. Along the length of the support frame (i.e., the optical path axial direction), the functional components are arranged sequentially in the order of tuning mechanism, first Brewster window 6, laser tube 2, second Brewster window 17, and output tube 11. The tuning mechanism is located at the upstream end of the optical path, used to achieve laser wavelength selection and tuning; the first Brewster window 6 and the second Brewster window 17 are respectively located at both ends of the laser tube 2, serving as transmission windows for the laser resonant cavity, while utilizing the Brewster angle incident characteristic to reduce reflection loss and achieve linearly polarized light output; the laser tube 2 serves as the gain medium carrier and the region where laser oscillation occurs; the output tube 11 is located at the downstream end of the optical path, used to couple the frequency-selected laser beam to the subsequent terahertz laser.

[0029] Laser tube 2 has an inner tube and an outer tube coaxially fitted together. The inner tube is coaxially positioned inside the outer tube, and its inner wall encloses a discharge chamber to contain the gain gas and generate glow discharge. A cooling cavity is formed between the outer wall of the inner tube and the inner wall of the outer tube. This cooling cavity is an annular sandwich structure that extends along the axial direction of laser tube 2 and contains a circulating cooling medium (such as cooling water) to achieve uniform heat dissipation from the discharge chamber. Through this double-layered tube structure, the cooling medium, as it circulates within the sandwich, can envelop the inner tube, continuously carrying away the Joule heat generated by the discharge and the radiative heat from the cavity, effectively controlling the temperature field uniformity in the discharge region and avoiding thermally induced refractive index changes and optical path disturbances.

[0030] The lead screw stepping structure 7 drives the diffraction grating sleeve 9 to rotate around a first direction to adjust the deflection angle of the diffraction grating, wherein the first direction is perpendicular to the length direction of the support frame. Specifically, the lead screw stepping structure 7 drives the diffraction grating sleeve 9 to rotate around this first direction, thereby changing the angle between the diffraction grating blazing surface and the incident light, and realizing the frequency-selective output of lasers of different wavelengths. Through the precise micro-feeding of the lead screw stepping structure 7, the step-by-step precise adjustment of the diffraction grating angle can be achieved, with high angular resolution and good repeatability.

[0031] The optical path exit of the diffraction grating sleeve 9, the optical center of the first Brewster window 6, the cavity center of the laser tube 2, the optical center of the second Brewster window 17, and the optical path entrance of the light exit tube 11 are all located on the same axis. This axis is the main optical axis of the entire optical path, and the light transmission center of each optical element coincides with this main optical axis. Specifically, the optical path exit of the diffraction grating sleeve 9 is the center point of the exit aperture through which the emitted beam after diffraction by its internal diffraction grating passes; the optical center of the first Brewster window 6 is its geometric center and the center of its light transmission surface; the cavity center of the laser tube 2 is the cross-sectional center of the discharge chamber formed by the inner wall of its inner tube, extending axially to form a central axis; the optical center of the second Brewster window 17 is also its geometric center and the center of its light transmission surface; and the optical path entrance of the light exit tube 11 is the center point of its internal light transmission aperture. By setting the above-mentioned center points on the same axis, the pump laser is ensured to be transmitted smoothly along a straight optical path, avoiding coupling loss and beam quality degradation caused by optical path deflection or eccentricity.

[0032] The light-emitting tube 11 is located on the support frame at one end near the second Brewster window 17 (i.e., the downstream end of the optical path) and is used to transmit and output the laser portion that is oscillating and amplified in the resonant cavity.

[0033] The pump source structure of the optically pumped terahertz laser provided in this application embodiment ensures the relative position accuracy of each optical element by using a support frame as a rigid substrate, uses a lead screw stepping structure 7 to drive the diffraction grating sleeve 9 to achieve precise frequency selection, and uses the double-layer sleeve sandwich cooling structure of the laser tube 2 to ensure discharge stability. All functional components are arranged coaxially along the same axis, realizing high stability, narrow linewidth and wavelength adjustable output of the pump laser.

[0034] like Figures 1 to 2 As shown, in some embodiments of the present invention, the support frame includes a plurality of fixed baffles 10 and a plurality of connecting rods 5; the plurality of fixed baffles 10 are arranged in sequence, and the plurality of fixed baffles 10 are connected in series and fixed together by a plurality of connecting rods 5, and each of the plurality of fixed baffles 10 is provided with a light-transmitting hole for the light beam to pass through.

[0035] In a more specific implementation, this embodiment features a support frame with four fixed baffles 10 and three connecting rods 5. The four fixed baffles 10 are arranged parallel to each other along the optical path axis (i.e., the length direction of the support frame). The three connecting rods 5 are respectively inserted into mounting through holes at the corners of the four fixed baffles 10, and both ends can be secured with lock nuts, connecting the four fixed baffles 10 in series into a rigid structure. Each of the four fixed baffles 10 has a light-transmitting hole for the light beam to pass through, and the centers of all the light-transmitting holes are coaxial.

[0036] In practical applications, four fixed baffles 10 are arranged at a preset interval along the optical path. For example, from left to right, the four fixed baffles 10 are marked as fixed baffle 1#, fixed baffle 2#, fixed baffle 3#, and fixed baffle 4#. Fixed baffle 1# is used for the installation and fixation of the lead screw stepping structure 7 and the diffraction grating sleeve 9. The two ends of the laser tube 2 are respectively installed on fixed baffle 2# and fixed baffle 3#. The first Brewster window 6 is installed on the left side of fixed baffle 2#, the second Brewster window 17 is installed on the right side of fixed baffle 3#, and the light output tube 11 is installed on fixed baffle 4#.

[0037] As a preferred embodiment, the connecting rod 5 is made of Invar. Invar is an iron-nickel alloy with an extremely low coefficient of thermal expansion (α ≤ 1.2 × 10⁻⁶ near room temperature). -6The dimensions change minimally with temperature variations. Invar steel rods with a low coefficient of thermal expansion are selected as the connecting rod 5. Because the coefficient of thermal expansion of Invar steel is much lower than that of ordinary carbon steel and aluminum alloys, the thermal expansion and contraction of the connecting rod 5 is extremely small under temperature fluctuations caused by laser discharge heating and cooling water circulation. Utilizing the low thermal expansion characteristics of Invar steel, deformation of the support structure caused by heating and temperature rise can be effectively avoided, preventing changes in the axial spacing between the fixed baffles 10 and the relative positional shift of each fixed baffle 10, thereby preventing optical path eccentricity and optical axis drift. This ensures the optical path stability and wavelength stability of the entire machine under long-term continuous operation conditions, significantly improving the engineering reliability of the pump source.

[0038] like Figures 1 to 4 As shown, in some embodiments of the present invention, the cooling cavity has a water-cooled inlet and a water-cooled outlet, which are respectively used to connect to the water supply end and the water return end of an external cooling water source to form a series cooling circuit.

[0039] In practical applications, the external cooling water source is typically a chiller or a circulating water cooling system, with a chiller being preferred. The water inlet is connected to the external cooling water source via piping. Cooling water enters the cooling cavity from the inlet, flows along the annular interlayer along the entire length of the laser tube 2, absorbs the heat generated by the discharge within the inner tube, and then flows out from the outlet, returning to the external cooling water source via piping. During its flow within the cooling cavity, the cooling water coats the outer wall of the inner tube, continuously carrying away Joule heat from the electrodes and radiant heat from the cavity, achieving efficient cooling of the discharge chamber. The series cooling loop ensures unidirectional flow of the cooling water, avoids cooling dead zones, and ensures consistent heat dissipation.

[0040] like Figures 1 to 4 As shown, in some embodiments of the present invention, a cathode electrode structure 3 is provided on the outer tube of the laser tube 2 near the water-cooling inlet, and an anode electrode structure 4 is provided on the outer tube of the laser tube 2 near the water-cooling outlet; a closed cavity is formed between the first Brewster window 6, the inner tube of the laser tube 2, and the second Brewster window 17. The closed cavity is used to fill gain gas after vacuuming. The cathode electrode structure 3 and the anode electrode structure 4 are used to form glow discharge in the closed cavity after energization, so as to excite the gain gas to generate energy level transition and output laser.

[0041] In practical applications, cooling water first flows through the cathode region and then to the anode region. Since the heating power of the cathode region and the anode region is different (the anode region usually has more concentrated heating), this layout can achieve temperature difference compensation when the cooling water flows through different heating regions, ensuring that the temperature field distribution along the axis of the entire discharge chamber is more uniform and avoiding optical non-uniformity caused by local overheating.

[0042] Both cathode electrode structure 3 and anode electrode structure 4 can adopt a structure in which a metal electrode rod penetrates the tube wall. Electrical isolation and vacuum sealing can be achieved between the electrode rod and the tube wall through a ceramic insulating sleeve and a sealing ring, ensuring safe feeding of high-voltage power and zero leakage of working gas.

[0043] A closed cavity is formed between the first Brewster window 6, the inner tube of the laser tube 2, and the second Brewster window 17. Specifically, the left end of the laser tube 2 can be sealed and connected to the window seat of the first Brewster window 6 through a flange, and the right end of the laser tube 2 can be sealed and connected to the window seat of the second Brewster window 17 through a flange. The space between the first Brewster window 6 and the second Brewster window 17 (including the discharge chamber inside the inner tube of the laser tube 2 and the cavities inside the two Brewster windows) together constitute a sealed resonant cavity.

[0044] As an example, the left and right ends of the laser tube 2 are connected to two fixed baffles 10 via flanges, wherein the flange at the left end of the laser tube 2 is provided with an air extraction hole 1.

[0045] A closed cavity (i.e., a sealed resonant cavity) is formed between the first Brewster window 6, the inner tube of the laser tube 2, and the second Brewster window 17. The evacuation port 1 can be connected to an external vacuum pump pipeline and a shut-off valve.

[0046] The lower left side of the laser tube 2 interlayer has an interface that integrates the cathode electrode 3 and the water cooling inlet, while the upper right side integrates the anode electrode 4 and the water cooling outlet. The electrode seal penetrates the tube wall and extends into the discharge cavity. The external chiller pipeline is connected to the water cooling inlet and the water cooling outlet respectively. The cooling water circulates inside the double-layer interlayer (i.e., the cooling cavity) to continuously remove the Joule heat of the electrode and the radiant heat of the cavity.

[0047] In practical applications, the vacuum pump is started and pumped to a high vacuum level in the sealed resonant cavity through evacuation port 1, maintaining the vacuum level at 10. -3 ~10 -4 Pa. Carbon dioxide gain mixture is injected into the cavity through the reserved gas filling port, and the working gas pressure is controlled at 8-20 Torr; the positive and negative electrodes are connected to a high-voltage excitation power supply. After the power is turned on, the gas in the cavity will undergo glow discharge, and the energy level transition of gas molecules will generate stimulated emission, forming carbon dioxide laser oscillation in the 9-11 micrometer band.

[0048] like Figures 1 to 4 , Figures 8 to 9 As shown, in some embodiments of the present invention, the lead screw stepping structure 7 and the diffraction grating sleeve 9 are both mounted on the support frame, and the lead screw stepping structure 7 and the diffraction grating sleeve 9 are connected by a lever 8; the fulcrum of the lever 8 is hinged to the support frame, the output end of the lead screw stepping structure 7 is hinged to the short arm end of the lever 8, and the long arm end of the lever 8 is connected to the outer wall of the diffraction grating sleeve 9.

[0049] In practical applications, the lead screw stepping structure 7 is fixedly installed on the left end face of the fixed baffle 10 of the support frame. The lead screw nut of the lead screw stepping structure 7 serves as the output end, and its linear feed motion is transmitted to the short arm end of the lever 8 through a hinge. The main body of the lever 8 is a rigid rod, and its fulcrum can be connected to the fulcrum seat on the support frame through a hinge, forming the rotation fulcrum of the lever 8. The two ends of the lever 8 are the short arm end and the long arm end, respectively, and the distance from the short arm end to the fulcrum is less than the distance from the long arm end to the fulcrum. The long arm end of the lever 8 can be connected to the outer wall of the diffraction grating sleeve 9, specifically through a connecting rod or direct hinge, to convert the rotational motion of the lever 8 into the rotational motion of the diffraction grating sleeve 9 around the first direction.

[0050] During operation, the lead screw stepping structure 7 rotates by a predetermined angle, causing the lead screw nut to generate a minute linear feed displacement along the lead screw axis. Through this lever-driven transmission, the minute feed of the lead screw stepping structure 7 is amplified by the lever 8 and then drives the diffraction grating sleeve 9 to rotate slightly, simultaneously changing the angle between the diffraction grating and the optical axis, thus achieving precise frequency-selective output of a single carbon dioxide laser spectral line within the 9-11 micrometer range. This transmission structure has advantages such as a constant mechanical displacement ratio and no backlash, enabling precise matching of the pump absorption wavelengths of different terahertz gain media.

[0051] As an example, the bottom of the diffraction grating sleeve 9 is fixed on a wedge plate (or wedge base) with a fixed tilt angle. The initial angle between the grating and the system optical axis is preset by the tilt angle of the wedge plate, which satisfies the initial installation of the grating.

[0052] like Figures 1 to 4 , Figures 8 to 9 As shown, in some embodiments of the present invention, a water-cooling pipeline is also arranged on the diffraction grating sleeve 9, and a water chiller is connected to the outside of the water-cooling pipeline; the water-cooling pipeline is used to circulate water-cooling heat dissipation for the diffraction grating inside the diffraction grating sleeve 9.

[0053] In practical applications, diffraction gratings are irradiated by lasers during operation. The grating surface absorbs some light energy and converts it into heat, causing the grating temperature to rise. This temperature increase leads to thermal expansion of the grating material, altering the period and spacing of the grating lines, thus reducing diffraction efficiency and wavelength selection accuracy (i.e., thermal distortion). By arranging independent water-cooling pipes on the diffraction grating sleeve 9, which can be configured as a spiral coil surrounding the outer wall of the sleeve 9 or an annular flow channel within the sleeve wall, and connected to an external chiller to provide cooling water, the cooling water circulates within the water-cooling pipes, continuously carrying away the heat conducted from the grating to the sleeve, maintaining a constant grating operating temperature. This water-cooling design effectively prevents the grating from deteriorating its frequency selection accuracy due to thermal distortion, ensuring wavelength stability during long-term continuous operation of the pump source.

[0054] like Figures 1 to 4As shown, in some embodiments of the present invention, dustproof covers 12 are respectively provided at both ends of the support frame near the positions of the first Brewster window 6 and the second Brewster window 17.

[0055] In practical applications, the dust cover 12 is specifically positioned at the left end of the support frame (near the first Brewster window 6 and the diffraction grating sleeve 9) and the right end of the support frame (near the second Brewster window 17 and the light-emitting tube 11), respectively covering the area above the optical transmission surface between the diffraction grating sleeve 9 and the first Brewster window 6, and the area above the optical transmission surface between the light-emitting tube 11 and the second Brewster window 17. The dust cover 12 can be fixed to the upper surface of the fixed baffle 10 with screws, fully covering the area of ​​optical components such as the grating and the Brewster window. During normal operation, the dust cover 12 is closed, preventing dust in the ambient air from settling on the surface of the optical components and reducing optical scattering loss. When inspecting the grating and the Brewster window, the dust cover 12 can be directly removed for operation, making disassembly and assembly convenient.

[0056] like Figures 5 to 7 As shown, in some embodiments of the present invention, an annular piezoelectric ceramic 15 is provided on the side of the light-emitting tube 11 near the second Brewster window 17, and a coupling mirror flange structure 14 is provided on the side of the annular piezoelectric ceramic 15 away from the light-emitting tube 11; a coupling mirror 13 is provided inside the coupling mirror flange structure 14.

[0057] Among them, the ring-shaped piezoelectric ceramic 15 can be a piezoelectric ceramic actuator, which has the inverse piezoelectric effect, that is, it will expand and contract along the axis under the action of an external electric field. The coupling mirror 13 can be a partial reflector, used to transmit and output part of the laser beam oscillating and amplified in the resonant cavity.

[0058] In practical applications, the light-emitting tube 11 has a cylindrical structure, with a ring-shaped piezoelectric ceramic 15 coaxially bonded inside its right end (i.e., the end near the second Brewster window 17, which is also the optical path entrance end). The ring-shaped piezoelectric ceramic 15 is a thin ring structure with an inner diameter larger than the beam diameter, so it will not obstruct the optical path. The coupling mirror flange structure 14 is a disc-shaped flange with the output coupling mirror 13 bonded to the center of the disc. The coupling mirror flange structure 14 is concentrically glued and fixed to the left end face of the ring-shaped piezoelectric ceramic 15.

[0059] During laser operation, when the cavity length of the resonant cavity drifts due to changes in ambient temperature or fluctuations in internal heat generation, the supply voltage applied to the annular piezoelectric ceramic 15 is adjusted. This, relying on the inverse piezoelectric effect, drives the annular piezoelectric ceramic 15 to undergo slight axial expansion and contraction, causing the coupling mirror flange structure 14 and the coupling mirror 13 to shift axially. This real-time compensation for the cavity length error stabilizes the resonant cavity Q value and the pump laser output power. This method offers fast response speed and high adjustment precision, effectively improving the long-term stability of the pump source.

[0060] As an example, an axial limiting guide rail can also be provided between the outer ring of the annular piezoelectric ceramic 15 and the inner wall of the light-emitting tube 11. The guide rail supports the outer ring of the annular piezoelectric ceramic 15, counteracts the sag caused by the weight of the piezoelectric ceramic and the coupling mirror, and ensures the coaxiality of the assembly.

[0061] like Figures 5 to 7 As shown, in some embodiments of the present invention, the side wall of the light-emitting tube 11 is also provided with a lead wire routing port 16, through which the driving cable of the annular piezoelectric ceramic 15 is led out to the outside of the light-emitting tube 11.

[0062] In practical applications, the lead wire routing port 16 is a through hole or slot penetrating the side wall of the light-emitting tube 11, located near the mounting position of the annular piezoelectric ceramic 15. The positive and negative electrode leads of the annular piezoelectric ceramic 15 are led out from the piezoelectric ceramic body and pass through the lead wire routing port 16 to exit the side wall of the light-emitting tube 11, allowing for connection to an external high-precision piezoelectric drive power supply. The design of the lead wire routing port 16 eliminates the need for the drive cable to pass through the optical path inlet or outlet of the light-emitting tube 11, preventing the cable from obstructing the optical path or affecting the sealing of the optical components, while also facilitating cable fixation and protection. A sealing plug or protective sleeve can also be installed at the lead wire routing port 16 to prevent dust from entering the interior of the light-emitting tube 11 and contaminating the optical components.

[0063] The technical solution of the present invention will be further explained and illustrated below through a specific example.

[0064] This example provides a pump source structure for an optically pumped terahertz laser. The pump source structure uses a support frame as a rigid reference, and uses a lead screw stepping structure 7 in conjunction with a lever 8 to achieve step adjustment of the diffraction grating angle. The double-layer sleeve sandwich water-cooling structure of the laser tube 2 ensures the thermal stability of the discharge region, and the annular piezoelectric ceramic 15 achieves real-time compensation of the cavity length. Overall, it realizes a pump laser output with narrow linewidth and high stability.

[0065] Specifically, the support frame consists of four fixed baffles 10 arranged parallel to each other along the optical path axis. Three Invar connecting rods 5 are respectively inserted into the mounting through holes at the corners of the fixed baffles 10, and the two ends are fastened together by lock nuts to form a rigid support base for the whole machine. Utilizing the low thermal expansion characteristics of Invar, the deformation of the support caused by laser discharge heat and water cooling temperature rise is avoided, thus preventing optical path eccentricity and wobbling. During assembly, tooling is used for straightening to ensure that the reference holes of the four fixed baffles 10 are coaxial, and that the assembly references of the diffraction grating sleeve 9, the first Brewster window 6, the second Brewster window 17, the laser tube 2, and the light output tube 11 are coaxial.

[0066] Furthermore, the laser tube 2 adopts a double-layered structure with an inner and outer tube body coaxially fitted together. The interlayer is an annular cooling cavity (water-cooled flow channel), and the inner layer is a gas discharge chamber. The left end of the laser tube 2 is sealed with a welded metal flange, the outer edge of which is clamped onto the left fixed baffle 10. The right end of the flange is sealed and connected to the first Brewster window 6. A fluororubber O-ring is installed between the first Brewster window 6 and the flange to achieve a vacuum seal. The right end flange of the laser tube 2 is also sealed and fitted with a second Brewster window 17. The first Brewster window 6, the second Brewster window 17, and the inner cavity of the laser tube 2 together form a sealed resonant cavity. An interface integrating the cathode electrode structure 3 and the water-cooling inlet is opened on the lower left side of the interlayer of the laser tube 2, and the anode electrode structure 4 and the water-cooling outlet are integrated on the upper right side. The electrode seal penetrates the tube wall and extends into the discharge chamber. The external chiller piping is connected to the water cooling inlet and outlet respectively. The cooling water circulates inside the double-layer sandwich, continuously carrying away the Joule heat of the electrodes and the radiant heat of the cavity.

[0067] The vacuum pump is started, and the vacuum level is maintained at 10 through the evacuation port 1 of the sealed chamber to a high vacuum. -3 ~10 -4 Pa. Carbon dioxide gain mixture is introduced into the cavity through the reserved gas inlet, controlling the working gas pressure within the range of 8–20 Torr. The cathode electrode structure 3 and the anode electrode structure 4 are connected to an external high-voltage excitation power supply. After power is applied, the gas inside the cavity undergoes glow discharge, and the energy level transitions of carbon dioxide gas molecules generate stimulated emission, forming a 9–11 micrometer band carbon dioxide laser oscillation.

[0068] Meanwhile, the lead screw stepping structure 7 is fixed to the left end face of the left fixed baffle 10, and its output end is hinged to the short arm end of the lever 8. The fulcrum of the lever 8 is hinged to the grating sleeve fixing plate, and the long arm end of the lever 8 is connected to the outer wall of the diffraction grating sleeve 9. The diffraction grating is built inside the diffraction grating sleeve 9, and the bottom of the diffraction grating sleeve 9 is fixed on a wedge plate with a fixed tilt angle. The initial angle between the grating and the system optical axis is preset by the tilt angle of the wedge plate to meet the initial installation of the grating. During operation, the lead screw stepping structure 7 is controlled to feed slightly, which drives the diffraction grating sleeve 9 to rotate slightly around the first direction via the lever 8, and simultaneously changes the angle between the diffraction grating and the optical axis to achieve single-line frequency-selective output of carbon dioxide laser in the range of 9-11 micrometers. This can match the pump absorption wavelength of different terahertz gain media. An independent water-cooling pipeline is arranged at the rear end of the diffraction grating sleeve 9, and an external water chiller is connected to keep the grating at a constant temperature to avoid thermal distortion that degrades the frequency selection accuracy.

[0069] A ring-shaped piezoelectric ceramic 15 is coaxially bonded to the left end of the inner cavity of the laser output tube 11. An output coupling mirror 13 is bonded to the center of the disc surface of the coupling mirror flange structure 14. The coupling mirror flange structure 14 is concentrically glued and fixed to the left end face of the ring-shaped piezoelectric ceramic 15. An axial limiting guide rail is circumferentially provided on the inner wall of the laser output tube 11. The guide rail supports the outer ring of the ring-shaped piezoelectric ceramic 15, counteracting the downward sag of the piezoelectric ceramic and the coupling mirror, ensuring coaxial assembly. A lead wire routing port 16 is provided on the side wall of the laser output tube 11. The drive cable of the ring-shaped piezoelectric ceramic 15 is led out from the lead wire routing port 16 and connected to an external high-precision piezoelectric drive power supply. During laser operation, when cavity length drift occurs due to temperature changes, the supply voltage of the piezoelectric ceramic is adjusted. Relying on the inverse piezoelectric effect, the ring-shaped piezoelectric ceramic 15 is driven to axially extend and retract slightly, causing the output coupling mirror 13 to axially displace, thus compensating for the cavity length error in real time and stabilizing the Q value of the resonant cavity and the pump laser output power.

[0070] Dust covers 12 are respectively installed above the optical light-transmitting surfaces above the left diffraction grating sleeve 9 and the first Brewster window 6, and above the right light-emitting tube 11 and the second Brewster window 17. The dust covers 12 are fixed to the upper end of the fixed baffle 10 with screws, fully covering the area of ​​optical components such as the grating and Brewster window. During normal operation, the covers are closed, preventing environmental dust from settling on the surface of the optical components and reducing optical scattering loss. The covers can be directly removed for maintenance of the grating and windows, making disassembly and assembly convenient.

[0071] After the entire machine is assembled, coaxial calibration can be performed first, followed by sequential connection of the water cooling system, vacuum unit, electrode high-voltage source, and piezoelectric drive power supply. The water cooling system is first turned on to pre-cool the various heat-generating components, then a vacuum is drawn, working gas is introduced, and the electrode power supply is turned on to initiate oscillation and light output. The output wavelength is switched by adjusting the grating angle through the lead screw stepping structure 7, and the cavity length is optimized by simultaneously fine-tuning the piezoelectric ceramic voltage. Ultimately, a narrow-linewidth pump laser with selectable wavelength and stable power is obtained. The output beam is then connected to a downstream terahertz laser for pumping excitation.

[0072] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A pump source structure for an optically pumped terahertz laser, characterized in that, It includes a support frame and a tuning mechanism, a first Brewster window (6), a laser tube (2), a second Brewster window, and a light-emitting tube (11) arranged sequentially along the length of the support frame. The laser tube (2) has an inner tube body and an outer tube body that are coaxially sleeved together, and a cooling cavity is formed between the inner tube body and the outer tube body. The tuning mechanism includes a lead screw stepping structure (7) and a diffraction grating sleeve (9). The diffraction grating sleeve (9) is provided with a diffraction grating. The lead screw stepping structure (7) is used to drive the diffraction grating sleeve (9) to rotate around a first direction to adjust the deflection angle of the diffraction grating. The first direction is perpendicular to the length direction of the support frame. The optical path exit of the diffraction grating sleeve (9), the optical center of the first Brewster window (6), the cavity center of the laser tube (2), the optical center of the second Brewster window, and the optical path entrance of the light exit tube (11) are located on the same axis.

2. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, The support frame includes several fixed baffles (10) and several connecting rods (5); Multiple fixed baffles (10) are arranged in sequence and are connected in series by several connecting rods (5). Each fixed baffle (10) has a light-transmitting hole for the light beam to pass through.

3. The pump source structure for an optically pumped terahertz laser according to claim 2, characterized in that, The connecting rod (5) is made of Invar steel.

4. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, The cooling cavity has a water-cooled inlet and a water-cooled outlet, which are respectively used to connect to the supply end and return end of an external cooling water source to form a series cooling circuit.

5. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, The outer tube of the laser tube (2) is provided with a cathode electrode structure (3) on the side near the water-cooling inlet, and an anode electrode structure (4) is provided on the side near the water-cooling outlet. A closed cavity is formed between the first Brewster window (6), the inner tube of the laser tube (2), and the second Brewster window. The closed cavity is used to fill the gain gas after vacuuming. The cathode electrode structure (3) and the anode electrode structure (4) are used to form glow discharge in the closed cavity after energization, so as to excite the gain gas to generate energy level transition and output laser.

6. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, The lead screw stepping structure (7) and the diffraction grating sleeve (9) are both mounted on the support frame, and the lead screw stepping structure (7) and the diffraction grating sleeve (9) are connected by a lever (8). The fulcrum of the lever (8) is hinged to the support frame, the output end of the lead screw stepping structure (7) is hinged to the short arm end of the lever (8), and the long arm end of the lever (8) is connected to the outer wall of the diffraction grating sleeve (9).

7. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, The diffraction grating sleeve (9) is also provided with a water-cooling pipe, and the water-cooling pipe is connected to a water chiller. The water-cooling pipeline is used to circulate water to cool the diffraction grating inside the diffraction grating sleeve (9).

8. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, Dustproof covers (12) are provided at both ends of the support frame near the first Brewster window (6) and the second Brewster window, respectively.

9. The pump source structure for an optically pumped terahertz laser according to claim 1, characterized in that, The light-emitting tube (11) is provided with an annular piezoelectric ceramic (15) on the side near the second Brewster window, and a coupling mirror flange structure (14) is provided on the side of the annular piezoelectric ceramic (15) away from the light-emitting tube (11). The coupling mirror flange structure (14) is equipped with a coupling mirror (13). The annular piezoelectric ceramic (15) expands under electrical current, thereby adjusting the cavity length of the resonant cavity.

10. The pump source structure for an optically pumped terahertz laser according to claim 9, characterized in that, The side wall of the light-emitting tube (11) is also provided with a lead wire routing port (16), through which the driving cable of the annular piezoelectric ceramic (15) is led out to the outside of the light-emitting tube (11).

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