laser

Abstract

This invention provides a laser, relating to the technical field of lasers. The laser includes: a pump component, a spatial filter, a low-reflection grating, an optical gain fiber, and a high-reflection grating; the pump component is used to generate pump light; the pump light passes sequentially through the low-reflection grating, the optical gain fiber, and the high-reflection grating, which are used to convert the pump light input from the low-reflection grating into signal light, amplify it, and then output it from the low-reflection grating after reflection by the spatial filter.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a laser. Background Technology

[0002] Existing lasers include pump modules, reverse pump combiners, low-reflection gratings, optical fibers, and high-reflection gratings. Multiple pump modules are connected to the low-reflection gratings via a combiner. The pump light emitted by the pump modules is combined and enters the low-reflection grating. Then, after passing through the optical fiber and the high-reflection grating, it is reflected back to the reverse pump combiner and outputs signal light.

[0003] Furthermore, in the existing technology, once the size and numerical aperture of the optical gain fiber are determined, the reverse pump combiner is limited by the binder tapering process and the principle of brightness conservation. In addition, there is a signal light output channel in the middle of the reverse pump combiner, which occupies a certain amount of the coupling input channel. As a result, the input channel in the reverse pump combiner cannot meet the requirements of large fiber core diameter and high numerical aperture input of a high-power pump source, and thus cannot realize reverse pumping of high-power pump laser. Summary of the Invention

[0004] The purpose of this invention is to provide a laser that alleviates the technical problem that existing lasers cannot be matched with high-power pump sources to achieve high-power output.

[0005] The present invention provides a laser comprising: a pump assembly, a spatial filter, a low-reflection grating, an optical gain fiber, and a high-reflection grating;

[0006] The pump assembly is used to generate pump light;

[0007] The pump light passes sequentially through the low-reflection grating, the optical gain fiber, and the high-reflection grating. The low-reflection grating, the optical gain fiber, and the high-reflection grating are used to convert the pump light input from the low-reflection grating into signal light, amplify it, and then output it from the low-reflection grating after reflection by the spatial filter.

[0008] Furthermore, the low-reflection grating includes a first end and a second end opposite to each other, and the high-reflection grating includes a third end and a fourth end opposite to each other. The second end of the low-reflection grating is connected to one end of the optical gain fiber, and the other end of the optical gain fiber is connected to the third end of the high-reflection grating.

[0009] Furthermore, the spatial filter is disposed between the pump assembly and the low-reflection grating to transmit the pump light toward the first end of the low-reflection grating and to reflect the signal light emitted from the first end of the low-reflection grating.

[0010] Furthermore, the pump assembly includes a pump source, and at least one pump source emits light whose wavelength matches the absorption peak of the optical gain fiber.

[0011] Furthermore, the laser also includes a first converging lens, through which the pump light emitted from the spatial filter is converged and enters the low-reflection grating.

[0012] Furthermore, the laser also includes a second converging lens and an optical fiber output head. The signal light emitted from the signal light output side of the spatial filter is coupled into the optical fiber output head after passing through the second converging lens.

[0013] Furthermore, the laser also includes an optical fiber cladding stripper, through which the signal light emitted from the second converging lens is coupled into the optical fiber output head.

[0014] Furthermore, the laser also includes an indicator light source, the indicator light generated by the indicator light source is incident on the highly reflective grating and then output along the same path as the signal light.

[0015] Furthermore, the laser also includes a second filter, through which the indicator light emitted from the indicator light source is filtered before entering the high-reflectivity grating;

[0016] And / or, the spatial filter includes a first filter.

[0017] Furthermore, the pump assembly includes multiple pump sources, and the combined beam of light emitted from all the pump sources forms the pump light;

[0018] The pump assembly includes pump source n1 and pump source n2;

[0019] The pump assembly also includes a filter h1;

[0020] The filter h1 is used to transmit light emitted from pump source n1, reflect light emitted from pump source n2, and combine the two into a combined beam L1, where A1≥A2, A1 is the center wavelength interval between pump source n1 and pump source n2, and A2 is the smallest wavelength interval that filter h1 can distinguish.

[0021] Alternatively, the pump assembly may include a plurality of pump sources, and the combined beam of light emitted from all the pump sources forms the pump light;

[0022] The pumping assembly includes pump source n1, pump source n2, pump source n3... pump source n m m is greater than or equal to 3;

[0023] The pump assembly also includes filter h1, filter h2... filter h1 m-1 ;

[0024] The filter h1 is used to transmit light emitted from pump source n1, reflect light emitted from pump source n2, and combine the two into a combined beam L1, where A1≥A2, A1 is the center wavelength interval between pump source n1 and pump source n2, and A2 is the smallest wavelength interval that filter h1 can distinguish.

[0025] The filter h2 is used to transmit the combined light L1 and reflect the light emitted by the pump source n3 so that the two are combined to form the combined light L2, and A3≥A4, where A3 is the smallest wavelength interval between the center wavelengths of the pump source n3 and the pump source n1 and pump source n2 corresponding to the combined light L1, respectively, and A4 is the smallest wavelength interval that the filter h2 can distinguish.

[0026] And so on,

[0027] The filter h m-1 Used for transmitting beam combining light L m-2 and reflect the pump source n m The emitted light, and A n-1 ≥A n , A n-1 For pump source n m Separately with the combined beam L m-2 The corresponding pump source n1, pump source n 2…… Pump source n m-1 The minimum wavelength interval in the center wavelength interval, A n For filter h m-1 The minimum distinguishable wavelength interval is used to combine the two into a pump light.

[0028] This invention has at least the following advantages or beneficial effects:

[0029] The present invention provides a laser comprising: a pump component, a spatial filter, a low-reflection grating, an optical gain fiber, and a high-reflection grating; the pump component is used to generate pump light; the pump light passes sequentially through the low-reflection grating, the optical gain fiber, and the high-reflection grating, the low-reflection grating, the optical gain fiber, and the high-reflection grating being used to convert the pump light input from the low-reflection grating into signal light, amplify it, and then output it from the low-reflection grating after reflection by the spatial filter.

[0030] First, in this embodiment, a spatial filter, rather than a fiber combiner, is used to inject pump light and output signal light. This removes the power limitation of the pump source in the pump assembly, allowing for a higher power output without being affected by fiber size. Second, low-reflection gratings, optical gain fibers, and high-reflection gratings are used to achieve reverse pumping to amplify the signal light. This optimizes power distribution, reduces local power density, minimizes the interaction between signal and pump light, and suppresses nonlinear effects (such as SRS), while significantly improving the threshold for nonlinear effects. Finally, through a rational layout design of various optical components, not only can reverse pumping technology be applied, but the system's volume utilization rate can also be significantly improved. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.

[0032] Figure 1 A schematic diagram of a laser provided in an embodiment of the present invention.

[0033] Icons: 1-Pump assembly; 2-Spatial filter; 3-Low-reflection grating; 4-Optical gain fiber; 5-High-reflection grating; 6-First converging lens; 7-Second converging lens; 8-Fiber output head; 9-Fiber cladding stripper; 10-Indicator light source; 11-Second filter. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] like Figure 1 As shown, the laser provided by the present invention includes: a pump assembly 1, a spatial filter 2, a low-reflection grating 3, an optical gain fiber 4, and a high-reflection grating 5.

[0041] The pump assembly 1 includes a pump source, which can be one or more. In this embodiment, there are three pump sources. The light emitted by all the pump sources passes through the spatial filter 2 to form pump light.

[0042] Specifically, the pump assembly 1 may include pump source n1, pump source n2, pump source n3... pump source n m m is greater than or equal to 2; the pump assembly 1 also includes filter h1, filter h2... filter h m-1The filter h1 transmits light emitted from pump source n1, reflects light emitted from pump source n2, and combines the two into a combined beam L1, where A1 ≥ A2, A1 being the center wavelength interval between pump sources n1 and n2, and A2 being the smallest distinguishable wavelength interval by filter h1. The filter h2 transmits the combined beam L1 and reflects light emitted from pump source n3, so that the two combine into a combined beam L2, where A3 ≥ A4, A3 being the smallest wavelength interval between the center wavelength intervals of pump sources n1 and n2 corresponding to pump source n3 and the combined beam L1, respectively, and A4 being the smallest distinguishable wavelength interval by filter h2. And so on, the filter h... m-1 Used for transmitting beam combining light L m-2 and reflect the pump source n m The emitted light, and A n-1 ≥A n , A n-1 For pump source n m Separately with the combined beam L m-2 The corresponding pump source n1, pump source n 2…… Pump source n m-1 The minimum wavelength interval in the center wavelength interval, A n For filter h m-1 The minimum distinguishable wavelength interval is used to combine the two into a pump light.

[0043] Wherein, A3 is the minimum wavelength interval between the center wavelength intervals of pump source n3 and the center wavelength intervals of pump source n1 and pump source n2 corresponding to beam combiner L1, respectively. It includes: setting the center wavelength interval between the center wavelength of the light emitted by pump source n3 and the center wavelength of the light emitted by pump source n1 corresponding to beam combiner L1 as M, and setting the center wavelength interval between the center wavelength of the light emitted by pump source n3 and the center wavelength of the light emitted by pump source n2 corresponding to beam combiner L1 as N. If M>N, then A3 is the minimum wavelength interval between the center wavelength intervals of pump source n3 and the center wavelength intervals of pump source n1 and pump source n2 corresponding to beam combiner L1, respectively, and is N.

[0044] Among them, A n-1 For pump source n m Separately with the combined beam L m-2 The corresponding pump source n1, pump source n 2…… Pump source n m-1 The minimum wavelength interval in the center wavelength interval includes: obtaining the pump source n m The center wavelength and the combined beam L m-2 Each corresponding pump source (including pump source n1, pump source n) 2…… Pump source n m-1The center wavelength intervals of the center wavelengths are calculated, resulting in m-1 center wavelength intervals. The sizes of these m-1 center wavelength intervals are compared, and the smallest center wavelength interval is determined to be A. n-1 .

[0045] In this embodiment, m=3, meaning the pump assembly 1 has three pump sources and two filters. When pump sources of different wavelengths are coupled, the configuration requirements for the pump source wavelengths are as follows: Coupling of pump sources of different wavelengths is achieved through filters (e.g., a dual-color filter lens). Therefore, the center wavelength interval between pump sources of different wavelengths needs to be greater than or equal to the minimum wavelength interval that the filter can distinguish. Taking pump sources n1 and n2 as an example, A1≥A2, where A1 is the center wavelength interval between pump sources n1 and n2, and A2 is the minimum wavelength interval that filter h1 can distinguish. Typically, a dual-color filter lens can distinguish wavelengths of at least 30nm, meaning the center wavelength interval between pump sources n1 and n2 must be at least 30nm.

[0046] After the pump light is emitted, it enters the low-reflection grating 3, then passes through the optical gain fiber 4 and is directed towards the high-reflection grating 5. Specifically, the low-reflection grating 3 includes a first end and a second end opposite to each other, and the high-reflection grating 5 includes a third end and a fourth end opposite to each other. The second end of the low-reflection grating 3 is connected to one end of the optical gain fiber 4, and the other end of the optical gain fiber 4 is connected to the third end of the high-reflection grating 5. The distribution of the low-reflection grating 3, the optical gain fiber 4, and the high-reflection grating 5 is not limited to a linear arrangement in this embodiment; other arrangements can also be used depending on the internal space of the laser.

[0047] The low-reflection grating 3, the optical gain fiber 4, and the high-reflection grating 5 are used to convert the pump light input from the low-reflection grating 3 into signal light, amplify it, and then output it from the low-reflection grating 3 after reflection by the spatial filter 2.

[0048] The signal light is obtained by reverse pumping. This structure results in a more uniform power distribution of the pump and signal light in the fiber, avoiding the excessively high power of the signal light at the fiber end as seen in forward pumping. The uniform power distribution reduces local power peaks, thereby reducing the probability of nonlinear effects. Reverse pumping causes the signal light power to gradually increase in the fiber, rather than concentrating to a peak in a certain area, thus reducing the local power density. Simultaneously, a lower local power density means a higher threshold for nonlinear effects. In reverse pumping, the signal and pump light propagate in opposite directions, resulting in a shorter interaction time. This design reduces energy exchange and nonlinear interactions between the signal and pump light, thus suppressing nonlinear effects. Reverse pumping also makes the gain distribution more uniform in the fiber, avoiding the gain concentration at the fiber end as seen in forward pumping. A uniform gain distribution helps reduce power fluctuations in the signal light in the fiber, thus reducing nonlinear effects. By reducing the local power density of the signal light, reverse pumping can effectively increase the threshold of stimulated Brillouin scattering (SRS), thereby suppressing its occurrence.

[0049] In existing technologies, especially in high-power applications, it is theoretically possible to set up multiple laser chips / lasers, each laser chip / laser generating multiple beams with an optical fiber, and then using a beam combiner to combine the multiple beams to achieve reverse pumping and thus achieve signal light output. However, there are unresolved technical problems, including the fact that optical power is positively correlated with fiber size, and that achieving optical output based on a beam combiner will result in very high losses in the actual optical power. Furthermore, in existing technologies, it is impossible to achieve both pump light input and signal light output using a beam combiner.

[0050] First, in this embodiment, a spatial filter 2 is used instead of a fiber combiner to inject pump light and output signal light. Therefore, the power limitation of the pump source in pump assembly 1 is removed, allowing for a higher power output without being affected by fiber size. Simultaneously, a low-reflection grating 3, an optical gain fiber 4, and a high-reflection grating 5 are used to achieve reverse pumping to amplify the signal light. By optimizing power distribution, reducing local power density, minimizing the interaction between signal light and pump light, and suppressing nonlinear effects (such as SRS), the threshold for nonlinear effects is significantly improved.

[0051] Under the action of the pump source, ytterbium ions in the optical gain fiber 4 absorb the energy of the pump light and transition from the ground state to the excited state, forming a population inversion distribution. When the signal light passes through the optical gain fiber 4, the ytterbium ions in the excited state will transition to the ground state or a lower energy level and emit photons with the same or similar wavelength as the signal light, thereby amplifying the signal light. When the signal light propagates in the optical gain fiber 4, it stimulates the ytterbium ions in the excited state to produce stimulated emission. The emitted photons have the same frequency, phase, and propagation direction as the signal light. These additional photons are superimposed on the original signal light, thus enhancing the intensity of the signal light.

[0052] In one embodiment, the optical gain fiber 4 has a high doping concentration, good optical quality, and a suitable core diameter; the high doping concentration includes requiring the optical gain fiber 4 to have a high ytterbium ion doping concentration to provide sufficient gain medium. A higher doping concentration can increase the number of active ions per unit length of fiber, thereby improving the amplification capability of the signal light. However, a higher doping concentration is not always better; excessively high doping concentration may lead to enhanced interactions between ions, causing problems such as concentration quenching, and affecting the performance of the fiber.

[0053] Good optical quality includes low optical loss and high transparency in the optical fiber to ensure efficient transmission of pump and signal light. Optical loss mainly includes absorption loss and scattering loss. Low optical loss reduces energy loss during transmission, improving pump efficiency and signal amplification. Simultaneously, good refractive index uniformity is essential to avoid increased signal scattering and transmission loss due to refractive index inhomogeneity.

[0054] The appropriate core diameter of the fiber, particularly in optical gain fiber 4, affects the power density of the pump and signal lights and their overlap. For example, a core diameter of 10 μm-100 μm and a cladding diameter of 250-900 μm result in an overlap of 10 μm-100 μm. For reverse-pumping, a larger core diameter facilitates coupling between the pump and signal lights, reducing coupling loss. A larger core diameter also reduces the impact of nonlinear effects, such as self-phase modulation. However, an excessively large core diameter increases the fiber's mode volume, reducing the power density per unit area and hindering signal amplification. Therefore, a suitable core diameter must be selected based on specific application requirements.

[0055] The relationship between the wavelength of the pump light input into the optical gain fiber 4 and the output signal light includes the fact that the pump light enters the optical gain fiber 4 to excite the ytterbium ions in the optical gain fiber 4 to a high energy level, forming a population inversion distribution. This is one of the fundamental conditions for signal light amplification. When the signal light passes through the optical gain fiber 4 with a population inversion distribution, it stimulates the ytterbium ions at the high energy level to undergo stimulated emission, producing photons with the same or similar wavelength as the signal light, thereby amplifying the signal light. Different gain media have specific absorption spectral ranges, and the pump wavelength needs to match the absorption peak of the gain medium to ensure that the pump light can be effectively absorbed and converted into laser energy. To achieve effective amplification, the wavelength of the input pump light needs to match the absorption peak of the ytterbium ions in the optical gain fiber 4 to ensure that the pump light can be fully absorbed and converted into the excitation energy of the ytterbium ions. For example, the pump wavelength range is usually 880nm-1018nm, which coincides with the absorption peak of Yb³⁺ ions. The choice of pump source also affects the conversion efficiency of pump light to signal light: a suitable pump source wavelength can improve pump efficiency, reduce unnecessary energy loss, and thus enhance the amplification effect of signal light. Typically, the conversion efficiency of 976nm is 75%-85%, 915nm is 65%-75%, and 940nm is in between.

[0056] The spatial filter 2 can be disposed between the pump assembly 1 and the low-reflection grating 3. The spatial filter 2 may include a first filter for transmitting the pump light to the first end of the low-reflection grating 3 and reflecting the signal light emitted from the first end of the low-reflection grating 3. Both the pump light and the signal light propagate through the same component (i.e., the spatial filter 2), reducing space occupancy and product size.

[0057] A first converging lens 6 can be provided between the spatial filter 2 and the low-reflection grating 3 so that the pump light is converged and enters the low-reflection grating 3. By concentrating the pump light into a small area, the first converging lens 6 can significantly improve the energy density of that area, thereby improving the energy density and image quality.

[0058] The signal light output side of the spatial filter 2 can be sequentially equipped with a second converging lens 7 and an optical fiber output head 8. Similarly, the second converging lens 7 concentrates the signal light into a small area, which can significantly improve the energy density of that area, thereby increasing the energy density and improving the imaging quality.

[0059] A fiber cladding stripper 9 can be disposed between the second converging lens 7 and the fiber optic output head 8. The fiber cladding stripper 9 removes the cladding light while minimizing the impact on the main signal light.

[0060] The laser also includes an indicator light source 10. In this embodiment, the light-emitting end of the indicator light source 10 is connected to the fourth end of the high-reflectivity grating 5. The indicator light emitted by the indicator light source 10 has the same output path as the signal light. The indicator light source 10 can be red light, serving as an indicator. The indicator light and the signal light are output together. Specifically, after the indicator light enters the high-reflectivity grating 5, it passes sequentially through the optical gain fiber 4, the low-reflectivity grating 3, the first converging lens 6, the spatial filter 2, the second converging lens 7, and the fiber cladding stripper 9 before being coupled into the fiber output head 8, thereby facilitating the user to accurately determine the direction and position of the laser beam.

[0061] It is important to understand that the output path of the indicator light may pass through all or part of the first converging lens 6, spatial filter 2, second converging lens 7, fiber cladding stripper 9, and fiber output head 8; in actual production applications, it is only necessary to ensure that the optical paths of the signal light and the indicator light are consistent. The optical paths of the signal light and the indicator light are as follows: Figure 1 As shown by the dashed arrow in the image.

[0062] Furthermore, a second filter 11 may be provided between the indicator light source 10 and the high-reflectivity grating 5 to prevent the pump light leaked from the high-reflectivity grating 5 from affecting the indicator light source 10.

[0063] In this embodiment, the spatial positions of each optical device are not fixed, as long as the optical path requirements are met.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser, characterized in that, include: Pump assembly (1), spatial filter (2), low-reflection grating (3), optical gain fiber (4), and high-reflection grating (5); The pump assembly (1) is used to generate pump light; The pump light passes sequentially through the low-reflection grating (3), the optical gain fiber (4), and the high-reflection grating (5). The low-reflection grating (3), the optical gain fiber (4), and the high-reflection grating (5) are used to convert the pump light input from the low-reflection grating (3) into signal light and amplify it before it is emitted from the low-reflection grating (3) and reflected by the spatial filter (2). The pump assembly (1) includes multiple pump sources, and the combined beam of light emitted from all the pump sources forms the pump light; The pump assembly (1) includes pump source n1 and pump source n2; The pump assembly (1) also includes a filter plate h1; The filter h1 is used to transmit light emitted from pump source n1, reflect light emitted from pump source n2, and combine the two into a combined beam L1, where A1≥A2, A1 is the center wavelength interval between pump source n1 and pump source n2, and A2 is the smallest wavelength interval that filter h1 can distinguish. or, The pump assembly (1) includes pump source n1, pump source n2, pump source n3... pump source n m m is greater than or equal to 3; The pump assembly (1) also includes filter h1, filter h2... filter h m-1 ; The filter h1 is used to transmit light emitted from pump source n1, reflect light emitted from pump source n2, and combine the two into a combined beam L1, where A1≥A2, A1 is the center wavelength interval between pump source n1 and pump source n2, and A2 is the smallest wavelength interval that filter h1 can distinguish. The filter h2 is used to transmit the combined light L1 and reflect the light emitted by the pump source n3 so that the two are combined to form the combined light L2, and A3 ≥ A4, where A3 is the smallest wavelength interval between the center wavelengths of the pump source n3 and the pump source n1 and pump source n2 corresponding to the combined light L1, respectively, and A4 is the smallest wavelength interval that the filter h2 can distinguish. And so on, The filter h m-1 Used for transmitting beam combining light L m-2 and reflect the pump source n m The emitted light, and A n-1 ≥A n , A n-1 For pump source n m Separately with the combined beam L m-2 The corresponding pump sources n1, n2, ..., n are pump sources n m-1 The minimum wavelength interval in the center wavelength interval, A n For filter h m-1 The minimum distinguishable wavelength interval is used to combine the two into a pump light.

2. The laser according to claim 1, characterized in that, The low-reflection grating (3) includes a first end and a second end opposite to each other, and the high-reflection grating (5) includes a third end and a fourth end opposite to each other. The second end of the low-reflection grating (3) is connected to one end of the optical gain fiber (4), and the other end of the optical gain fiber (4) is connected to the third end of the high-reflection grating (5).

3. The laser according to claim 2, characterized in that, The spatial filter (2) is disposed between the pump assembly (1) and the low-reflection grating (3) to transmit the pump light to the first end of the low-reflection grating (3) and to reflect the signal light emitted from the first end of the low-reflection grating (3) for output.

4. The laser according to claim 1, characterized in that, The pump assembly (1) includes a pump source, and at least one pump source emits light whose wavelength matches the absorption peak of the optical gain fiber (4).

5. The laser according to claim 1, characterized in that, The laser also includes a first converging lens (6), through which the pump light emitted from the spatial filter (2) is converged and enters the low-reflection grating (3).

6. The laser according to claim 1, characterized in that, The laser also includes a second converging lens (7) and an optical fiber output head (8). The signal light emitted from the signal light output side of the spatial filter (2) is coupled into the optical fiber output head (8) after passing through the second converging lens (7).

7. The laser according to claim 6, characterized in that, The laser also includes a fiber cladding stripper (9), and the signal light emitted from the second converging lens (7) is coupled into the fiber output head (8) after passing through the fiber cladding stripper (9).

8. The laser according to any one of claims 1-7, characterized in that, The laser also includes an indicator light source (10), and the indicator light generated by the indicator light source (10) is emitted along the same path as the signal light after entering the high-reflectivity grating (5).

9. The laser according to claim 8, characterized in that, The laser also includes a second filter (11), through which the indicator light emitted from the indicator light source (10) is filtered and then enters the high-reflectivity grating (5). And / or, the spatial filter (2) includes a first filter.

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