A high power ultra-narrow linewidth fiber laser source module

Abstract

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

Description

Technical Field

[0001] This invention belongs to the field of fiber laser technology, and particularly relates to a high-power ultra-narrow linewidth fiber laser source module. Background Technology

[0002] Ultra-narrow linewidth laser sources have important applications in coherent lidar, dense wavelength division multiplexing (DWDM) optical communication, gravitational wave detection, and quantum optics. For example, in coherent wind lidar, the ultra-narrow linewidth of the laser source is beneficial for detecting small frequency shift signals in Doppler wind measurement, which corresponds to low wind speed measurement scenarios. In data centers of optical communication networks, the ultra-narrow linewidth of the laser source helps to increase the communication capacity of DWDM fiber optic links, meeting the high-speed and high-capacity requirements of modern data transmission. Currently, although the combination of semiconductor lasers and high-quality factor microcavity technology has enabled ultra-narrow linewidth lasers to achieve significant breakthroughs in miniaturization and high performance, limitations still exist, such as low output power and reliance on fiber amplifiers for further high-power output.

[0003] Compared to semiconductor narrow-linewidth laser sources, fiber laser sources offer a range of advantages, including high output power, superior beam quality, stable optical path structure, and ease of all-fiber integration. Currently, the realization of ultra-narrow linewidth fiber laser sources is largely based on further linewidth narrowing of single-frequency fiber lasers. However, limited by their short-cavity structure, they suffer from low output power, reliance on specialized highly doped fibers for high-power laser output, and difficulties in achieving further high-power breakthroughs. Multi-mode fiber lasers possess high laser output power, but their realization of single-mode operation relies on ultra-narrowband FP and WGM filters, resulting in high insertion loss, poor stability, high cost, and difficulties in system integration. These issues severely hinder the industrial promotion and application of high-performance, high-power ultra-narrow linewidth fiber lasers. Summary of the Invention

[0004] To address the problems existing in the current technology, it is necessary to design a high-power ultra-narrow linewidth fiber laser source module that has good all-fiber integration and low cost.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A high-power ultra-narrow linewidth fiber laser source 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, forming an optical feedback loop;

[0007] The laser output from the multi-longitudinal-mode fiber laser is transmitted sequentially through the second and third ports of the fiber circulator to the input port of the fiber beam splitter; the laser output from the first output port of the fiber beam splitter serves as the output of the entire laser source module; 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, resonates and outputs through the fourth port of the high-quality factor fiber ring cavity, and the resonant 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 has a different cavity length than 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 fiber ring cavity under the vernier effect. This longitudinal mode is fed back into the resonant cavity of the multi-longitudinal-mode fiber laser via an optical feedback loop, realizing ultra-narrow linewidth and single-longitudinal-mode excitation of the multi-longitudinal-mode fiber laser.

[0009] Furthermore, the multi-longitudinal-mode fiber laser uses double-clad gain fiber as the gain medium in the resonant cavity, and employs a multi-longitudinal-mode laser diode and a pump signal beam combiner to pump the gain medium, so that the resonant cavity of the laser can achieve single-longitudinal-mode output without shortening the cavity length or reducing the reflection bandwidth of the resonant cavity end face mirror; conversely, when there is no optical feedback, the resonant cavity of the laser exhibits a multi-longitudinal-mode state.

[0010] Furthermore, the high-quality factor fiber ring cavity is fabricated by fiber fusion splicing and includes two sets of coupling fibers, both of which are coupled to the fiber ring cavity through a potential field between them, forming four input / output ports. 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 achieved by fusing a whole fiber into a fiber ring, and then coupling two coupling fibers to the fiber ring with tapered coupling; or it can be achieved by directly fusing the auxiliary fibers of two commercial small-splitting-ratio fiber couplers into a fiber ring.

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

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

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

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The high-power ultra-narrow linewidth fiber laser source module provided by this invention achieves single-longitudinal-mode resonant output by designing the resonant cavity of the multi-longitudinal-mode fiber laser to have a different cavity length than the high-quality factor fiber ring cavity, and utilizing the vernier effect. Then, the single-longitudinal-mode is fed back into the resonant cavity of the multi-longitudinal-mode fiber laser through an optical feedback loop, realizing single-longitudinal-mode and ultra-narrow linewidth excitation of the entire laser source module. This breaks through the dependence of high-power single-frequency fiber lasers on short resonant cavities and highly doped gain fibers, and overcomes the limitation of traditional long-cavity fiber lasers that rely on ultra-narrowband filters such as FP and WGM for single-longitudinal-mode selection. It has advantages such as high power and ultra-narrow linewidth.

[0017] Secondly, the high-power ultra-narrow linewidth fiber laser source module provided by the present invention is made using all-fiber devices and fiber fusion splicing, and has advantages in structure such as good all-fiber integration, good environmental stability, and easy miniaturization. Attached Figure Description

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

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

[0020] The following are the labeling instructions in the diagram: 1. Multimode fiber laser; 1-1. Fiber end face mirror; 1-2. Double-clad gain fiber; 1-3. Double-clad fiber grating; 1-4. Pump signal beam combiner; 1-5. Multimode 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 Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in further 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 with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0023] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0024] like Figure 2 As shown, the present invention provides a high-power ultra-narrow linewidth laser source module, including 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 interconnected 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, forming an optical feedback loop;

[0025] The laser output from the multi-longitudinal-mode fiber laser 1 is transmitted sequentially through the second port 2-2 and the third port 2-3 of the fiber circulator 2 to the input port 3-1 of the fiber beam splitter 3. The laser output from the first output port 3-2 of the fiber beam splitter 3 serves as the output of the entire laser source module. 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 resonantly output through the fourth port 4-2-1 of the high-quality factor fiber ring cavity 4. The laser resonantly 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, such as Figure 1As shown, the laser resonant cavity of the multi-longitudinal-mode fiber laser 1 is formed by fusing a fiber end-face 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 both ends of a double-clad gain fiber 1-2. The double-clad gain fiber 1-2 is a double-clad ytterbium-erbium co-doped single-mode fiber of model DCE-EY-10 / 128P manufactured by Coractive, with a length of 70cm. The reflection bandwidth of the double-clad fiber Bragg grating 1-3 is 0.02nm. A multimode laser diode 1-5 with a center 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. The generated laser is output from the input signal fiber of the pump signal optical combiner 1-4.

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

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

[0029] The resonant fiber length of the multi-longitudinal-mode fiber laser 1 is ~1m; the ring cavity fiber length of the high-quality factor fiber ring cavity 4 is ~1.2m, and the realized fiber ring cavity has a quality factor of 8.7×10⁻⁶. 7 In practice, this quality factor may be affected by the splitting ratio accuracy of the selected fiber coupler, the insertion loss of the coupler, and the fusion splice quality, but the quality factor achieved in this step should be greater than 10. 7 .

[0030] To achieve single-longitudinal-mode, ultra-narrow linewidth output from the entire laser source module, the specific adjustment process is as follows: The wavelength of the multi-longitudinal-mode fiber laser 1 is adjusted 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 and be output from the fourth port 4-2-1. The single-longitudinal-mode laser output 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 449Hz for the output laser.

[0031] This invention presents a high-power ultra-narrow linewidth fiber laser source module. It achieves high power for the fiber laser based on a long resonant cavity structure of a multi-longitudinal-mode fiber laser. Single-longitudinal-mode feedback is achieved by varying the cavity lengths of the fiber laser's resonant cavity and the external high-quality factor fiber ring cavity. Ultra-narrow linewidth single-longitudinal-mode excitation of the multi-longitudinal-mode fiber laser is achieved through single-longitudinal-mode feedback injection outside the high-quality factor ring cavity. Its all-fiber system integration provides a stable, reliable, low-loss, and low-cost method for realizing high power in ultra-narrow linewidth laser sources.

[0032] The above description is merely a preferred embodiment of the module of the present invention and does not limit the patent scope of the present invention. Any equivalent structure made using the contents of the present invention specification and drawings without departing from the principles of the present invention is included within the protection scope of the present invention patent.

Claims

1. A high power ultra-narrow linewidth fiber laser source module, characterized in that, The module mainly comprises a multi-longitudinal mode fiber laser, a fiber circulator, a fiber beam splitter and a high-quality factor fiber ring cavity; an output end of the multi-longitudinal mode fiber laser is connected with a second port of the fiber circulator, a third port of the fiber circulator is connected with an input port of the fiber beam splitter, a second output port of the fiber beam splitter is connected with a first port of the high-quality factor fiber ring cavity, and a fourth port of the high-quality factor fiber ring cavity is connected with a first port of the fiber circulator, forming a light 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 output as the output of the whole 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 through the fourth port of the high-quality factor fiber ring cavity, and fed back into 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, a vernier effect is generated, and by adjusting the cavity lengths of the two, only one longitudinal mode resonates through the high-quality factor fiber ring cavity under the vernier effect; the longitudinal mode is fed back into the resonant cavity of the multi-longitudinal mode fiber laser through the light feedback loop, and super-narrow linewidth and single-longitudinal-mode excitation of the multi-longitudinal mode fiber laser are realized.

2. The high power ultra-narrow linewidth fiber laser source module of claim 1, wherein, The multi-longitudinal mode fiber laser adopts a double-clad gain fiber as the gain medium in the resonant cavity and adopts a multimode laser diode and a pump signal light combiner for pumping.

3. The high power ultra-narrow linewidth fiber laser source module of claim 1, wherein, The high-quality factor fiber ring cavity is made by fusing a whole fiber into a ring, contains two groups of coupled fibers, and is coupled with the fiber ring cavity through evanescent field, to form four input / output ports; 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. The high power ultra-narrow linewidth fiber laser source module of claim 3, wherein, The high-quality factor fiber ring cavity can be realized by fusing a whole fiber into a ring, coupling two coupled fibers with the fiber ring through tapering, or directly fusing two auxiliary fibers of a commercial small-split-ratio fiber coupler into a fiber ring.

5. The high power ultra-narrow linewidth fiber laser source module of any of claims 1-4, wherein, The high-power super-narrow-linewidth fiber laser source module is connected by fusing the fibers between the fiber elements, to form a full-fiber structure.

6. The high power ultra-narrow linewidth fiber laser source module of claim 5, wherein, The high-power super-narrow-linewidth fiber laser source module is packaged in a soundproof material.

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