4μm band laser generation method and fiber-optic gas laser generation device

Abstract

A 4μm band laser generation method and a fiber gas laser generating device achieve 4μm band laser output by generating an intrinsic absorption transition between a 2μm band pump laser and a working gas filled in an anti-resonant hollow core fiber. The working gas is HBr, or a mixture of HBr and CO2. The anti-resonant hollow core fiber can provide a nearly ideal environment for the interaction between gas and pump light. It can effectively confine the pump light to a micron-sized fiber core, greatly improving the pump intensity and effective action distance. The present invention improves the utilization rate of HBr molecules and combines the advantages of a gas laser, such as high output power, high damage threshold, and high competitive nonlinear effect threshold, with the advantages of a fiber laser, such as compact structure, stable performance, good beam quality, and high conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of laser generating equipment, and in particular to a 4μm band laser generating method and an optical fiber gas laser generating device. Background Art

[0002] Mid-infrared laser wavelengths cover most molecular vibration absorption peaks, showing great application prospects in military, biomedicine, atmospheric communications and other fields, and are a hot topic of international research.

[0003] There are multiple ways to generate mid-infrared lasers, which can generally be divided into two categories: direct generation through laser oscillation amplification (linear method); and nonlinear frequency conversion. The former includes solid-state lasers, semiconductor quantum cascade lasers, free electron lasers, chemical and gas lasers, over-frequency CO lasers, and fiber lasers, while the latter mainly includes optical parametric oscillators (OPOs) and optical frequency-doubling lasers (frequency-doubling of CO2 lasers). Quantum cascade lasers generate a lot of heat during continuous operation and have a large excited region, making it difficult to achieve high-power single-mode output. Electron vibration solid-state lasers can achieve efficient output in the 2-5μm range, but thermal lensing limits their power increase. Optical parametric oscillators can achieve tunable mid-infrared output at power levels of several watts, but they have high requirements for the pump source linewidth and polarization state. Currently, holmium-doped fluoride fiber lasers can achieve laser output in the 3-4μm range, but the power level and slope efficiency are both low, and wavelength expansion to longer wavelengths is also difficult.

[0004] Among them, fiber lasers have attracted widespread attention due to their advantages such as long operating distance, good beam quality, high stability, high conversion efficiency, and good heat dissipation. They are the most promising for achieving portable, stable, and efficient mid-infrared laser output. However, the output power of fiber lasers is limited by stimulated Raman scattering, stimulated Brillouin scattering, and thermal lensing. Silicate glass, a common material in optical fibers, has a phonon energy of up to 1100 cm -1 , with strong absorption at wavelengths greater than 2.2 μm, resulting in significant losses. Fluoride glass and chalcogenide glass have wider transmission bands and are more advantageous than silicate glass in the long-wavelength band. However, due to immature drawing processes, expensive materials, and poor strength, their applications are not as widespread as silicate glass fibers. The output power of fiber lasers decreases exponentially with increasing emission wavelength.

[0005] Compared with solid-state lasers and doped solid fiber lasers, gas lasers have high thresholds for competitive nonlinear effects and optical damage thresholds, and have potential advantages in beam quality and power levels.

[0006] The emergence of hollow-core fiber offers a new solution to the problems inherent in traditional fiber lasers. Compared to the gas cavity of traditional gas lasers, the core area of ​​hollow-core fiber is very small, on the micron scale, allowing for a longer range of tens of meters, more effective results, a more compact and robust structure, and improved connectivity with other devices. Hollow-core fiber-based gas lasers combine the advantages of both fiber and gas lasers, offering potential advantages over solid-core doped fiber in terms of laser output power, linewidth, and wavelength selection. They are a promising approach to achieving high-power tunable mid-infrared laser output. Summary of the Invention

[0007] In view of the defects in the prior art, the present invention proposes a 4μm band laser generation method and a fiber gas laser generating device.

[0008] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are as follows:

[0009] The present invention provides a first technical solution: a method for generating a 4μm-band laser, which realizes 4μm-band laser output by intrinsic absorption transition between a 2μm-band pump laser and a working gas filled in an anti-resonant hollow-core optical fiber. The working gas is HBr, or the working gas is a mixture of HBr and CO2. If the working gas is HBr gas, the HBr gas intrinsically absorbs the 2μm-band pump light and then transitions to generate a 4μm-band laser. If the working gas is a mixture of HBr and CO2, the HBr and CO2 gases have overlapping absorption bands in the 2μm band. By tuning the center wavelength of the pump source to align with the different absorption lines of HBr and CO2, 4μm-band laser output is realized.

[0010] The second technical solution provided by the present invention is a 4μm-band laser fiber gas laser generator, comprising a 2μm-band semiconductor laser pump source system, an input solid-core fiber, an antiresonant hollow-core fiber, and an output device. The input solid-core fiber, the antiresonant hollow-core fiber, and the output device are sequentially connected along the transmission path of the 2μm-band pump light output by the 2μm-band semiconductor laser pump source system. The antiresonant hollow-core fiber is filled with a working gas that intrinsically absorbs the 2μm-band pump light and then generates 4μm laser light through transition. The output device outputs 4μm laser light in the mid-infrared band. The working gas is HBr, or a mixture of HBr and CO2. Specifically, the output device is an output solid-core fiber. The two ends of the input solid-core fiber are fused to the output pigtail of the 2μm-band semiconductor laser pump source system and the input end of the antiresonant hollow-core fiber, respectively. The other end of the antiresonant hollow-core fiber is fused to the input end of the output solid-core fiber. This solution solves the technical problems of low pump coupling efficiency and system instability of spatial structure fiber gas lasers. It is an all-fiber structure gas laser generating device with compact structure, stable performance, narrow linewidth, low pump threshold, high conversion efficiency and good beam quality.

[0011] Preferably, the anti-resonant hollow-core fiber described in the second technical solution of the present invention has low transmission loss in the 2 μm pump band and the generated 4 μm laser band. Specifically, the transmission loss of the anti-resonant hollow-core fiber in the 2 μm pump band and the generated 4 μm laser band is less than 0.15 dB / m.

[0012] Preferably, the 4μm band laser fiber gas laser generating device in the second technical solution of the present invention also includes an isolator for preventing the reversely transmitted pump light from returning to the 2μm band semiconductor laser pump source system, and the isolator is fused to the input solid core optical fiber.

[0013] Preferably, the input solid-core fiber in the 4μm-band laser fiber gas laser generator of the second technical solution of the present invention is inscribed with an input Bragg grating that forms a high reflection for 4μm laser light in the mid-infrared band. The input Bragg grating is arranged on the input solid-core fiber after the isolator, and the peak reflectivity of the input Bragg grating is greater than 95%. The output device is an output solid-core fiber, and the output solid-core fiber is sequentially inscribed with a feedback grating that forms a high reflection for 2μm-band pump light and an output Bragg grating that partially reflects 4μm laser light in the mid-infrared band. The reflectivity of the feedback grating for 2μm-band pump light is greater than 95%, and the transmittance of the output Bragg grating for 4μm laser light in the mid-infrared band is 10% to 90%.

[0014] Preferably, the 2 μm band semiconductor laser pump source system in the 4 μm band laser fiber gas laser generating device in the second technical solution of the present invention includes a first pump source, a second pump source and a 2×1 pump combiner for coupling the pump lasers emitted by the two pump sources together. The central wavelength of the first pump source is 1971.67 nm, corresponding to the HBr molecule v 0→ v 2 transition R (2) absorption line, can make HBr molecules v 0 vibration dynamics J =2 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the central wavelength of the second pump source is 2018.14 nm, corresponding to the HBr molecule v 0→ v 2 transition P (4) absorption line, can make HBr molecules v 0 vibration dynamics J =4 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions per second, the first pump source and the second pump source can pump HBr molecules at different lower energy levels to the same upper energy level, thereby utilizing more HBr molecules.

[0015] The principle behind the second technical solution of the present invention is that antiresonant hollow-core fiber provides a nearly ideal environment for the interaction between gas and pump light. It effectively confines the pump light to a micron-sized fiber core, significantly improving the pump intensity and effective range. Furthermore, by combining the respective advantages of gas lasers and fiber lasers, the transmission loss spectrum of the antiresonant hollow-core fiber is designed to achieve low transmission losses in both the pump and generated laser bands, enabling efficient mid-infrared laser output. HBr is a diatomic molecule with only one vibrational state. The rotation of HBr molecules in each vibrational state induces a series of rotational states. Pump sources of different wavelengths can utilize HBr molecules in different lower energy level rotational states, pumping them to the same upper energy level rotational state. The transition then generates corresponding 4μm-band laser light, improving conversion efficiency.

[0016] The present invention provides a third technical solution: a 4μm-band laser fiber gas laser generator, comprising a 2μm-band semiconductor laser pump source system, a pump coupling device for coupling the pump laser to the antiresonant hollow-core fiber, the antiresonant hollow-core fiber, and an output device; the transmission path of the 2μm-band pump light output by the 2μm-band semiconductor laser pump source system is sequentially connected to the pump coupling device, the antiresonant hollow-core fiber, and the output device; the pump coupling device couples the 2μm-band pump light to the antiresonant hollow-core fiber, the antiresonant hollow-core fiber is filled with a working gas for generating 4μm laser light by intrinsically absorbing the 2μm-band pump light and then transitioning; the output device outputs 4μm laser light in the mid-infrared band. The working gas is HBr, or a mixture of HBr and CO2.

[0017] Preferably, the antiresonant hollow-core fiber in the 4μm-band laser fiber gas laser generator of Technical Solution 3 of the present invention has low transmission loss in both the 2μm pump band and the generated 4μm laser band. Specifically, the transmission loss of the antiresonant hollow-core fiber in both the 2μm pump band and the generated 4μm laser band is less than 0.15dB / m.

[0018] Preferably, in the 4μm band laser fiber gas laser generating device in the technical solution three of the present invention, the input end and the output end of the anti-resonant hollow-core fiber are respectively sealed in the input end sealed gas cavity and the output end sealed gas cavity, and the pump coupling device couples the 2μm band pump light to the anti-resonant hollow-core fiber through the input end sealed gas cavity, and the mid-infrared band 4μm laser generated in the anti-resonant hollow-core fiber is transmitted to the output device through the output end sealed gas cavity.

[0019] Preferably, in the 4μm band laser fiber gas laser generating device in the technical solution three of the present invention, the input end sealed gas cavity and the output end sealed gas cavity are respectively provided with an input window and an output window that can pass light (such as a sapphire window that can pass light), and the pump coupling device couples the 2μm band pump light to the input end of the anti-resonant hollow-core fiber in the input end sealed gas cavity through the input window on the input end sealed gas cavity, and the mid-infrared band 4μm laser generated in the anti-resonant hollow-core fiber is emitted to the output device through the output window on the output end sealed gas cavity; the input end sealed gas cavity and / or the output end sealed gas cavity are provided with an air inlet interface, which is connected to a sealed pipe through the air inlet interface, and a valve is provided on the sealed pipe, and the sealed pipe is connected to an exhaust device and an inflation device to facilitate exhaust / inflation operations.

[0020] Preferably, the 2μm band semiconductor laser pump source system in the 4μm band laser fiber gas laser generating device in the third technical solution of the present invention includes a first pump source, a second pump source, a third pump source, a fourth pump source and a 4×1 pump combiner for coupling the pump lasers output by the four pump sources. The central wavelength of the first pump source is 1971.67nm, corresponding to H 79 Br molecule v 0→ v 2 transition R (2) absorption line, can turn H 79 Br molecule v 0 vibration dynamics J =2 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the central wavelength of the second pump source is 2018.14 nm, corresponding to H 79 Br molecule v 0→ v 2 transition P (4) absorption line, can H 79 Br molecule v 0 vibration dynamics J =4 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the first pump source and the second pump source can convert H 79 Br molecules are pumped to the same upper energy level, utilizing more H 79 Br molecules, the central wavelength of the third pump source is 1971.96 nm, corresponding to H 81 Br molecule v 0→ v 2 transition R (2) absorption line, can turn H 81 Br molecule v 0 vibration dynamics J =2 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the central wavelength of the fourth pump source is 2018.43 nm, corresponding to H 81 Br molecule v 0→ v 2 transition P (4) absorption line, can H 81 Br molecule v 0 vibration dynamics J =4 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the third pump source and the fourth pump source can convert H 81 Br molecules are pumped to the same upper energy level, utilizing more H 81The number of Br molecules is increased by using four pump sources simultaneously, which can effectively utilize HBr molecular isotopes and the number of molecules at different energy levels, effectively improving the conversion efficiency. This solution is a fiber gas laser generator that generates 4μm lasers using multi-wavelength pumping with compact structure, stable performance, narrow linewidth, high conversion efficiency, and good beam quality.

[0021] Preferably, the pump coupling device in the 4μm-band laser fiber gas laser generator in the third technical solution of the present invention includes a first plano-convex lens, a first high-reflective mirror, a second high-reflective mirror, and a second plano-convex lens arranged in sequence, and the second plano-convex lens is optically connected to the input end of the anti-resonant hollow-core fiber. The 2μm-band semiconductor laser pump source system is optically connected to the first plano-convex lens, the first high-reflective mirror, the second high-reflective mirror, and the second plano-convex lens in sequence, and the second plano-convex lens is optically connected to the input end of the anti-resonant hollow-core fiber. The laser output from the 4×1 pump combiner pigtail of the 2μm-band semiconductor laser pump source system is expanded by the first plano-convex lens, then adjusted by the first and second high-reflective mirrors for optical path collimation, and finally focused and coupled into the input end of the anti-resonant hollow-core fiber through the second plano-convex lens.

[0022] Preferably, the output device in the 4μm-band laser fiber gas laser generator of the third technical solution of the present invention is a filtering and collimating device, comprising a 4μm-band bandpass filter and a third plano-convex lens arranged in sequence. The output end of the antiresonant hollow-core fiber is optically connected to the 4μm-band bandpass filter and the third plano-convex lens in sequence. The 4μm-band bandpass filter can filter out residual pump light output, so that only the generated 4μm-band laser light remains after passing through the 4μm-band bandpass filter, and is then output through the third plano-convex lens.

[0023] The principle of the third technical solution of the present invention is that the anti-resonant hollow-core fiber can provide a nearly ideal environment for the interaction between gas and pump light. It can effectively confine the pump light to the micron-scale fiber core, greatly improving the pump intensity and effective action distance. In addition, it combines the respective advantages of gas lasers and fiber lasers, and designs the transmission loss spectrum of the anti-resonant hollow-core fiber so that the pump band and the generated laser band have lower transmission loss, thus achieving effective mid-infrared laser output. 79 Br and H 81The two isotopes of Br have roughly the same ratio of 50.5% and 49.5% respectively. The mismatch between the same energy levels of the isotopes is about 50GHz. HBr is a diatomic molecule with only one vibrational state. The rotation of the HBr molecule in each vibrational state causes a series of rotational states. Pump sources with different wavelengths can utilize the two HBr molecular isotopes and HBr molecules with different lower energy level rotational states, pump them to the same upper energy level rotational state, and then transition to produce the corresponding 4μm band laser, thereby improving the conversion efficiency. Specifically, when the HBr molecule is irradiated by R( i ) absorption line pump, which v 0 vibration ground state J = i The rotational state transitions to the upper energy level v 2. Vibration dynamics J = i +1 rotation state, when the HBr molecule is P ( i+2 ) absorption line pump, which v 0 vibration ground state J = i+2 The rotation state also transitions to the upper energy level v 2. Vibration dynamics J = i +1 rotation state. Then according to the transition selection law Δ J = ±1(Δ J = +1 corresponds to R branch, Δ J = -1 corresponds to the P branch), the excited upper energy level v 2 vibrational particles transition to v 1 Vibration dynamics J = i and J = i +2 rotation, respectively launch R ( i ) and P( i +2) Two laser transition lines. Then v 1. The particles in the vibrational state transition back to the vibrational ground state through vibrational relaxation (non-radiative transition) caused by collision.

[0024] The present invention provides a fourth technical solution: a 4μm-band laser fiber gas laser generator. Specifically, it is an all-fiber structure 4μm-band fiber gas laser generator, comprising a 2μm-band semiconductor laser pump source system, an input solid-core fiber, an anti-resonant hollow-core fiber, and an output device. The output end of the 2μm-band semiconductor laser pump source system is connected to the input end of the input solid-core fiber, the output end of the input solid-core fiber is tapered and coupled to the input end of the anti-resonant hollow-core fiber, the anti-resonant hollow-core fiber is filled with a working gas for generating 4μm laser light by intrinsically absorbing 2μm-band pump light and then transitioning. The output end of the anti-resonant hollow-core fiber is connected to the output device, and the output device outputs 4μm laser light in the mid-infrared band. The working gas is HBr, or a mixture of HBr and CO2.

[0025] Preferably, the 2μm band semiconductor laser pump source system in the fourth technical solution of the present invention includes a first pump source, a second pump source, a third pump source, a fourth pump source and a 4×1 pump combiner for coupling the pump lasers output by the four pump sources together. The central wavelength selection principle of the first pump source, the second pump source, the third pump source and the fourth pump source is to make the different isotopes of HBr molecules H 79 Br and H 81 The lower energy level of Br jumps to the same upper energy level through the P branch and the R branch. The corresponding one is H 79 Br and H 81 Br isotope molecules are respectively P ( i ) absorption line and R ( i -2) absorption line, P ( i ) Absorption line pumping can make v 0 vibration ground state J = i The rotational state transitions to the upper energy level v 2. Vibration dynamics J = i -1 rotation dynamics, R ( i -2) Absorption line pumping can make v 0 vibration ground state J = i- The rotational state of 2 transitions to the upper energy level v 2. Vibration dynamics J = i The first pump source, the second pump source, the third pump source and the fourth pump source can pump the lower energy level HBr molecules of different isotopes to the same upper energy level, thereby utilizing more HBr molecules.

[0026] Preferably, the input end of the antiresonant hollow-core fiber in the fourth technical solution of the present invention is sealed in a sealed gas cavity, and the output end of the input solid-core fiber is tapered and coupled to the input end of the antiresonant hollow-core fiber in the sealed gas cavity. The output end of the input solid-core fiber is tapered by heat, causing the core and cladding of the output end to decrease in proportion, ultimately resulting in a tapered end with a conical deformation. The tapered end is then directly coupled into the core region of the input end of the antiresonant hollow-core fiber to achieve a coupled connection with the input end of the antiresonant hollow-core fiber.

[0027] Preferably, the sealed gas cavity in the fourth technical solution of the present invention is provided with an air inlet interface, which is connected to a sealed pipe via the air inlet interface, the sealed pipe is provided with a valve, and the sealed pipe is connected to an air extraction device and an air filling device. Through the air extraction device and the air filling device and the corresponding valves, the sealed gas cavity can be evacuated / inflated. Furthermore, the sealed gas cavity can also be connected to a monitoring component for air pressure monitoring via the sealed pipe and the valve on the sealed pipe, thereby realizing real-time monitoring of the air pressure in the sealed gas cavity and the anti-resonance hollow-core optical fiber.

[0028] Preferably, an isolator is fused onto the input solid-core optical fiber in the fourth technical solution of the present invention to prevent the pump light from returning to the pump source. The isolator can effectively prevent the pump light from transmitting in the reverse direction and protect the pump source.

[0029] Preferably, the output device in the fourth technical solution of the present invention is an output fiber end cap, the antiresonant hollow-core fiber being fused to the output fiber end cap, and the output fiber end cap being made of a crystal that is transparent to mid-infrared light. Alternatively, the output device in the second technical solution of the present invention may be an output solid-core fiber, the input and output ends of the antiresonant hollow-core fiber being sealed in an input-end sealed gas cavity and an output-end sealed gas cavity, respectively, the input end of the output solid-core fiber being tapered and then coupled to the output end of the antiresonant hollow-core fiber in the output-end sealed gas cavity.

[0030] Preferably, the anti-resonant hollow-core optical fiber in the fourth technical solution of the present invention has low transmission loss in both the 1.5 μm pump band and the generated 3 μm laser band, specifically, the transmission loss is less than 0.15 dB / m.

[0031] The principle of the fourth technical solution of the present invention is that the antiresonant hollow-core fiber can provide a nearly ideal environment for the interaction between gas and pump light. It can effectively confine the pump light to the micron-scale fiber core, greatly improving the pump intensity and effective action distance. In addition, it combines the respective advantages of gas lasers and fiber lasers, and designs the transmission loss spectrum of the antiresonant hollow-core fiber so that the pump band and the generated laser band have low transmission loss, achieving effective mid-infrared laser output. When HBr gas absorbs the 1.5μm band pump light, the ground state HBr molecules will transition to the upper energy level of the laser, forming a population inversion. According to the selection rule, they will transition to the lower energy level, and simultaneously generate two 4μm band spectral lines. Pump sources of different wavelengths can utilize HBr molecules in different lower energy level rotation states, pumping them to the same upper energy level rotation state, and then transition to produce corresponding 4μm band lasers, improving conversion efficiency.

[0032] The beneficial effects of the present invention are as follows:

[0033] (1) The present invention improves the utilization rate of HBr molecules;

[0034] (2) The present invention utilizes anti-resonant hollow-core fiber to effectively confine the pump light in a micron-scale fiber core. Compared with the traditional gas cavity, it greatly improves the pump intensity and effective action distance, enhances the interaction intensity between the pump light and the gain gas, and at the same time, utilizes the specially designed anti-resonant hollow-core fiber with a transmission loss spectrum to achieve low transmission loss for the pump wavelength and the generated laser wavelength.

[0035] (3) The present invention combines the advantages of gas lasers, such as high output power, high damage threshold, and high competitive nonlinear effect threshold, with the advantages of fiber lasers, such as compact structure, stable performance, good beam quality, and high conversion efficiency. Compared with existing mid-infrared laser technology, the present invention has greater potential advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0037] Figure 1 This is a schematic structural diagram of Example 1;

[0038] Figure 2 This is a schematic structural diagram of Example 2;

[0039] Figure 3 This is a schematic structural diagram of Example 3;

[0040] Description of the numbers in the figure:

[0041] 1. First pump source; 2. Second pump source; 3. 2×1 pump combiner; 4. First isolator; 5. First input solid-core fiber; 6. Input Bragg grating; 7. First fusion splice; 8. Antiresonant hollow-core fiber; 9. Second fusion splice; 10. Output solid-core fiber; 11. Feedback grating; 12. Output Bragg grating; 13. Third pump source; 14. Fourth pump source; 15. Fifth pump source; 16. Sixth pump source; 17. First 4×1 pump combiner; 18. First plano-convex lens; 19. First high-reflection mirror; 20. Second high-reflection mirror; 21. Second plano-convex lens; 22. Input window; 23. Output window Input sealed gas cavity; 24, first sealed pipe; 25, first pumping device; 26, first filling device; 27, output sealed gas cavity; 28, output window; 29, 4μm bandpass filter; 30, third plano-convex lens; 31, seventh pump source; 32, eighth pump source; 33, ninth pump source; 34, tenth pump source; 35, second 4×1 pump combiner; 36, second isolator; 37, second input solid-core optical fiber; 38, sealed gas cavity; 39, input tapered end; 40, second sealed pipe; 41, second pumping device; 42, second filling device; 43, output optical fiber end cap. DETAILED DESCRIPTION

[0042] In order to make the technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Embodiment 1:

[0044] like Figure 1 As shown, the 4μm-band laser fiber gas laser generating device of this embodiment includes a first pump source 1, a second pump source 2, a 2×1 pump combiner 3, a first isolator 4, a first input solid core fiber 5, an input Bragg grating 6, a first fusion point 7, an anti-resonant hollow core fiber 8, a second fusion point 9, an output solid core fiber 10, a feedback grating 11, and an output Bragg grating 12.

[0045] The first pump source 1, the second pump source 2 and the 2×1 pump combiner 3 constitute a 2μm band semiconductor laser pump source system. The first pump source 1 and the second pump source 2 are connected to the two input ends of the 2×1 pump combiner 3 respectively. The 2×1 pump combiner 3 couples the pump lasers emitted by the two pump sources together and outputs them. The central wavelength of the first pump source is 1971.67nm, corresponding to the HBr molecule v 0→ v2 transition R (2) absorption line, the central wavelength of the second pump source is 2018.14nm, corresponding to the HBr molecule v 0→ v 2 transition P (4) absorption line.

[0046] The transmission path of the output pump light of the 2μm-band semiconductor laser pump source system is sequentially provided with a first isolator 4 for preventing reverse-propagating pump light from returning to the pump source, a first input solid-core fiber 5, an input Bragg grating 6, a first fusion point 7, an antiresonant hollow-core fiber 8, a second fusion point 9, an output solid-core fiber 10, a feedback grating 11, and an output Bragg grating 12. The input end of the first input solid-core fiber 5 is fused to the output pigtail of the 2×1 pump combiner 3. The isolator 4 is fused to the first input solid-core fiber 5. The input Bragg grating 6 is inscribed on the first input solid-core fiber 5 between the first isolator 4 for preventing reverse-propagating pump light from returning to the 2μm-band semiconductor laser pump source system and the antiresonant hollow-core fiber 8. The peak reflectivity of the input Bragg grating is greater than 95%. The output end of the first input solid-core fiber 5 is low-loss fused to the input end of the antiresonant hollow-core fiber 8 via a first fusion splice 7. The output end of the antiresonant hollow-core fiber 8 is then fused to the output solid-core fiber 10 via a second fusion splice 9. The output solid-core fiber 10 is sequentially inscribed with a feedback grating 11 that highly reflects 2μm-band pump light and an output Bragg grating 12 that partially reflects 4μm laser light in the mid-infrared band. The feedback grating 11 has a reflectivity greater than 95% for 2μm-band pump light, and the output Bragg grating 12 has a transmittance of 10% to 90% for the 4μm mid-infrared band.

[0047] The antiresonant hollow-core fiber 8 is filled with HBr gas, which is used to generate 4μm laser light by intrinsically absorbing the 2μm pump light and then transitioning to generate 4μm laser light. The antiresonant hollow-core fiber 8 has a specially designed transmission loss spectrum and exhibits low transmission loss (<0.15dB / m) in both the 2μm pump band and the generated 4μm laser band.

[0048] This embodiment is a compact, narrow-linewidth, high-quality fiber gas laser. It utilizes the intrinsic absorption transitions of the HBr working gas to extend the near-infrared laser wavelength of the pump light output further into the mid-infrared direction. During operation, the pump laser light output by the first pump source 1 and the second pump source 2 in the near-infrared 2μm band enters the first input solid-core fiber 5 through a 2×1 pump combiner. It then passes through the input Bragg grating 6 and the first fusion point 7 where the first input solid-core fiber 5 is low-loss fused with the antiresonant hollow-core fiber 8. Finally, it enters the antiresonant hollow-core fiber 8 filled with HBr working gas. The pump light interacts with the HBr gas in the fiber core, generating intrinsic absorption transitions to produce 4μm mid-infrared laser light. The pump light enters the output solid core fiber 10 through the second fusion splice point 9 where the antiresonant hollow core fiber 8 and the output solid core fiber 10 are fused at a low loss. The feedback grating 11 inscribed on the output solid core fiber 10 will reflect the residual pump light back into the antiresonant hollow core fiber 8 for further use to lower the pump threshold. The generated 4μm mid-infrared band laser resonates under the multiple reflections of the output Bragg grating 12 inscribed on the output solid core fiber 10 and the input Bragg grating 6, and a portion of the generated 4μm mid-infrared band laser is coupled out.

[0049] In this embodiment, the anti-resonant hollow-core fiber 8 uses a negative curvature anti-resonant hollow-core fiber 8 with a specially designed transmission loss spectrum. It has a hollow-core structure on the micron scale. Compared with a traditional gas cavity, the anti-resonant hollow-core fiber 8 confines the pump light to an area of ​​tens of microns in the fiber core, thereby increasing the pump intensity by 3 to 5 orders of magnitude and the effective action distance by 1 to 2 orders of magnitude. Compared with rare-earth ion-doped fiber lasers, the gain medium selection of gas lasers based on hollow-core fibers is much more flexible. Not only is the variety richer, but it is also easy to replace. More laser wavelengths can be achieved as needed, and it is designed to have multiple transmission bands in the near-infrared and mid-infrared. Its transmission loss spectrum is based on the anti-resonant optical waveguide model, that is, the position and loss of the transmission band can be controlled by parameters such as the thickness of the fiber cladding capillary wall and the fiber core size, so that the pump band and the generated laser band have lower transmission loss.

[0050] In this embodiment, the 2μm band semiconductor laser pump source system includes a first pump source, a second pump source, and a 2×1 pump combiner that couples the two pump lasers together. HBr is a diatomic molecule with only one vibrational state. The rotation of the HBr molecule in each vibrational state causes a series of rotational states. Pump sources of different wavelengths can utilize HBr molecules with different lower energy level rotational states, pump them to the same upper energy level rotational state, and then transition to generate corresponding 4μm band lasers, thereby improving conversion efficiency. Specifically, when the HBr molecule is pumped by R( i ) absorption line pump, which v 0 vibration ground state J = iThe rotational state transitions to the upper energy level v 2. Vibration dynamics J = i +1 rotation state, when the HBr molecule is P ( i+2 ) absorption line pump, which v 0 vibration ground state J = i+ 2 The rotation state also transitions to the upper energy level v 2. Vibration dynamics J = i +1 rotation state. Then according to the transition selection law Δ J = ±1(Δ J = +1 corresponds to R branch, Δ J = -1 corresponds to the P branch), the excited upper energy level v 2 vibrational particles transition to v 1 Vibration dynamics J = i and J = i +2 rotation, respectively launch R ( i ) and P( i +2) Two laser transition lines. Then v The particle in the vibrational state transitions back to the vibrational ground state through vibrational relaxation (non-radiative transition) caused by collision. The central wavelength of the first pump source is 1971.67nm, corresponding to the HBr molecule v 0→ v 2 transition R (2) absorption line, can make HBr molecules v 0 vibration dynamics J =2 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the central wavelength of the second pump source is 2018.14 nm, corresponding to the HBr molecule v 0→ v 2 transition P (4) absorption line, can make HBr molecules v 0 vibration dynamics J =4 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the first pump source and the second pump source can pump HBr molecules of different lower energy levels to the same upper energy level, utilizing more HBr molecules.

[0051] This embodiment achieves a compact all-fiber structure by fusing a solid-core fiber with an antiresonant hollow-core fiber. Bragg gratings are added at both ends of the antiresonant hollow-core fiber to form a resonant cavity, resolving the high pump threshold issue associated with continuous laser output in a single-pass structure. This allows for 4μm continuous laser output at relatively low pump power levels. Furthermore, compared to spatially coupled hollow-core fiber gas laser systems, this system is more stable, portable, and has a wider range of applications. This embodiment achieves 4μm laser output by generating intrinsic absorption transitions between a 2μm-band pump laser and HBr gas filled in the antiresonant hollow-core fiber. By utilizing two pump sources of different wavelengths, the number of HBr molecules in different lower energy levels is utilized, thereby improving HBr molecule utilization.

[0052] Example 2:

[0053] like Figure 2 As shown, the fiber gas laser generating device for generating 4 μm laser by multi-wavelength pumping in this embodiment includes a third pump source 13, a fourth pump source 14, a fifth pump source 15, a sixth pump source 16, a 4×1 pump combiner 17, a first plano-convex lens 18, a first high-reflection mirror 19, a second high-reflection mirror 20, a second plano-convex lens 21, an input window 22, an input-end sealed gas cavity 23, a first sealed pipe 24, a first pumping device 25, a first filling device 26, an anti-resonant hollow-core fiber 8, an output-end sealed gas cavity 27, an output window 28, a 4 μm band-pass filter 29, and a third plano-convex lens 30.

[0054] The third pump source 13, the fourth pump source 14, the fifth pump source 15, the sixth pump source 16 and the first 4×1 pump combiner 17 constitute a 2μm band semiconductor laser pump source system. The third pump source 13, the fourth pump source 14, the fifth pump source 15 and the sixth pump source 16 are respectively connected to the four input ends of the first 4×1 pump combiner 17. The first 4×1 pump combiner 17 couples the pump lasers emitted by the four pump sources together and outputs them. The central wavelength of the first pump source is 1971.67nm, corresponding to H 79 Br molecule v 0→ v 2 transition R (2) absorption line, the central wavelength of the second pump source is 2018.14nm, corresponding to H 79 Br molecule v 0→ v 2 transition P (4) absorption line, the central wavelength of the third pump source is 1971.96nm, corresponding to H 81 Br molecule v 0→ v 2 transition R (2) absorption line, the central wavelength of the fourth pump source is 2018.43nm, corresponding to H 81 Br molecule v0→ v 2 transition P (4) absorption line.

[0055] A first plano-convex lens 18, a first highly reflective mirror 19, a second highly reflective mirror 20, and a second plano-convex lens 21 form a pump coupling device for coupling the pump laser into the antiresonant hollow-core fiber. The pump laser output from the first 4×1 pump combiner 17 in the 2μm-band semiconductor laser pump source system sequentially passes through the first plano-convex lens 18, the first highly reflective mirror 19, the second highly reflective mirror 20, and the second plano-convex lens 21. The pump coupling device is adjusted by first coarse adjustment and then fine adjustment, so that the pump laser passing through the second plano-convex lens 21 is coupled into the input end of the antiresonant hollow-core fiber 8 with high coupling efficiency.

[0056] The input and output ends of the antiresonant hollow-core fiber 8 are sealed in an input sealed gas chamber 23 and an output sealed gas chamber 27, respectively. The input sealed gas chamber 23 and the output sealed gas chamber 27 are each equipped with an input window 22 and an output window 28, respectively, which allow light to pass through. For example, the input sealed gas chamber 23 and the output sealed gas chamber 27 may employ light-permeable sapphire windows. Both the input sealed gas chamber 23 and the output sealed gas chamber 27 are provided with an air inlet interface, which is connected to a first sealed conduit 24. The first sealed conduit 24 is provided with a valve, and the first sealed conduit 24 is connected to a first air extraction device 25 and a first air filling device 26. The input sealed gas chamber 23 and the output sealed gas chamber 27 are connected to the first air extraction device 25 and the first air filling device 26 via the sealed conduit and valve, enabling air extraction and air filling operations. Furthermore, the input sealed gas chamber 23 and the output sealed gas chamber 27 may also be equipped with a monitoring component for air pressure monitoring via the sealed conduit and valve. By connecting the anti-resonant hollow-core fiber 8 filled with working gas in this manner, the working gas can be replaced without removing the connections between the components, and the gas in the anti-resonant hollow-core fiber 8 can be evacuated at the same time, thereby improving working efficiency. The pump coupling device is optically connected to the input end of the anti-resonant hollow-core fiber 8 through the input window 22 on the input-end sealed gas cavity 23, and the output end of the anti-resonant hollow-core fiber 8 is optically connected to the filtering and collimating device through the output window on the output-end sealed gas cavity 27. 4μm band laser light is emitted from the output end of the collimating filter device.

[0057] In this embodiment, the anti-resonant hollow-core fiber 8 is filled with HBr gas, which is used to intrinsically absorb 2μm-band pump light and then transition to generate 4μm laser light. At the same time, the anti-resonant hollow-core fiber 8 confines the 2μm-band pump light in its core, allowing the 2μm-band pump light and the HBr working gas to interact within the core, thereby extending the effective interaction distance between the pump laser and the working gas, thereby increasing the pump intensity and lowering the pump threshold. In addition, after using HBr working gas, due to the characteristics of the atomic and molecular gas transition itself, the generated laser linewidth is very narrow, and no additional linewidth reduction technology is required, resulting in a narrow linewidth of the resulting output laser. The damage threshold of the HBr working gas is much higher than that of the solid-core glass fiber. A high damage threshold means that it can withstand higher power and achieve high-power output.

[0058] The transmission loss spectrum of the antiresonant hollow-core fiber 8 is based on the antiresonant optical waveguide model, that is, the position of the transmission band can be controlled by parameters such as the thickness of the fiber cladding capillary wall and the core diameter. It has low transmission loss (<0.15 dB / m) in both the 2μm pump band and the generated 4μm laser band.

[0059] In this embodiment, HBr molecules exist in nature. 79 Br and H 81 The two isotopes of Br have roughly the same ratio of 50.5% and 49.5% respectively. The mismatch between the same energy levels of the isotopes is about 50 GHz. HBr is a diatomic molecule with only one vibrational state. The rotation of the HBr molecule in each vibrational state causes a series of rotational states. Pump sources with different wavelengths can utilize the two HBr molecular isotopes and HBr molecules with different lower energy level rotational states, pumping them to the same upper energy level rotational state, and then transitioning to produce the corresponding 4μm band laser, thereby improving the conversion efficiency. Specifically, when the HBr molecule is irradiated by R( i ) absorption line pump, which v 0 vibration ground state J = i The rotational state transitions to the upper energy level v 2. Vibration dynamics J = i +1 rotation state, when the HBr molecule is P ( i+2 ) absorption line pump, which v 0 vibration ground state J = i+2 The rotation state also transitions to the upper energy level v 2. Vibration dynamics J = i +1 rotation state. Then according to the transition selection law Δ J = ±1(Δ J = +1 corresponds to R branch, Δ J = -1 corresponds to the P branch), the excited upper energy levelv 2 vibrational particles transition to v 1 Vibration dynamics J = i and J = i +2 rotation, respectively launch R ( i ) and P( i +2) Two laser transition lines. Then v 1 vibration state particles transition back to the vibration ground state through vibration relaxation (non-radiative transition) caused by collision. In this embodiment, the third pump source 13, the fourth pump source 14, the fifth pump source 15, the sixth pump source 16 and the 4×1 pump combiner 17 constitute a 2μm band semiconductor laser pump source system. The central wavelength of the third pump source 13 is 1971.67nm, corresponding to H 79 Br molecule v 0→ v 2 transition R (2) absorption line, can turn H 79 Br molecule v 0 vibration dynamics J =2 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the central wavelength of the fourth pump source 14 is 2018.14 nm, corresponding to H 79 Br molecule v 0→ v 2 transition P (4) absorption line, can H 79 Br molecule v 0 vibration dynamics J =4 turns dynamic pump to v 2. Vibration dynamics J =3 turns, the third pump source 13 and the fourth pump source 14 can convert H 79 Br molecules are pumped to the same upper energy level, utilizing more H 79 Br molecules, the central wavelength of the fifth pump source 15 is 1971.96 nm, corresponding to H 81 Br molecule v 0→ v 2 transition R (2) absorption line, can turn H 81 Br molecule v 0 vibration dynamics J =2 turns dynamic pump to v 2. Vibration dynamics J =3 revolutions, the central wavelength of the sixth pump source 16 is 2018.43 nm, corresponding to H 81 Br molecule v 0→ v 2 transition P (4) absorption line, can H 81 Br molecule v 0 vibration dynamicsJ =4 turns dynamic pump to v 2. Vibration dynamics J =3 turns, the fifth pump source 15 and the sixth pump source 16 can convert H 81 Br molecules are pumped to the same upper energy level, utilizing more H 81 The number of HBr molecules can be increased by using four pump sources simultaneously to effectively utilize the isotopes of HBr molecules and the number of molecules at different energy levels, thereby effectively improving the conversion efficiency.

[0060] In this embodiment, the filtering and collimating device includes a 4μm band bandpass filter 29 and a third plano-convex lens 30. The output end of the anti-resonant hollow-core optical fiber 8 is optically connected to the 4μm band bandpass filter 29 and the third plano-convex lens 30 in sequence. The 2μm band pump laser undergoes intrinsic absorption transition with the HBr working gas filled therein in the core of the anti-resonant hollow-core optical fiber 8, so that part of the 2μm band pump laser is converted into 4μm band laser, and part becomes residual pump laser that does not participate in the conversion. The two together pass through the 4μm band bandpass filter 29 to filter out the residual pump laser. The light emitted from the 4μm band bandpass filter 29 is the 4μm band laser, and is finally output through the third plano-convex lens 30.

[0061] This embodiment achieves 4μm laser output by generating intrinsic absorption transitions between a 2μm-band pump laser and HBr gas filled in an antiresonant hollow-core fiber. Four pump sources with different wavelengths utilize the two isotopes of HBr molecules and the populations of particles in different lower energy level rotation states, thereby improving the utilization rate of HBr molecules.

[0062] Example 3:

[0063] like Figure 3 As shown, an all-fiber structure 4μm band fiber gas laser generating device of this embodiment includes a seventh pump source 31, an eighth pump source 32, a ninth pump source 33, a tenth pump source 34, a second 4×1 pump combiner 35, a second isolator 36 for preventing reversely transmitted pump light from returning to the pump source, a second input solid-core fiber 37, a sealed gas cavity 38, an input tapered end 39, a second sealed pipe 40, a second pumping device 41, a second gas filling device 42 and an output fiber end cap 43.

[0064] The seventh pump source 31, the eighth pump source 32, the ninth pump source 33, the tenth pump source 34 and the second 4×1 pump combiner 35 constitute a 2μm band semiconductor laser pump source system. The seventh pump source 31, the eighth pump source 32, the ninth pump source 33 and the tenth pump source 34 are respectively connected to the four input ends of the second 4×1 pump combiner 35. The 4×1 pump combiner 17 couples the pump lasers emitted by the four pump sources together and outputs them. The central wavelength selection principle of the seventh pump source 31, the eighth pump source 32, the ninth pump source 33 and the tenth pump source 34 is to make the HBr molecules with different isotopes H 79 Br and H 81 The lower energy level of Br transitions to the same upper energy level through the P branch and the R branch. For example, the central wavelength of the seventh pump source 31 is 1971.67 nm, corresponding to H 79 Br molecule v 0→ v 2 transition R (2) absorption line, the central wavelength of the eighth pump source 32 is 2018.14 nm, corresponding to H 79 Br molecule v 0→ v 2 transition P (4) absorption line, the central wavelength of the ninth pump source 33 is 1971.96 nm, corresponding to H 81 Br molecule v 0→ v 2 transition R (2) absorption line, the central wavelength of the tenth pump source 34 is 2018.43 nm, corresponding to H 81 Br molecule v 0→ v 2 transition P (4) absorption line.

[0065] The output end of the 2μm-band semiconductor laser pump source system is fused to the input end of a second input solid-core fiber 37. A second isolator 36 is fused to the second input solid-core fiber 37 to prevent pump light from returning to the pump source system. The output end of the second input solid-core fiber 37 is thermally tapered, causing the core and cladding at the output end to decrease in proportion, ultimately resulting in a tapered input end 39.

[0066] The input end of the anti-resonant hollow-core fiber 8 is sealed in a sealed gas cavity 38. The output end of the second input solid-core fiber 37 is tapered into an input tapered end 39 and then sealed and extended into the sealed gas cavity 38. The input tapered end 39 is directly coupled into the core area of ​​the input end of the anti-resonant hollow-core fiber 8 to achieve a coupled connection with the input end of the anti-resonant hollow-core fiber 8.

[0067] The sealed gas cavity 38 is provided with an air inlet interface, which is connected to a second sealed pipe 40 through the air inlet interface. The second sealed pipe 40 is provided with a valve. The sealed gas cavity 38 is connected to a second air pumping device 41 and a second air filling device 42 through the second sealed pipe 40 and the valve on the second sealed pipe 40. Through the second air pumping device 41 and the second air filling device 42 and the corresponding valves, the sealed gas cavity 38 and the hollow core of the anti-resonant hollow-core optical fiber 8 can be evacuated / filled. In a specific application, the sealed gas cavity 38 in this embodiment can also be configured with a monitoring component for air pressure monitoring through the second sealed pipe 40 and the valve on the second sealed pipe 40. The anti-resonant hollow-core optical fiber 8 filled with working gas connected in this way can realize the replacement of the working gas without removing the connection of each component, and at the same time realize the emptying of the gas in the anti-resonant hollow-core optical fiber 8, thereby improving work efficiency.

[0068] The anti-resonant hollow-core fiber 8 is filled with HBr gas for intrinsically absorbing 2μm-band pump light and then transitioning to generate 4μm laser light through a gas filling device. The output end of the anti-resonant hollow-core fiber 8 is fused with an output fiber end cap 43, and the output fiber end cap 43 outputs 4μm laser light. The output fiber end cap 43 is made of a crystal that can transmit mid-infrared light. It can transmit the generated 4μm-band laser light and filter out the residual 2μm-band pump light, so that the final output is a laser output with a narrow linewidth in the 4μm band. Furthermore, the output fiber end cap 43 can also be replaced with an output solid-core fiber. Similar to the situation in which the output end of the second input solid-core fiber 37 is tapered and then coupled to the input end of the anti-resonant hollow-core fiber 8 in the sealed gas cavity 38, the output end of the anti-resonant hollow-core fiber 8 is sealed in the sealed gas cavity, and the input end of the output solid-core fiber is tapered and then coupled to the output end of the anti-resonant hollow-core fiber 8 in the sealed gas cavity.

[0069] Example 4

[0070] The structure of the 4μm band laser fiber gas laser generator provided in this embodiment is exactly the same as that of embodiment 1. Figure 1 As shown, it includes a first pump source 1, a second pump source 2, a 2×1 pump combiner 3, a first isolator 4, a first input solid core fiber 5, an input Bragg grating 6, a first fusion point 7, an anti-resonant hollow core fiber 8, a second fusion point 9, an output solid core fiber 10, a feedback grating 11 and an output Bragg grating 12.

[0071] The difference from Example 1 is that each pump source uses a 2μm wavelength tunable semiconductor laser pump source, whose wavelength can be tuned in a small range from 1940nm to 2100nm. The working gas filled in the antiresonant hollow-core fiber 8 is replaced by a mixed gas containing both HBr and CO2 instead of a single HBr gas. The HBr and CO2 gases have overlapping absorption bands in the 2μm band. By tuning the center wavelength of the pump source to align with the different absorption lines of HBr and CO2, 4μm band laser output is achieved. Specifically, a wide range of tunable mid-infrared laser output of up to 650nm can be achieved from a tuning range of 3800nm ​​to 4450nm.

[0072] Example 5

[0073] The structure of the 4μm band laser fiber gas laser generator provided in this embodiment is exactly the same as that of embodiment 2. Figure 2 As shown, it includes a third pump source 13, a fourth pump source 14, a fifth pump source 15, a sixth pump source 16, a 4×1 pump combiner 17, a first plano-convex lens 18, a first high-reflection mirror 19, a second high-reflection mirror 20, a second plano-convex lens 21, an input window 22, an input-end sealed gas cavity 23, a first sealed pipe 24, a first pumping device 25, a first filling device 26, an anti-resonant hollow-core optical fiber 8, an output-end sealed gas cavity 27, an output window 28, a 4μm band band-pass filter 29, and a third plano-convex lens 30.

[0074] The difference from Example 2 is that each pump source uses a 2μm wavelength-tunable semiconductor laser pump source, whose wavelength can be tuned in a small range from 1940nm to 210nm. The working gas filled in the antiresonant hollow-core fiber 8 is replaced by a mixed gas containing both HBr and CO2 instead of a single HBr gas. The HBr and CO2 gases have overlapping absorption bands in the 2μm band. By tuning the center wavelength of the pump source to align with the different absorption lines of HBr and CO2, 4μm band laser output is achieved. Specifically, a wide range of tunable mid-infrared laser output of up to 650nm can be achieved from a tuning range of 3800nm ​​to 4450nm.

[0075] Example 6

[0076] The structure of the 4μm band laser fiber gas laser generator provided in this embodiment is exactly the same as that of embodiment 2. Figure 3As shown, it includes a seventh pump source 31, an eighth pump source 32, a ninth pump source 33, a tenth pump source 34, a second 4×1 pump combiner 35, a second isolator 36 for preventing the reversely transmitted pump light from returning to the pump source, a second input solid core optical fiber 37, a sealed gas cavity 38, an input tapered end 39, a second sealed pipe 40, a second pumping device 41, a second filling device 42 and an output optical fiber end cap 43.

[0077] The difference from Example 3 is that each pump source uses a 2μm wavelength tunable semiconductor laser pump source, whose wavelength can be tuned in a small range from 1940nm to 2100nm. The working gas filled in the antiresonant hollow-core fiber 8 is replaced by a single HBr gas with a mixed gas containing both HBr and CO2. The HBr and CO2 gases have overlapping absorption bands in the 2μm band. By tuning the center wavelength of the pump source to align with the different absorption lines of HBr and CO2, 4μm band laser output is achieved. Specifically, a wide range of tunable mid-infrared laser output of up to 650nm can be achieved from a tuning range of 3800nm ​​to 4450nm.

[0078] In summary, although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. 4μm band laser fiber gas laser generating device, characterized in that: The invention comprises a 2μm-band semiconductor laser pump source system, an input solid-core fiber, an anti-resonant hollow-core fiber and an output device. The transmission path of the 2μm-band pump light output by the 2μm-band semiconductor laser pump source system is connected in sequence to the input solid-core fiber, the output device is an output solid-core fiber, the two ends of the input solid-core fiber are fused with the output pigtail of the 2μm-band semiconductor laser pump source system and the input end of the anti-resonant hollow-core fiber respectively, and the other end of the anti-resonant hollow-core fiber is fused with the input end of the output solid-core fiber. The anti-resonant hollow-core fiber is filled with a working gas for generating 4μm laser by intrinsically absorbing the 2μm-band pump light and then transitioning. The output device outputs 4μm laser in the mid-infrared band, wherein the working gas is HBr. The 2μm-band semiconductor laser pump source system comprises a first pump source, a second pump source and a 2×1 pump combiner for coupling the pump lasers emitted by the two pump sources together. The central wavelength of the first pump source is 1971.67 nm, corresponding to HBr molecules v 0→ v 2 transition R (2) absorption line, the central wavelength of the second pump source is 2018.14 nm, corresponding to the HBr molecule v 0→ v 2 transition P (4) absorption line, each pump source adopts a 2μm band wavelength tunable semiconductor laser pump source, whose wavelength can be tuned in the range of 1940 nm to 2100 nm.

2. The 4μm band laser fiber gas laser generator according to claim 1, characterized in that: The transmission loss of the anti-resonant hollow-core optical fiber in the 2 μm pump band and the generated 4 μm laser band is less than 0.15 dB / m.

3. The 4μm band laser fiber gas laser generator according to claim 1, characterized in that: The system also includes an isolator for preventing reversely transmitted pump light from returning to the 2 μm band semiconductor laser pump source system. The isolator is fused onto the input solid core optical fiber.

4. The 4μm band laser fiber gas laser generator according to claim 3, characterized in that: The input solid core optical fiber is engraved with an input Bragg grating that forms a high reflection for 4 μm laser in the mid-infrared band. The input Bragg grating is arranged on the input solid core optical fiber after the isolator, and the peak reflectivity of the input Bragg grating is greater than 95%; The output solid-core optical fiber is sequentially inscribed with a feedback grating that forms a high reflection for 2μm band pump light and an output Bragg grating that partially reflects 4μm laser in the mid-infrared band. The reflectivity of the feedback grating for 2μm band pump light is greater than 95%, and the transmittance of the output Bragg grating for 4μm laser in the mid-infrared band is 10% to 90%. 5.4μm band laser fiber gas laser generating device, characterized in that: The invention comprises a 2μm-band semiconductor laser pump source system, a pump coupling device for coupling the pump laser to the antiresonant hollow-core fiber, an antiresonant hollow-core fiber and an output device; the transmission path of the 2μm-band pump light output by the 2μm-band semiconductor laser pump source system is sequentially connected with the pump coupling device, the antiresonant hollow-core fiber and the output device, the pump coupling device couples the 2μm-band pump light to the antiresonant hollow-core fiber, the antiresonant hollow-core fiber is filled with a working gas for generating a 4μm laser by intrinsically absorbing the 2μm-band pump light and then transitioning, the output device outputs a 4μm laser in the mid-infrared band, wherein the working gas is HBr, the 2μm-band semiconductor laser pump source system comprises a first pump source, a second pump source, a third pump source, a fourth pump source and a 4×1 pump combiner for coupling the pump lasers output by the four pump sources together, the central wavelength of the first pump source is 1971.67 nm, corresponding to HBr. 79 Br molecule v 0→ v 2 transition R (2) absorption line, the central wavelength of the second pump source is 2018.14 nm, corresponding to H 79 Br molecule v 0→ v 2 transition P (4) absorption line, the central wavelength of the third pump source is 1971.96 nm, corresponding to H 81 Br molecule v 0→ v 2 transition R (2) absorption line, the central wavelength of the fourth pump source is 2018.43 nm, corresponding to H 81 Br molecule v 0→ v 2 transition P (4) absorption line, each pump source adopts a 2μm band wavelength tunable semiconductor laser pump source, whose wavelength can be tuned in the range of 1940 nm to 2100 nm.

6. The 4μm band laser fiber gas laser generator according to claim 5, characterized in that: The transmission loss of the anti-resonant hollow-core optical fiber in the 2 μm pump band and the generated 4 μm laser band is less than 0.15 dB / m.

7. The 4μm band laser fiber gas laser generator according to claim 5, characterized in that: The input end and output end of the antiresonant hollow-core fiber are sealed in the input end sealed gas cavity and the output end sealed gas cavity, respectively. The pump coupling device couples the 2 μm band pump light into the antiresonant hollow-core fiber through the input end sealed gas cavity. The mid-infrared band 4 μm laser generated in the antiresonant hollow-core fiber is transmitted to the output device through the output end sealed gas cavity.

8. The 4μm band laser fiber gas laser generator according to claim 7, characterized in that: The input-end sealed gas cavity and the output-end sealed gas cavity are respectively provided with an input window and an output window. The pump coupling device couples 2μm-band pump light to the input end of the anti-resonant hollow-core fiber in the input-end sealed gas cavity through the input window on the input-end sealed gas cavity. The mid-infrared band 4μm laser generated in the anti-resonant hollow-core fiber is emitted to the output device through the output window on the output-end sealed gas cavity. The input-end sealed gas cavity and / or the output-end sealed gas cavity are provided with an air inlet interface, which is connected to a sealed pipe through the air inlet interface. The sealed pipe is provided with a valve, and the sealed pipe is connected to an exhaust device and an inflation device.

9. The 4 μm band laser fiber gas laser generator according to claim 5, 6, 7 or 8, characterized in that: The pump coupling device comprises a first plano-convex lens, a first high-reflection mirror, a second high-reflection mirror and a second plano-convex lens which are arranged in sequence. The second plano-convex lens is optically connected to the input end of the anti-resonance hollow-core optical fiber.

10. The 4μm band laser fiber gas laser generator according to claim 9, characterized in that: The output end of the anti-resonant hollow-core optical fiber is optically connected to the filtering and collimating device through an output window on the output-end sealed gas cavity. The 4μm band laser is emitted from the output end of the filtering and collimating device. The filtering and collimating device includes a 4μm band bandpass filter and a third plano-convex lens arranged in sequence. 11.4μm band laser fiber gas laser generating device, characterized in that: The invention comprises a 2μm-band semiconductor laser pump source system, an input solid-core fiber, an antiresonant hollow-core fiber, and an output device. The output end of the 2μm-band semiconductor laser pump source system is connected to the input end of the input solid-core fiber, the output end of the input solid-core fiber is tapered and coupled into the input end of the antiresonant hollow-core fiber, the antiresonant hollow-core fiber is filled with a working gas for generating 4μm laser by intrinsically absorbing 2μm-band pump light and then transitioning, the output end of the antiresonant hollow-core fiber is connected to the output device, and the output device outputs 4μm laser in the mid-infrared band, wherein the working gas is HBr. The 2μm-band semiconductor laser pump source system comprises a first pump source, a second pump source, a third pump source, a fourth pump source, and a 4×1 pump combiner for coupling the pump lasers output by the four pump sources together; the central wavelength selection principle of the first pump source, the second pump source, the third pump source, and the fourth pump source is to make the HBr molecules with different isotopes H 79 Br and H 81 The lower energy level of Br jumps to the same upper energy level through the P branch and the R branch. The corresponding one is H 79 Br and H 81 Br isotope molecules are respectively P ( i ) absorption line and R ( i -2) absorption line, P ( i ) Absorption line pumping makes v 0 vibration ground state J = i The rotational state transitions to the upper energy level v 2. Vibration dynamics J = i -1 rotation dynamics, R ( i -2) Absorption line pumping v 0 vibration ground state J = i- The rotational state of 2 transitions to the upper energy level v 2. Vibration dynamics J = i -1 rotation state, each pump source adopts a 2μm wavelength tunable semiconductor laser pump source, and its wavelength can be tuned in the range of 1940 nm to 2100 nm.

12. The 4μm band laser fiber gas laser generator according to claim 11, characterized in that: The input end of the anti-resonance hollow core fiber is sealed in a sealed gas cavity, and the output end of the input solid core fiber is tapered and coupled to the input end of the anti-resonance hollow core fiber in the sealed gas cavity.

13. The 4 μm band laser fiber gas laser generator according to claim 12, characterized in that: The sealed gas cavity is provided with an air inlet interface, which is connected to a sealed pipe. A valve is provided on the sealed pipe, and the sealed pipe is connected to an air extraction device and an air charging device.

14. The 4 μm band laser fiber gas laser generator according to claim 13, characterized in that: The sealed gas chamber is connected to a monitoring component for air pressure monitoring via a sealed pipe and a valve on the sealed pipe.

15. The 4 μm-band laser fiber gas laser generator according to any one of claims 11 to 14, characterized in that: An isolator is fused onto the input solid core optical fiber to prevent the pump light from returning to the pump source.

16. The 4 μm band laser fiber gas laser generator according to claim 11, characterized in that: The output device is an output fiber end cap, which is made of a crystal that can transmit mid-infrared light. The anti-resonance hollow core fiber is fused with the output fiber end cap.

17. The 4 μm band laser fiber gas laser generator according to claim 11, characterized in that: The output device is an output solid core optical fiber, the output end of the antiresonant hollow core optical fiber is sealed in the output end sealed gas cavity, and the input end of the output solid core optical fiber is tapered and coupled to the output end of the antiresonant hollow core optical fiber in the output end sealed gas cavity.

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