Semiconductor laser collimation system and fiber laser

Abstract

A semiconductor laser collimation system (10) and a fiber laser, the semiconductor laser collimation system (10) comprising: a collimation module, used for fixing a collimating lens (102) and a pump source fiber (103); a pump chip (101), used for emitting pump light; a collimating lens (102), located on a light emitting side of the pump chip (101) and used for collimating the pump light; and a pump source fiber (103), located on a light emitting side of the collimating lens (102), the pump source fiber (103) comprising a fiber grating (104) formed by means of fiber inscription. The pump chip (101), the collimating lens (102) and the pump source fiber (103) are all arranged in a housing. The fiber laser comprises the semiconductor laser collimation system (10) and a gain fiber (20) arranged on a light emitting side of the fiber grating (104). The fiber grating (104) is formed by performing fiber inscription on the pump source fiber (103), and the fiber grating (104) is integrated in the semiconductor laser collimation system (10), such that there is no need for an external grating, thus reducing the number of gratings and reducing the cost and also reducing the number of fusion splicing points and reducing the problem of poor fusion splicing.

Description

Semiconductor laser collimation system and fiber laser TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor lasers, and particularly relates to a semiconductor laser collimation system and a fiber laser. BACKGROUND

[0002] Semiconductor lasers are increasingly widely used in the fields of communication, military affairs, medical treatment and the like. As a semiconductor component, the market demand for semiconductor lasers is increasing. In recent years, high-power and high-beam-quality semiconductor lasers have developed rapidly. At present, a traditional method for preparing semiconductor lasers is to fuse a fiber grating to a pump source fiber and then fuse an active fiber, and the pump source fiber is generally different from the active fiber. This preparation method produces more fusion points and is prone to poor fusion.

[0003] CONTENT

[0004] Embodiments of the present application provide a semiconductor laser collimation system and a fiber laser. The number of fusion points is reduced by forming a fiber grating through fiber inscription, and the problem of poor fusion is avoided.

[0005] In one aspect, the present application provides a semiconductor laser collimation system, which comprises:

[0006] a housing;

[0007] a pump chip configured to emit pump light;

[0008] a collimation module configured to fix a collimation lens and a pump source fiber;

[0009] a collimation lens located on the light emitting side of the pump chip, the collimation lens being configured to collimate the pump light;

[0010] a pump source fiber located on the light emitting side of the collimation lens, the pump source fiber comprising a fiber grating formed by fiber inscription;

[0011] The pump chip, the collimation module, the collimation lens and the pump source fiber are all arranged in the housing.

[0012] In some possible embodiments, the semiconductor laser collimation system further comprises an end cap arranged between the collimation lens and the pump source fiber.

[0013] In some possible embodiments, the distance between the fiber grating and the end cap is 5-10 mm.

[0014] In some possible embodiments, the bandwidth of the fiber grating is 38-40 mm.

[0015] In some possible embodiments, the fiber grating is a high reflection grating.

[0016] In some possible embodiments, the pump source fiber is a passive fiber.

[0017] In the second aspect, the embodiments of the present application provide a fiber laser, which comprises the semiconductor laser collimation system as any one of the above, and further comprises: a gain fiber, which is arranged on the light output side of the fiber grating.

[0018] In some possible embodiments, the gain fiber comprises a first-stage gain fiber and a second-stage gain fiber, and the semiconductor laser further comprises a low reflection grating, which is arranged between the first-stage gain fiber and the second-stage gain fiber.

[0019] In some possible embodiments, the gain fiber and the pump source fiber are fibers of the same specification.

[0020] In some possible embodiments, the semiconductor laser further comprises a mode stripper, which is located on the light output side of the second-stage gain fiber.

[0021] The present application provides a semiconductor laser collimation system and a fiber laser. The collimation system comprises: a collimation module for fixing a lens and a fiber, a pump chip for emitting pump light, a collimation lens group located on the light output side of the pump chip for collimating the pump light, a pump source fiber located on the light output side of the collimation lens, and a fiber grating formed by fiber inscription on the pump source fiber. The pump source, the collimation lens and the pump source fiber are arranged in a housing. The present application forms a fiber grating by fiber inscription on the pump source fiber, and integrates the fiber grating in the collimation system, without an external grating. The number of gratings is reduced, the number of fusion points is reduced, and the problem of poor fusion is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] FIG. 1 is a schematic diagram of one embodiment of the semiconductor laser collimation system provided by the present application;

[0024] FIG. 2 is a schematic diagram of one embodiment of the semiconductor laser provided by the present application. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application 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 application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0028] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplifying the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art can realize the application of other processes and / or the use of other materials.

[0030] Specifically, please refer to Figure 1 for an embodiment of a semiconductor laser collimation system provided by the present application. As shown in Figure 1, the semiconductor laser collimation system 10 comprises:

[0031] The pump chip 101 is used to emit pump light;

[0032] The collimation lens 102 is located on the light emitting side of the pump chip 101, and the pump chip 101 is used to collimate the pump light.

[0033] The pump source fiber 103 is located on the light emitting side of the collimation lens 102, and the pump source fiber 103 includes a fiber grating 104 formed by fiber inscription.

[0034] It should be noted that in the actual semiconductor laser collimation system, the semiconductor laser collimation system further comprises an external shell and a collimation module for fixing the collimation lens and the pump source fiber, and the collimation module, the pump chip 101, the collimation lens 102 and the pump source fiber 103 are integrated in the shell, thereby forming the semiconductor laser collimation system.

[0035] The present application provides a semiconductor laser collimation system and a fiber laser, the collimation system comprising: a collimation module for fixing a lens and a fiber, a pump chip for emitting pump light, a collimation lens group located on the light emitting side of the pump chip for collimating the pump light; a pump source fiber, the pump source fiber is located on the light emitting side of the collimation lens, and the pump source fiber includes a fiber grating formed by fiber inscription; the pump source, the collimation lens and the pump source fiber are arranged in the shell. The present application forms a fiber grating on the pump source fiber by fiber inscription, and integrates the fiber grating in the collimation system, without external grating; reducing the number of gratings reduces the cost, while also reducing the number of fusion points, reducing the problem of poor fusion.

[0036] The pump chip 101 provided in the application is used for emitting pump light. In a specific embodiment, the pump chip can be an infrared laser for emitting corresponding infrared light. The semiconductor laser collimation system provided in the application further comprises a collimation module for fixing a collimation lens and a pump source optical fiber; the collimation lens is mainly used for performing the collimation function. The pump chip 101 usually comprises a fast collimation lens and a slow collimation lens, that is, the pump light usually needs to be collimated twice, that is, fast collimation and slow collimation; the specific collimation process can refer to the prior art, and will not be described here. The collimated pump light is injected into the pump source optical fiber 103 and is emitted from the semiconductor laser through the pump light optical fiber and the subsequent connected optical grating and the like.

[0037] Please refer to FIG. 1. In the embodiment shown in FIG. 1, the semiconductor laser collimation system further comprises an end cap 105; wherein the end cap 105 is a high-power device designed for the output end face of a high-power optical fiber laser, which can effectively reduce the beam distortion of the pump light. The end cap 105 in the application is located between the collimation lens 102 and the pump source optical fiber 103; for example, in the structure shown in FIG. 1, the end cap 105 is located on the light-emitting side of the collimation lens, and the collimated pump light is directly injected into the end cap 105; and the other end of the end cap is fused with the pump source optical fiber, and the pump light is injected into the pump source optical fiber through the end cap 105. The fiber grating 104 is further formed on the pump source optical fiber 103 away from the end cap 105, and the fiber grating 104 is formed by fiber writing on the pump source optical fiber 103, rather than being fused with the grating on the side of the pump source optical fiber away from the end cap as shown in the conventional technology. In this way, the fiber grating 104 and the pump source optical fiber 103 are not fused, which effectively saves the number of fusion points and fusion time, so as to solve the problem of poor fusion.

[0038] In some embodiments, when the semiconductor collimation system is actually prepared, the pump source optical fiber is first obtained, and then the pump source optical fiber is subjected to fiber writing to obtain the pump source optical fiber comprising the fiber grating 104; then the pump source optical fiber comprising the fiber grating 104 and the pump chip, the collimation lens and the like are integrated in the shell, so as to form the semiconductor laser collimation system comprising the fiber grating 104. That is, the semiconductor laser collimation system provided in the application needs to integrate the fiber grating 104 formed by fiber writing on the pump source optical fiber in the collimation system, without fusing the fiber grating 104 outside the collimation system, and the collimation system itself can complete the application requirement of the pump plus the fiber grating 104.

[0039] In a specific embodiment, the process of fiber writing on the pump source can comprise:

[0040] The fiber to be written fiber grating 104 is determined, that is, the pump source fiber is determined, and the pump source fiber is placed horizontally along the x direction; then the refractive index range of the fiber to be written fiber grating 104 is determined, and the shape and size of the corresponding fiber grating 104 are determined; then the average power of the laser and the diameter of the laser beam during writing are determined according to the foregoing part parameters of the fiber grating. In actual writing, the writing position of the fiber grating 104 in the pump source fiber is determined, that is, it is determined which section of the pump source fiber needs to be written. Then the laser is incident and focused on the writing position by using the average power and the beam diameter determined by the laser, and the laser is controlled to move uniformly by a set distance, so as to realize the writing of the pump source fiber and obtain the fiber grating 104. The foregoing writing process simply describes how to write the pump source fiber to obtain the fiber grating 104, and the specific writing process can refer to the prior art, which is not limited here.

[0041] In the embodiment of the present application, the fiber grating 104 can be a Bragg grating obtained by fiber writing. Due to the characteristics of the Bragg grating, when the grating is written, the sensitivity of the grating to temperature and stress is determined. However, in the actual use scene of the semiconductor laser, the temperature around the grating and the stress borne by the grating may also change, which causes the characteristics of the Bragg grating to change, so that the central wavelength of the pump light penetrating the Bragg grating is offset. Therefore, the present application additionally increases a pump light detection module for detecting the light emitted by the fiber grating 104; when the offset of this part of light exceeds a set threshold, it can be determined that the light grating at this time may have an abnormality, which needs to be alarmed in time. Therefore, the pump light detection module in the present application is usually arranged on the light emitting side of the fiber grating 104, and the pump light detection module can be arranged inside the semiconductor laser collimation system or outside the semiconductor laser collimation system.

[0042] It should be noted that in the embodiment of the present application, the pump source fiber is usually a passive fiber; the pump source fiber is written, that is, the passive fiber is written. Compared with writing a doped fiber, since the passive fiber does not contain other impurities, the actual writing difficulty is lower, the process requirement is not high, and it is easy to realize. When the collimation system is actually prepared, the distance between the fiber grating 104 and the end cap is 5-10 mm, such as 5 mm, and the bandwidth of the fiber grating 104 is 38-40 mm, such as 40 mm.

[0043] As shown in FIG. 2, an embodiment structure schematic diagram of the fiber laser provided by the embodiment of the present application is shown. In the embodiment shown in FIG. 2, the fiber laser comprises a pump source, and the pump source comprises the aforementioned semiconductor laser collimation system 10, and further comprises a gain fiber 20; and the gain fiber 20 is arranged at the light emitting side of the fiber grating 104, that is, the gain fiber is located at the light emitting side of the entire semiconductor laser collimation system 10. In FIG. 2, the gain fiber 20 can comprise a first-stage gain fiber 201 and a second-stage gain fiber 202, and the first-stage gain fiber 201 and the second-stage gain fiber 202 are arranged in sequence at the light emitting side of the entire semiconductor laser collimation system 10. The semiconductor laser further comprises a low-reflection grating 30, and the low-reflection grating 30 is located between the first-stage gain fiber 201 and the second-stage gain fiber 202. The low-reflection grating 30 and the fiber grating 104 in the collimation system together constitute a resonant cavity in the semiconductor laser. Among them, the fiber grating 104 is a high-reflection grating, and the reflectivity of the high-reflection grating pumped light is usually greater than 90%; and the reflectivity of the low-reflection grating 30 to the signal is less than 12%, and the two constitute the resonant cavity of the laser. In some embodiments, the low-reflection grating 30 can be fused between the first-stage gain fiber 201 and the second-stage gain fiber 202; in other embodiments, the low-reflection grating 30 can also be a grating obtained by fiber inscription, so that there is no fusion point between the low-reflection grating 30 and the first-stage gain fiber 201 and the second-stage gain fiber 202, thereby further reducing the fusion point and reducing the probability of poor fusion. However, since the gain fiber is an active fiber, it is difficult to inscribe the active fiber, so usually only the high-reflection grating is formed by inscribing the passive fiber, and whether the low-reflection grating is formed by inscription can be determined according to actual needs. In other embodiments, the gain fiber 20 in the present application can only comprise a first-stage gain fiber, and not comprise a first-stage gain fiber and a second-stage gain fiber at the same time; the specific setting can be determined according to actual needs, which is not limited here.

[0044] In the embodiments of the present application, the gain fiber 20 is an active fiber, that is, both the first gain fiber 201 and the second gain fiber 202 are active fibers. Specifically, the gain fiber 20 can be a double-clad or triple-clad fiber with a core doped with rare earth elements, such as one or more of ytterbium, erbium, holmium, thulium, samarium, bismuth, and the like, so as to realize output of different laser wavelengths. In a specific embodiment, the gain fiber can be a double-clad ytterbium-doped fiber. The gain fiber 20 and the pump source fiber 103 in the present application can be the same specification fiber; here, the same specification fiber mainly refers to the core and the cladding; that is, the two can have the same geometric size of the core and the same geometric size of the cladding. The fiber laser provided in the present application is highly integrated and has a large power, so that there is no need to set a fiber combiner in the fiber laser, and there is no need to use the fiber combiner to couple multiple pump lights and then transmit the pump light into the resonant cavity. Using one high-power pump chip instead of multiple low-power pump chips reduces the number of pump chips and thus reduces the number of pump chip fusion points. While increasing the power of the fiber laser, the laser structure design can also be simplified, the fusion working hours can be reduced, and the fusion defects can be reduced. At the same time, since the combiner is omitted, the problem of divergence of the pump light by the combiner is eliminated, so that the divergence angle of the pump light output by the pump source can be effectively controlled, the conversion efficiency of the gain fiber 20 is improved; so that the power of the output laser is improved under the condition that the input power is unchanged, that is, the overall power of the semiconductor laser is improved, and the preparation of a high-power laser is realized.

[0045] In other embodiments, the gain fiber 20 still includes the first gain fiber 201 and the second gain fiber 202, but different from the foregoing embodiments, the first gain fiber 201 is a passive fiber, and the second gain fiber 202 is an active fiber; and the low reflection grating 30 arranged at the light output side of the first gain fiber 201 is a passive fiber matched with the first gain fiber, and the low reflection grating can also be obtained by writing the first gain fiber 201. At this time, the semiconductor laser collimation system can include multiple pump chips, such as a main pump chip and an auxiliary pump chip, which respectively emit main pump light and auxiliary pump light; and the semiconductor laser collimation system also includes a combiner, and the main pump light and the auxiliary pump light need to pass through the combiner for beam combination and then enter the collimation lens for collimation; the beam after beam combination and collimation is also injected into the pump source fiber, and is emitted through the fiber grating 104 on the pump source fiber 103.

[0046] In the above embodiment, the fiber grating 104, the first gain fiber 201 and the low reflection grating 30 jointly constitute a fiber oscillator assembly; at this time, the combined light obtained after the main pump light and the auxiliary pump light are combined is injected into the fiber oscillator assembly. The combined light is converted into over-pumped light with a wavelength between the wavelength of the main pump light and the wavelength of the auxiliary pump light by the fiber oscillator assembly, and is then injected into the second gain fiber 202. The gain fiber mainly serves as a transmission for the main pump light, and the second gain fiber 202 amplifies the main pump light, and the auxiliary pump light provides energy for the amplification of the main pump light, so that the semiconductor laser outputs high-power main pump light, ensuring the quality and power of the laser output. Although the embodiment includes multiple pump chips and a combiner, only one main pump chip and one auxiliary pump chip are generally required in the present application, and the number of pump sources can be reduced compared to the two or more pump sources in the prior art, thereby reducing the number of fusion points between the pump chips and the combiner. In the embodiment, the fiber grating 104 is still connected to the pump source fiber by the fiber writing method, and there is no fusion point between the two, which also reduces the number of fusion points. Therefore, the embodiment can realize high-power laser output while reducing the number of fusion points and reducing the risk of poor fusion.

[0047] In the above embodiment, the first gain fiber 201 and the second gain fiber 202 are both multi-clad fibers, and the main pump light and the auxiliary pump light can be amplified and transmitted through different fiber cross-sectional areas of the two gain fibers, respectively, and the process is relatively independent, and heat dissipation is performed respectively, thereby reducing the influence of thermal effects in the laser amplification process. The semiconductor laser provided by the present application can further be provided with a temperature control device and a heat dissipation device, wherein the temperature control device is mainly used for detecting the temperature change of the gain fiber 20 (including the low reflection grating 30), and the specific structure and position of the temperature control device can be changed according to actual needs, which is not limited herein. The heat dissipation device can dissipate heat for the gain fiber 20. In some embodiments, a heat dissipation medium can be coated on the surface of the gain fiber 20 to dissipate heat for the gain fiber 20 and improve the beam quality. In a specific embodiment, heat dissipation glue can be coated on the surface of the gain fiber 20 to dissipate heat.

[0048] In the foregoing embodiment, the fiber grating 104 and the low reflection grating 30 form a resonant cavity; in other embodiments, there can be multiple low reflection gratings, and the multiple low reflection gratings form a multi-core low reflection grating array. The multi-core low reflection grating array can form multiple resonant cavities together with the fiber grating to select wavelengths, and after multiple oscillations, different lasers can be stably output. In other embodiments, there can be multiple fiber gratings and multiple low reflection gratings, and the multiple fiber gratings and the multiple low reflection gratings can be arranged in a cross manner, and a resonant cavity can be formed between any adjacent fiber grating and low reflection grating, and the same wavelength selection function of outputting different lasers can also be achieved. In a specific embodiment, the semiconductor laser can include two fiber gratings and two low reflection fibers, and the fiber gratings and the low reflection fibers are arranged in the order of fiber grating-1, low reflection grating 1, fiber grating 2, and low reflection grating 2, and a gain fiber is further arranged between the two adjacent gratings. At this time, the fiber grating 1 and the low reflection grating 1 form a resonant cavity, and the low reflection grating 1 and the fiber grating 2 also form a resonant cavity. That is, in this embodiment, the gratings between different resonant cavities can be shared, which can reduce the number of gratings, reduce the cost, and reduce the number of fusion points.

[0049] It should be noted that in the foregoing embodiment, the high reflection grating closest to the semiconductor laser collimation system is formed by fiber inscription and integrated in the semiconductor laser collimation system. In this way, compared with the prior art, the number of fusion points can be reduced, and the fusion failure can be reduced. If there are multiple fiber gratings, in addition to the fiber gratings integrated in the collimation system, whether the other fiber gratings are obtained by fiber inscription, and whether the inscription is performed on the active fiber or the passive fiber, can be adjusted according to actual needs. Similarly, for the low reflection grating and the gain fiber, the gain fiber can include an active fiber or a passive fiber, and the position of the low reflection grating in the fiber laser and whether the low reflection grating is obtained by inscription, and whether the inscription is performed on the active fiber or the passive fiber in the gain fiber, can be adjusted according to actual needs. In this application, no limitation is made, and other schemes do not represent a limitation on the application.

[0050] In the embodiment shown in FIG. 2, the semiconductor laser further includes a mode stripper 40 and a fiber output head 50. The mode stripper 40 is a forward mode stripper, which is used to filter out cladding pump light and high-order mode laser. The fiber output head 50 is used as a fiber output device to output the signal laser for beam expansion, and the fiber output head 50 can effectively reduce the energy density of the output laser and improve the overall reliability of the laser. In other embodiments, a fiber isolator can also be connected to the output side of the mode stripper 40, and the fiber isolator is arranged between the mode stripper and the fiber output head. The fiber isolator is mainly used to isolate the return light and determine the unidirectional propagation of the output laser.

[0051] In some embodiments, the operating wavelength of the semiconductor laser is usually one of 915 nm, 940 nm or 976 nm, or a combination of multiple wavelengths, and the wavelength of the semiconductor laser can also be other wavelengths according to actual needs, and the selection is flexible, which is not limited herein.

[0052] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0053] The above describes in detail a semiconductor laser collimation system and a semiconductor laser provided by the embodiments of the present application. The principles and implementation manners of the present application are described by applying specific examples. The above embodiment descriptions are only used to help understand the technical solutions and core ideas of the present application. Those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some technical features can be replaced equivalently, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A semiconductor laser collimation system, characterized by, The semiconductor laser collimation system comprises: a housing; a pump chip for emitting pump light; a collimation module for fixing a collimation lens and a pump source fiber; a collimation lens located at the light emitting side of the pump chip, for collimating the pump light; a pump source fiber located at the light emitting side of the collimation lens, the pump source fiber comprising a fiber grating formed by fiber inscription; the pump chip, the collimation module, the collimation lens and the pump source fiber are all arranged in the housing.

2. The semiconductor laser collimation system of claim 1, wherein, The semiconductor laser collimation system further comprises an end cap arranged between the collimation lens and the pump source fiber, the end cap being fused with the pump source fiber.

3. The semiconductor laser collimation system of claim 2, wherein, The distance between the fiber grating and the end cap is 5-10 mm.

4. The semiconductor laser collimation system of claim 1, wherein, The bandwidth of the fiber grating is 38-40 mm.

5. The semiconductor laser collimation system of claim 1, wherein, The fiber grating is a high reflection grating.

6. The semiconductor laser collimation system of claim 1, wherein, The pump source fiber is a passive fiber.

7. A fiber laser, characterized by, The fiber laser comprises the semiconductor laser collimation system according to any one of claims 1-6, and further comprises a gain fiber arranged at the light emitting side of the fiber grating.

8. The fiber laser of claim 7, wherein, The gain fiber comprises a primary gain fiber and a secondary gain fiber, and the semiconductor laser further comprises a low reflection grating arranged between the primary gain fiber and the secondary gain fiber.

9. The fiber laser of claim 7, wherein, The gain fiber and the pump source fiber are the same specification fiber.

10. The fiber laser of claim 7, wherein, The semiconductor laser further comprises a mode stripper located at the light emitting side of the secondary gain fiber.

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