1.9 μm band thulium-doped fiber laser pumped by a Sb-chalcogenide semiconductor laser

Abstract

The utility model provides a kind of 1.9 μm waveband stibonium semiconductor laser same band pumping thulium-doped fiber laser, belong to fiber laser technical field;Solve the severe heat load problem that thulium-doped fiber laser system faces under high power output;The laser includes pump source module, optical isolator, laser resonant cavity assembly and output optical fiber, the output end of pump source module is connected with the input end of optical isolator, the output end of optical isolator is connected with the input end of laser resonant cavity assembly, and thulium-doped fiber laser generated after laser resonant cavity assembly is exported from output optical fiber tail end;The utility model uses 1.9 μm waveband stibonium semiconductor laser as pump source, and thulium-doped fiber is pumped with same band, with simple structure, waste heat ratio is low, quantum efficiency is high, stable performance, easy to manufacture and miniaturization and the like advantages.

Description

Technical Field

[0001] This invention provides a 1.9μm band antimonide semiconductor laser with a co-pumped thulium-doped fiber laser, belonging to the field of fiber laser technology. Background Technology

[0002] In recent years, fiber lasers have become a focus of research and application in the optoelectronic field due to their unique advantages such as high output power, good beam quality, high conversion efficiency, and compact structure. In particular, the emission spectrum of 2μm thulium-doped fiber lasers covers 1.7-2.1μm, a band with numerous dense absorption lines for H2O and CO2, making it valuable for applications in many fields. In the biomedical field, this laser band falls within the eye-safe range and the water absorption peak, exhibiting low penetration depth and good medical precision in various soft and hard human tissues, and is often used for high-precision surgical cutting and medical diagnosis. In the communications field, 2μm lasers are located near the atmospheric window, resulting in low loss in long-distance laser communication. Furthermore, 2μm lasers are ideal light sources for generating 3-5μm mid-infrared laser output. In addition, they also have significant practical applications in lidar, remote sensing technology, spectroscopy, and optoelectronic countermeasures.

[0003] Thulium-doped fiber lasers play a role that near-infrared lasers cannot replace, but currently lack more efficient pump sources, resulting in problems such as low laser efficiency, limited power, and severe thermal load. Traditionally, thulium-doped fiber lasers mostly employ crossband pumping, which results in a large difference in pump source wavelength and a high quantum defect, leading to power thermal saturation and limited power improvement. Same-band pumping technology provides a new solution for improving the optical-to-optical conversion efficiency and power of thulium-doped fiber laser systems.

[0004] Thulium-doped fiber lasers have three main pump bands: 793nm, 1.6μm, and 1.9μm. Currently, thulium-doped fiber lasers typically use 793nm commercial semiconductor lasers (LDs) as pump sources. Benefiting from the cross-relaxation process, this approach can achieve quantum efficiencies exceeding 100%, but its overall slope efficiency is low, resulting in poor optical-to-optical conversion efficiency. Furthermore, it generates significant waste heat within the gain fiber (waste heat to output power ratio as high as approximately 80%), and the fiber end-face temperature is relatively high. This severe heat generation poses a significant challenge to system thermal management and power enhancement. Over the past decade, the output power level of thulium-doped fiber lasers pumped by common 793nm LDs has not shown a significant improvement.

[0005] In-band pumping is an effective mechanism and technique for improving the slope efficiency and reducing waste heat generation in fiber laser systems. In thulium-doped fiber lasers, both 1.6 μm and 1.9 μm fall within the in-band pumping band. The 1.6 μm band can use erbium-doped fiber lasers or erbium-ytterbium co-doped fiber lasers as pump sources. However, compared to 793 nm LD pumping, it is limited by quantum efficiency and cannot significantly improve system efficiency, nor can it fundamentally solve the severe heat load problem faced by thulium-doped fiber laser systems at high power output. The 1.9 μm in-band pumped laser system has low quantum defect, high conversion efficiency, and controllable heat load, with a quantum efficiency exceeding 90% and a low waste heat ratio, which can greatly reduce the thermal management difficulty of the laser system. Utility Model Content

[0006] To address the severe heat load problem faced by thulium-doped fiber laser systems under high power output, this invention proposes a method for co-pumping a thulium-doped fiber laser with a 1.9μm band antimonide semiconductor laser. The 1.9μm antimonide semiconductor laser is used as the pump source to co-pump the thulium-doped fiber.

[0007] The technical solution adopted in this utility model is as follows: a 1.9μm band antimony semiconductor laser with a co-pumped thulium-doped fiber laser, including a pump source module, an optical isolator, a laser resonator assembly and an output fiber. The output end of the pump source module is connected to the input end of the optical isolator, and the output end of the optical isolator is connected to the input end of the laser resonator assembly. The thulium fiber laser generated by the laser resonator assembly is output from the tail end of the output fiber. The pump source module uses an antimonide semiconductor laser in the 1.9μm band as the pump source.

[0008] Furthermore, the pump source module includes a first pump source, a second pump source, and a pump combiner. The first pump source and the second pump source are respectively connected to the two input ports of the pump combiner, and the output port of the pump combiner is connected to the input port of the optical isolator.

[0009] Furthermore, both the first and second pump sources employ GaSb semiconductor lasers with a wavelength of 1908nm±10nm.

[0010] Furthermore, the optical isolator operates at a wavelength of 1940 nm.

[0011] Furthermore, the laser resonant cavity assembly includes a high-reflectivity fiber Bragg grating, a thulium-doped fiber, and a low-reflectivity fiber Bragg grating connected in sequence. The input end of the high-reflectivity fiber Bragg grating is connected to the output end of the optical isolator. The high-reflectivity fiber Bragg grating and the low-reflectivity fiber Bragg grating constitute the resonant cavity, and the gain medium is thulium-doped fiber.

[0012] Furthermore, the high-reflectivity fiber Bragg grating is non-directional, with a center wavelength of 1940 nm, a reflectivity greater than 99%, and a reflectivity of less than 10% at the pump wavelength of a 1908 nm GaSb semiconductor laser.

[0013] Furthermore, the low-reflectivity fiber Bragg grating is non-directional, with its center wavelength being the same as the operating wavelength of the GaSb semiconductor laser pump source. It has a reflectivity greater than 99%, a bandwidth of 1nm-2nm, and a reflectivity of less than 10% at the operating wavelength of the 1940nm laser resonator assembly.

[0014] Furthermore, thulium-doped fiber is a centimeter-scale high-gain Tm-doped fiber. 3+ germanate glass optical fiber.

[0015] Furthermore, high-reflectivity fiber Bragg gratings and low-reflectivity fiber Bragg gratings are etched onto SM1950 optical fibers using femtosecond direct-write technology.

[0016] The advantages of this invention compared to existing technologies are as follows: Compared to current thulium-doped fiber lasers, this invention, based on co-band pumping technology, has advantages such as high efficiency, low quantum defect, and low heat load. It uses a 1908nm antimonide semiconductor laser for direct pumping, and the quantum efficiency can theoretically reach 98%. This can effectively solve the problems of precise control of fiber doping concentration and thermal effects caused by quantum defect in other pumping bands. The laser optical path has almost no heat, which can greatly reduce the thermal load of active fiber, reduce the thermal effect of fiber, improve temporal stability, and increase the upper limit of laser power. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of this utility model; In the figure: 1 is the pump source module, 2 is the optical isolator, 3 is the laser resonator assembly, 4 is the output fiber, 5 is the first pump source, 6 is the second pump source, 7 is the pump combiner, 8 is the high reflectivity fiber Bragg grating, 9 is the thulium-doped fiber, and 10 is the low reflectivity fiber Bragg grating. Detailed Implementation

[0018] like Figure 1 As shown, this invention provides a high-efficiency, low-heat-dissipation 1.9μm band (1908nm±10nm) antimonide semiconductor laser with band-pumped thulium-doped fiber laser. By precisely controlling the wavelength and power of the pump source, the thulium-doped fiber is effectively excited, thereby obtaining stable and efficient laser output.

[0019] The laser consists of four parts: a pump source module 1, an optical isolator 2, a laser resonant cavity assembly 3, and an output fiber 4. The pump source module 1 includes a first pump source 5, a second pump source 6, and a pump combiner 7. The pump combiner 7 has three ports: two pump light input ports and one output port. The first pump source 5 and the second pump source 6 are connected to the two pump light input ports in a one-to-one correspondence, and the output port is connected to the input end of the optical isolator 2. The laser resonant cavity assembly 3 includes a high-reflectivity fiber Bragg grating 8, a thulium-doped fiber 9, and a low-reflectivity fiber Bragg grating 10 connected in sequence. The high-reflectivity fiber Bragg grating 8 is connected to the output end of the optical isolator 2. The two fiber Bragg gratings form a resonant cavity, with the gain medium being the thulium-doped fiber 9. To match the mode field area with the thulium-doped fiber 9 and minimize fiber splicing loss, the grating devices involved in this invention are all directly etched onto SM1950 fiber using femtosecond direct-write technology.

[0020] In this embodiment, both the first pump source 5 and the second pump source 6 are 1908nm GaSb LD lasers, which have a compact structure, low threshold current, high efficiency, and good thermal stability.

[0021] In this embodiment, the optical isolator 2 operates at a wavelength of 1940nm to prevent the 1908nm LD laser from being damaged by the laser generated in the laser resonant cavity.

[0022] In this embodiment, the high-reflectivity fiber Bragg grating 8 is non-directional, has a center wavelength of 1940nm, a reflectivity greater than 99%, and a reflectivity of less than 10% at the 1908nm pump source operating wavelength.

[0023] In this embodiment, the thulium-doped fiber 9 is a centimeter-scale high-gain Tm-doped fiber. 3+ Germanate glass optical fiber, compared with traditional quartz optical fiber, has better thermal stability and lower infrared transmission loss, especially near the 2μm band, which helps to improve the overall efficiency of fiber lasers.

[0024] In this embodiment, the low-reflectivity fiber Bragg grating 10 is non-directional, with a center wavelength of 1908nm, which is the same as the working wavelength of the GaSb semiconductor laser pump source. It has a reflectivity greater than 99%, a bandwidth of 1nm-2nm, and a reflectivity of less than 10% at the working wavelength of the 1940nm resonant cavity component.

[0025] The working principle of this utility model is as follows: the two pump lights (1908nm) emitted by the first pump source 5 and the second pump source 6 are output as one pump light after passing through the pump combiner 7. The pump light enters the laser resonant cavity assembly 3 after passing through the optical isolator 2. Under the action of the laser resonant cavity assembly 3, a thulium fiber laser with a center wavelength of 1940nm is generated and output from the tail end of the output fiber 4.

[0026] The thulium-doped fiber laser based on a 1.9μm antimony LD and co-pumped by this invention has the advantages of simple structure, low waste heat ratio, high quantum efficiency, stable performance, easy fabrication and miniaturization.

[0027] This invention proposes a co-band pumping mechanism for 1908nm GaSb semiconductor lasers based on high stability and low thermal effect, which breaks through the bottlenecks of severe thermal effect and low TMI threshold under traditional pumping structures, thereby realizing thulium-doped fiber laser output in the 2.0μm band with power of hundreds of watts, high slope efficiency, and low noise. This invention proposes a centimeter-scale high-gain Tm-doped [material / technology]. 3+ Germanium glass fiber is used as the gain medium, and the fiber core is pumped in the same direction to reduce waste heat generation and thermal noise, thereby achieving low noise and stable single longitudinal mode output of thulium-doped fiber laser.

[0028] Regarding the specific structure of this utility model, it should be noted that the connection relationships between the various component modules adopted in this utility model are definite and achievable. Except as specifically described in the embodiments, their specific connection relationships can bring about corresponding technical effects and solve the technical problems proposed by this utility model without relying on the execution of corresponding software programs. The models of the components, modules, and specific components appearing in this utility model, the connection methods between them, and the conventional usage methods and expected technical effects brought about by the above-mentioned technical features, unless specifically described, are all publicly disclosed content in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by those skilled in the art before the application date, or belong to conventional technology, common knowledge, and other existing technologies in this field. There is no need to elaborate, which makes the technical solution provided in this case clear, complete, and achievable, and can reproduce or obtain corresponding physical products based on this technical means.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser, characterized in that: It includes a pump source module (1), an optical isolator (2), a laser resonator assembly (3), and an output fiber (4). The output end of the pump source module (1) is connected to the input end of the optical isolator (2), and the output end of the optical isolator (2) is connected to the input end of the laser resonator assembly (3). The thulium fiber laser generated by the laser resonator assembly (3) is output from the tail end of the output fiber (4). The pump source module (1) uses an antimonide semiconductor laser in the 1.9μm band as the pump source.

2. The 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 1, characterized in that: The pump source module (1) includes a first pump source (5), a second pump source (6) and a pump combiner (7). The first pump source (5) and the second pump source (6) are respectively connected to the two input ports of the pump combiner (7), and the output port of the pump combiner (7) is connected to the input end of the optical isolator (2).

3. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 2, characterized in that: Both the first pump source (5) and the second pump source (6) are GaSb semiconductor lasers with a wavelength of 1908nm±10nm.

4. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 3, characterized in that: The optical isolator (2) operates at a wavelength of 1940 nm.

5. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 2, characterized in that: The laser resonant cavity assembly (3) includes a high reflectivity fiber Bragg grating (8), a thulium-doped fiber (9), and a low reflectivity fiber Bragg grating (10) connected in sequence. The input end of the high reflectivity fiber Bragg grating (8) is connected to the output end of the optical isolator (2). The high reflectivity fiber Bragg grating (8) and the low reflectivity fiber Bragg grating (10) constitute a resonant cavity, and the gain medium is thulium-doped fiber (9).

6. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 5, characterized in that: The high reflectivity fiber Bragg grating (8) is non-directional, with a center wavelength of 1940 nm and a reflectivity greater than 99%. Moreover, its reflectivity is less than 10% at the pump wavelength of the 1.9 μm GaSb semiconductor laser.

7. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 6, characterized in that: The low reflectivity fiber Bragg grating (10) is non-directional, with the center wavelength being the same as the working wavelength of the GaSb semiconductor laser pump source. It has a reflectivity greater than 99%, a bandwidth of 1nm-2nm, and a reflectivity of less than 10% at the working wavelength of the 1940nm laser resonator assembly (3).

8. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 5, characterized in that: Thulium-doped fiber (9) is a centimeter-scale high-gain Tm-doped fiber. 3+ germanate glass optical fiber.

9. A 1.9μm band antimonyide semiconductor laser co-pumped thulium-doped fiber laser according to claim 5, characterized in that: High reflectivity fiber Bragg grating (8) and low reflectivity fiber Bragg grating (10) are etched onto SM1950 fiber using femtosecond direct writing technology.

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