A high-pumping-efficiency low-nonlinear-effect fiber laser

Abstract

The application discloses a kind of high pumping efficiency low nonlinear effect fiber laser, sequentially connected seed source, isolator, first circulator, first combiner, first gain fiber, fiber grating, second gain fiber, second combiner, second circulator, still include first pump source, second pump source and output collimator;Fiber grating is total reflection grating, center wavelength is consistent with seed light wavelength, is set between first gain fiber and second gain fiber;Utilize fiber grating, realize the original light path reflection of seed light and secondary amplification, while pumping light transmission to fiber grating will be transmitted to continue transmission.The application can increase the action distance of seed light and gain fiber under the condition that gain fiber is shorter, secondary amplification is carried out to seed light, while effectively inhibiting spontaneous emission effect and nonlinear effect in fiber laser, while secondary utilization is carried out to residual pumping light, effectively improve pumping efficiency, and improve fiber laser performance.

Description

Technical Field

[0001] This invention relates to the field of fiber laser and fiber amplifier technology, and in particular to an all-fiber structure fiber laser based on a fiber grating with high pump efficiency, low ASE and low nonlinear effect. Background Technology

[0002] Fiber lasers possess advantages such as high stability, strong anti-interference capability, long coherence length, good beam quality, high coupling and conversion efficiency, and convenient system integration, making them increasingly popular in industrial processing, lidar, scientific research, and defense industries. Especially in recent years, with advancements in materials science, fiber optic technology, and semiconductor technology, fiber lasers have experienced rapid development.

[0003] There are two common methods to increase the output laser power of conventional fiber lasers: one is to use longer gain fibers and increase the power of the pump light; the other is to increase the number of amplification stages in the MOPA system's fiber laser amplifier. The former, by increasing the transmission distance and power density of the optical field in the fiber, makes it highly susceptible to nonlinear effects such as spontaneous emission (ASE), stimulated Brillouin scattering (SBS), and stimulated Raman scattering (SRS) during seed light amplification, thus limiting the power increase of the fiber laser and even damaging the fiber components. The latter requires additional fiber components, pump sources, and driving circuits for each amplification stage, making the system structure complex and increasing the cost of the fiber laser. Furthermore, in conventional fiber lasers, excess pump light is usually stripped from the optical path, resulting in wasted pump light and reduced pump efficiency. Summary of the Invention

[0004] The main objective of this invention is to provide a fiber laser with high pump efficiency and low nonlinear effects. By using a fiber grating to increase the interaction distance between the seed light and the gain fiber, effective amplification of the seed light can be achieved using a shorter gain fiber. At the same time, by improving the utilization efficiency of the pump light, the power requirement of the pump light is reduced, and the ASE effect and SBS and SRS nonlinear effects in the fiber laser are effectively suppressed.

[0005] The technical solution adopted in this invention is:

[0006] A fiber laser with high pump efficiency and low nonlinear effects is provided, comprising:

[0007] The seed source, isolator, first circulator, first combiner, first gain fiber, fiber grating, second gain fiber, second combiner, and second circulator are connected in sequence, and also include a first pump source, a second pump source, and an output collimator.

[0008] The fiber grating is a total internal reflection grating with a center wavelength that is the same as the seed light wavelength, and it is placed between the first gain fiber and the second gain fiber.

[0009] The output of the first pump source is fused to the pump light input of the first beam combiner to couple the pump light into the optical path; the output of the second pump source is fused to the pump light input of the second beam combiner to couple the pump light into the optical path.

[0010] Port 1 of the first circulator is fused to the output of the isolator; port 2 of the first circulator is fused to the seed light input of the first beam combiner; port 3 of the first circulator is fused to port 1 of the second circulator; port 2 of the second circulator is fused to the seed light input of the second beam combiner; and port 3 of the second circulator is fused to the output collimator.

[0011] Following the above-described termination scheme, the first circulator, the first combiner, and the first gain fiber are sequentially connected to the second gain fiber, the second combiner, and the second circulator, which are respectively arranged symmetrically about the fiber grating.

[0012] Following the above termination scheme, the first circulator is positioned before the first combiner to output the seed light amplified by the first gain fiber to the amplification optical path of the second gain fiber, and the second circulator is positioned after the second combiner to output the seed light amplified by the second gain fiber to the output collimator.

[0013] Following the above-mentioned termination scheme, both the first and second pump sources are fiber-coupled semiconductor lasers, and the pumping methods are cladding pumping or core pumping.

[0014] Following the above termination scheme, the first and second combiners are either fiber N×1 pumped combiners or wavelength division multiplexers.

[0015] Following the above termination scheme, the first gain fiber and the second gain fiber are double-clad fibers or single-clad fibers with rare earth ions doped in the core.

[0016] Following the above-mentioned termination scheme, the first gain fiber and the second gain fiber can also be photonic crystal fiber or other special active fibers.

[0017] Following the above termination scheme, the output collimator is used to output the amplified seed light.

[0018] Following the above termination scheme, the gain bands of the first gain fiber and the second gain fiber cover the wavelength of the seed source.

[0019] Following the above termination scheme, the absorption bands of the first gain fiber and the second gain fiber cover the wavelengths of the first pump source and the second pump source.

[0020] The beneficial effects of this invention are as follows: This invention provides a fiber laser with high pump efficiency and low nonlinear effects. It utilizes a total internal reflection fiber grating positioned between two gain fibers, with a center wavelength matching the output wavelength of the seed source. This achieves the original optical path reflection and secondary amplification of the seed light. Simultaneously, when the pump light reaches the fiber grating, it is transmitted through and continues to propagate, pumping the gain fiber positioned opposite the fiber grating, thus achieving secondary utilization of the remaining pump light. This invention increases the interaction distance between the seed light and the gain fiber even with a short gain fiber. While performing secondary amplification of the seed light, it effectively suppresses spontaneous emission and nonlinear effects in the fiber laser, and simultaneously utilizes the remaining pump light, effectively improving pump efficiency and enhancing the performance of the fiber laser. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a fiber laser structure with high pump efficiency, low ASE and low nonlinear effect based on fiber grating according to Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of seed light and pump light transmission near fiber optic grating 7 in Embodiment 1 of the present invention;

[0024] Figure 3 This is a schematic diagram of a simplified implementation of a fiber laser with high pump efficiency, low ASE, and low nonlinear effect based on a fiber grating, according to Embodiment 2 of the present invention.

[0025] (Seed source 1, isolator 2, first pump source 3, first circulator 4, first combiner 5, first gain fiber 6, fiber grating 7, second gain fiber 8, second combiner 9, second circulator 10, second pump source 11, output collimator 12). Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] This invention provides a fiber laser with high pump efficiency and low nonlinear effects, comprising:

[0028] like Figure 1As shown, the sequence of components—seed source 1, isolator 2, first circulator 4, first combiner 5, first gain fiber 6, fiber grating 7, second gain fiber 8, second combiner 9, and second circulator 10—also includes a first pump source 3, a second pump source 11, and an output collimator 12. Seed source 1 can be either a continuous laser or a pulsed laser. Isolator 2 is installed after seed source 1 to protect it and prevent damage from reflected light.

[0029] Fiber Bragg grating 7 is a total internal reflection grating with a center wavelength matching the seed light wavelength. It is positioned between the first gain fiber 6 and the second gain fiber 8. Figure 2 As shown, the seed light is reflected after passing through the gain fiber to the fiber grating 7, so that the seed light passes through the gain fiber again to complete the secondary amplification.

[0030] The output of the first pump source 3 is fused with the pump light input of the first beam combiner 5 to couple the pump light into the optical path. The output of the second pump source 11 is fused with the pump light input of the second beam combiner 9 to couple the pump light into the optical path. The first pump source 3 and the second pump source 11, which serve as pump sources, can be a single pump source or multiple pump sources.

[0031] The first port of the first circulator 4 is fused to the output of the isolator 2, the second port of the first circulator 4 is fused to the seed light input of the first beam combiner 5, the third port of the first circulator 4 is fused to the first port of the second circulator 10, the second port of the second circulator 10 is fused to the seed light input of the second beam combiner 9, and the third port of the second circulator 10 is fused to the output collimator 12.

[0032] In a preferred embodiment, the first circulator 4, the first combiner 5, and the first gain fiber 6 are sequentially connected to the second gain fiber 8, the second combiner 9, and the second circulator 10, which are respectively connected sequentially, and are symmetrically arranged about the fiber grating 7. This symmetrical arrangement allows the seed light passing through the gain fiber to return along its original optical path for secondary amplification, while simultaneously enabling the pump light passing through the fiber grating 7 to couple to the gain fiber of the other fiber for seed light amplification. This achieves secondary utilization of the remaining pump light, effectively improving pump efficiency and enhancing the performance of the fiber laser.

[0033] In a preferred embodiment, the first circulator 4 is disposed before the first combiner 5 and is used to output the seed light after secondary amplification of the first gain fiber 6 to the amplification optical path of the second gain fiber 8. The second circulator 10 is disposed after the second combiner 9 and is used to output the seed light after secondary amplification of the second gain fiber 8 to the output collimator 12.

[0034] In a preferred embodiment, both the first pump source 3 and the second pump source 11 are fiber-coupled semiconductor lasers, and the pumping method is cladding pumping or core pumping.

[0035] In a preferred embodiment, the first combiner 5 and the second combiner 9 are fiber N×1 pumped combiners or wavelength division multiplexers.

[0036] In a preferred embodiment, the first gain fiber 6 and the second gain fiber 8 are double-clad fibers or single-clad fibers with cores doped with rare earth ions.

[0037] In a preferred embodiment, the first gain fiber 6 and the second gain fiber 8 may also be photonic crystal fibers or other special active fibers, and the pump source may be one or more.

[0038] In a preferred embodiment, the output collimator 12 is used to output the amplified seed light.

[0039] In a preferred embodiment, the gain bands of the first gain fiber 6 and the second gain fiber 8 cover the wavelength of the seed source 1.

[0040] In a preferred embodiment, the absorption bands of the first gain fiber 6 and the second gain fiber 8 cover the wavelengths of the first pump source 3 and the second pump source 11.

[0041] As a preferred embodiment 1, including all the devices of the present invention, the first circulator 4, the first combiner 5, and the first gain fiber 6 are sequentially connected and symmetrically arranged with the second gain fiber 8, the second combiner 9, and the second circulator 10, which are sequentially connected, about the fiber grating 7.

[0042] The first port of the first circulator 4 is fused to the output of the isolator 2, the second port of the first circulator 4 is fused to the seed light input of the first beam combiner 5, the third port of the first circulator 4 is fused to the first port of the second circulator 10, the second port of the second circulator 10 is fused to the seed light input of the second beam combiner 9, and the third port of the second circulator 10 is fused to the output collimator 12.

[0043] The output of the first pump source 3 is fused with the pump light input of the first beam combiner 5 to couple the pump light into the optical path. The output of the second pump source 11 is fused with the pump light input of the second beam combiner 9 to couple the pump light into the optical path. The first pump source 3 and the second pump source 11, which serve as pump sources, can be a single pump source or multiple pump sources.

[0044] The working principle of Example 1 is as follows:

[0045] Seed source 1 can be either a continuous laser or a pulsed laser.

[0046] The seed light output from seed source 1 is input to the first port of the first circulator 4 after passing through isolator 2, and is output to the seed light input end of the first combiner 5 after passing through the second port of the first circulator 4. The first combiner 5 couples the seed light and the pump light of the first pump source 3 to the first gain fiber 6 for seed light amplification.

[0047] Seed light 1 is amplified once by the first gain fiber 6 and then reflected back to the first gain fiber 6 by the fiber grating 7 for secondary amplification. The seed light, after secondary amplification by the first gain fiber 6, is output from port 3 of the first circulator 1 to port 1 of the second circulator 10, where the second combiner 9 couples the seed light and pump light into the second gain fiber 8. The seed light is then amplified once by the second gain fiber 8 and reflected back to the second gain fiber 8 by the fiber grating 7 for secondary amplification. The amplified seed light is then output from port 3 of the second circulator 10 by the output collimator 12.

[0048] The remaining pump light in the first gain fiber 6 is injected into the second gain fiber 8 through the fiber grating 7 to pump the second gain fiber 8. Correspondingly, the remaining pump light in the second gain fiber 8 is injected into the first gain fiber 6 through the fiber grating 7 to pump the first gain fiber 6.

[0049] The fiber grating 7 enables secondary amplification of the seed light through a shorter gain fiber, increasing the interaction distance between the seed light and the gain fiber. Furthermore, the fiber grating 7 completely transmits the pump light band. The remaining pump light in the first gain fiber 6 is injected into the second gain fiber 8 through the fiber grating 7 to pump the second gain fiber 8. Conversely, the remaining pump light in the second gain fiber 8 is injected into the first gain fiber 6 through the fiber grating 7 to pump the first gain fiber 6. This fiber laser utilizes a shorter gain fiber to effectively amplify the seed light, effectively suppressing the ASE effect and nonlinear effects in the fiber laser. By recycling the pump light, the pump efficiency is improved.

[0050] like Figure 3 The illustrated embodiment 2 is a simplified implementation of the present invention. Compared to embodiment 1, embodiment 2 only requires a single gain fiber for optical amplification. That is, the second gain fiber 8, second combiner 9, second circulator 10, and second pump source 11 are no longer fused after the fiber grating 7. Instead, the output end of the fiber grating 7 is fused to another pump input end of the first combiner 5. Pump light not fully absorbed by the first gain fiber 6 is directly output to the pump light input end of the first combiner 5 after passing through the fiber grating 7, and is then coupled back into the first gain fiber 6 by the first combiner 5 to achieve pump light recycling.

[0051] The specific working principle is as follows: The seed light output from seed source 1 is input to port 1 of the first circulator 4 after passing through isolator 2, and then output to the seed light input end of the first combiner 5 through port 2 of the first circulator 4. The first combiner 5 couples the seed light, the pump light from pump source 3, and the recycled pump light into the first gain fiber 6 for seed light amplification. After the seed light is amplified for the first time by the first gain fiber 6, it is reflected back to the first gain fiber 6 by fiber grating 7 for a second amplification. The output collimator 12 is fused to port 3 of the first circulator 4, and the seed light amplified twice by the first gain fiber 6 is output from port 3 of the first circulator 4 to the output collimator, which finally outputs the amplified seed light.

[0052] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0053] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A fiber laser with high pump efficiency and low nonlinear effects, characterized in that, include: The seed source, isolator, first circulator, first combiner, first gain fiber, fiber grating, second gain fiber, second combiner, and second circulator are connected in sequence, and also include a first pump source, a second pump source, and an output collimator. The fiber grating is a total internal reflection grating with a center wavelength that is the same as the seed light wavelength. It is placed between the first gain fiber and the second gain fiber, realizing the original optical path reflection and secondary amplification of the seed light. At the same time, when the pump light is transmitted to the fiber grating, it will be transmitted through and continue to be transmitted to pump the gain fiber placed on the opposite side of the fiber grating, realizing the secondary utilization of the remaining pump light. The output of the first pump source is fused to the pump light input of the first beam combiner to couple the pump light into the optical path; the output of the second pump source is fused to the pump light input of the second beam combiner to couple the pump light into the optical path. The first port of the first circulator is fused to the output of the isolator, the second port of the first circulator is fused to the seed light input of the first beam combiner, the third port of the first circulator is fused to the first port of the second circulator, the second port of the second circulator is fused to the seed light input of the second beam combiner, and the third port of the second circulator is fused to the output collimator.

2. The fiber laser according to claim 1, characterized in that, The first circulator, the first combiner, and the first gain fiber are sequentially connected to the second gain fiber, the second combiner, and the second circulator, which are respectively arranged symmetrically about the fiber grating.

3. The fiber laser according to claim 1, characterized in that, The first circulator is positioned before the first combiner and is used to output the seed light amplified by the first gain fiber to the amplification optical path of the second gain fiber. The second circulator is positioned after the second combiner and is used to output the seed light amplified by the second gain fiber to the output collimator.

4. The fiber laser according to claim 1, characterized in that, Both the first pump source and the second pump source are fiber-coupled semiconductor lasers, and the pumping method is cladding pumping or core pumping.

5. The fiber laser according to claim 1, characterized in that, The first and second combiners are fiber N×1 pumped combiners or wavelength division multiplexers.

6. The fiber laser according to claim 1, characterized in that, The first gain fiber and the second gain fiber are double-clad fibers or single-clad fibers with rare earth ions doped in the core.

7. The fiber laser according to claim 1, characterized in that, The first gain fiber and the second gain fiber are photonic crystal fibers or other special active fibers.

8. The fiber laser according to claim 1, characterized in that, The output collimator is used to output the amplified seed light.

9. The fiber laser according to claim 1, characterized in that, The gain bands of the first gain fiber and the second gain fiber cover the wavelength of the seed source.

10. The fiber laser according to claim 1, characterized in that, The absorption bands of the first gain fiber and the second gain fiber cover the wavelengths of the first pump source and the second pump source.

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