A 3μm fiber laser based on fluoride-doped phase-shifted grating feedback

Abstract

The invention discloses a 3μm fiber laser based on fluoride-doped phase-shift grating feedback, which belongs to the technical field of fiber lasers. The invention comprises an LD pumped laser source group, a fiber beam combiner, an optical isolator, a fiber grating, a first high-germanium-doped fiber, a second high-germanium-doped fiber and a double-cladding Ho-doped fiber engraved with a random phase-shift grating. 3+ The present invention is composed of a double cladding doped with Ho 3+ Random phase-shifted gratings are written on fluoride optical fibers and pumped by a pump source laser. 3+ It absorbs pump light and generates stimulated radiation. When the output laser threshold is reached, random laser output is generated. The pump laser oscillates back and forth through the fiber grating reflection, which can effectively reduce the pump threshold power and improve the pump efficiency. The laser has the characteristics of low threshold power, high conversion efficiency, compact structure, and all-fiber.

Description

Technical Field

[0001] The invention relates to a random fiber laser, in particular to a 3μm fiber laser based on fluoride-doped phase-shift grating feedback, belonging to the technical field of fiber lasers. Background Art

[0002] Random fiber laser is a new type of fiber laser. Different from traditional lasers, it uses multiple scattering of disordered gain medium to form coherent light. It does not have a general resonant cavity. It has no reflectors in structure. The feedback of light is realized through random feedback in the optical fiber. The interference effect of scattered light is used to generate a resonance mode of a specific frequency to achieve random laser output. Its lasing principle is based on random distribution Rayleigh scattering and Raman amplification effect. However, the Rayleigh scattering that forms feedback is weak. This random fiber laser often requires a long distance of optical fiber (tens of kilometers) to meet the requirements of the gain medium and feedback medium in terms of working length, and has high threshold power and low conversion efficiency. At present, the output wavelength of random lasers has just begun to develop from the optical communication wavelength of 1.0-1.5μm to the wavelength of 2μm, and there is no random fiber laser in the 3μm band mid-infrared. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a 3μm fiber laser based on fluoride-doped phase-shift grating feedback, which has the characteristics of low threshold power, high conversion efficiency, compact structure, and all-fiber.

[0004] The technical solution adopted by the present invention to solve the technical problem is:

[0005] A 3 μm fiber laser based on fluoride-doped phase-shift grating feedback, comprising an LD pump laser source group (1), a fiber combiner (2), an optical isolator (3), a first highly-doped germanium fiber (4), a double-cladding Ho-doped 3+ Fluoride optical fiber (5), inscribed on the double cladding doped with Ho 3+ A random phase shift grating (6), a second high-gemandium-doped optical fiber (7), and an optical fiber grating (8) on a fluoride optical fiber (5); the LD pump laser source group (1) is connected to one end of an optical fiber combiner (2); the other end of the optical fiber combiner (2) is connected to one end of an optical isolator (3); the other end of the optical isolator (3) is connected to one end of a first high-gemandium-doped optical fiber (4); the other end of the first high-gemandium-doped optical fiber (4) is connected to a double-clad Ho-doped optical fiber. 3+ One end of the fluoride optical fiber (5) is connected to the double cladding doped with Ho 3+ The other end of the fluoride optical fiber (5) is connected to one end of the second high-doped germanium optical fiber (7), and the other end of the second high-doped germanium optical fiber (7) is connected to the fiber grating (8). The center wavelength of the fiber grating (8) is consistent with the laser wavelength of the LD pump laser source group (1), providing pump light reflection.3+ The random phase shift grating (6) inscribed on the fluoride optical fiber (5) provides random light feedback, and the random laser is output from the other end of the optical fiber grating (8). The optical fiber end faces at the left and right ends of the entire laser are polished at an angle of 8°.

[0006] Beneficial effects of the present invention:

[0007] 1. Double cladding doped with Ho 3+ Fluoride optical fiber and cladding pumping can adapt to the transmission of high-power pump light in optical fiber and increase the power handling capacity of optical fiber;

[0008] 2. Use Ho doping in double cladding 3+ Writing random phase-shift gratings on fluoride optical fibers can provide random feedback and optical gain, which can effectively reduce the laser threshold power, increase the laser output power, and shorten the optical fiber length required for optical feedback.

[0009] 3. Use fiber grating to reflect pump light, improve pump light utilization and conversion efficiency, and reduce pump threshold;

[0010] 4. Use high-germanium doped optical fiber with a low melting point, which can be used as Ho-doped 3+ End caps for fluoride optical fibers to protect Ho-doped 3+ Fluoride optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of a 3μm fiber laser based on fluoride-doped phase-shift grating feedback of the present invention.

[0012] 1 is the LD pump laser source group, 2 is the fiber combiner; 3 is the optical isolator; 4 is the first high-gemandium-doped fiber; 5 is the double-cladding Ho-doped 3+ fluoride optical fiber; 6 is a random phase shift grating inscribed on the double-clad Ho3+ doped fluoride optical fiber 5; 7 is a second high-germanium doped optical fiber; 8 is a fiber grating.

[0013] Specific implementation method

[0014] The following is a detailed description of the structure and working principle of the present invention:

[0015] Figure 1 In the invention, a 3 μm fiber laser based on fluoride-doped phase-shift grating feedback comprises an LD pump laser source group 1, a fiber combiner 2, an optical isolator 3, a first highly-doped germanium fiber 4, a double-clad Ho-doped 3+ Fluoride fiber 5, writing on the double cladding doped with Ho 3+The random phase shift grating 6, the second high-gemandium-doped fiber 7, and the fiber grating 8 on the fluoride fiber 5; the LD pump laser source group 1 is connected to one end of the fiber combiner 2, the other end of the fiber combiner 2 is connected to one end of the optical isolator 3, the other end of the optical isolator 3 is connected to one end of the first high-gemandium-doped fiber 4, and the other end of the first high-gemandium-doped fiber 4 is connected to the double-clad Ho-doped 3+ One end of the fluoride optical fiber 5 is connected to the double cladding doped with Ho 3+ The other end of the fluoride fiber 5 is connected to one end of the second high-germanium-doped fiber 7, and the other end of the second high-germanium-doped fiber 7 is connected to the fiber grating 8. The center wavelength of the fiber grating 8 is consistent with the laser wavelength of the LD pump laser source group 1, providing pump light reflection. 3+ The random phase-shift grating 6 written on the fluoride optical fiber 5 provides random light feedback, and the random laser is output from the other end of the fiber grating 8 .

[0016] Working principle of a 3μm fiber laser based on fluoride-doped phase-shift grating feedback:

[0017] A 3μm fiber laser based on fluoride-doped phase-shift grating feedback Figure 1 The components shown are connected well. The 1150nm pump light output by the LD pump laser source group 1 is coupled into the linear optical path by the fiber combiner 2, passes through the optical isolator 3 and the first high-doped germanium fiber 4, and enters the double-clad Ho-doped 3+ In the fluoride optical fiber 5, the double cladding with random phase shift grating 6 is doped with Ho 3+ The fluoride fiber 5 acts as both an optical gain and random feedback medium. Holmium ions absorb pump light, causing population inversion and generating random feedback of laser oscillation. The fiber grating 8 acts as a reflector of pump light. Its central wavelength is consistent with the wavelength of the pump light, which can reduce the pump threshold power and improve the pump efficiency and utilization of the pump light. When the pump threshold power is reached, the pump light passes through the double cladding doped with Ho. 3+ The fluoride optical fiber 5 oscillates in the random phase-shift grating 6 to perform mode and frequency selection, and finally obtains random laser which is output from the other end of the optical fiber grating 8. Example

[0018] Figure 1 The schematic diagram of the structure of a 3μm fiber laser based on fluoride-doped phase-shift grating feedback of the present invention. The laser wavelength of the LD pump laser source group 1 is 1150nm, the fiber combiner 2 is (6+1)×1, the working wavelength is 1150nm / 2860nm, and the central wavelength of the optical isolator 3 is 1150nm. The concentration of the first high-doped germanium fiber 4 and the second high-doped germanium fiber 7 is 75wt.%, and the length is 10cm. The double-clad Ho-doped 3+ The length of the fluoride optical fiber 5 is 2 m, and the random phase shift grating 6 is in the double cladding doped with Ho 3+The fluoride optical fiber 5 is engraved with a reflectivity of 50% to 95% and a length of 5 cm. The fiber grating 8 is engraved with a high-gemanium-doped optical fiber, with a length of 2 cm, a reflectivity of 95% to 99%, and a central wavelength of 1150 nm. The LD pump laser source group 1 is connected to one end of the optical fiber combiner 2, the other end of the optical fiber combiner 2 is connected to one end of the optical isolator 3, the other end of the optical isolator 3 is connected to one end of the first high-gemanium-doped optical fiber 4, and the other end of the first high-gemanium-doped optical fiber 4 is connected to the double-clad Ho-doped optical fiber. 3+ One end of the fluoride optical fiber 5 is connected to the double cladding doped with Ho 3+ The other end of the fluoride fiber 5 is connected to one end of the second high-doped germanium fiber 7 , and the other end of the second high-doped germanium fiber 7 is connected to the fiber grating 8 , and finally the random laser is output from the other end of the fiber grating 8 .

[0019] The 1150nm pump light output by the LD pump laser source group 1 is coupled into the linear optical path by the fiber combiner 2, passes through the optical isolator 3 and the first high-doped germanium fiber 4, and enters the double-clad Ho-doped 3+ In the fluoride optical fiber 5, the double cladding with random phase shift grating 6 is doped with Ho 3+ The fluoride fiber 5 acts as both an optical gain and random feedback medium. Holmium ions absorb pump light, causing population inversion and generating random feedback of laser oscillation. The fiber grating 8 acts as a reflector of pump light. Its central wavelength is consistent with the wavelength of the pump light, which can reduce the pump threshold power and improve the pump efficiency and utilization of the pump light. When the pump threshold power is reached, the pump light passes through the double cladding doped with Ho. 3+ The fluoride optical fiber 5 oscillates in the random phase-shift grating 6 to perform mode and frequency selection, and finally obtains a random laser with a central wavelength of 2860 nm, which is output from the other end of the optical fiber grating 8.

[0020] The above embodiment is only one of the preferred solutions among all the solutions of the present invention. Other simple changes to a 3μm fiber laser based on fluoride-doped phase-shift grating feedback fall within the scope of protection of the present invention.

Claims

1. A 3 μm fiber laser based on fluoride-doped phase-shift grating feedback, comprising an LD pump laser source group (1), a fiber combiner (2), an optical isolator (3), a first highly-doped germanium fiber (4), a double-clad Ho-doped 3+ Fluoride optical fiber (5), inscribed on the double cladding doped with Ho 3+ A random phase shift grating (6), a second high-gemandium-doped optical fiber (7), and an optical fiber grating (8) on a fluoride optical fiber (5); the LD pump laser source group (1) is connected to one end of an optical fiber combiner (2); the other end of the optical fiber combiner (2) is connected to one end of an optical isolator (3); the other end of the optical isolator (3) is connected to one end of a first high-gemandium-doped optical fiber (4); the other end of the first high-gemandium-doped optical fiber (4) is connected to a double-clad Ho-doped optical fiber. 3+ One end of the fluoride optical fiber (5) is connected to the double cladding doped with Ho 3+ The other end of the fluoride optical fiber (5) is connected to one end of a second high-germanium-doped optical fiber (7), and the other end of the second high-germanium-doped optical fiber (7) is connected to a fiber grating (8); the center wavelength of the fiber grating (8) is consistent with the laser wavelength of the LD pump laser source group (1), providing pump light reflection; the double cladding Ho doped 3+ The random phase shift grating (6) inscribed on the fluoride optical fiber (5) provides random light feedback, and the random laser is output from the other end of the optical fiber grating (8). The optical fiber end faces at the left and right ends of the entire laser are polished at an angle of 8°; The pump light output by the LD pump laser source group (1) is coupled into the linear optical path by the optical fiber combiner (2), passes through the optical isolator (3) and the first high-doped germanium optical fiber (4), and enters the double-clad Ho-doped 3+ In a fluoride optical fiber (5), a double cladding of Ho doped optical fibers engraved with a random phase shift grating (6) is formed. 3+ The fluoride optical fiber (5) acts as an optical gain and random feedback medium at the same time. Holmium ions absorb pump light and undergo population inversion, thereby generating random feedback of laser oscillation. When the pump threshold power is reached, the pump light passes through the double cladding doped with Ho 3+ The fluoride optical fiber (5) oscillates in the random phase shift grating (6), performs mode and frequency selection, and finally obtains random laser light which is output from the other end of the optical fiber grating (8).

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