A high-energy single-frequency pulse amplifier integrating pump and active optical fiber

Abstract

The present invention discloses a high-energy single-frequency pulse amplifier integrating pump and active optical fiber, which relates to the field of pulse laser amplification technology, including: a single-frequency seed source, a modulator, a first integrated structure, a first isolation filter, a second integrated structure, a second isolation filter, a third integrated structure, and an output head; the present invention mainly replaces the traditional transmission optical fiber connection in the manufacturing process by a wavelength division multiplexer and a pump combiner, and directly adopts the two ends of the gain optical fiber for welding, so as to build a high-energy single-frequency pulse amplification structure. The technical solution proposed by the present invention can shorten the system optical fiber by 3.5-6.5 meters, reduce 7 welding points, improve the stimulated Brillouin scattering threshold in the process of high-energy single-frequency pulse amplification, and improve the laser output power and system stability.

Description

Technical Field

[0001] The invention relates to the technical field of pulse laser amplification, and more particularly to a large-energy single-frequency pulse amplifier integrating pumping and active optical fiber. Background Art

[0002] At present, single-frequency fiber lasers can be widely used in many fields such as fiber-optic communication, fiber-optic sensing, coherent detection, quantum information, etc., and therefore are valued by many research institutions at home and abroad. Compared with continuous single-frequency fiber lasers, the research on pulsed single-frequency fiber lasers has greater technical difficulty, especially the research progress of single-frequency pulsed fiber lasers with large energy and high peak power with a line width of kilohertz is relatively slow, and this type of fiber laser is also a high-quality light source urgently needed in the fields of laser radar, laser ranging, laser velocity measurement, cloud height meter, etc. The 1.5μm band is an atmospheric transmission window, which is a band with very small transmission loss of electromagnetic radiation in the atmosphere. Therefore, it is an ideal light source in many fields such as laser radar, coherent detection, laser ranging, etc. The 1.5μm single-frequency pulse laser generally uses a single-frequency seed source to achieve pulse modulation through a modulator, and then amplifies it through optical fiber to achieve high-energy, high-peak value laser pulse output.

[0003] However, during the fiber amplification process, the peak power and single pulse energy will be limited by a variety of nonlinear effects, especially the stimulated Brillouin scattering (SBS) effect, resulting in the inability to increase the pulse energy and the distortion of the pulse waveform, which ultimately makes it difficult to increase the laser power and the single pulse energy is low, resulting in limited laser applications.

[0004] Therefore, for single-frequency, high-energy pulsed fiber lasers, how to effectively suppress the nonlinear effects during the amplification process is an urgent problem that technicians in this field need to solve. Summary of the invention

[0005] In view of this, the present invention provides a high-energy single-frequency pulse amplifier integrating pump and active fiber, the purpose of which is to solve the problem of nonlinear suppression in the amplification process of single-frequency high-energy pulse fiber laser. Through the integrated design of pump and active fiber, the fusion point and fiber length of the laser are greatly reduced, the stimulated Brillouin scattering threshold of the fiber laser is increased, and the pulse laser output power is further increased.

[0006] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a high-energy single-frequency pulse amplifier integrating pump and active fiber, comprising: a single-frequency seed source, a modulator, a first integrated structure, a first isolation filter, a second integrated structure, a second isolation filter, a third integrated structure, and an output head;

[0007] The output of the single-frequency seed source is fused and connected to the input of the modulator, the output of the modulator is fused and connected to the input of the first integrated structure, and the output of the first integrated structure is fused and connected to the input of the first isolation filter;

[0008] The output of the first isolation filter is fused and connected to the input of the second integrated structure, and the output of the second integrated structure is fused and connected to the input of the second isolation filter;

[0009] The output of the second isolation filter is fused and connected to the input of the third integrated structure, and the third integrated structure is connected to the output head.

[0010] Preferably, the first integrated structure includes a forward wavelength division multiplexer, a first gain fiber and a reverse wavelength division multiplexer; the front end of the first gain fiber is directly fused to the forward wavelength division multiplexer, and the rear end of the first gain fiber is directly fused to the reverse wavelength division multiplexer.

[0011] The first integrated structure can realize the first-level pre-amplification of pulsed laser; when making a wavelength division multiplexer, it replaces the traditional transmission optical fiber and directly uses the front and back ends of the first gain optical fiber for welding. During the system pulse amplification process, two welding points can be reduced and the optical fiber can be shortened by at least 1-2 meters.

[0012] Preferably, the output of the modulator is fusion-connected to the input of the forward wavelength division multiplexer; and the output of the reverse wavelength division multiplexer is fusion-connected to the input of the first isolation filter.

[0013] The single-frequency seed source is modulated into a pulse laser output by a modulator, enters the first integrated structure, is pre-amplified by the first integrated structure, and then enters the first isolation filter to filter out clutter.

[0014] Preferably, the first gain optical fiber is an erbium-doped single-mode optical fiber, which has small coupling loss with the line and low noise.

[0015] Preferably, the second integrated structure includes a first forward combiner, a second gain fiber and a first reverse combiner; the front end of the second gain fiber is directly fused to the first forward combiner, and the rear end of the second gain fiber is directly fused to the first reverse combiner.

[0016] The second integrated structure realizes secondary amplification of the pulsed laser, and is directly fused with the first forward combiner and the first reverse combiner through the second gain fiber, thereby reducing two fusion points in the second integrated structure and shortening the transmission fiber by 1-2 meters.

[0017] Preferably, the output of the first isolation filter is fused to the input of the first forward combiner; and the output of the first reverse combiner is fused to the input of the second isolation filter.

[0018] The residual pump light and other stray light generated by amplification are filtered out through the isolation filter, and then the pulse laser is amplified twice through the second integrated structure and enters the second isolation filter to complete the filtering process again.

[0019] Preferably, the second gain optical fiber is a 6 / 126, 10 / 125, or 12 / 130 μm double-clad erbium-ytterbium co-doped optical fiber.

[0020] Preferably, the third integrated structure includes a second forward combiner, a third gain fiber and a second reverse combiner; the front end of the third gain fiber is directly fused to the second forward combiner, and the rear end of the third gain fiber is directly fused to the second reverse combiner.

[0021] The third integrated structure is the pulse laser main amplification structure, which is directly fused with the second forward combiner and the second reverse combiner through the third gain fiber, eliminating the transmission fiber in the combiner, and directly fused the output head to the output fiber of the second reverse combiner, reducing 3 fusion points in the third integrated structure and shortening the transmission fiber by 1.5-2.5 meters.

[0022] Preferably, the output of the second isolation filter is fused and connected to the input of the second forward combiner; and the second reverse combiner is connected to the output head.

[0023] Preferably, the third gain fiber adopts 25 / 300 double-clad erbium co-doped fiber; the use of 25 / 300 double-clad erbium co-doped fiber is easy to achieve high coupling efficiency, and at the same time, the large core diameter (25μm) maintains a large mode field diameter, reducing the length of the optical fiber used, thereby reducing the nonlinear effect of the optical fiber that deteriorates the system performance.

[0024] It can be seen from the above technical solution that, compared with the prior art, the present invention provides a high-energy single-frequency pulse amplifier integrating pump and active optical fiber, including: a single-frequency seed source, a modulator, a first integrated structure, a first isolation filter, a second integrated structure, a second isolation filter, a third integrated structure, and an output head; the present invention mainly replaces the traditional transmission optical fiber connection through a wavelength division multiplexer and a pump combiner in the manufacturing process, and directly uses the two ends of the gain optical fiber for welding, so as to build a high-energy single-frequency pulse amplification structure.

[0025] The technical solution proposed in the present invention has the following beneficial effects: through the integrated amplification structure, the system optical fiber can be shortened by 3.5-6.5 meters, the number of fusion points can be reduced by 7, the stimulated Brillouin scattering threshold in the process of high-energy single-frequency pulse amplification can be improved, the laser output power and the stability of the system can be improved, and the current laser power output power level can be broken through, providing a reliable and stable high-energy pulse light source for application expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the structure provided by the present invention.

[0028] Among them, in the figure, 1-single frequency seed source, 2-fusion point, 3-modulator, 4-forward wavelength division multiplexer, 5-first gain fiber, 6-reverse wavelength division multiplexer, 7-first isolation filter, 8-first forward combiner, 9-second gain fiber, 10-first reverse combiner, 11-second isolation filter, 12-second forward combiner, 13-third gain fiber, 14-second reverse combiner, 15-output head. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The embodiment of the present invention discloses a high-energy single-frequency pulse amplifier integrating pump and active fiber, such as Figure 1 As shown, it includes: a single-frequency seed source 1, a modulator 3, a first integrated structure, a first isolation filter 7, a second integrated structure, a second isolation filter 11, a third integrated structure, and an output head 15;

[0031] The output of the single-frequency seed source 1 is fused and connected to the input of the modulator 3, the output of the modulator 3 is fused and connected to the input of the first integrated structure, and the output of the first integrated structure is fused and connected to the input of the first isolation filter 7;

[0032] The output of the first isolation filter 7 is fused and connected to the input of the second integrated structure, and the output of the second integrated structure is fused and connected to the input of the second isolation filter 11;

[0033] The output of the second isolation filter 11 is fused and connected to the input of the third integrated structure, and the third integrated structure is connected to the output head 15 .

[0034] In one embodiment of the present invention, a single-frequency seed source 1 is modulated into a pulsed laser output by a modulator 3, and the pulsed laser undergoes a first-level pre-amplification through a first integrated structure; after the first-level pre-amplification, the residual pump light and stray light generated by other amplification are filtered out through a first isolation filter 7, and then a second-level amplification is performed through a second integrated structure; after the second-level amplification, it passes through a second isolation filter 11 and enters a third integrated structure for amplification, and finally is connected to the output head 10 through the output end of the second reverse combiner 14.

[0035] Furthermore, the first integrated structure includes a forward wavelength division multiplexer 4, a first gain fiber 5 and a reverse wavelength division multiplexer 6; the front end of the first gain fiber 5 is directly fused with the forward wavelength division multiplexer 4, and the rear end of the first gain fiber 5 is directly fused with the reverse wavelength division multiplexer 6.

[0036] The first integrated structure can realize the first-level pre-amplification of the pulse laser; when making a wavelength division multiplexer, instead of the traditional transmission optical fiber, the front and rear ends of the first gain optical fiber 5 are directly fused. During the system pulse amplification process, two fusion points can be reduced, and the optical fiber can be shortened by at least 1-2 meters.

[0037] Furthermore, the output of the modulator 3 is fusion-connected to the input of the forward wavelength division multiplexer 4 ; and the output of the reverse wavelength division multiplexer 6 is fusion-connected to the input of the first isolation filter 7 .

[0038] The single-frequency seed source 1 is modulated into a pulse laser output by the modulator 3, enters the first integrated structure, is pre-amplified by the first integrated structure, and then enters the first isolation filter 7 to filter out clutter.

[0039] In one embodiment of the present invention, a single-frequency seed source 1 is modulated into a pulsed laser output by a modulator 3, and the pulsed laser is pre-amplified in one stage through a first integrated structure. The forward wavelength division multiplexer 4, the first gain fiber 5 and the reverse wavelength division multiplexer 6 are integrated. That is, when manufacturing the wavelength division multiplexer, the transmission optical fibers at both ends of the first gain optical fiber 5 are removed, and the front and rear ends of the first gain optical fiber 5 are directly welded with the forward wavelength division multiplexer 4 and the reverse wavelength division multiplexer 6. Compared with the existing traditional wavelength division multiplexer manufacturing process using transmission optical fiber, two welding points can be reduced during the system pulse amplification process, and the optical fiber can be shortened by at least 1-2 meters.

[0040] Furthermore, the first gain fiber 5 adopts erbium-doped single-mode fiber; since erbium-doped fiber has a gain spectrum profile of 80nm wide, its operating wavelength just falls in the optimal wavelength region of optical fiber communication (1.31-1.55μm), the gain is relatively high, and the required pump power is relatively low. In addition, erbium-doped fiber itself is a gain medium, so the coupling loss with the line is very small and the noise is low.

[0041] Further, the second integrated structure includes a first forward beam combiner 8, a second gain fiber 9 and a first reverse beam combiner 10;

[0042] The front end of the second gain optical fiber 9 is directly fused to the first forward combiner 8 , and the rear end of the second gain optical fiber 9 is directly fused to the first reverse combiner 10 .

[0043] The second integrated structure realizes secondary amplification of the pulsed laser, and is directly fused with the first forward combiner 8 and the first reverse combiner 10 through the second gain fiber 9, thereby reducing two fusion points in the second integrated structure and shortening the transmission fiber by 1-2 meters.

[0044] Furthermore, the output of the first isolation filter 7 is fused and connected to the input of the first forward combiner 8 ; the output of the first reverse combiner 10 is fused to the input of the second isolation filter 11 .

[0045] The residual pump light and other stray light generated by amplification are filtered out by the first isolation filter 7, and then the pulse laser is amplified twice by the second integrated structure and enters the second isolation filter 11 to complete filtering again.

[0046] In one embodiment of the present invention, after the primary prevention amplification by the first integrated structure, the residual pump light and the stray light generated by other amplification are filtered out by the first isolation filter 7, and then the secondary amplification is performed by the second integrated structure of the first forward combiner 8, the first reverse combiner 10 and the second gain fiber 9. Similar to the amplification structure in the first integrated structure, the first forward combiner 8 and the first reverse combiner 10 are directly fused with the front and rear ends of the second gain fiber 9 during the manufacturing process, eliminating the transmission optical fiber at both ends of the second gain fiber 9. Compared with the existing traditional structure, two fusion points can be reduced in the secondary amplification, and the transmission optical fiber can be shortened by 1-2 meters.

[0047] Furthermore, the second gain optical fiber 9 adopts a small core diameter double-clad erbium-ytterbium co-doped optical fiber, including 6 / 126, 10 / 125, and 12 / 130 μm double-clad erbium-ytterbium co-doped optical fibers.

[0048] Further, the third integrated structure includes a second forward combiner 12, a third gain fiber 13 and a second reverse combiner 14;

[0049] The front end of the third gain fiber 13 is directly fused to the second forward combiner 12 , and the rear end of the third gain fiber 13 is directly fused to the second reverse combiner 14 .

[0050] The third integrated structure is a pulse laser main amplification structure, which is directly fused with the second forward combiner 12 and the second reverse combiner 14 through the third gain fiber 13. At the same time, the second reverse combiner 14 is directly fused with the output head 15. In the third integrated structure, three fusion points can be reduced and the transmission optical fiber can be shortened by 1.5-2.5 meters.

[0051] Furthermore, the output of the second isolation filter 11 is fused and connected to the input of the second forward combiner 12 ; and the second reverse combiner 14 is connected to the output head 15 .

[0052] In one embodiment of the present invention, after passing through the secondary amplification structure of the second integrated structure, the second isolation filter 11 enters the main amplification structure, and the main amplification structure also adopts a double-ended pumping structure. The second forward combiner 12 and the second reverse combiner 14 are directly fused with the two ends of the third gain fiber 13 during the manufacturing process, eliminating the transmission fiber at both ends of the third gain fiber 13, and finally directly make an output head at the output end of the second reverse combiner 14, eliminating the transmission fiber at the output end of the second reverse combiner 14. Compared with the existing traditional structure, the main amplification structure adopts the integrated manufacturing of beam combining gain, which can reduce 3 fusion points and shorten the optical fiber by 1.5-2.5 meters.

[0053] Among them, the combiner is used as a pump combiner. Through the integrated design of pump and active fiber, it greatly reduces the laser's fusion point and fiber length, improves the stimulated Brillouin scattering threshold of the fiber laser, and further improves the pulsed laser output power.

[0054] Furthermore, the third gain fiber 13 is a 25 / 300 double-clad erbium-ytterbium co-doped fiber.

[0055] The 25 / 300 double-clad Er-Yb co-doped fiber adopts a unique low numerical aperture (NA=0.09) Er-Yb co-doped core design. For applications requiring high power output and high output beam quality (close to single mode), the high numerical aperture (NA=0.46) 300μm diameter cladding waveguide of the 25 / 300 double-clad Er-Yb co-doped fiber allows high-power pumping and is easy to achieve high coupling efficiency. At the same time, the large core diameter (25μm) maintains a large mode field diameter, reducing the length of the optical fiber used, thereby reducing the nonlinear effect of the optical fiber that deteriorates the system performance.

[0056] This design directly uses gain fiber instead of transmission fiber in the integrated structure to make wavelength division multiplexer and combiner. The input and output of the combiner of the traditional amplifier are both transmission fiber, which is then fused with the gain fiber. This integrated technology saves the transmission fiber for fusion of the combiner and the gain fiber, and directly uses the gain fiber as a signal end of the combiner when making the combiner. On the one hand, this solution reduces the system fusion point and improves the stability and reliability of the amplification system. On the other hand, it reduces the fiber length of the amplification system, increases the stimulated Brillouin scattering threshold, and increases the laser output power.

[0057] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred 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.

[0058] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-energy single-frequency pulse amplifier integrating pump and active fiber, characterized in that: include: A single-frequency seed source (1), a modulator (3), a first integrated structure, a first isolation filter (7), a second integrated structure, a second isolation filter (11), a third integrated structure, and an output head (15); The output of the single-frequency seed source (1) is fused connected to the input of the modulator (3), the output of the modulator (3) is fused connected to the input of the first integrated structure, and the output of the first integrated structure is fused connected to the input of the first isolation filter (7); The output of the first isolation filter (7) is fused connected to the input of the second integrated structure, and the output of the second integrated structure is fused connected to the input of the second isolation filter (11); The output of the second isolation filter (11) is fused and connected to the input of the third integrated structure, and the third integrated structure is connected to the output head (15); The first integrated structure comprises a forward wavelength division multiplexer (4), a first gain optical fiber (5) and a reverse wavelength division multiplexer (6); the front end of the first gain optical fiber (5) is directly fused to the forward wavelength division multiplexer (4), and the rear end of the first gain optical fiber (5) is directly fused to the reverse wavelength division multiplexer (6); The second integrated structure comprises a first forward beam combiner (8), a second gain optical fiber (9) and a first reverse beam combiner (10); The front end of the second gain optical fiber (9) is directly fused to the first forward beam combiner (8), and the rear end of the second gain optical fiber (9) is directly fused to the first reverse beam combiner (10); The third integrated structure comprises a second forward beam combiner (12), a third gain optical fiber (13) and a second reverse beam combiner (14); The front end of the third gain optical fiber (13) is directly fused to the second forward beam combiner (12), and the rear end of the third gain optical fiber (13) is directly fused to the second reverse beam combiner (14).

2. A high energy single frequency pulse amplifier integrating pump and active fiber according to claim 1, characterized in that: The output of the modulator (3) is fusion-connected to the input of the forward wavelength division multiplexer (4); and the output of the reverse wavelength division multiplexer (6) is fusion-connected to the input of the first isolation filter (7).

3. The high energy single frequency pulse amplifier integrating pump and active fiber according to claim 1, characterized in that: The first gain optical fiber (5) is an erbium-doped single-mode optical fiber.

4. The high energy single frequency pulse amplifier integrating pump and active fiber according to claim 1, characterized in that: The output of the first isolation filter (7) is fused to the input of the first forward beam combiner (8); and the output of the first reverse beam combiner (10) is fused to the input of the second isolation filter (11).

5. The high energy single frequency pulse amplifier integrating pump and active fiber according to claim 1, characterized in that: The second gain optical fiber (9) is a double-clad erbium-ytterbium co-doped optical fiber.

6. The high energy single frequency pulse amplifier integrating pump and active fiber according to claim 1, characterized in that: The output of the second isolation filter (11) is fused and connected to the input of the second forward beam combiner (12); and the second reverse beam combiner (14) is connected to the output head (15).

7. The high energy single frequency pulse amplifier integrating pump and active fiber according to claim 1, characterized in that: The third gain optical fiber (13) is a 25 / 300 double-clad erbium-ytterbium co-doped optical fiber.

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