High-power intermediate infrared optical fiber gas laser based on spectral beam combination

Abstract

The invention discloses a high-power intermediate infrared optical fiber gas laser based on spectral beam combination. The high-power intermediate infrared optical fiber gas laser comprises an acetylene optical fiber gas laser, a dichroic mirror, a reflector group and a diffraction grating, the acetylene optical fiber gas laser devices are divided into five paths and are used as laser light sources for grating beam combination, and a laser spectrum output by each path of acetylene optical fiber gas laser device contains two different wavelengths; dichroic mirrors are respectively arranged on output light paths of the acetylene optical fiber gas lasers, and the dichroic mirrors are used for separating lasers with two wavelength components in the lasers output by the corresponding acetylene optical fiber gas lasers; the five paths of acetylene optical fiber gas lasers are split by the corresponding dichroic mirrors respectively to obtain ten paths of laser with different wavelengths; the ten paths of laser are incident to the diffraction grating at different angles after light paths of the ten paths of laser are adjusted by the corresponding reflecting mirror groups respectively; the ten paths of incident laser are diffracted in the same direction on the diffraction grating and have the same diffraction angle, spectrum beam combination is achieved, and therefore the existing upper power limit is broken through.

Description

Technical Field

[0001] The invention mainly relates to the technical field of fiber gas lasers, in particular to a high-power mid-infrared fiber gas laser based on spectral beam combining. Background Art

[0002] Mid-infrared lasers in the 3 μm band have important application value in the fields of biomedicine, environmental monitoring, and material processing. The main means of realization include gas lasers, solid lasers, fiber lasers, quantum cascade lasers, etc. Among them, fiber lasers have the characteristics of compact structure, convenient thermal management, high conversion efficiency, and good beam quality. They are an important way to achieve efficient, compact, and high-power mid-infrared laser output. However, the soft glass optical fiber used in traditional mid-infrared fiber lasers has problems such as poor chemical stability and low damage threshold, which restricts the increase of laser power. The emergence of hollow-core optical fiber provides a new way to realize mid-infrared lasers. Gas is filled into the hollow-core optical fiber, and the interaction between light and gas is used to achieve laser output, which has developed into a new type of laser-fiber gas laser.

[0003] At present, there are mainly the following types of fiber gas lasers that produce this band: single-pass structure fiber gas lasers, resonant cavity structure fiber gas lasers, and amplifier structure fiber gas lasers. Single-pass structure fiber gas lasers are usually difficult to achieve high-power output, because the laser only passes through the optical fiber once, there is no opportunity for multiple round trips to amplify, and the hollow-core fiber coupling end face is easily damaged under high-power pumping. Although the resonant cavity structure fiber gas laser can ensure that the laser can travel back and forth in the cavity multiple times and effectively amplify, the resonant cavity structure requires precise design, high alignment accuracy, and requires additional cavity mirrors and support structures, which increases the complexity of the design. At the same time, the resonant cavity structure requires more frequent maintenance and adjustment, which increases the cost. Also limited by the limitation that the hollow-core fiber coupling end face is easily damaged under high-power pumping, the output power of the resonant cavity structure fiber gas laser in the 3 μm band is also very limited. Amplifier structure Fiber gas lasers usually require a high-power pump light source to achieve effective light amplification. However, it is difficult to develop a high-power, narrow-linewidth, and high-beam-quality pump source. In addition, the amplifier structure requires a complex feedback control system to maintain a stable laser output, which increases the complexity of the system and potential failure points. Summary of the invention

[0004] In view of the technical problems existing in the prior art, the present invention proposes a high-power mid-infrared fiber gas laser based on spectral beam combining.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a high-power mid-infrared fiber gas laser based on spectral beam combining, comprising an acetylene fiber gas laser, a dichroic mirror, a reflector group and a diffraction grating; There are five acetylene fiber gas lasers, which are used as laser light sources for grating beam combining. The laser spectrum output by each acetylene fiber gas laser contains two different wavelengths. A dichroic mirror is respectively arranged on the output optical path of each acetylene fiber gas laser, and the dichroic mirror is used to separate the laser beams of two wavelength components in the output laser beam of the corresponding acetylene fiber gas laser; After five acetylene fiber gas lasers pass through corresponding dichroic mirrors, ten lasers with different wavelengths are obtained. The ten lasers with different wavelengths are respectively adjusted through corresponding reflector groups to make the ten lasers with different wavelengths incident on the diffraction grating at different angles; Ten incident lasers with different incident angles and wavelengths are diffracted in the same direction at the diffraction grating with the same diffraction angle, completing spectral beam combining.

[0006] Furthermore, the diffraction grating of the present invention is a reflective diffraction grating.

[0007] Furthermore, the acetylene fiber gas laser of the present invention comprises a fiber laser, a focusing lens, a gas cavity group, a hollow-core fiber and acetylene gas sealed in the gas cavity, wherein the gas cavity group comprises two gas cavities, namely an input end gas cavity and an output end gas cavity, and the two ends of the hollow-core fiber are respectively placed in the input end gas cavity and the output end gas cavity, and the acetylene gas enters the hollow-core fiber through the gas cavity group; the fiber laser is used to output pump light in the 1.5 μm band, and after the pump light in the 1.5 μm band enters the hollow-core fiber through the focusing lens, the acetylene gas absorbs the pump light energy to generate a particle number inversion, and then generates a laser output in the 3.1 μm band through energy level transition, and the laser spectrum of the output laser contains two wavelength components.

[0008] Furthermore, the five-channel acetylene fiber gas lasers in the present invention are respectively a first acetylene fiber gas laser, a second acetylene fiber gas laser, a third acetylene fiber gas laser, a fourth acetylene fiber gas laser, and a fifth acetylene fiber gas laser. The pump sources of the five-channel acetylene fiber gas lasers are fiber lasers with different output wavelengths. The five pump source wavelengths of the five-channel acetylene fiber gas lasers respectively correspond to the five absorption lines of acetylene gas.

[0009] Furthermore, in the present invention, the laser spectrum output by the first acetylene fiber gas laser contains two wavelengths of 3177.488 nm and 3110.420 nm, the laser spectrum output by the second acetylene fiber gas laser contains two wavelengths of 3172.444 nm and 3114.640 nm, the laser spectrum output by the third acetylene fiber gas laser contains two wavelengths of 3167.464 nm and 3118.918 nm, the laser spectrum output by the fourth acetylene fiber gas laser contains two wavelengths of 3162.547 nm and 3123.255 nm, and the laser spectrum output by the fifth acetylene fiber gas laser contains two wavelengths of 3157.694 nm and 3127.651 nm.

[0010] Furthermore, in the present invention, the pump source wavelengths of the first acetylene fiber gas laser, the second acetylene fiber gas laser, the third acetylene fiber gas laser, the fourth acetylene fiber gas laser, and the fifth acetylene fiber gas laser are 1534.099 nm, 1532.830 nm, 1531.588 nm, 1530.371 nm, and 1529.180 nm, respectively, corresponding to the five absorption lines of acetylene gas P(15), P(13), P(11), P(9), and P(7), respectively.

[0011] Furthermore, in the present invention, ten incident laser beams with different incident angles and different wavelengths are diffracted along the same direction at the diffraction grating, and the ten incident laser beams have the same diffraction angle. , and the incident angles of the incident lasers of different wavelengths must satisfy the grating equation: ; in m is the diffraction order, d is the grating constant, It is n The incident angle of the incident laser, is the diffraction angle, Indicates n The wavelength of the incident laser, n =1,2,3,......,10; According to the above grating equation, the incident angles of ten incident lasers are adjusted so that ten incident lasers with different wavelengths are diffracted along the same direction on the diffraction grating.

[0012] Among the ten incident lasers, the longer the wavelength, the larger the corresponding incident angle.

[0013] Spectral beam combining is an important way to achieve high-power output. The present invention uses grating devices to combine multiple stable mid-infrared fiber gas lasers, ultimately obtaining high-power laser output while ensuring performance stability. Compared with the prior art, the technical effects of the present invention are: 1. The present invention adopts acetylene gas as the gain medium, uses hollow-core optical fiber as the place where light interacts with matter, and realizes laser output in the 3 μm band through acetylene gas particle number inversion.

[0014] 2. The present invention adopts a reflective diffraction grating as a beam combining device to perform spectral beam combining on a 3 μm band acetylene fiber gas laser to obtain a high-power 3 μm band laser output.

[0015] 3. The present invention combines five acetylene fiber gas lasers, and each laser system works in a stable state, thereby obtaining high-power 3 μm band output while avoiding the risk of hollow-core fiber damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 Schematic diagram of the structure of a high-power mid-infrared fiber gas laser based on spectral beam combining in one embodiment; Figure 2 It is a schematic structural diagram of a high-power mid-infrared fiber gas laser based on spectral beam combining in another embodiment; Figure 3 Schematic diagram of energy level transition of acetylene (C2H2) molecule absorption line pumping; Figure 4 Schematic diagram of grating beam combining principle; Figure 5 This is a schematic diagram of the absorption spectrum of acetylene gas; Figure 6 This is a schematic diagram of the output spectrum of an acetylene fiber gas laser under a certain absorption line measured in an experiment; Numbers in the figure: A, the first acetylene fiber gas laser; 1, the first acetylene fiber gas laser pump source; 6, the first hollow core fiber; f1, the first focusing lens; g1, the first gas cavity group; f6, the first collimating lens; B, second acetylene fiber gas laser; 2, second acetylene fiber gas laser pump source; 7, second hollow core fiber; f2, second focusing lens; g2, second gas cavity group; f7, second collimating lens; C, the third acetylene fiber gas laser; 3, the third acetylene fiber gas laser pump source; 8, the third hollow core fiber; f3, the third focusing lens; g3, the third gas cavity group; f8, the third collimating lens; D, the fourth acetylene fiber gas laser; 4, the fourth acetylene fiber gas laser pump source; 9, the fourth hollow core fiber; f4, the fourth focusing lens; g4, the fourth gas cavity group; f9, the fourth collimating lens; E, fifth acetylene fiber gas laser; 5, fifth acetylene fiber gas laser pump source; 10, fifth hollow core fiber; f5, fifth focusing lens; g5, fifth gas cavity group; f 10 , the fifth collimating lens; M1, first dichroic mirror; M2, second dichroic mirror; M3, third dichroic mirror; M4, fourth dichroic mirror; M5, fifth dichroic mirror; M6, first reflector; M7, second reflector; M8, third reflector; M9, fourth reflector; M10, fifth reflector; M11, sixth reflector; M12, seventh reflector; M13, eighth reflector; M14, ninth reflector; M15, tenth reflector; M16, eleventh reflector; M17 , the twelfth reflector; M18, the thirteenth reflector; M19, the fourteenth reflector; M20 is the fifteenth reflector; M21, the sixteenth reflector; M22, the seventeenth reflector; M23, the eighteenth reflector; M24, the nineteenth reflector; M25, the twentieth reflector; M26, the twenty-first reflector; M27, the twenty-second reflector; M28, the twenty-third reflector; M29, the twenty-fourth reflector; M30, the twenty-fifth reflector; 11. Reflective diffraction grating. DETAILED DESCRIPTION

[0018] 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.

[0019] Reference Figure 1In one embodiment of the present invention, a high-power mid-infrared fiber gas laser based on spectral beam combining is provided, comprising an acetylene fiber gas laser, a dichroic mirror, a reflector group and a diffraction grating; the acetylene fiber gas laser has five paths, which are used as laser light sources for grating beam combining; the dichroic mirror is used to separate the laser light containing two wavelength components output by each acetylene fiber gas laser; the reflector is used to adjust the optical path, and is used to make laser light of different wavelengths incident on the diffraction grating; the diffraction grating diffracts the incident light of different wavelengths for spectral beam combining.

[0020] There are five acetylene fiber gas lasers, which are used as laser light sources for grating beam combining. The laser spectrum output by each acetylene fiber gas laser contains two different wavelengths. The five acetylene fiber gas lasers are the first acetylene fiber gas laser A, the second acetylene fiber gas laser B, the third acetylene fiber gas laser C, the fourth acetylene fiber gas laser D, and the fifth acetylene fiber gas laser E. The pump sources of the five acetylene fiber gas lasers are fiber lasers with different output wavelengths. The five pump source wavelengths of the five acetylene fiber gas lasers correspond to the five absorption lines of acetylene gas. The laser spectrum output by the first acetylene fiber gas laser A contains , Two different wavelengths. The laser spectrum output by the second acetylene fiber gas laser B contains , Two different wavelengths. The laser spectrum output by the third acetylene fiber gas laser C contains , Two different wavelengths. The laser spectrum output by the fourth acetylene fiber gas laser D contains , Two different wavelengths. The laser spectrum output by the fifth acetylene fiber gas laser E contains , Two different wavelengths.

[0021] A dichroic mirror is provided on the output optical path of each acetylene fiber gas laser. The dichroic mirror is used to separate the two wavelength components of the laser light outputted by the corresponding acetylene fiber gas laser. A first dichroic mirror M1 is provided on the output optical path of the first acetylene fiber gas laser A. The first dichroic mirror M1 is used to separate the two wavelength components of the laser light outputted by the corresponding acetylene fiber gas laser. With high transmittance, A second dichroic mirror M2 is arranged on the output optical path of the second acetylene fiber gas laser B. With high transmittance, A third dichroic mirror M3 is arranged on the output optical path of the third acetylene fiber gas laser C. With high transmittance, A fourth dichroic mirror M4 is arranged on the output optical path of the fourth acetylene fiber gas laser D. With high transmittance, The fifth dichroic mirror M5 is arranged on the output optical path of the fifth acetylene fiber gas laser E. With high transmittance, Has high reflectivity.

[0022] Five acetylene fiber gas lasers are respectively passed through the corresponding dichroic mirrors to obtain ten lasers with different wavelengths. ~ Indicates that each of the wavelengths is in the 3 μm band.

[0023] Reference Figure 1 There are 25 reflectors in total, which reflect the 10 different wavelengths of laser light output by the five-way acetylene fiber gas laser and adjust the beam path so that the beam is incident on the diffraction grating at a specific angle. The diffraction grating is a reflective grating that combines incident beams of different incident angles and wavelengths.

[0024] Reflectors M6~M10, respectively ~ With high reflectivity. Reflectors M11~M15 are respectively ~ With high reflectivity. Reflectors M16~M20 are respectively ~ With high reflectivity. Reflectors M21~M25 are respectively ~ With high reflectivity. Reflectors M26~M30 are respectively ~ Has high reflectivity.

[0025] A fifth reflecting mirror M10, a sixth reflecting mirror M11, and a twenty-fifth reflecting mirror M30 are sequentially arranged on the reflecting light path of the first dichroic mirror M1. The fifth reflecting mirror M10, the sixth reflecting mirror M11, and the twenty-fifth reflecting mirror M30 reflect the wavelength of The laser has high reflectivity.

[0026] A fifteenth reflecting mirror M20 and a sixteenth reflecting mirror M21 are sequentially arranged on the transmission light path of the first dichroic mirror M1. The fifteenth reflecting mirror M20 and the sixteenth reflecting mirror M21 reflect the light of wavelength The laser has high reflectivity.

[0027] A fourth reflecting mirror M9, a seventh reflecting mirror M12, and a twenty-fourth reflecting mirror M29 are sequentially arranged on the reflected light path of the second dichroic mirror M2. The fourth reflecting mirror M9, the seventh reflecting mirror M12, and the twenty-fourth reflecting mirror M29 reflect the wavelength of The laser has high reflectivity.

[0028] The transmission light path of the second dichroic mirror M2 is provided with a fourteenth reflecting mirror M19 and a seventeenth reflecting mirror M22 in sequence. The fourteenth reflecting mirror M19 and the seventeenth reflecting mirror M22 are adapted to transmit light of wavelength The laser has high reflectivity.

[0029] The third reflecting mirror M8, the eighth reflecting mirror M13, and the twenty-third reflecting mirror M28 are sequentially arranged on the reflecting light path of the third dichroic mirror M3. The third reflecting mirror M8, the eighth reflecting mirror M13, and the twenty-third reflecting mirror M28 reflect the wavelength of The laser has high reflectivity.

[0030] The thirteenth reflecting mirror M18 and the eighteenth reflecting mirror M23 are arranged in sequence on the transmission light path of the third dichroic mirror M3. The thirteenth reflecting mirror M18 and the eighteenth reflecting mirror M23 reflect the wavelength of The laser has high reflectivity.

[0031] The second reflector M7, the ninth reflector M14, and the twenty-second reflector M27 are sequentially arranged on the reflection light path of the fourth dichroic mirror M4. The second reflector M7, the ninth reflector M14, and the twenty-second reflector M27 reflect the wavelength of The laser has high reflectivity.

[0032] The transmission light path of the fourth dichroic mirror M4 is provided with a twelfth reflecting mirror M17 and a nineteenth reflecting mirror M24 in sequence. The twelfth reflecting mirror M17 and the nineteenth reflecting mirror M24 are adapted to transmit light of wavelength The laser has high reflectivity.

[0033] The first reflector M6, the tenth reflector M15, and the twenty-first reflector M26 are sequentially arranged on the reflected light path of the fifth dichroic mirror M5. The first reflector M6, the tenth reflector M15, and the twenty-first reflector M26 reflect the wavelength of The laser has high reflectivity.

[0034] The eleventh reflecting mirror M16 and the twentieth reflecting mirror M25 are arranged in sequence on the transmission light path of the fifth dichroic mirror M5. The eleventh reflecting mirror M16 and the twentieth reflecting mirror M25 reflect the wavelength of The laser has high reflectivity.

[0035] The optical paths of the ten laser beams with different wavelengths are adjusted through the corresponding reflective mirror groups respectively, so that the ten laser beams with different wavelengths are incident on the reflective diffraction grating 11 at different angles.

[0036] Ten incident laser beams with different incident angles and wavelengths are diffracted in the same direction at the reflective diffraction grating 11 and have the same diffraction angle, thus completing spectral beam combining.

[0037] In one embodiment, referring to Figure 2 , provides a high-power mid-infrared fiber gas laser based on spectral beam combining, including an acetylene fiber gas laser, a dichroic mirror, a reflector group and a diffraction grating; the acetylene fiber gas laser has a total of five channels, which are used as laser light sources for grating beam combining; the dichroic mirror is used to separate the laser light containing two wavelength components output by each acetylene fiber gas laser; the reflector is used to adjust the optical path, and is used to make laser light of different wavelengths incident on the diffraction grating; the diffraction grating diffracts the incident light of different wavelengths for spectral beam combining. The structures of the acetylene fiber gas lasers are the same. The acetylene fiber gas lasers include a fiber laser, a focusing lens, a gas cavity group, a hollow-core fiber and acetylene gas sealed in the gas cavity. The gas cavity group includes two gas cavities, namely an input end gas cavity and an output end gas cavity. The two ends of the hollow-core fiber are respectively placed in the input end gas cavity and the output end gas cavity. The acetylene gas enters the hollow-core fiber through the gas cavity group. The fiber laser is used to output pump light in the 1.5 μm band. After the pump light in the 1.5 μm band enters the hollow-core fiber through the focusing lens, the acetylene gas absorbs the pump light energy to generate a particle number inversion, and then generates a laser output in the 3.1 μm band through energy level transition, and the laser spectrum of the output laser contains two wavelength components.

[0038] Specifically, the first acetylene fiber gas laser A comprises a first acetylene fiber gas laser pump source 1, a first hollow core fiber 6, a first focusing lens f1, a first gas cavity group g1, and a first collimating lens f6; The second acetylene fiber gas laser B comprises a second acetylene fiber gas laser pump source 2, a second hollow core optical fiber 7, a second focusing lens f2, a second gas cavity group g2, and a second collimating lens f7; A third acetylene fiber gas laser C, a third acetylene fiber gas laser pump source 3, a third hollow core optical fiber 8, a third focusing lens f3, a third gas cavity group g3, a third collimating lens f8; A fourth acetylene fiber gas laser D, a fourth acetylene fiber gas laser pump source 4, a fourth hollow core optical fiber 9, a fourth focusing lens f4, a fourth gas cavity group g4, and a fourth collimating lens f9; The fifth acetylene fiber gas laser E, the fifth acetylene fiber gas laser pump source 5, the fifth hollow core fiber 10, the fifth focusing lens f5, the fifth gas cavity group g5, the fifth collimating lens f 10 .

[0039] The wavelengths of the first acetylene fiber gas laser pump source 1, the second acetylene fiber gas laser pump source 2, the third acetylene fiber gas laser pump source 3, the fourth acetylene fiber gas laser pump source 4, and the fifth acetylene fiber gas laser pump source 5 are 1534.099 nm, 1532.830 nm, 1531.588 nm, 1530.371 nm, and 1529.18 nm, respectively, corresponding to the five absorption lines of acetylene gas P(15), P(13), P(11), P(9), and P(7), as shown in FIG. Figure 5 Refer to Table 1 for a comparison of the pump absorption lines and emission lines of the acetylene fiber gas laser.

[0040] Table 1

[0041] The first acetylene fiber gas laser pump source 1, the second acetylene fiber gas laser pump source 2, the third acetylene fiber gas laser pump source 3, the fourth acetylene fiber gas laser pump source 4, and the fifth acetylene fiber gas laser pump source 5 are used as pump sources for the acetylene fiber gas laser. Lenses f1~f5 are focusing lenses, which are used to focus the light beam output by the 1.5 μm band fiber laser into the hollow core fiber; lenses f6~f7 are used to focus the light beam output by the 1.5 μm band fiber laser into the hollow core fiber; lenses f7~f8 are used to focus the light beam output by the 1.5 μm band fiber laser into the hollow core fiber. 10 is a collimating lens used to collimate the laser output by the acetylene fiber gas laser. Furthermore, g1~g5 are five groups of gas cavities used to seal the acetylene gas. Each hollow-core fiber serves as a place for the 1.5 μm pump light and acetylene gas to interact with matter.

[0042] When the 1.5 μm pump light is coupled into the hollow-core fiber, a mid-infrared laser output in the 3.1 μm band is generated; because the wavelengths of the five 1.5 μm pump sources are different, the five acetylene fiber gas laser outputs are also different, and each acetylene fiber gas laser contains two different wavelength components.

[0043] Figure 3 Schematic diagram of the energy level transition of acetylene (C2H2) molecule pumped by the P(i) absorption line. On the vibration ground state The rotational state transitions to the upper energy level Vibrational state According to the Boltzmann distribution, at room temperature, except The vibration ground state, the number of particles in other vibration states is almost 0, and the upper energy level Vibrational states and lower energy levels The vibrational state forms a population inversion. According to the transition selection law ( Corresponding to R branch, Corresponding to branch P, where refers to the difference between the upper rotational energy level and the lower rotational energy level), the excited upper energy level Vibrational particles transition to Vibrational state and The rotational dynamics of and Two laser transition lines, i -2 and i Represents the rotational quantum number of the energy level under the transition.

[0044] Figure 4 Schematic diagram of grating beam combining principle. , and represents the angle of incidence (the angle between the incident light and the normal to the grating plane), Represents the diffraction angle (the angle between the diffracted light and the normal line of the grating plane). The incident light of different directions and wavelengths is incident on the grating, and after being diffracted by the grating, it is emitted in the same direction. This process needs to satisfy the grating equation: ; Where m is the diffraction order, d is the grating constant, (correspond Figure 4 In , or ) is the angle of incidence, (correspond Figure 4 In ) is the diffraction angle, Indicates wavelength.

[0045] According to the present invention, ten incident laser beams with different incident angles and different wavelengths are diffracted along the same direction on the diffraction grating, and the ten incident laser beams have the same diffraction angle. , and the incident angles of the incident lasers of different wavelengths must satisfy the grating equation: ; in m is the diffraction order, d is the grating constant, It is n The incident angle of the incident laser, is the diffraction angle, Indicates n The wavelength of the incident laser, n =1,2,3,......,10; According to the above grating equation, the incident angles of the ten incident lasers are adjusted so that the ten incident lasers of different wavelengths are diffracted in the same direction by the diffraction grating and emitted in the same direction, that is, the diffraction angles are the same. Among the ten incident lasers, the longer the wavelength, the larger the corresponding incident angle. Therefore, spectral beam combining can be achieved by incident lasers of different wavelengths at a certain angle.

[0046] Figure 5 This is a schematic diagram of the absorption spectrum of acetylene gas. Acetylene gas contains multiple absorption lines, among which the shorter wavelength is the R branch absorption line, and the longer wavelength is the P branch absorption line.

[0047] Figure 6 Schematic diagram of the output spectrum of acetylene fiber gas laser under a certain absorption line measured experimentally. The output laser is in the 3 μm band, and the laser spectrum contains two different wavelength components.

[0048] The output wavelength of the first acetylene fiber gas laser pump source 1 is 1534.099 nm. After focusing and coupling into the hollow-core fiber in the gas cavity, the generated laser contains two wavelengths of 3177.488 nm and 3110.420 nm, respectively. and The first dichroic mirror M1, for wavelength The laser has high transmittance and is The laser has high reflectivity; the output wavelength of the second acetylene fiber gas laser pump source 2 is 1532.830 nm. After focusing and coupling into the hollow-core fiber in the gas cavity, the generated laser contains two wavelengths of 3172.444 nm and 3114.640 nm, respectively. and The second dichroic mirror M2 is The laser has high transmittance and is The laser has high reflectivity. The output wavelength of the third acetylene fiber gas laser pump source 3 is 1531.588 nm. After focusing and coupling into the hollow-core fiber in the gas cavity, the generated laser contains two wavelengths of 3167.464 nm and 3118.918 nm, respectively. and The third dichroic mirror M3 is The laser has high transmittance and is The laser has high reflectivity; the output wavelength of the fourth acetylene fiber gas laser pump source 4 is 1530.371 nm. After focusing and coupling into the hollow-core fiber in the gas cavity, the generated laser contains two wavelengths of 3162.547 nm and 3123.255 nm, respectively. and The fourth dichroic mirror M4 has a wavelength of The laser has high transmittance and is The laser has high reflectivity; the fifth acetylene fiber gas laser pump source 5 has an output wavelength of 1529.18 nm. After focusing and coupling into the hollow-core fiber in the gas cavity, the generated laser contains two wavelengths of 3157.694 nm and 3127.651 nm, respectively. and The fifth dichroic mirror M5 has a wavelength of The laser has high transmittance and is The laser has high reflectivity.

[0049] Reflectors M6~M10, respectively ~ With high reflectivity. Reflectors M11~M15 are respectively ~ With high reflectivity. Reflectors M16~M20 are respectively ~ With high reflectivity. Reflectors M21~M25 are respectively ~ With high reflectivity. Reflectors M26~M30 are respectively ~ Has high reflectivity.

[0050] The laser emitted by the five-way acetylene fiber gas laser is split into two parts after passing through the dichroic mirrors M1~M5. One part continues to propagate along the original optical path due to the high transmittance of the dichroic mirror, and the other part continues to propagate after the optical path is deflected due to the high reflectivity of the dichroic mirror. Reflectors M6~M20 are 45° reflectors, which are used to deflect the optical path and guide the propagation of the beam. Reflectors M21~M25, by adjusting the angle, reflect ~ The laser is incident on the reflective diffraction grating 11 at a specific angle. The reflective mirrors M26 to M30 are adjusted to reflect ~ The laser is incident on the grating at a specific angle. ~ The wavelength decreases, and the angle of incidence on the reflective diffraction grating 11 decreases. According to the grating equation, as long as the incident angle is adjusted appropriately, the ten light beams will be diffracted along the same direction and have the same diffraction angle, thus achieving spectral beam combining.

[0051] The present invention is based on spectral beam combining and breaks through the power upper limit of 3 μm band acetylene fiber gas laser. Each acetylene fiber gas laser operates in a stable state, and the output power of each acetylene fiber gas laser is in a safe state, avoiding damage to the hollow-core fiber coupling end face. After beam combining, high-power 3 μm band laser output with good stability can be achieved. In other non-spectral beam combining technical solutions, the output of the fiber gas laser will become unstable under high-power pumping, and a complex feedback control system is required to maintain stable laser output, which increases the complexity of the system and potential failure points, and therefore does not have the advantages of the present invention.

[0052] The present invention uses a diffraction grating to combine the output lasers of mid-infrared fiber gas lasers, thereby breaking through the existing power limit. In other non-spectral beam combining technical solutions, in order to achieve the same effect, the pump power needs to be greatly increased, and high-power pumping will cause damage to the coupling end face of the hollow-core fiber, restricting the increase in output power.

[0053] Matters not covered by the present invention are known technologies.

[0054] 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.

[0055] 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.

[0056] 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. High-power mid-infrared fiber gas laser based on spectral beam combining, characterized in that: It includes an acetylene fiber gas laser, a dichroic mirror, a reflector set and a diffraction grating; There are five acetylene fiber gas lasers, which are used as laser light sources for grating beam combining. The laser spectrum output by each acetylene fiber gas laser contains two different wavelengths. The five acetylene fiber gas lasers are the first acetylene fiber gas laser, the second acetylene fiber gas laser, the third acetylene fiber gas laser, the fourth acetylene fiber gas laser, and the fifth acetylene fiber gas laser. The pump sources of the five acetylene fiber gas lasers are fiber lasers with different output wavelengths. The five pump source wavelengths of the five acetylene fiber gas lasers correspond to the five absorption lines of acetylene gas. A dichroic mirror is respectively arranged on the output optical path of each acetylene fiber gas laser, and the dichroic mirror is used to separate the laser beams of two wavelength components in the output laser beam of the corresponding acetylene fiber gas laser; Five acetylene fiber gas lasers pass through corresponding dichroic mirrors to obtain ten lasers with different wavelengths. The ten lasers with different wavelengths are respectively adjusted through corresponding reflector groups to make the ten lasers with different wavelengths incident on the diffraction grating at different angles; Ten incident lasers with different incident angles and wavelengths are diffracted in the same direction at the diffraction grating with the same diffraction angle, completing spectral beam combining.

2. The high-power mid-infrared fiber gas laser based on spectral beam combining according to claim 1, characterized in that: The diffraction grating is a reflective diffraction grating.

3. The high-power mid-infrared fiber gas laser based on spectral beam combining according to claim 2, characterized in that: The acetylene fiber gas laser comprises a fiber laser, a focusing lens, a gas cavity group, a hollow-core fiber and acetylene gas sealed in the gas cavity, wherein the gas cavity group comprises two gas cavities, namely an input end gas cavity and an output end gas cavity, two ends of the hollow-core fiber are respectively placed in the input end gas cavity and the output end gas cavity, and the acetylene gas enters the hollow-core fiber through the gas cavity group; the fiber laser is used to output pump light in the 1.5 μm band, after the pump light in the 1.5 μm band enters the hollow-core fiber through the focusing lens, the acetylene gas absorbs the pump light energy to generate a particle number inversion, and then generates a laser output in the 3.1 μm band through energy level transition, and the laser spectrum of the output laser contains two wavelength components.

4. The high-power mid-infrared fiber gas laser based on spectral beam combining according to claim 3, characterized in that: The laser spectrum output by the first acetylene fiber gas laser contains two wavelengths of 3177.488 nm and 3110.420 nm, the laser spectrum output by the second acetylene fiber gas laser contains two wavelengths of 3172.444 nm and 3114.640 nm, the laser spectrum output by the third acetylene fiber gas laser contains two wavelengths of 3167.464 nm and 3118.918 nm, the laser spectrum output by the fourth acetylene fiber gas laser contains two wavelengths of 3162.547 nm and 3123.255 nm, and the laser spectrum output by the fifth acetylene fiber gas laser contains two wavelengths of 3157.694 nm and 3127.651 nm.

5. The high-power mid-infrared fiber gas laser based on spectral beam combining according to claim 3, characterized in that: The pump source wavelengths of the first acetylene fiber gas laser, the second acetylene fiber gas laser, the third acetylene fiber gas laser, the fourth acetylene fiber gas laser, and the fifth acetylene fiber gas laser are 1534.099 nm, 1532.830 nm, 1531.588 nm, 1530.371 nm, and 1529.180 nm, respectively, corresponding to the five absorption lines of acetylene gas P(15), P(13), P(11), P(9), and P(7), respectively.

6. The high-power mid-infrared fiber gas laser based on spectral beam combining according to any one of claims 1 to 5, characterized in that: Ten incident lasers with different incident angles and wavelengths are diffracted in the same direction on the diffraction grating, and the ten incident lasers have the same diffraction angle. , and the incident angles of the incident lasers of different wavelengths must satisfy the grating equation: ； in m is the diffraction order, d is the grating constant, It is n The incident angle of the incident laser, is the diffraction angle, Indicates n The wavelength of the incident laser, n =1,2,3,......,10; According to the above grating equation, the incident angles of ten incident lasers are adjusted so that ten incident lasers with different wavelengths are diffracted along the same direction on the diffraction grating.

7. The high-power mid-infrared fiber gas laser based on spectral beam combining according to claim 6, characterized in that: Among the ten incident lasers, the longer the wavelength, the larger the corresponding incident angle.

Images