A high-power mid-infrared hollow-core fiber gas laser

Abstract

The present invention provides a high-power mid-infrared hollow-core fiber gas laser, comprising a hollow-core fiber gas laser and a dichroic mirror; the hollow-core fiber gas laser comprises a first hollow-core fiber gas laser generating a 3.1μm to 3.2μm mid-infrared laser, a second hollow-core fiber gas laser generating a 3.8μm to 4.2μm mid-infrared laser, a third hollow-core fiber gas laser generating a 4.2μm to 4.5μm mid-infrared laser, and a fourth hollow-core fiber gas laser generating a 4.6μm to 5μm mid-infrared laser; the dichroic mirror comprises a first dichroic mirror, a second dichroic mirror, and a third dichroic mirror, which are used to combine and output the lasers transmitted to the dichroic mirror. The present invention combines the lasers output by multiple hollow-core fiber gas lasers by using a plurality of specially made dichroic mirrors, thereby obtaining a mid-infrared high-power laser output covering the entire band of 3.1 to 5μm.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber lasers, and in particular relates to a high-power mid-infrared hollow-core optical fiber gas laser. Background Art

[0002] Mid-infrared lasers have important military applications. The mid-infrared lasers in the prior art include solid-state lasers, semiconductor lasers, gas lasers in traditional gas pools, etc. The beam quality output by solid-state lasers is poor, the output line width is difficult to stabilize, and it is difficult to fine-tune the output wavelength. Semiconductor lasers have the problem of poor output beam quality at high power and the inability to achieve narrow line width output, and the manufacturing process of semiconductor lasers is relatively complicated. Gas lasers in traditional gas pools are bulky and have poor output beam quality.

[0003] Compared with other forms of mid-infrared lasers such as solid-state lasers, semiconductor lasers, and gas lasers in traditional gas pools, mid-infrared fiber lasers have the advantages of compact size, stable structure, good beam quality, and the ability to adapt to complex environments.

[0004] Traditional mid-infrared fiber lasers mostly use soft glass fibers doped with rare earth ions. Soft glass fibers have poor robustness, are easily damaged, and have limited power boost capabilities. In addition, due to the limited number of rare earth ions, the emission spectrum range of each rare earth ion is limited, resulting in a limited output band of the laser. In addition, it is difficult to write gratings on soft glass fibers, so it is difficult for the laser to achieve narrow linewidth output. Summary of the invention

[0005] In view of the defects of the prior art, the present invention proposes a high-power mid-infrared hollow-core fiber gas laser to obtain a mid-infrared high-power laser output covering the entire band of 3.1~5μm.

[0006] In order to achieve the above technical objectives, the specific technical solutions adopted by the present invention are as follows:

[0007] A high-power mid-infrared hollow-core fiber gas laser comprises a hollow-core fiber gas laser and a dichroic mirror;

[0008] The hollow-core fiber gas laser comprises a first hollow-core fiber gas laser generating a 3.1 μm to 3.2 μm mid-infrared laser, a second hollow-core fiber gas laser generating a 3.8 μm to 4.2 μm mid-infrared laser, a third hollow-core fiber gas laser generating a 4.2 μm to 4.5 μm mid-infrared laser, and a fourth hollow-core fiber gas laser generating a 4.6 μm to 5 μm mid-infrared laser.

[0009] The dichroic mirrors include a first dichroic mirror, a second dichroic mirror, and a third dichroic mirror, and are used to combine and output the laser beams transmitted to the dichroic mirrors;

[0010] The first dichroic mirror combines and outputs the laser output from the first hollow-core fiber gas laser with the laser output from the second hollow-core fiber gas laser, the second dichroic mirror combines and outputs the laser output from the first dichroic mirror with the laser output from the third hollow-core fiber gas laser, and the third dichroic mirror combines and outputs the laser output from the second dichroic mirror with the laser output from the fourth hollow-core fiber gas laser.

[0011] Further, the hollow-core fiber gas laser comprises a pump light source, a pump collimating lens, a focusing lens, an input sealed gas cavity, an output sealed gas cavity, a vacuum pumping and gas filling system, a hollow-core fiber, and a laser collimating lens;

[0012] The pump laser output by the pump light source is collimated by the pump collimator lens and then injected into the focusing lens. The focusing lens focuses the pump laser and then couples it into the hollow-core optical fiber. The input end and the output end of the hollow-core optical fiber are sealed in the input sealed gas cavity and the output sealed gas cavity respectively. The vacuum pumping and gas filling system is connected to the input sealed gas cavity or the output sealed gas cavity. The vacuum pumping and gas filling system is used to vacuum the hollow-core optical fiber and fill the hollow-core optical fiber with a gain gas with a certain air pressure. After the pump laser and the gain gas interact with each other in the hollow-core optical fiber, the pump laser with a target output wavelength range is output. The pump laser with a target output wavelength range output by the hollow-core optical fiber is collimated by the laser collimator lens and then emitted.

[0013] Furthermore, the first dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 3.2μm band and high reflectance in the 3.8μm to 4.2μm band; the second dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 4.2μm band and high reflectance in the 4.2μm to 4.5μm band; the third dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 4.5μm band and high reflectance in the 4.6μm to 5μm band.

[0014] Furthermore, the pump light source is a narrow linewidth pump light source with a central wavelength corresponding to the gain gas absorption line and a linewidth less than 300 MHz.

[0015] Furthermore, the input sealed gas cavity and the output sealed gas cavity are respectively provided with an input window plate and an output window plate; the input window plate has high transmittance to the pump laser band; the output window plate has high transmittance to the output laser band.

[0016] Furthermore, the vacuuming and charging system includes a vacuum pump, a gas cylinder, a pressure regulating valve, and a barometer, which are used to adjust and monitor the pressure of the gain gas in the hollow-core optical fiber.

[0017] Furthermore, the laser collimating lens is a positive lens which has high transmittance to mid-infrared laser and can collimate the laser beam, so that the spot diameter of the collimated beam is greater than 1 mm.

[0018] Furthermore, after the lasers output by the first hollow-core fiber gas laser, the second hollow-core fiber gas laser, the third hollow-core fiber gas laser, and the fourth hollow-core fiber gas laser are collimated by a laser collimating lens, the light spots of the light beams have the same spot diameter.

[0019] Furthermore, the hollow core optical fiber can transmit the pump laser band and the output laser band with low loss.

[0020] Furthermore, the focusing lens is a positive lens which has high transmittance to the pump laser wavelength band and can focus the pump laser, and is used to match the pump laser with the mode of the hollow core optical fiber.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The present invention provides a high-power mid-infrared hollow-core fiber gas laser. The present invention uses a plurality of specially made dichroic mirrors to spectrally combine the lasers output by a plurality of hollow-core fiber gas lasers, thereby obtaining a mid-infrared high-power laser output covering the entire band of 3.1 to 5 μm. In addition, the present invention uses a hollow-core fiber gas laser as a light source to obtain a narrow-linewidth mid-infrared output laser. The present invention also controls the spot diameters of the lasers output by different hollow-core fiber gas lasers to be consistent, so as to ensure that the beam combination can be successful.

[0023] The present invention adopts an optical fiber structure, and the light is bound in a hollow core optical fiber, which is not easily affected by the external environment. Therefore, the present invention has the advantages of simple and compact structure, high stability, high light beam quality, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0025] Figure 1 A schematic diagram of the structure of a high-power mid-infrared hollow-core fiber gas laser provided by an embodiment;

[0026] Figure 2 A schematic diagram of the structure of a hollow-core fiber gas laser provided by an embodiment;

[0027] Figure 3An emission spectrum diagram of a high-power mid-infrared hollow-core fiber gas laser provided in an embodiment;

[0028] Figure 4 A schematic diagram of the energy level of stimulated radiation transition of acetylene gas molecules provided by an embodiment;

[0029] Figure 5 A schematic diagram of the energy level of carbon dioxide gas molecules stimulated by radiation transition provided by an embodiment;

[0030] Figure 6 A schematic diagram of the energy level of stimulated radiation transition of hydrogen bromide and carbon monoxide gas molecules provided in an embodiment;

[0031] Figure 7 The output power diagram of a hollow-core fiber gas laser with acetylene as the gain gas under different gas pressures provided in an embodiment when the pump light source is 50W;

[0032] Figure 8 A graph showing the relationship between the output power of a hollow-core fiber gas laser with hydrogen bromide as the gain gas and the power of a pump light source at different gas pressures provided by an embodiment;

[0033] Fig. 9 The output power diagram of a hollow-core fiber gas laser with carbon monoxide as the gain gas at different gas pressures when the pump light source provided in an embodiment is 2W;

[0034] Fig.10 A graph showing the relationship between the output power of a hollow-core fiber gas laser with carbon dioxide as the gain gas and the power of a pump light source at different gas pressures provided by an embodiment.

[0035] Figure annotation:

[0036] 1. The first hollow-core fiber gas laser; 2. The second hollow-core fiber gas laser; 3. The first dichroic mirror; 4. The third hollow-core fiber gas laser; 5. The second dichroic mirror; 6. The fourth hollow-core fiber gas laser; 7. The third dichroic mirror; 8. The pump light source; 9. The pump collimating lens; 10. The focusing lens; 11. The input window; 12. The input sealed gas cavity; 13. The vacuum pumping and inflation system; 14. The hollow-core fiber; 15. The output sealed gas cavity; 16. The output window; 17. The laser collimating lens. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Reference Figure 1 , In one embodiment, there is provided a high-power mid-infrared hollow-core fiber gas laser, comprising a hollow-core fiber gas laser and a dichroic mirror;

[0039] The hollow-core fiber gas laser comprises a first hollow-core fiber gas laser 1 generating a 3.1 μm to 3.2 μm mid-infrared laser, a second hollow-core fiber gas laser 2 generating a 3.8 μm to 4.2 μm mid-infrared laser, a third hollow-core fiber gas laser 4 generating a 4.2 μm to 4.5 μm mid-infrared laser, and a fourth hollow-core fiber gas laser 6 generating a 4.6 μm to 5 μm mid-infrared laser.

[0040] The dichroic mirror comprises a first dichroic mirror 3, a second dichroic mirror 5, and a third dichroic mirror 7, which are used to combine and output the laser beams transmitted to the dichroic mirrors;

[0041] The first dichroic mirror 3 combines the laser output from the first hollow-core fiber gas laser 1 with the laser output from the second hollow-core fiber gas laser 2 and outputs them, the second dichroic mirror 5 combines the laser output from the first dichroic mirror 3 with the laser output from the third hollow-core fiber gas laser 4 and outputs them, and the third dichroic mirror 7 combines the laser output from the second dichroic mirror 5 with the laser output from the fourth hollow-core fiber gas laser 6 and outputs them.

[0042] The first dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 3.2μm band and high reflectance in the 3.8μm to 4.2μm band; the second dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 4.2μm band and high reflectance in the 4.2μm to 4.5μm band; the third dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 4.5μm band and high reflectance in the 4.6μm to 5μm band.

[0043] Reference Figure 2 The hollow-core fiber gas laser comprises a pump light source 8, a pump collimating lens 9, a focusing lens 10, an input sealed gas chamber 12, an output sealed gas chamber 15, a vacuum pumping and gas filling system 13, a hollow-core fiber 14, and a laser collimating lens 17;

[0044] The pump laser output by the pump light source 8 is collimated by the pump collimating lens 9 and then injected into the focusing lens 10. The focusing lens 10 focuses the pump laser and couples it into the hollow-core optical fiber 14. The input end and the output end of the hollow-core optical fiber 14 are respectively sealed in the input sealed gas cavity 12 and the output sealed gas cavity 15. The vacuum pumping and gas filling system 13 is connected to the input sealed gas cavity 12 or the output sealed gas cavity 15. The vacuum pumping and gas filling system 13 is used to vacuum the hollow-core optical fiber 14 and fill the hollow-core optical fiber 14 with a gain gas with a certain air pressure. After the pump laser and the gain gas interact with each other in the hollow-core optical fiber 14, a pump laser with a target output wavelength range is output. The pump laser with the target output wavelength range output by the hollow-core optical fiber 14 is collimated by the laser collimating lens 17 and then emitted.

[0045] The pump light source 8 is a narrow linewidth pump light source with a central wavelength corresponding to the gain gas absorption line and a linewidth less than 300 MHz.

[0046] The input sealed gas cavity 12 and the output sealed gas cavity 15 are respectively provided with an input window plate 11 and an output window plate 16; the input window plate 11 has high transmittance to the pump laser band; the output window plate 16 has high transmittance to the output laser band.

[0047] The vacuuming and gas filling system 13 includes a vacuum pump, a gas cylinder, a pressure regulating valve, and a barometer, and is used to adjust and monitor the pressure of the gain gas in the hollow core optical fiber.

[0048] The laser collimating lens 17 is a positive lens that has high transmittance to mid-infrared laser and can collimate the laser beam, so that the spot diameter of the collimated beam is greater than 1 mm.

[0049] After the lasers output by the first hollow-core fiber gas laser 1, the second hollow-core fiber gas laser 2, the third hollow-core fiber gas laser 4, and the fourth hollow-core fiber gas laser 6 are collimated by a laser collimating lens, the light spots of the light beams have the same spot diameter.

[0050] The hollow core optical fiber 14 can transmit the pump laser band and the output laser band with low loss.

[0051] The focusing lens 10 is a positive lens having high transmittance to the pump laser wavelength band and capable of focusing the pump laser, and is used to achieve mode matching between the pump laser and the hollow core optical fiber 14 .

[0052] In one embodiment, the first hollow-core fiber gas laser is a hollow-core fiber acetylene gas laser filled with acetylene as a gain gas, and the pump light source is a narrow-linewidth pump light source in the 1.51 μm to 1.54 μm band that matches the absorption line of acetylene gas; Figure 4As shown, the pump light source in the 1.51μm to 1.54μm band pumps the acetylene gas molecules from the ground state to the excited state by aligning with the P-branch or R-branch absorption line of the acetylene molecules. The excited acetylene gas molecules transition to the lower laser energy level through stimulated radiation, and output mid-infrared lasers in the range of 3.1μm to 3.2μm.

[0053] The second hollow-core fiber gas laser is a hollow-core fiber hydrogen bromide gas laser filled with hydrogen bromide as a gain gas, and the pump light source is a narrow-linewidth pump light source in the 1.94 μm to 2.11 μm band that matches the absorption line of hydrogen bromide gas; Figure 6 As shown, the pump light source in the 1.94μm to 2.11μm band pumps the hydrogen bromide gas molecules from the ground state to the excited state by aligning with the P-branch or R-branch absorption line of the hydrogen bromide molecules. The excited hydrogen bromide gas molecules transition to the lower laser energy level through stimulated radiation, and output mid-infrared lasers in the range of 3.8μm to 4.2μm.

[0054] The third hollow-core fiber gas laser is a hollow-core fiber carbon dioxide gas laser filled with carbon dioxide as a gain gas, and the pump light source is a narrow-linewidth pump light source in the 1.99 μm to 2.03 μm band that matches the carbon dioxide gas absorption line; Figure 5 As shown, the pump light source in the 1.99μm to 2.03μm band pumps the carbon dioxide gas molecules from the ground state to the excited state by aligning with the P-branch or R-branch absorption line of the carbon dioxide molecules. The excited carbon dioxide gas molecules transition to the lower laser energy level through stimulated radiation, and output mid-infrared lasers in the range of 4.2μm to 4.5μm.

[0055] The fourth hollow-core fiber gas laser is a hollow-core fiber carbon monoxide gas laser filled with carbon monoxide as a gain gas, and the pump light source is a narrow-linewidth pump light source in the 2.3 μm to 2.4 μm band that matches the carbon monoxide gas absorption line; Figure 6 As shown, the pump light source in the 2.3μm to 2.4μm band pumps the carbon monoxide gas molecules from the ground state to the excited state by aligning with the P-branch or R-branch absorption line of the carbon monoxide molecules. The excited carbon monoxide gas molecules transition to the lower laser energy level through stimulated radiation, and output mid-infrared lasers in the range of 4.6μm to 5μm.

[0056] For the four gain gases of acetylene, hydrogen bromide, carbon dioxide, and carbon monoxide, the appropriate gas pressure filled with the gain gas is related to the power of the pump light source. When the power of the pump light source is less than 30W, the appropriate gas pressure of the four gain gases is between 2 and 7mbar; when the power of the pump light source is 30W to 70W, the appropriate gas pressure of the four gain gases is between 5 and 10mbar; when the power of the pump light source is 70W to 150W, the appropriate gas pressure of the four gain gases is between 7 and 15mbar. The present application controls the power of the pump light source and the gas pressure of the gain gas in each hollow-core fiber gas laser to achieve regulation of the output power of each hollow-core fiber gas laser, thereby achieving regulation of the output power of the high-power mid-infrared hollow-core fiber gas laser, so that the high-power mid-infrared hollow-core fiber gas laser outputs a mid-infrared laser of the required power.

[0057] Reference Figure 7 In one embodiment, when the pump light source is 50W, acetylene gain gas is filled when the gas pressure is 0.5mbar. The output power of the hollow-core gas laser filled with acetylene gain gas increases with the increase of gas pressure, and the increasing trend is relatively stable. The output power reaches the maximum when the gas pressure is 5.3mbar, and then the output power decreases with the continued increase of gas pressure, showing a rapid downward trend between 5.3mbar-6mbar, and the downward trend begins to slow down between 6mbar-7.3mbar.

[0058] Reference Figure 8 In one embodiment, for a hollow-core fiber gas laser whose pump light source output power is 0.3W-25W and whose gain gas is hydrogen bromide and whose gas pressure is between 0.8mbar-6.3mbar, the output power of the laser increases with the increase of the pump light source power. When the pump light source output power is constant, the gas pressure is between 0.8mbar-2.5mbar, and the output power of the laser increases with the increase of the gas pressure; when the gas pressure is between 2.5mbar-3.7mbar, the output power of the laser is optimal; when the gas pressure is greater than 3.7mbar, the output power of the laser decreases with the increase of the gas pressure.

[0059] Reference Fig. 9In one embodiment, when the pump light source is 2W, carbon monoxide gain gas is filled when the gas pressure is 0.5mbar. The output power of the hollow core gas laser filled with carbon monoxide gain gas generally increases with the increase of gas pressure, and shows a rapid increase trend between 0.5mbar-0.8mbar, a slight decrease between 0.8mbar-1mbar, and a steady increase trend between 1mbar-2mbar. The output power reaches a maximum at 2mbar, and then decreases with the continued increase of gas pressure, and shows a rapid decrease trend between 2mbar-5mbar. At 5mbar, the output power drops to 0.8W.

[0060] Reference Fig.10 In one embodiment, for a hollow-core fiber gas laser with a pump light source output power of 3W-70W and a gain gas of carbon dioxide at an air pressure between 1.2mbar-6.2mbar, the output power of the laser increases with the increase of the pump light source power. When the pump light source output power is constant, the air pressure is between 1.2mbar-5.1mbar, and the output power of the laser increases with the increase of the air pressure; when the air pressure is greater than 5.1mbar, the output power of the laser decreases with the increase of the air pressure. When the air pressure is 5.1mbar, the output power of the laser increases steadily with the increase of the pump light source output power, and the growth trend is faster than when the air pressure is at other values.

[0061] The examples do not exhaustively display all data, and only representative data are selected for specific description.

[0062] The 3.1μm to 3.2μm band laser generated by the hollow-core fiber acetylene gas laser is transmitted after passing through the first dichroic mirror 3, and the 3.8μm to 4.2μm band laser generated by the hollow-core fiber hydrogen bromide gas laser is reflected after passing through the first dichroic mirror 3. The transmitted light beam and the reflected light beam are spectrally combined by the first dichroic mirror 3 to form a 3.1μm to 4.2μm band laser and output; the laser output by the first dichroic mirror 3 is transmitted after passing through the second dichroic mirror 5, and the 4.2μm to 4.2μm band laser generated by the hollow-core fiber carbon dioxide gas laser is reflected after passing through the first dichroic mirror 3. μm to 4.5μm band laser passes through the second dichroic mirror 5 and is reflected, and the transmitted light beam and the reflected light beam are spectrally combined by the second dichroic mirror 5 to form a 3.1μm to 4.5μm band laser and output; the laser output by the second dichroic mirror 5 passes through the third dichroic mirror 7 and is transmitted, and the 4.6μm to 5μm band laser generated by the hollow-core fiber carbon monoxide gas laser passes through the third dichroic mirror 7 and is reflected, and the transmitted light beam and the reflected light beam are spectrally combined by the third dichroic mirror 7 to form a 3.1μm to 5μm band laser and output. Figure 3 As shown, the emission spectrum of the high-power mid-infrared hollow-core fiber gas laser can cover the 3.1μm to 5μm band.

[0063] Matters not covered by the present invention are known technologies.

[0064] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-power mid-infrared hollow-core fiber gas laser, characterized in that: Includes hollow-core fiber gas laser and dichroic mirror; The hollow-core fiber gas laser comprises a first hollow-core fiber gas laser generating a 3.1 μm to 3.2 μm mid-infrared laser, a second hollow-core fiber gas laser generating a 3.8 μm to 4.2 μm mid-infrared laser, a third hollow-core fiber gas laser generating a 4.2 μm to 4.5 μm mid-infrared laser, and a fourth hollow-core fiber gas laser generating a 4.6 μm to 5 μm mid-infrared laser. The first hollow-core fiber gas laser is a hollow-core fiber acetylene gas laser filled with acetylene as a gain gas; the second hollow-core fiber gas laser is a hollow-core fiber hydrogen bromide gas laser filled with hydrogen bromide as a gain gas; the third hollow-core fiber gas laser is a hollow-core fiber carbon dioxide gas laser filled with carbon dioxide as a gain gas; the fourth hollow-core fiber gas laser is a hollow-core fiber carbon monoxide gas laser filled with carbon monoxide as a gain gas; The dichroic mirrors include a first dichroic mirror, a second dichroic mirror, and a third dichroic mirror, and are used to combine and output the laser beams transmitted to the dichroic mirrors; The first dichroic mirror combines the laser light outputted by the first hollow-core fiber gas laser and the laser light outputted by the second hollow-core fiber gas laser and outputs the laser light; the second dichroic mirror combines the laser light outputted by the first dichroic mirror and the laser light outputted by the third hollow-core fiber gas laser and outputs the laser light; the third dichroic mirror combines the laser light outputted by the second dichroic mirror and the laser light outputted by the fourth hollow-core fiber gas laser and outputs the laser light; The first dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 3.2μm band and high reflectance in the 3.8μm to 4.2μm band; the second dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 4.2μm band and high reflectance in the 4.2μm to 4.5μm band; the third dichroic mirror is a dichroic mirror coated with high transmittance in the 3.1μm to 4.5μm band and high reflectance in the 4.6μm to 5μm band; When the power of the pump light source is less than 30W, the gas pressures of the four gain gases are between 2 and 7mbar; when the power of the pump light source is between 30W and 70W, the gas pressures of the four gain gases are between 5 and 10mbar; when the power of the pump light source is between 70W and 150W, the gas pressures of the four gain gases are between 7 and 15mbar.

2. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 1, characterized in that: The hollow-core fiber gas laser comprises a pump light source, a pump collimating lens, a focusing lens, an input sealed gas cavity, an output sealed gas cavity, a vacuum pumping and gas filling system, a hollow-core fiber, and a laser collimating lens; The pump laser output by the pump light source is collimated by the pump collimator lens and then injected into the focusing lens. The focusing lens focuses the pump laser and then couples it into the hollow-core optical fiber. The input end and the output end of the hollow-core optical fiber are sealed in the input sealed gas cavity and the output sealed gas cavity respectively. The vacuum pumping and gas filling system is connected to the input sealed gas cavity or the output sealed gas cavity. The vacuum pumping and gas filling system is used to vacuum the hollow-core optical fiber and fill the hollow-core optical fiber with a gain gas with a certain air pressure. After the pump laser and the gain gas interact with each other in the hollow-core optical fiber, the pump laser with a target output wavelength range is output. The pump laser with a target output wavelength range output by the hollow-core optical fiber is collimated by the laser collimator lens and then emitted.

3. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 2, characterized in that: The pump light source is a narrow line width pump light source with a central wavelength corresponding to the gain gas absorption line and a line width less than 300 MHz.

4. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 2, characterized in that: The input sealed gas cavity and the output sealed gas cavity are respectively provided with an input window plate and an output window plate; the input window plate has high transmittance to the pump laser band; the output window plate has high transmittance to the output laser band.

5. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 2, characterized in that: The vacuuming and gas filling system comprises a vacuum pump, a gas cylinder, a gas pressure regulating valve and a barometer, and is used to adjust and monitor the gas pressure of the gain gas in the hollow core optical fiber.

6. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 2, characterized in that: The laser collimating lens is a positive lens which has high transmittance to mid-infrared laser and can collimate the laser beam, so that the spot diameter of the collimated beam is greater than 1 mm.

7. A high-power mid-infrared hollow-core fiber gas laser according to any one of claims 1 or 2, characterized in that: After the lasers output by the first hollow-core fiber gas laser, the second hollow-core fiber gas laser, the third hollow-core fiber gas laser, and the fourth hollow-core fiber gas laser are collimated by a laser collimating lens, the light spots of the light beams have the same spot diameter.

8. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 2, characterized in that: The hollow core optical fiber can transmit the pump laser band and the output laser band with low loss.

9. A high-power mid-infrared hollow-core fiber gas laser as claimed in claim 2, characterized in that: The focusing lens is a positive lens which has high transmittance to the pump laser wavelength band and can focus the pump laser, and is used to match the pump laser with the mode of the hollow core optical fiber.

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