A mid-infrared fiber laser with dual-wavelength laser switchable output

Abstract

The invention discloses a mid-infrared fiber laser with dual-wavelength laser switchable output, comprising a first laser pump source, a first collimating lens, a first dichroic mirror, a first focusing lens, a first fiber grating, a first Er-doped 3+ Ion fiber, second fiber Bragg grating, fiber fusion point, third fiber Bragg grating, second Er-doped 3+ Optical fiber, a fourth optical fiber Bragg grating, a fifth optical fiber Bragg grating, a second focusing lens, a second dichroic mirror, a second collimating lens and a second laser pump source, a second optical fiber Bragg grating and a first Er-doped 3+ The straight cut end face of the ion fiber forms the first pair of resonant cavities for outputting 2.8 μm lasers; the fourth fiber grating and the first Er-doped 3+ The straight cut end faces of the ion fiber form a second pair of resonant cavities for outputting 2.8 μm lasers; the third fiber grating and the fifth fiber grating form a third resonant cavity for outputting 3.5 μm lasers; the fifth fiber grating and the first fiber grating form a fourth resonant cavity for outputting 3.5 μm lasers.

Description

Technical Field

[0001] The invention relates to the technical field of mid-infrared fiber lasers, and in particular to a mid-infrared fiber laser with switchable dual-wavelength laser outputs. Background Art

[0002] In recent years, lasers in the mid-infrared band have received more and more attention, especially in the 2-4μm band, because it has great application prospects in the fields of laser medicine, material processing, national defense and military industry, spectral sensing, environmental monitoring, atmospheric communication, etc. At present, there are many methods to produce lasers in the mid-infrared band, such as semiconductor quantum cascade lasers, optical frequency doubling lasers, fiber lasers, etc. Among them, rare earth doped ion fiber lasers have the advantages of high efficiency, good heat dissipation, good beam quality, stable operation, compact size, etc., and have gained more favor.

[0003] Research on rare earth doped ion lasers mainly focuses on two aspects: (1) Single wavelength laser output: In 2007, Zhu Xiushan's team at the University of New Mexico used Er-doped 3+ Using fluoride fiber as a gain medium, it has achieved the output of 2.8μm laser at the ten-watt level for the first time. In 2015, Vincent Fortin's team at Laval University in Canada used self-made fluoride fiber as the tail feedback of the resonant cavity to build an all-fiber erbium-doped laser, which output 30W of high-power 2.94μm laser. The following year, Vincent Fortin's team again used the composite wavelength excitation of the all-fiber structure to dope Er ion fluoride fiber laser, increasing the power of 3.5μm laser to 1.5W. In 2019, CXZhang et al. from Hunan University studied a dual-wavelength pumped Er-doped fiber with a concentration of 1mol.% and a length of 5m. 3+ : ZBLAN fiber, achieving a maximum output power of 1.72W for 3.5μm laser output; in January 2022, the Fortin team at Laval University in Canada once again broke the new record of 3.5μm continuous light laser power, with an operating wavelength of 3.55μm and an output power of 14.9W. (2) Dual-wavelength laser output: In 2015, Li Jianfeng's team at the University of Electronic Science and Technology of China used Ho-doped 3+ The fluoride fiber obtained dual-wavelength laser output of 3μm and 2μm; in 2017, Chenglai Jia's team at McGill University in Canada obtained dual-wavelength laser output of 3μm and 2μm by doping Tm 3+ Fluoride optical fiber has obtained dual-wavelength laser output of 1.9μm and 2.3μm; in 2017, Chunyu Guo et al. of Shenzhen University based on Er 3+ / Yb 3+The co-doped optical fiber obtained dual-wavelength laser output of 1μm and 1.5μm; in 2021, the invention patent applied by Li Jianfeng's team of the University of Electronic Science and Technology mentioned the use of Dy doped 3+ :InF 3 The optical fiber can achieve dual output and free switching of 3μm laser and 4.3μm laser.

[0004] However, there is no single fiber laser that can control the generation of 2.8μm or 3.5μm single wavelength lasers, and can also achieve the generation of 2.8μm and 3.5μm dual wavelength lasers. If the output fiber laser is to contain two wavelengths at the same time, it is necessary to combine the lasers output by multiple independent fiber lasers, which makes the system large, complex and expensive.

[0005] In summary, the traditional single mid-infrared fiber laser has the problem of being unable to achieve dual-wavelength laser generation of 2.8μm and 3.5μm. Summary of the invention

[0006] In view of this, the present invention provides a mid-infrared fiber laser with dual-wavelength laser switchable output, using Er-doped 3+ The energy level transitions between the 2.8μm laser and the 3.5μm laser generated in the optical fiber have overlapping characteristics. By adjusting the optical path, a single fiber laser can output three modes of lasers, solving the problem that the traditional single mid-infrared fiber laser cannot produce dual-wavelength lasers of 2.8μm and 3.5μm.

[0007] In order to solve the above problems, the technical solution of the present invention is to use a fiber laser with switchable dual-wavelength laser, including: a first laser pump source of 976nm, a first collimating lens, a first dichroic mirror, a first focusing lens, a first fiber grating, a first Er-doped 3+ Ion fiber, second fiber Bragg grating, fiber fusion point, third fiber Bragg grating, second Er-doped 3+ optical fiber, a fourth fiber grating, a fifth fiber grating, a second focusing lens, a second dichroic mirror, a second collimating lens and a second laser pump source of 1973 nm, wherein the second fiber grating and the first Er-doped 3+ The straight cut end face of the ion fiber forms a first pair of resonant cavities for outputting 2.8 μm lasers; the fourth fiber grating and the first Er-doped 3+ The straight-cut end faces of the ion fiber form a second pair of resonant cavities for outputting 2.8 μm lasers; the third fiber grating and the fifth fiber grating form a third resonant cavity for outputting 3.5 μm lasers; the fifth fiber grating and the first fiber grating form a fourth resonant cavity for outputting 3.5 μm lasers.

[0008] Optionally, a first laser output point is provided on the first dichroic mirror, wherein, when only the first laser pump source outputs 976nm laser, the first pair of resonant cavities and the second pair of resonant cavities output 2.8μm laser to the first dichroic mirror, and are reflected by the first dichroic mirror and emitted from the first laser output point.

[0009] Optionally, a second laser output point is provided on the second dichroic mirror, wherein the first laser pump source outputs 976nm laser, the second laser pump source outputs 1973nm laser and the second Er-doped 3+ The 1973nm laser power of the optical fiber is related to the incident first Er-doped 3+ When the ratio of the 976nm laser optical power of the optical fiber is greater than or equal to the first threshold, the third pair of resonant cavities and the fourth pair of resonant cavities output 3.5μm laser to the second dichroic mirror, which is reflected by the second dichroic mirror and emitted from the second laser output point.

[0010] Optionally, the first laser pump source outputs 976 nm laser light, the second laser pump source outputs 1973 nm laser light and the second Er-doped 3+ The 1973nm laser power of the optical fiber is related to the incident first Er-doped 3+ When the ratio of the 976 nm laser light power of the optical fiber is lower than the first threshold, the first laser output point emits 2.8 μm laser light while the second laser output point emits 3.5 μm laser light.

[0011] Optionally, the first Er-doped 3+ The doping concentration of the ion fiber is 7 mol.%.

[0012] Optionally, the second Er-doped 3+ The doping concentration of the ion fiber is 1.5 mol.%.

[0013] Optionally, the first dichroic mirror is a dichroic mirror having high transmittance to 976 nm laser and high reflectivity to 2.8 μm laser.

[0014] Optionally, the second dichroic mirror is a dichroic mirror having high transmittance to 1973 nm laser and high reflectivity to 3.5 μm laser.

[0015] The primary improvement of the present invention is to provide a mid-infrared fiber laser with dual-wavelength laser switchable output, using Er-doped 3+The energy level transitions between the 2.8μm laser and the 3.5μm laser generated in the optical fiber have overlapping characteristics. By adjusting the optical path, when only the first laser pump source outputs 976nm laser, the mid-infrared fiber laser can output 2.8μm laser; when the first laser pump source outputs 976nm laser and the second laser pump source outputs 1973nm laser, if the second Er-doped 3+ The 1973nm laser power of the optical fiber is related to the incident first Er-doped 3+ The ratio of the 976nm laser light power of the optical fiber is lower than the first threshold value, and the mid-infrared fiber laser can only output 3.5μm laser. 3+ The 1973nm laser power of the optical fiber is related to the incident first Er-doped 3+ The ratio of the 976nm laser light power of the optical fiber is lower than the first threshold value, and the mid-infrared fiber laser can output 2.8μm laser and 3.5μm laser at the same time. The present invention realizes a single fiber laser with three modes of laser output, solving the problem that the traditional single mid-infrared fiber laser cannot realize the dual-wavelength laser generation of 2.8μm and 3.5μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a simplified structural connection diagram of the mid-infrared fiber laser with dual-wavelength laser switchable output of the present invention;

[0017] Figure 2 This invention is Er 3+ Simplified example diagram of energy levels and energy level transitions. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] like Figure 1 As shown, a fiber laser capable of switching dual-wavelength lasers comprises: a first laser pump source 1 of 976 nm, a first collimating lens 3, a first dichroic mirror 7, a first focusing lens 4, a first fiber grating 12, a first Er-doped 3+ Ion fiber 9, second fiber Bragg grating 13, fiber fusion point 11, third fiber Bragg grating 14, second Er-doped 3+ Optical fiber 10, fourth fiber grating 15, fifth fiber grating 16, second focusing lens 6, second dichroic mirror 8, second collimating lens 5 and second laser pump source 2 of 1973nm, wherein the second fiber grating 13 and the first Er-doped 3+ The straight cut end faces of the ion fiber 9 form a first pair of resonant cavities for outputting 2.8 μm lasers; the fourth fiber grating 15 and the first Er-doped3+ The straight-cut end faces of the ion fiber 9 constitute a second pair of resonant cavities for outputting 2.8 μm lasers; the third fiber grating 14 and the fifth fiber grating 16 constitute a third resonant cavity for outputting 3.5 μm lasers; the fifth fiber grating 16 and the first fiber grating 12 constitute a fourth resonant cavity for outputting 3.5 μm lasers.

[0020] Furthermore, the first Er-doped 3+ The core diameter and NA of the ion fiber 9 can be 15 and 0.12 respectively, the inner cladding cross section is a circular cross section with two sides cut off symmetrically, and the two axis distances can be 260 μm and 240 μm respectively. 3+ The end face of the ion fiber 9 close to the first laser pump source 1 is cut straight to provide a feedback of about 4% for the 2.8 μm laser.

[0021] Furthermore, the second Er-doped 3+ The core diameter and NA of the ion fiber 10 may be 16.5 and 0.15 respectively, the inner cladding cross section is a circular cross section with two sides cut off symmetrically, and the two axis distances may be 260 μm and 240 μm respectively. 3+ The end surface of the ion optical fiber 10 close to the second laser pump source 2 is beveled, and the bevel angle may be 7°.

[0022] Furthermore, although the energy levels of erbium ions in low-concentration and high-concentration erbium-doped fibers are consistent, the energy level transitions are also the same. Figure 2 As shown, 4 I 15 / 2 (19) The energy level is Er in erbium-doped fiber 3+ The ground state energy level is 4 I 15 / 2 (19) → 4 I 11 / 2 The starting energy level of the energy level transition process (24) of (21) is relatively stable and has a large number of particles; 4 I 13 / 2 (20) Yes 3+ The first excited state energy level is 4 I 11 / 2 (21)→ 4 I 13 / 2 The termination energy level of the energy level transition process (26) of (20); 4 I 11 / 2 (21) Yes 3+ The second excited state energy level is 4 I 11 / 2 (21)→ 4 F 9 / 2The starting energy level of the energy level transition process (23) (25) and 4 I 11 / 2 (21)→ 4 I 13 / 2 (20) The starting energy level of the energy level transition process; 4 I 9 / 2 (22) Yes 3+ The third excited state energy level is 4 F 9 / 2 (23)→ 4 I 9 / 2 The termination energy level of the energy level transition process (27) of (22); 4 F 9 / 2 (23) Yes 3+ The fourth excited state energy level is 4 I 11 / 2 (21)→ 4 F 9 / 2 The energy level transition process of (23) and the terminal energy level of (25) 4 F 9 / 2 (23)→ 4 I 9 / 2 The starting energy level of the energy level transition process (27) of (22); 4 I 15 / 2 (19) → 4 I 11 / 2 The energy level transition process (24) of (21) absorbs the 976nm pump laser and converts 4 I 15 / 2 (19) The particles on the energy level are pumped to 4 I 11 / 2 (21) Energy level; 4 I 11 / 2 (21)→ 4 F 9 / 2 (23) energy level transition process (25), this process 4 I 15 / 2 (19) → 4 I 11 / 2 Based on the energy level transition process (24) of (21), absorbing the 1973nm pump laser, 4 I 11 / 2 (21) The particles on the energy level are pumped to 4 F 9 / 2 (23) Energy level; 4 I 11 / 2 (21)→ 4 I 13 / 2 (20) energy level transition process (26), which converts 4 I 11 / 2 (21) The particles on the energy level are released to4 I 13 / 2 (20) At the energy level, a laser with a wavelength of 2.8 μm is simultaneously generated; 4 F 9 / 2 (23)→ 4 I 9 / 2 (22) energy level transition process (27), which converts 4 F 9 / 2 (23) The particles on the energy level are released to 4 I 9 / 2 (22) At the energy level, a laser with a wavelength of 3.5 μm is generated simultaneously.

[0023] However, 2.8μm laser is mainly generated by high-concentration erbium-doped fiber, because high-concentration erbium-doped fiber can absorb more 976nm pump light, thereby increasing the output power of 2.8μm laser; while 3.5μm laser is mainly generated by low-concentration doped fiber, because high-concentration erbium-doped fiber absorbs too much 976nm pump light. To generate 3.5μm laser, more 1973nm pump light is required. Excessive pump power will generate high heat, and there will be laser quenching, which is not conducive to the generation of 3.5μm laser. Therefore, the first Er-doped 3+ The doping concentration of the ion fiber 9 can be 7 mol%. 3+ The doping concentration of the ion fiber 10 may be 1.5 mol.%.

[0024] Furthermore, the first fiber grating 12 and the second fiber grating 13 can be directly engraved on the first Er-doped 3+ Bragg diffraction gratings at the left and right ends of the ion fiber 9. The first fiber grating 12 has a high reflectivity for 3.5 μm laser, the reflectivity is ≥95%, and the second fiber grating 13 has a high reflectivity for 2.8 μm laser, the reflectivity is ≥95%.

[0025] Furthermore, the third fiber grating 14, the fourth fiber grating 15 and the fifth fiber grating 16 can be directly engraved on the second Er-doped 3+ Bragg diffraction gratings at the left and right ends of the optical fiber 10. The fifth optical fiber grating 16 has a high reflectivity for 3.5 μm laser, the reflectivity is ≥95%, the third optical fiber grating 14 has a high reflectivity for 2.8 μm laser, the reflectivity is ≥95%, and the fourth optical fiber grating 15 has a reflectivity for 3.5 μm laser between 50% and 65%.

[0026] Furthermore, a first laser output point 17 is provided on the first dichroic mirror 7, wherein, when only the first laser pump source 1 outputs 976nm laser, the first pair of resonant cavities and the second pair of resonant cavities output 2.8μm laser to the first dichroic mirror 7, and are reflected by the first dichroic mirror 7 and emitted from the first laser output point 17.

[0027] Furthermore, when only the first laser pump source 1 outputs 976 nm laser light, the 976 nm laser light is first collimated by the first collimating lens 3, then transmitted to the first focusing lens 4 through the first dichroic mirror 7 for focusing, and then coupled into the first Er-doped 3+ The cladding of the ion fiber 9 is absorbed by it, and the remaining 976nm pump light that has not been completely absorbed enters the second Er-doped 3+ The optical fiber 10 is composed of a first Er-doped 3+ Ion fiber 9 (with a straight cut left end face), second fiber grating 13, second Er-doped 3+ The laser composed of the optical fiber 10 and the fourth optical fiber grating 15 is doped with the second Er 3+ Fiber 10 continues to absorb and generate 2.8 μm laser (the erbium-doped fiber 4 I 15 / 2 (19) After the ground state level absorbs the 976nm pump laser, it forms 4 I 15 / 2 (19) → 4 I 11 / 2 The energy level transition process (24) of (21) is originally 4 I 15 / 2 Under the stimulation, a large number of ions (19) rise to 4 I 11 / 2 (21) At the energy level, 4 I 15 / 2 (19) Energy levels and 4 I 11 / 2 (21) When the energy level reaches the particle number inversion condition, 4 I 11 / 2 (21)→ 4 I 13 / 2 After the energy level transition process (26) of (20) generates 2.8 μm laser), it is output to the first dichroic mirror 7 through the first pair of resonant cavities and the second pair of resonant cavities, and is reflected by the first dichroic mirror 7 and emitted from the first laser output point.

[0028] Furthermore, a second laser output point 18 is provided on the second dichroic mirror 8, wherein the first laser pump source 1 outputs 976nm laser, the second laser pump source 2 outputs 1973nm laser and the second Er-doped 3+The 1973 nm laser light power of the optical fiber 10 is related to the incident first Er-doped 3+ When the ratio of the 976nm laser optical power of the optical fiber 9 is greater than or equal to the first threshold, the third pair of resonant cavities and the fourth pair of resonant cavities output 3.5μm laser to the second dichroic mirror 8, and are reflected by the second dichroic mirror 8 and emitted from the second laser output point 18.

[0029] Furthermore, the first threshold value may be 1.6, and the present invention does not specifically limit its value. Specifically, the laser may enter the second Er-doped 3+ The ratio of the laser light power of the optical fiber 10 to the laser light power emitted by the pump source fluctuates. Therefore, the present application limits the incident second Er-doped 3+ The 1973 nm laser light power of the optical fiber 10 is related to the incident first Er-doped 3+ The ratio of the 976nm laser light power of optical fiber 9 is used to avoid influencing factors such as system errors.

[0030] Furthermore, the first laser pump source 1 outputs 976nm laser, the second laser pump source 2 outputs 1973nm laser and the second Er-doped 3+ The 1973 nm laser light power of the optical fiber 10 is related to the incident first Er-doped 3+ When the ratio of the 976nm laser light power to the optical fiber 9 is 1, the 1973nm laser first passes through the second collimating lens 5 to collimate the beam, and then passes through the second dichroic mirror 8 to the first focusing lens 6 for focusing, and then couples into the second Er-doped 3+ In the core of optical fiber 10, the 976nm pump laser passes through the first Er-doped 3+ The remaining unabsorbed 976nm pump laser after ion fiber 9 enters the second Er-doped 3 + After optical fiber 10, originally in the second Er-doped 3+ The 1973nm pump laser of the optical fiber 10 is partially absorbed, and the unabsorbed 1973nm pump laser passes through the optical fiber fusion point 11 and enters the first Er-doped 3+ The ion fiber 9 continues to be absorbed by it, and then the first fiber grating 12 and the first Er-doped 3+ Ion fiber 9, third fiber grating 14, second Er-doped 3+ The laser composed of the optical fiber 10 and the fifth optical fiber grating 16 generates a 3.5 μm laser (when the first laser pump source 1 is turned on, the I in the erbium-doped optical fiber 15 / 2 (19) After the ground state level absorbs the 976nm pump laser, it forms 4 I 15 / 2 (19) → 4 I11 / 2 The energy level transition process (24) of (21) is originally 4 I 15 / 2 Under the stimulation, a large number of ions (19) rise to 4 I 11 / 2 (21) energy level, at this time, the 1973nm pump light output by the second laser pump source (2) is absorbed, forming 4 I 11 / 2 (21)→ 4 F 9 / 2 The energy level transition process of (23) (25), 4 I 11 / 2 (21) The particles on the energy level rise again in large numbers to 4 F 9 / 2 (23) Energy level, when 4 F 9 / 2 (23) Energy levels and 4 I 9 / 2 (22) When the energy level reaches the particle number inversion condition, 4 F 9 / 2 (23)→ 4 I 9 / 2 The energy level transition process (27) of (22) occurs, generating 3.5 μm laser, and due to the incident second Er-doped 3+ The 1973 nm laser light power of the optical fiber 10 is related to the incident first Er-doped 3+ The ratio of the 976nm laser light power of optical fiber 9 reaches the first threshold, so that the 976nm laser is fully absorbed and cannot be generated. 4 I 11 / 2 (21)→ 4 I 13 / 2 (20) undergoes an energy level transition process (26), so only 3.5 μm laser light will be generated), and the 3.5 μm laser light is output to the second dichroic mirror 8 via the third pair of resonant cavities and the fourth pair of resonant cavities, and is reflected by the second dichroic mirror 8 and emitted from the second laser output point.

[0031] Furthermore, when the first laser pumping source 1 outputs 976nm laser and the second laser pumping source 2 outputs 1973nm laser and reaches a first threshold value, so that the 976nm laser is fully absorbed and cannot produce a light below the first threshold value, the first laser output point emits 2.8μm laser and the second laser output point emits 3.5μm laser.

[0032] Furthermore, when the first laser pump source 1 is turned on, the I 15 / 2 (19) After the ground state level absorbs the 976nm pump laser, it forms 4 I 15 / 2 (19) →4 I 11 / 2 The energy level transition process (24) of (21) is originally 4 I 15 / 2 Under the stimulation, a large number of ions (19) rise to 4 I 11 / 2 (21) energy level, at this time, the 1973nm pump light output by the second laser pump source (2) is absorbed, forming 4 I 11 / 2 (21)→ 4 F 9 / 2 The energy level transition process of (23) (25), 4 I 11 / 2 (21) The particles on the energy level rise again in large numbers to 4 F 9 / 2 (23) Energy level, when 4 F 9 / 2 (23) Energy levels and 4 I 9 / 2 (22) When the energy level reaches the particle number inversion condition, 4 F 9 / 2 (23)→ 4 I 9 / 2 The energy level transition process (27) of (22) occurs, generating 3.5 μm laser. 3+ The 1973 nm laser light power of the optical fiber (10) is related to the incident first Er-doped 3+ The proportion of the 976nm laser light power of the optical fiber (9) does not reach the first threshold value, and after the 1973nm laser light is completely absorbed, there is still residual 976nm pump light, so that 4 I 11 / 2 (21) Some particles on the energy level occur 4 I 11 / 2 (21)→ 4 I 13 / 2 The energy level transition process (26) of (20) also produces 2.8μm laser output.

[0033] The present invention utilizes Er-doped 3+ The energy level transitions between the 2.8μm laser and the 3.5μm laser generated in the optical fiber have overlapping characteristics. By adjusting the optical path, when only the first laser pump source outputs 976nm laser, the mid-infrared fiber laser can output 2.8μm laser; when the first laser pump source outputs 976nm laser and the second laser pump source outputs 1973nm laser, if the second Er-doped 3+ The ratio of the 1973nm laser light power to the 976nm laser light power of the optical fiber is lower than the first threshold value, and the mid-infrared fiber laser can only output 3.5μm laser light.3+ The ratio of the 1973nm laser optical power to the 976nm laser optical power of the optical fiber is lower than the first threshold, and the mid-infrared fiber laser can output 2.8μm laser and 3.5μm laser at the same time. The present invention realizes a single fiber laser with three modes of laser output, solving the problem that the traditional single mid-infrared fiber laser cannot realize the dual-wavelength laser generation of 2.8μm and 3.5μm.

[0034] The above is a fiber laser with switchable dual-wavelength laser provided in an embodiment of the present invention. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0035] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented with electronic hardware, computer software or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to the function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention. The steps of the method or algorithm described in conjunction with the embodiments disclosed herein can be directly implemented with a software module executed by a hardware or processor, or a combination of the two. The software module can be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the technical field.

Claims

1. A mid-infrared fiber laser with dual-wavelength laser switchable output, characterized in that: include: A first laser pump source (1) of 976 nm, a first collimating lens (3), a first dichroic mirror (7), a first focusing lens (4), a first fiber grating (12), a first Er-doped 3+ Optical fiber (9), a second optical fiber Bragg grating (13), an optical fiber fusion point (11), a third optical fiber Bragg grating (14), a second Er-doped 3+ An optical fiber (10), a fourth optical fiber grating (15), a fifth optical fiber grating (16), a second focusing lens (6), a second dichroic mirror (8), a second collimating lens (5) and a second laser pump source (2) of 1973 nm, wherein: The second fiber grating (13) and the first Er-doped 3+ The straight cut end faces of the optical fiber (9) form a first pair of resonant cavities for outputting 2.8 μm laser light; The fourth fiber grating (15) and the first Er-doped 3+ The straight cut end faces of the optical fiber (9) form a second pair of resonant cavities for outputting 2.8 μm laser light; The third fiber grating (14) and the fifth fiber grating (16) form a third resonant cavity for outputting 3.5 μm laser light; The fifth fiber grating (16) and the first fiber grating (12) form a fourth resonant cavity for outputting 3.5 μm laser light; the first dichroic mirror (7) is provided with a first laser output point, wherein when only the first laser pump source (1) outputs 976 nm laser light, the first pair of resonant cavities and the second pair of resonant cavities output 2.8 μm laser light to the first dichroic mirror (7), and the light is reflected by the first dichroic mirror (7) and emitted from the first laser output point; the second dichroic mirror (8) is provided with a second laser output point, wherein when the first laser pump source (1) outputs 976 nm laser light, the second laser pump source (2) outputs 1973 nm laser light and the second Er-doped laser pump source (2) is incident on the first pair of resonant cavities. 3+ The 1973 nm laser light power of the optical fiber (10) is related to the incident first Er-doped 3+ When the ratio of the 976nm laser light power of the optical fiber (9) is greater than or equal to a first threshold value, the third pair of resonant cavities and the fourth pair of resonant cavities output 3.5μm laser light to the second dichroic mirror (8), and the 3.5μm laser light is reflected by the second dichroic mirror (8) and emitted from the second laser output point; when the first laser pump source (1) outputs 976nm laser light, the second laser pump source (2) outputs 1973nm laser light and the second Er-doped 3+ The 1973 nm laser light power of the optical fiber (10) is related to the incident first Er-doped 3+ When the ratio of the 976 nm laser light power of the optical fiber (9) is lower than a first threshold value, the first laser output point emits a 2.8 μm laser while the second laser output point emits a 3.5 μm laser; the first Er-doped 3+ The optical fiber (9) is a high concentration erbium-doped optical fiber. 3+ The optical fiber (10) is a low-concentration erbium-doped optical fiber.

2. The fiber laser according to claim 1, characterized in that: The first Er-doped 3+ The doping concentration of the optical fiber (9) is 7 mol%.

3. The fiber laser according to claim 1, characterized in that: The second Er-doped 3+ The doping concentration of the optical fiber (10) is 1.5 mol%.

4. The fiber laser according to claim 1, characterized in that: The first dichroic mirror (7) is a dichroic mirror having high transmittance for 976 nm laser and high reflectivity for 2.8 μm laser.

5. The fiber laser according to claim 1, characterized in that: The second dichroic mirror (8) is a dichroic mirror having high transmittance to 1973 nm laser and high reflectivity to 3.5 μm laser.

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