High-power ultra-narrow linewidth fiber laser source module

Abstract

The invention provides a high-power ultra-narrow linewidth optical fiber laser source module. The laser source module comprises a multi-longitudinal-mode optical fiber laser, an optical fiber circulator, an optical fiber beam splitter and a high-quality-factor optical fiber annular cavity. Laser output by the multi-longitudinal-mode fiber laser sequentially passes through a second port and a third port of the fiber circulator to reach an input port of the fiber beam splitter; the laser output from the first output port of the optical fiber beam splitter is used as the output of the whole laser source module; and the laser output from the second output port of the optical fiber beam splitter sequentially passes through the first port and the fourth port of the high-quality factor optical fiber annular cavity and returns to the resonant cavity of the multi-longitudinal mode optical fiber laser from the first port of the optical fiber circulator to form an optical feedback loop. Compared with a traditional ultra-narrow linewidth fiber laser source, the ultra-narrow linewidth fiber laser source can break through dependence of the traditional ultra-narrow linewidth fiber laser source on a single-frequency fiber laser, and further has the advantages of being high in output power, narrow in spectral linewidth and good in all-fiber system integration.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber lasers, and in particular relates to a high-power ultra-narrow linewidth optical fiber laser source module. Background Art

[0002] Ultra-narrow linewidth laser sources have important applications in coherent lidar, dense wavelength division multiplexing optical communications, gravitational wave detection, quantum optics and other fields. For example, in coherent wind lidar, the ultra-narrow linewidth of the laser source is conducive to the detection of small frequency shift signals in Doppler wind measurement, which corresponds to the scenario of low wind speed measurement. For example, in the data center of the optical communication network, the ultra-narrow linewidth of the laser source is conducive to improving the communication capacity of the dense wavelength division multiplexing optical fiber link and meeting the high-speed and high-capacity requirements of our modern data transmission. At present, the combination of semiconductor lasers and high-quality factor microcavity technology has achieved major breakthroughs in miniaturization and high performance of ultra-narrow linewidth lasers, but there are still limitations such as low output power and further high-power output relying on optical fiber amplifiers.

[0003] Compared with semiconductor narrow-linewidth laser sources, fiber laser sources have a series of advantages such as high output power, good beam quality, stable optical path structure, and easy all-fiber integration. At present, the realization of ultra-narrow linewidth fiber laser sources is mostly based on the further narrowing of the linewidth of single-frequency fiber lasers. Limited by their short cavity structure, they have the limitations of low output power, high-power laser output relying on special highly doped optical fibers, and difficulty in further high-power breakthroughs. Multi-longitudinal mode fiber lasers have high laser output power, but they need to rely on ultra-narrowband FP and WGM filters to realize single longitudinal mode. There are a series of problems such as high insertion loss, poor stability, high cost, and difficulty in system integration, which seriously hinder the industrial promotion and application of high-performance, high-power ultra-narrow linewidth fiber lasers. Summary of the invention

[0004] In view of the problems existing in the prior art, it is necessary to design a high-power ultra-narrow linewidth fiber laser source module with good all-fiber integration and low cost.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A high-power ultra-narrow linewidth fiber laser source module mainly comprises a multi-longitudinal mode fiber laser, a fiber circulator, a fiber beam splitter and a high-quality factor fiber ring cavity; the output end of the multi-longitudinal mode fiber laser is connected to the second port of the fiber circulator, the third port of the fiber circulator is connected to the input port of the fiber beam splitter, the second output port of the fiber beam splitter is connected to the first port of the high-quality factor fiber ring cavity, and the fourth port of the high-quality factor fiber ring cavity is connected to the first port of the fiber circulator to form an optical feedback loop;

[0007] The laser output by the multi-longitudinal mode fiber laser is transmitted to the input port of the fiber beam splitter through the second port and the third port of the fiber circulator in sequence; the laser output from the first output port of the fiber beam splitter is used as the output of the entire laser source module, and the laser output from the second output port of the fiber beam splitter is injected into the first port of the high-quality factor fiber ring cavity, and resonatedly output through the fourth port of the high-quality factor fiber ring cavity, and the resonantly output laser is fed back to the resonant cavity of the multi-longitudinal mode fiber laser through the first port of the fiber circulator;

[0008] The resonant cavity of the multi-longitudinal mode fiber laser is inconsistent with the cavity length of the high-quality factor fiber ring cavity, resulting in a vernier effect. By adjusting the cavity lengths of the two, it is ensured that only one longitudinal mode resonates through the high-quality factor ring cavity under the vernier effect; this single longitudinal mode is fed back into the resonant cavity of the multi-longitudinal mode fiber laser through an optical feedback loop, thereby realizing ultra-narrow linewidth and single longitudinal mode excitation of the multi-longitudinal mode fiber laser.

[0009] Furthermore, the multi-longitudinal mode fiber laser adopts a double-clad gain fiber as the gain medium in the resonant cavity, and adopts a multi-longitudinal mode laser diode and a pump signal photosynthesizer to pump the gain medium, so that the resonant cavity of the laser can achieve single longitudinal mode output without shortening the cavity length and reducing the reflection bandwidth of the resonant cavity end mirror; on the contrary, when there is no optical feedback, the resonant cavity of the laser presents a multi-longitudinal mode state.

[0010] Furthermore, the high-quality factor fiber ring cavity is manufactured by fusing optical fibers into a ring, and comprises two sets of coupled optical fibers, both of which are coupled with the fiber ring cavity through the potential field between the fiber ring cavity, thereby forming four input / output ports together; and when the input laser frequency is at the resonant frequency of the high-quality factor fiber ring cavity and is input from the first port, the fourth port of the high-quality factor fiber ring cavity is in a high transmittance state of resonant transmission.

[0011] Furthermore, the high-quality factor fiber ring cavity can be realized by fusing the entire optical fiber into a fiber ring, and then the two coupling optical fibers are respectively coupled to the fiber ring by taper coupling; it can also be realized by directly fusing the auxiliary fibers of two commercial small-splitting ratio fiber couplers into a fiber ring.

[0012] Furthermore, the optical fiber beam splitter is implemented by using a tapered optical fiber coupler.

[0013] Furthermore, the optical fiber components of the high-power ultra-narrow linewidth optical fiber laser source module are connected by optical fiber fusion splicing to form an all-optical fiber structure.

[0014] Furthermore, the high-power ultra-narrow linewidth fiber laser source module is entirely encapsulated in sound insulation material to further reduce external interference and improve the quality of laser output.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The high-power ultra-narrow linewidth fiber laser source module provided by the present invention realizes single longitudinal mode resonant output by designing the resonant cavity of the multi-longitudinal mode fiber laser to be inconsistent with the cavity length of the high-quality factor fiber ring cavity, and then injects the single longitudinal mode feedback into the resonant cavity of the multi-longitudinal mode fiber laser through an optical feedback loop, so as to realize single longitudinal mode and ultra-narrow linewidth excitation of the entire laser source module, breaking through the dependence of high-power single-frequency fiber laser on short resonant cavity and highly doped gain fiber, and overcoming the limitation of traditional long-cavity fiber laser in single longitudinal mode selection relying on ultra-narrowband filters such as FP and WGM, and having the advantages of high power, ultra-narrow linewidth, etc.

[0017] Secondly, the high-power ultra-narrow linewidth fiber laser source module provided by the present invention is manufactured by adopting all-fiber devices and fiber fusion splicing, and has the advantages of good all-fiber integration, good environmental stability, and easy miniaturization in structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a multi-longitudinal mode fiber laser provided in an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of the structure of a high-power ultra-narrow linewidth fiber laser source module provided by an embodiment of the present invention;

[0020] Explanation of the numbers in the figure: 1. multi-longitudinal mode fiber laser, 1-1. fiber end face reflector, 1-2. double-clad gain fiber, 1-3. double-clad fiber grating, 1-4. pump signal photosynthesizer, 1-5. multi-mode laser diode; 2. fiber circulator, 2-1. first port of fiber circulator, 2-2. second port of fiber circulator, 2-3. third port of fiber circulator; 3. fiber beam splitter, 3-1. input port of fiber beam splitter, 3-2. first output port of fiber beam splitter, 3-3. second output port of fiber beam splitter; 4. high quality factor fiber ring cavity, 4-1. fiber coupler, 4-2. fiber coupler, 4-1-1. first port of high quality factor fiber ring cavity, 4-1-2. second port of high quality factor fiber ring cavity, 4-2-1. fourth port of high quality factor fiber ring cavity, 4-1-2. second port of high quality factor fiber ring cavity, 4-2-2. third port of high quality factor fiber ring cavity. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0023] In addition, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus.

[0024] like Figure 2 As shown, a high-power ultra-narrow linewidth laser source module provided by the present invention comprises a multi-longitudinal mode fiber laser 1, a fiber circulator 2, a fiber beam splitter 3, and a high-quality factor fiber ring cavity 4, which are connected to each other by fiber fusion splicing; the output end of the multi-longitudinal mode fiber laser 1 is connected to the second port 2-2 of the fiber circulator 2, the third port 2-3 of the fiber circulator 2 is connected to the input port 3-1 of the fiber beam splitter 3, the second output port 3-3 of the fiber beam splitter 3 is connected to the first port 4-1-1 of the high-quality factor fiber ring cavity 4, and the fourth port 4-2-1 of the high-quality factor fiber ring cavity 4 is connected to the first port 2-1 of the fiber circulator 2, so as to form an optical feedback loop;

[0025] The laser output by the multi-longitudinal mode fiber laser 1 is transmitted to the input port 3-1 of the fiber beam splitter 3 through the second port 2-2 and the third port 2-3 of the fiber circulator 2 in sequence; the laser output from the first output port 3-2 of the fiber beam splitter 3 is used as the output of the entire laser source module, and the laser output from the second output port 3-3 of the fiber beam splitter 3 is injected into the first port 4-1-1 of the high-quality factor fiber ring cavity 4, and is resonated and output through the fourth port 4-2-1 of the high-quality factor fiber ring cavity 4, and the laser resonated and output from the fourth port 4-2-1 is fed back to the resonant cavity of the multi-longitudinal mode fiber laser 1 through the first port 2-1 of the fiber circulator 2.

[0026] As a specific implementation method, Figure 1As shown, the laser resonant cavity of the multi-longitudinal mode fiber laser 1 is formed by welding a fiber end reflector 1-1 with a reflectivity of 99.8%@1550nm and a double-clad fiber Bragg grating 1-3 with a reflectivity of ~60%@1550nm at the two ends of a double-clad gain fiber 1-2, wherein the double-clad gain fiber 1-2 is a double-clad ytterbium erbium co-doped single-mode fiber of model DCE-EY-10 / 128P produced by Coractive Company, and its length is 70cm, and the reflection bandwidth of the double-clad fiber Bragg grating 1-3 is 0.02nm; a multi-mode laser diode 1-5 with a central wavelength of 976nm and a maximum output power of 1.5W pumps the resonant cavity of the multi-longitudinal mode fiber laser 1 through a pump signal optical combiner 1-4, and the generated laser is output from the input signal fiber of the pump signal optical combiner 1-4.

[0027] The optical fiber beam splitter 3 is a 10 / 90 tapered optical fiber coupler, and the laser output power ratio of the first output port 3-2 and the second output port 3-3 is 90 / 10.

[0028] The high quality factor annular cavity 4 is composed of two tapered fiber couplers 4-1 and 4-2 with a splitting ratio of 2 / 98, and is made by fusing the output auxiliary fiber of the fiber coupler 4-1 with the output auxiliary fiber of the fiber coupler 4-2, and fusing the input auxiliary fiber of the fiber coupler 4-1 with the input auxiliary fiber of the fiber coupler 4-2 into a ring.

[0029] The resonant cavity fiber length of the multi-longitudinal mode fiber laser 1 is 1 m; the ring cavity fiber length of the high quality factor ring cavity 4 is 1.2 m, and the quality factor of the fiber ring cavity is 8.7×10 7 In the specific implementation process, this quality factor may be affected by the splitting ratio accuracy of the selected fiber coupler, the insertion loss of the coupler, and the quality of the fusion splice, but the quality factor achieved in this step should be greater than 10 7 .

[0030] In order to achieve single longitudinal mode and ultra-narrow linewidth output of the entire laser source module, the specific adjustment process is as follows: adjust the wavelength of the multi-longitudinal mode fiber laser 1 so that the frequency of one of the longitudinal modes is located at the resonant frequency of the high-quality factor fiber ring cavity 4. Due to the vernier effect, only this longitudinal mode can resonate in the high-quality factor fiber ring cavity 4 at this time, and resonate and output from the fourth port 4-2-1. The resonantly output single longitudinal mode laser is fed back to the resonant cavity of the multi-longitudinal mode fiber laser 1 through the first port 2-1 of the fiber circulator 2, thereby affecting the longitudinal mode competition of the multi-longitudinal mode fiber laser and forming a single longitudinal mode competitive advantage. Finally, the entire laser source module achieves high-power, single longitudinal mode, ultra-narrow linewidth laser output, with a maximum output power of 303mW and a basic linewidth of the output laser of 449Hz.

[0031] The present invention demonstrates a high-power ultra-narrow linewidth fiber laser source module, which realizes the high power of the fiber laser based on the long resonant cavity structure of the multi-longitudinal mode fiber laser, realizes single longitudinal mode feedback through the inconsistency between the resonant cavity of the fiber laser and the cavity length of the high-quality factor fiber ring cavity outside the feedback, and realizes ultra-narrow linewidth single longitudinal mode excitation of the multi-longitudinal mode fiber laser through single longitudinal mode feedback injection outside the high-quality factor ring cavity. The system integration of its all-fiber structure provides a stable, reliable, low-loss and low-cost implementation method for realizing the high power of the ultra-narrow linewidth laser source.

[0032] The above description is only a preferred implementation structure of the module of the present invention, and does not limit the patent scope of the present invention. Without departing from the principles of the present invention, all equivalent structures made using the contents of the present invention description and drawings are included in the protection scope of the patent of the present invention.

Claims

1. A high-power ultra-narrow linewidth fiber laser source module, characterized in that: The module mainly includes a multi-longitudinal mode fiber laser, a fiber circulator, a fiber beam splitter and a high-quality factor fiber ring cavity; the output end of the multi-longitudinal mode fiber laser is connected to the second port of the fiber circulator, the third port of the fiber circulator is connected to the input port of the fiber beam splitter, the second output port of the fiber beam splitter is connected to the first port of the high-quality factor fiber ring cavity, and the fourth port of the high-quality factor fiber ring cavity is connected to the first port of the fiber circulator to form an optical feedback loop; The laser output by the multi-longitudinal mode fiber laser is transmitted to the input port of the fiber beam splitter through the second port and the third port of the fiber circulator in sequence; The laser output from the first output port of the fiber beam splitter is used as the output of the entire laser source module, and the laser output from the second output port of the fiber beam splitter is injected into the first port of the high-quality factor fiber ring cavity, resonated and output through the fourth port of the high-quality factor fiber ring cavity, and fed back to the resonant cavity of the multi-longitudinal mode fiber laser through the first port of the fiber circulator; The resonant cavity of the multi-longitudinal mode fiber laser is inconsistent with the cavity length of the high-quality factor fiber ring cavity, resulting in a vernier effect. By adjusting the cavity lengths of the two, only one longitudinal mode resonates through the high-quality factor ring cavity under the vernier effect; this single longitudinal mode is fed back into the resonant cavity of the multi-longitudinal mode fiber laser through an optical feedback loop, thereby realizing ultra-narrow linewidth and single longitudinal mode excitation of the multi-longitudinal mode fiber laser.

2. A high-power ultra-narrow linewidth fiber laser source module according to claim 1, characterized in that: The multi-longitudinal mode fiber laser adopts double-clad gain fiber as the gain medium in the resonant cavity, and adopts a multi-mode laser diode and a pump signal optical combiner for pumping.

3. A high-power ultra-narrow linewidth fiber laser source module according to claim 1, characterized in that: The high-quality factor fiber ring cavity is manufactured by fusing optical fibers into a ring, and comprises two groups of coupling optical fibers, both of which are coupled with the fiber ring cavity through the potential field between the fiber ring cavity and the fiber ring cavity, thereby forming four input / output ports together; and when the input laser frequency is at the resonant frequency of the high-quality factor fiber ring cavity and is input from the first port, the fourth port of the high-quality factor fiber ring cavity is in a high transmittance state of resonant transmission.

4. A high-power ultra-narrow linewidth fiber laser source module according to claim 3, characterized in that: The high quality factor fiber ring cavity can be realized by fusing the entire optical fiber into a fiber ring, and then tapering and coupling two coupling optical fibers to the fiber ring respectively, or by directly fusing the auxiliary fibers of two commercial small splitting ratio fiber couplers into a fiber ring.

5. A high-power ultra-narrow linewidth fiber laser source module according to any one of claims 1 to 4, characterized in that: The optical fiber components of the high-power ultra-narrow linewidth optical fiber laser source module are connected by optical fiber fusion splicing to form an all-optical fiber structure.

6. A high-power ultra-narrow linewidth fiber laser source module according to claim 5, characterized in that: The high-power ultra-narrow linewidth fiber laser source module is entirely encapsulated in sound insulation material.

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