Power amplifier and fiber laser

Abstract

The present application is applicable to the field of laser amplification technology, and proposes a power amplification device connected to a signal optical fiber and a pump optical fiber, the power amplification device comprising: an equipment box and a first integrated device, an active optical fiber and a second integrated device arranged in the equipment box; the signal optical fiber is connected to one end of the first integrated device, and the first integrated device is used to allow the front-stage signal light introduced by the signal optical fiber to pass through; one end of the active optical fiber is connected to the other end of the first integrated device, and the other end of the active optical fiber is connected to the second integrated device; the pump optical fiber is connected to one end of the second integrated device connected to the active optical fiber, and is used to transmit pump light to the second integrated device; the present application also proposes a fiber laser, including a power amplification device; the power amplification device and the fiber laser provided by the present application have a simple structure, a few devices, can efficiently amplify the signal light, and can also effectively reduce the space occupied by the equipment, reduce the assembly and adjustment process, reduce the cost, and have strong practicality.

Description

Technical Field

[0001] The present application relates to the field of laser amplification technology, and in particular to a power amplification device and a fiber laser. Background Art

[0002] With the vigorous development of lasers, integration and miniaturization are a development direction. Conventional high-power fiber lasers generally undergo multiple stages of amplification, and each amplification stage requires multiple devices such as mode field adapters (MFA), cladding power strippers (CPS), isolators, beam expanders, and beam combiners. Therefore, there are many optical components and complex optical paths in high-power lasers, and there are many problems such as large space occupation, many installation and adjustment procedures, low efficiency, and high cost. Many devices will also deteriorate the beam quality in various links such as assembly and fiber winding, affecting the processing capabilities of the laser. Summary of the invention

[0003] In response to the above problems, the present application provides a power amplifier device and a fiber laser, which at least solves the problem that the laser in the prior art requires numerous components, resulting in large space occupancy, many assembly and adjustment steps, low efficiency, and affected laser quality.

[0004] The embodiment of the present application provides a power amplifier device connected to a signal optical fiber and a pump optical fiber, and the power amplifier device includes:

[0005] An equipment box and a first integrated device, an active optical fiber and a second integrated device arranged in the equipment box;

[0006] The signal optical fiber is connected to one end of the first integrated device, and the first integrated device is used to allow the preceding signal light introduced by the signal optical fiber to pass through;

[0007] One end of the active optical fiber is connected to the other end of the first integrated device, and the other end of the active optical fiber is connected to the second integrated device;

[0008] The pump optical fiber is connected to one end of the second integrated device connected to the active optical fiber, and is used to transmit pump light to the second integrated device;

[0009] After the pump light enters the second integrated device, it enters the active optical fiber in the reverse direction, and part of the pump light enters the first integrated device and is filtered; the preceding signal light enters the active optical fiber in the forward direction through the signal optical fiber and the first integrated device, and the preceding signal light is amplified by the pump light in the active optical fiber and then transmitted to the second integrated device, and is output after being collimated and expanded by the second integrated device.

[0010] In one embodiment, the first integrated device includes a packaging box and a high-refractive-index packaging glue, a fixing portion, and a tapered portion contained in the packaging box;

[0011] The high refractive index packaging glue is used to filter the pump light;

[0012] One end of the fixing portion is connected to the signal optical fiber and the other end passes through the high refractive index packaging glue and is connected to the tapered portion;

[0013] The other end of the tapered portion opposite to the fixing portion is connected to the active optical fiber.

[0014] In one embodiment, the tapered region of the tapered portion has a length of 5 mm, and a terminal cladding diameter of 83.3 mm.

[0015] In one embodiment, the second integrated device includes a C lens, a filter, an isolator core, and a magnifying lens group arranged in sequence;

[0016] The amplified signal light emitted from the active optical fiber passes through the C lens, the filter, and the isolator core in sequence, and then is amplified by the amplifying lens group to enlarge the beam diameter and collimated for output;

[0017] The pump signal emitted from the pump optical fiber passes through the C lens, is reflected by the filter, passes through the C lens again, and then is emitted into the active optical fiber.

[0018] In one embodiment, the second integrated device further comprises a glass tube, the C lens is disposed in the glass tube, and the filter is disposed at an end of the glass tube away from the active optical fiber.

[0019] In one embodiment, the amplifying lens group includes a biconcave lens and a plano-convex lens, and the amplified signal light passing through the isolator core is incident on the biconcave lens and passes through the plano-convex lens before being output.

[0020] In one embodiment, the C lens is made of quartz, has a radius of curvature of 2.2 mm, and a length of 7.1 mm, and the output beam diameter of the C lens is 0.3 mm;

[0021] The magnification of the magnifying lens group is 20 times.

[0022] In one embodiment, the signal fiber is a 10 / 125 fiber, the active fiber is a 30 / 250 fiber, and the pump fiber is a 105 / 125 fiber.

[0023] In one embodiment, the power amplification device further comprises a device box, wherein the signal optical fiber, the pump optical fiber, the active optical fiber, the first integrated device, and the second integrated device are all accommodated in the device box;

[0024] A water cooling component is also provided in the equipment box, and the active optical fiber is arranged beside the water cooling component, and the water cooling component is used to dissipate heat for the active optical fiber.

[0025] The embodiment of the present application also provides a fiber laser, comprising the power amplification device described above.

[0026] This application aims to improve the laser amplifier in the prior art by designing a large number of components, which results in large space occupation, many assembly and adjustment steps, low efficiency, and poor laser quality.

[0027] 1. Integrate the functions of MFA and CPS into the first integrated device, and integrate the functions of the combiner, isolator and beam expander into the second integrated device, so as to reduce the volume of the entire power amplifier device, the number of components, the assembly and adjustment process, and the cost;

[0028] 2. Use reverse pump light to amplify the previous signal light, thereby increasing the laser output power;

[0029] The present application has a simple structure, few components, and can efficiently amplify signal light. It can also effectively reduce the space occupied by the equipment, reduce the installation and adjustment process, reduce costs, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0031] Figure 1 A schematic diagram of the structural principle of a power amplification device provided in an embodiment of the present application.

[0032] Figure 2 for Figure 1 A schematic diagram of the structural principle of the first integrated device in the power amplifier device shown.

[0033] Figure 3 for Figure 1 A schematic diagram of the structural principle of the second integrated device in the power amplifier device shown.

[0034] The meanings of the marks in the figure are:

[0035] 1. Signal fiber; 2. Pump fiber;

[0036] 3. First integrated device; 31. Packaging box; 32. High refractive index packaging glue; 33. Fixing part; 34. Taper part; 35. Fixing glue.

[0037] 4. Active optical fiber;

[0038] 5. Second integrated device; 51. C lens; 52. Filter; 53. Isolator core; 54. Magnifying lens group; 541. Double concave lens; 542. Plano-convex lens; 55. Glass tube;

[0039] 6. Equipment box. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings, i.e., embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the patent. The terms "first" and "second" are only used for the convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0042] It should also be noted that, in the embodiments of the present application, the same figure mark is used to represent the same component or the same part. For the same parts in the embodiments of the present application, the figure may only mark one of the parts or components as an example. It should be understood that the figure mark also applies to other identical parts or components.

[0043] In order to illustrate the technical solution described in this application, the following is a description with reference to specific drawings and embodiments.

[0044] The present application provides a power amplifier device for use in a fiber laser, which uses integrated and miniaturized devices to replace a large number of devices that occupy a large space. While reducing the space occupied, it also optimizes the optical path, reduces the quality degradation caused by the propagation of the light beam in many devices, and improves the efficiency and quality of laser amplification.

[0045] Embodiment 1

[0046] refer to Figure 1The power amplifier device provided in the embodiment of the present application is connected to the signal optical fiber 1 and the pump optical fiber 2. The power amplifier device includes a device box 6 and a first integrated device 3, an active optical fiber 4 and a second integrated device 5 arranged in the device box 6.

[0047] The device box 6 is used to provide a fixing foundation. One end of the signal optical fiber 1 , one end of the pump optical fiber 2 , the active optical fiber 4 , the first integrated device 3 , and the second integrated device 5 are all accommodated in the device box 6 .

[0048] The signal optical fiber 1 is used to transmit the preceding signal light.

[0049] The pump optical fiber 2 is used to transmit pump light.

[0050] The first integrated device 3 is used to filter the pump light and allow the preceding signal light to pass through with low loss, wherein the effect of filtering the pump light is the same as that of CPS; the effect of the gradual transition of the optical fiber core diameter, allowing the preceding signal light to pass through and reducing the passing loss is the same as that of MFA, and the first integrated device 3 realizes the technical effects of MFA and CPS at the same time.

[0051] The second integrated device 5 is used to realize the introduction of pump light, that is, to introduce the pump light into the active optical fiber 4; the second integrated device 5 is also used for reverse isolation of signal light to prevent reflection of signal light and reverse input of other signal light; the second integrated device 5 is also used to collimate and expand the output of the previous signal light.

[0052] The second integrated device 5 simultaneously realizes the effects of a beam combiner, an isolator and a beam expander.

[0053] The connection relationship among the signal optical fiber 1, the pump optical fiber 2, the active optical fiber 4, the first integrated device 3, and the second integrated device 5 is as follows:

[0054] The signal optical fiber 1 is connected to one end of the first integrated device 3, and is used to transmit the front-stage signal light to the first integrated device 3; one end of the active optical fiber 4 is connected to the other end of the first integrated device 3, and the other end of the active optical fiber 4 is connected to one end of the second integrated device 5, and the active optical fiber 4 is used to transmit the signal light output by the first integrated device 3 to the second integrated device 5; one end of the pump optical fiber 2 is connected to the second integrated device 5, and the pump optical fiber 2 transmits the pump light to the second integrated device 5.

[0055] The optical path of the front-stage signal light in the power amplifier device is: the front-stage signal light is output after passing through the signal optical fiber 1, the first integrated device 3, the active optical fiber 4, and the second integrated device 5 in sequence. This direction is the forward direction, and the transmission direction opposite to the front-stage signal light is called the reverse direction.

[0056] The optical path of the pump light in the power amplifier device is as follows: the pump light is transmitted to the second integrated device 5 via the pump optical fiber 2, then reversed in the second integrated device 5 and transmitted into the active optical fiber 4, and some residual pump light enters the first integrated device 3 and is filtered.

[0057] The operation process of this embodiment is as follows: the preceding signal light is transmitted forward to the first integrated device 3 via the signal optical fiber 1; at the same time, after the pump light enters the second integrated device 5, it enters the active optical fiber 4 in the reverse direction under the action of the second integrated device 5, and is combined with the preceding signal light in the active optical fiber 4, and some residual pump light enters the first integrated device 3 and is filtered; the preceding signal light is amplified in power by the pump light in the active optical fiber 4, and the amplified signal light enters the second integrated device 5, and is output after being combined, isolated, collimated and expanded by the second integrated device 5.

[0058] The beneficial effects of this embodiment are as follows: the functions of MFA and CPS are integrated into the first integrated device 3, and the functions of the combiner, isolator and beam expander are integrated into the second integrated device 5, thereby reducing the volume of the entire power amplifier device, reducing the number of devices, reducing the assembly and adjustment steps, and reducing costs; and using reverse pump light to amplify the previous stage signal light, thereby improving the amplification efficiency.

[0059] Optionally, a water cooling component is further provided in the equipment box 6, which is used to dissipate heat for the active optical fiber 4; the active optical fiber 4 is arranged next to the water cooling component, and when the power amplifier device is manufactured, the active optical fiber 4 is set close to the bottom plate and close to the water cooling component, and the heat generated by the active optical fiber 4 is carried away by the water flow to avoid heat accumulation.

[0060] Furthermore, the water cooling element is a water cooling groove provided in the bottom plate of the equipment box 6, and cooling water flows in the water cooling groove. The active optical fiber 4 is attached to the bottom plate, thereby further improving the heat dissipation effect of the water cooling element on the active optical fiber 4.

[0061] refer to Figure 2 In one embodiment, the first integrated device 3 includes a packaging box 31 , a high refractive index packaging glue 32 , a fixing portion 33 and a tapered portion 34 .

[0062] The packaging box 31 is used to provide a fixing foundation for the high refractive index packaging glue 32 , the fixing portion 33 and the tapered portion 34 .

[0063] The fixing portion 33 is disposed in the packaging box 31 , and one end of the fixing portion 33 is integrally connected to the signal optical fiber 1 , that is, the fixing portion 33 is a part of the signal optical fiber 1 ; the other end of the fixing portion 33 is connected to the tapered portion 34 .

[0064] The tapered portion 34 is disposed in the packaging box 31 . The tapered portion 34 is a columnar structure with a pointed tip at one end. The tip of the tapered portion 34 is connected to the fixing portion 33 . The other end of the tapered portion 34 is integrally connected to the active optical fiber 4 , that is, the tapered portion 34 is a part of the active optical fiber 4 .

[0065] The tapered portion 34 is connected to the fixed portion 33 by welding. The preceding signal light will have a large loss when passing through the welding joint. The tapered portion 34 is used to enable the preceding signal light to obtain a larger pass rate at the welding joint, thereby reducing the loss of the preceding signal light passing through the welding joint between the fixed portion 33 and the tapered portion 34.

[0066] The high refractive index packaging glue 32 is arranged in the packaging box 31, and one end of the fixing part 33 passes through the high refractive index packaging glue 32 and is connected to the tapered part 34, that is, the high refractive index packaging glue 32 wraps part of the fixing part 33, and the high refractive index packaging glue 32 is used to filter out residual pump light.

[0067] The beneficial effects of this embodiment are: the technical effect of CPS is achieved by utilizing a small-volume tapered portion 34, and the technical effect of MFA is achieved by utilizing a small-volume high-refractive index packaging glue 32, and the tapered portion 34 and the high-refractive index packaging glue 32 are both arranged in the packaging box 31 and integrated into the first integrated device 3, which effectively reduces the space occupied by the power amplifier equipment.

[0068] Optionally, the tapered region length of the tapered portion 34 is 5 mm, and the end cladding diameter is 83.3 mm, wherein the tapered region is the length of the tip portion of the tapered portion 34 , and the end is the end of the tapered portion 34 connected to the active optical fiber 4 .

[0069] The tapered portion 34 is formed by tapering a single optical fiber. After being tapered, the tapered portion 34 is flattened by a cutter and then fused with the signal optical fiber 1 by a fusion splicer and placed in the packaging box 31 .

[0070] Optionally, the first integrated device 3 further includes a fixing glue 35 , and the fixing portion 33 and the tapered portion 34 are both fixed to the packaging box 31 by the fixing glue 35 .

[0071] refer to Figure 3 In one embodiment, the second integrated device 5 includes a C lens 51, a filter 52, an isolator core 53, and a magnifying lens group 54 arranged in sequence, and the optical axes of the C lens 51, the filter 52, the isolator core 53, and the magnifying lens group 54 are all coaxial.

[0072] The horizontal surface of the C lens 51 faces the active optical fiber 4 and the convex surface faces away from the active optical fiber 4 . The C lens 51 is used to focus the amplified signal light injected through the active optical fiber 4 and also to focus the pump light injected from the pump optical fiber 2 .

[0073] The filter 52 is used to filter and refract the pump light. Specifically, the amplified signal light and the pump light focused by the C lens 51 are both incident on the filter 52, wherein the amplified signal light directly passes through the filter 52, while the pump light is reflected by the filter 52 and then incident on the C lens 51, and after being restored by the C lens 51, it is incident on the first integrated device 3 through the active optical fiber 4.

[0074] The isolator core 53 is used to transmit the amplified signal light to the amplifying lens group 54 and is also used to isolate the reverse light.

[0075] The magnifying lens group 54 is used to expand and collimate the incident amplified signal light.

[0076] In this embodiment, the transmission optical path of the front-stage signal light is as follows: the amplified signal light is emitted from the active optical fiber 4 and then injected into the C lens 51, after being combined by the C lens 51, passes through the filter 52 and the isolator core 53, and then is amplified and expanded by the magnifying lens group 54 and output.

[0077] In this embodiment, the transmission optical path of the pump light is as follows: the pump light is emitted from the pump optical fiber 2 and then enters the C lens 51, is combined by the C lens 51 and then emitted to the filter 52, is reflected by the filter 52 and then restored by the C lens, and is emitted to the first integrated device 3 through the active optical fiber 4.

[0078] The beneficial effects of this embodiment are: the technical effect of a beam combiner is achieved by utilizing a small-volume C lens 51, the technical effect of an isolator is achieved by utilizing a small-volume filter 52 and an isolator core 53, the technical effect of a beam expander is achieved by utilizing a small-volume magnifying lens group 54, and the C lens 51, the filter 52, the isolator core 53, and the magnifying lens group 54 are integrated into one, thereby effectively reducing the space occupied by the equipment during power amplification.

[0079] The optical path scheme of this embodiment adopts the back pumping method, and the active optical fiber 4 is directly transmitted behind the C lens 51 without connecting other passive optical fibers. The overall optical path is the shortest, which effectively reduces nonlinearity and achieves the effect of optimizing beam quality.

[0080] Optionally, the second integrated device 5 also includes a glass tube 55, which is used to provide a fixing base for the C lens 51 and the filter 52. The glass tube 55 is a hollow tube, the C lens 51 is accommodated in the glass tube 55, and the filter 52 is connected to the end of the glass tube 55 away from the active optical fiber 4.

[0081] Optionally, the material of the C lens 51 is quartz.

[0082] Optionally, the ends of the active optical fiber 4 and the pump optical fiber 2 connected to the second integrated device 5 are directly fused to the horizontal plane of the C lens 51 .

[0083] Optionally, the magnifying lens group 54 includes a biconcave lens 541 and a plano-convex lens 542 .

[0084] The amplified signal light emitted from the isolator core 53 enters from one side of the biconcave lens 541 , and is diffused and emitted in an off-axis direction after being transformed by the biconcave lens 541 .

[0085] The light emitted from the biconcave lens 541 enters the plano-convex lens 542 , and the plano-convex lens 542 is used to convert the incident light into parallel light, thereby completing the expansion of the signal light.

[0086] Embodiment 2

[0087] On the basis of the first embodiment, the signal optical fiber 1 is a 10 / 125 optical fiber; the pump optical fiber 2 is a 200 / 220 optical fiber, and the 976nm pump light is injected into the second integrated device 5 from the pump optical fiber 2; the active optical fiber 4 is a 30 / 250 optical fiber, and the length is 4m; wherein, the core diameter of the 10 / 125 optical fiber is 10 microns and the outer diameter of the cladding is 125 microns, the core diameter of the 200 / 220 optical fiber is 200 microns and the outer diameter of the cladding is 220 microns, and the core diameter of the 30 / 250 optical fiber is 30 microns and the outer diameter of the cladding is 250 microns.

[0088] The filter 52 is a T1064 / R976 filter; the radius of curvature of the C lens 51 is 2.2 mm, and the length is 7.1 mm, and the diameter of the light beam output by the C lens 51 is 0.3 mm; the magnification of the magnifying lens group 54 is 20 times.

[0089] At this time, with a pump power of 285W and a signal light input of 1W, the output power of the power amplifier device is 200W, achieving a 200-fold amplification; the output beam quality M2 is less than 1.2, while the conventional machine M2 is 1.4, and the output beam quality is significantly improved; where M2 is the laser beam quality parameter, the smaller the value of M2, the higher the beam quality.

[0090] Embodiment 3

[0091] On the basis of the first or second embodiment, this embodiment provides a fiber laser, which uses the power amplification device in the first or second embodiment, and has a smaller size, a larger amplification factor, and a higher output beam quality.

[0092] The beneficial effects of this application are:

[0093] 1. The functions of MFA and CPS are integrated into the first integrated device 3, and the functions of the combiner, isolator and beam expander are integrated into the second integrated device 5. The optical path has no fusion breakpoints, which effectively shortens the length of the optical fiber and suppresses the nonlinear effect; the volume of the entire power amplifier equipment is reduced, the number of components is reduced, the assembly and adjustment process is reduced, and the cost is reduced;

[0094] 2. Use reverse pump light to amplify the previous signal light, thereby increasing the laser output power;

[0095] 3. The signal light has the shortest optical fiber transmission link, which reduces nonlinearity and improves the beam quality of the laser output.

[0096] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A power amplifier device connected to a signal optical fiber (1) and a pump optical fiber (2), characterized in that: The power amplification device comprises: A device box (6) and a first integrated device (3), an active optical fiber (4) and a second integrated device (5) arranged in the device box (6); The signal optical fiber (1) is connected to one end of the first integrated device (3), and the first integrated device (3) is used to allow the preceding signal light introduced by the signal optical fiber to pass through; One end of the active optical fiber (4) is connected to the other end of the first integrated device (3), and the other end of the active optical fiber (4) is connected to the second integrated device (5); The pump optical fiber (2) is connected to one end of the second integrated device (5) connected to the active optical fiber (4), and is used to transmit pump light to the second integrated device (5); After the pump light enters the second integrated device (5), it enters the active optical fiber (4) in the reverse direction, and part of the pump light enters the first integrated device (3) and is filtered; the front-stage signal light enters the active optical fiber (4) in the forward direction through the signal optical fiber (1) and the first integrated device (3), and the front-stage signal light is amplified by the pump light in the active optical fiber (4) and then transmitted to the second integrated device (5), and is collimated and expanded by the second integrated device (5) before being output; The first integrated device (3) comprises a packaging box (31), and a high-refractive-index packaging glue (32), a fixing portion (33), and a tapered portion (34) contained in the packaging box (31); The high refractive index packaging glue (32) is used to filter the pump light; One end of the fixing portion (33) is connected to the signal optical fiber (1) and the other end passes through the high refractive index packaging glue (32) and is connected to the tapered portion (34); One end of the tapered portion (34) facing away from the fixing portion (33) is connected to the active optical fiber (4); The second integrated device (5) comprises a C lens (51), a filter (52), an isolator core (53), and a magnifying lens group (54) which are arranged in sequence; The amplified signal light emitted from the active optical fiber (4) passes through the C lens (51), the filter (52), and the isolator core (53) in sequence, and then passes through the amplifying lens group (54) to enlarge the beam diameter and collimate the output; The pump signal emitted from the pump optical fiber (2) passes through the C lens (51), is reflected by the filter (52), passes through the C lens (51) again, and then is emitted into the active optical fiber (4).

2. The power amplification device according to claim 1, characterized in that: The tapered region length of the tapered portion (34) is 5 mm, and the terminal cladding diameter is 83.3 mm.

3. The power amplification device according to claim 1, characterized in that: The second integrated device (5) further comprises a glass tube (55), the C lens (51) is accommodated in the glass tube (55), and the filter (52) is connected to an end of the glass tube (55) facing away from the active optical fiber (4).

4. The power amplification device according to claim 1, characterized in that: The amplifying lens group (54) includes a biconcave lens (541) and a plano-convex lens (542). The amplified signal light passing through the isolator core (53) is incident on the biconcave lens (541) and is output after passing through the plano-convex lens (542).

5. The power amplification device according to any one of claims 1 to 4, characterized in that: The C lens (51) is made of quartz, has a curvature radius of 2.2 mm, and a length of 7.1 mm; the output beam diameter of the C lens (51) is 0.3 mm; The magnification of the magnifying lens group (54) is 20 times.

6. The power amplification device according to claim 1, characterized in that: The signal optical fiber (1) is a 10 / 125 optical fiber, the active optical fiber (4) is a 30 / 250 optical fiber, and the pump optical fiber (2) is a 105 / 125 optical fiber.

7. The power amplification device according to claim 1, characterized in that: A water cooling component is also provided in the equipment box (6), and the active optical fiber (4) is arranged beside the water cooling component, and the water cooling component is used to dissipate heat for the active optical fiber (4).

8. A fiber laser, characterized in that: The invention comprises a power amplifying device as claimed in any one of claims 1 to 7.

Images