Fiber laser device

Abstract

Provided is a fiber laser device capable of suppressing the deterioration of the beam quality of output laser light and obtaining a stable beam quality. The fiber laser device (1) comprises: an amplifying optical fiber (20) capable of amplifying laser light; an excitation light source (30, 40) capable of generating excitation light; an output optical fiber (60) comprising a core (601) for propagating the laser light amplified by the amplifying optical fiber (20) and a cladding (602) having a lower refractive index than the core (601) and covering the periphery of the core (601); and a transmission optical fiber (70) comprising a core (701) optically coupled to the core (601) of the output optical fiber (60) and a cladding (702) having a lower refractive index than the core (701) and covering the periphery of the core (701). The outer diameter of the cladding (702) of the transmission optical fiber (70) is larger than the outer diameter of the cladding (602) of the output optical fiber (60). The transmission optical fiber (70) extends from the inside of a storage unit (12) to the outside.

Description

Technical Field

[0001] The present invention relates to a fiber laser device, and more particularly to a fiber laser device that generates high-output laser light using excitation light. Background Art

[0002] Compared with the carbon dioxide laser used in the past to cut metal, the fiber laser device has better beam quality, can reduce the beam spot, and has a higher power density. Therefore, it has been more widely used in metal material cutting, welding and other processing in recent years. In such a fiber laser device, excitation light is supplied to an amplifying optical fiber containing a core added with rare earth elements, so that the core of the amplifying optical fiber absorbs the excitation light, thereby amplifying the laser. The laser amplified by the excitation light supplied to the amplifying optical fiber propagates in the transmission optical fiber and is output from the output end (for example, refer to Patent Document 1).

[0003] In the existing fiber laser device, the amplification optical fiber and the output end are stored in different storage units. Therefore, for the transmission optical fiber extending from the amplification optical fiber to the output end, the transmission optical fiber is led out from the storage unit storing the amplification optical fiber, and after being arranged in the desired path, it is introduced into the storage unit where the output end is set. When arranging the transmission optical fiber in this way, the transmission optical fiber has to be bent due to space constraints. The core of the bent transmission optical fiber will be subjected to lateral pressure, which may cause the beam quality of the laser propagating inside it to deteriorate. In addition, the shape of the bent transmission optical fiber is easy to change, and the beam quality of the laser is difficult to stabilize.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-168772 Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] The present invention has been made in view of the above-mentioned problems in the prior art, and an object of the present invention is to provide a fiber laser device which suppresses the deterioration of the beam quality of output laser light and can obtain a stable beam quality.

[0009] (II) Technical solution

[0010] According to one embodiment of the present invention, a fiber laser device is provided, which suppresses the deterioration of the beam quality of the output laser and can obtain a stable beam quality. The fiber laser device includes: an amplification optical fiber that can amplify the laser; at least one excitation light source that can generate excitation light supplied to the amplification optical fiber; an output optical fiber that includes a first core that propagates the laser amplified by the amplification optical fiber, and a first cladding that has a lower refractive index than the first core and covers the periphery of the first core; a transmission optical fiber that includes a second core that is optically coupled to the first core of the output optical fiber, and a second cladding that has a lower refractive index than the second core and covers the periphery of the second core; and a first storage unit that stores the amplification optical fiber and the output optical fiber inside. The outer diameter of the second cladding of the transmission optical fiber is larger than the outer diameter of the first cladding of the output optical fiber. The transmission optical fiber extends from the inside of the first storage unit to the outside of the first storage unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram schematically showing the overall structure of a fiber laser device according to one embodiment of the present invention.

[0012] Figure 2 To indicate Figure 1 A cross-sectional view of an amplifying optical fiber in a fiber laser device shown.

[0013] Figure 3 To indicate Figure 1 A cross-sectional view of the front light combiner and the front excitation fiber in the fiber laser device shown.

[0014] Figure 4 To indicate Figure 1 A cross-sectional view of the rear light combiner and rear excitation fiber in the fiber laser device shown. DETAILED DESCRIPTION

[0015] Below, refer to Figures 1 to 4 The embodiments of the fiber laser device of the present invention are described in detail. Figures 1 to 4 The same or corresponding components are denoted by the same reference numerals and repeated descriptions are omitted. Figures 1 to 4 In the following description, unless otherwise specified, the terms "first", "second", etc. are used only to distinguish between components and do not indicate a specific order or sequence.

[0016] Figure 1 FIG. 1 is a diagram schematically showing the overall structure of a fiber laser device 1 according to an embodiment of the present invention. Figure 1As shown, the fiber laser device 1 includes a plurality of storage units 11 to 14 stacked up and down. Figure 1 In the figure, the storage units 11 to 14 are shown separated from each other for easy understanding. However, in reality, the storage units 11 to 14 are stacked up and down in contact with each other.

[0017] like Figure 1 As shown in FIG. 1 , the fiber laser device 1 includes: an amplification optical fiber 20 capable of amplifying laser light; a high reflection portion 21 reflecting light in a predetermined wavelength band with high reflectivity; a low reflection portion 22 reflecting light in the wavelength band with a reflectivity lower than that of the high reflection portion 21; a plurality of front excitation light sources 30 supplying excitation light to the amplification optical fiber 20 from one end side (front side) of the amplification optical fiber 20; a front optical combiner 31 coupling the excitation light output from the front excitation light source 30 and introducing it to the amplification optical fiber 20; a plurality of rear excitation light sources 40 supplying excitation light to the amplification optical fiber 20 from the other end side (rear side) of the amplification optical fiber 20; a rear optical combiner 41 coupling the excitation light output from the rear excitation light source 40 and introducing it to the amplification optical fiber 20; and a beam output end 50 outputting laser light amplified by the excitation light supplied to the amplification optical fiber 20. In addition, in this specification, unless otherwise specified, the direction from the amplification optical fiber 20 toward the beam output end 50 is referred to as the "downstream side", and the opposite direction is referred to as the "upstream side".

[0018] As the front excitation light source 30 and the rear excitation light source 40, for example, a high-output multimode semiconductor laser (LD) with a wavelength of 975 nm can be used. The wavelength of the laser generated by the front excitation light source 30 and the wavelength of the laser generated by the rear excitation light source 40 can be the same or different. In addition, the high reflection part 21 and the low reflection part 22 are composed of, for example, a fiber Bragg grating formed by periodically changing the refractive index of the optical fiber and a reflector.

[0019] The storage unit 12 on the second upper layer stores the amplification optical fiber 20, the high reflection unit 21, the low reflection unit 22, the front optical combiner 31, and the rear optical combiner 41. Inside the storage unit 12, the high reflection unit 21 is connected to the amplification optical fiber 20 via the fusion splice 23, and is connected to the front optical combiner 31 via the fusion splice 25. In addition, the low reflection unit 22 is connected to the amplification optical fiber 20 via the fusion splice 24, and is connected to the rear optical combiner 41 via the fusion splice 26.

[0020] Figure 2 FIG. 2 is a schematic cross-sectional view of the amplification optical fiber 20. Figure 2As shown, the amplification optical fiber 20 is composed of, for example, a double-clad optical fiber, and has, for example: a core 201 doped with rare earth elements such as ytterbium (Yb), erbium (Er), thulium (Tr), and neodymium (Nd); an inner cladding 202 formed around the core 201; and an outer cladding 203 formed around the inner cladding 202. The inner cladding 202 is composed of a material (e.g., SiO2) having a lower refractive index than the core 201, and the interior of the core 201 becomes an optical waveguide for propagating laser light (signal light). In addition, the outer cladding 203 is composed of a resin (e.g., a low-refractive-index polymer) having a lower refractive index than the inner cladding 202, and the interiors of the core 201 and the inner cladding 202 become an optical waveguide for propagating the excitation light P.

[0021] The storage unit 13 (third storage unit) on the third layer from the top stores the front excitation light source 30. The front excitation optical fibers 33 extend from the front excitation light source 30 in the storage unit 13 on the third layer to the front light combiner 31 in the storage unit 12 on the second layer. In addition, the storage unit 14 (third storage unit) on the bottom layer stores the rear excitation light source 40. The rear excitation optical fibers 43 extend from the rear excitation light source 40 in the storage unit 14 on the bottom layer to the rear light combiner 41 in the storage unit 12 on the second layer.

[0022] Figure 3 Schematically shows a cross-sectional view of the front optical combiner 31 and the front excitation optical fiber 33. Figure 3 As shown in FIG. 1 , the forward excitation optical fiber 33 includes a core 331, a cladding 332 covering the core 331, and a coating (not shown) covering the cladding 332. The refractive index of the cladding 332 is lower than that of the core 331. Therefore, the interior of the core 331 of the forward excitation optical fiber 33 becomes an optical waveguide for propagating the excitation light from the forward excitation light source 30.

[0023] The front optical combiner 31 includes a core 311, a cladding 312 covering the core 311, and a coating 313 covering the cladding 312. The refractive index of the cladding 312 is lower than that of the core 311, and an optical waveguide for propagating excitation light is formed inside the core 311. Each front excitation optical fiber 33 is fusion-connected to the front optical combiner 31 in such a manner that the core 331 of the front excitation optical fiber 33 is located within the region of the core 311 of the front optical combiner 31. The coating of the front excitation optical fiber 33 and the coating 313 of the front optical combiner 31 are removed near the fusion-connected portion between the front excitation optical fiber 33 and the front optical combiner 31. Thus, the excitation light generated by the front excitation light source 30 propagates in the core 331 of the front excitation optical fiber 33 and is introduced into the core 311 of the front optical combiner 31, and propagates in the core 311 of the front optical combiner 31. Alternatively, an air layer may be formed around the core 311 of the front optical combiner 31 , and the air layer may be used as the cladding 312 .

[0024] The high reflection part 21 of this embodiment is composed of a double-clad optical fiber formed with a fiber Bragg grating. That is, the high reflection part 21 has: a core, an inner cladding covering the periphery of the core, and an outer cladding covering the periphery of the inner cladding. Figure 1 ), the core 311 of the front optical combiner 31 (refer to Figure 3 ) is optically coupled to the inner cladding of the high reflection portion 21. Figure 1 ), the core 201 of the amplification optical fiber 20 (refer to Figure 2 ) is optically coupled to the core of the high reflection portion 21, and the inner cladding 202 (refer to Figure 2 ) is optically coupled to the inner cladding of the high reflection portion 21.

[0025] Figure 4 FIG. 4 is a cross-sectional view schematically showing the rear optical combiner 41 and the rear excitation optical fiber 43. Figure 4 As shown in FIG. 1 , the rear excitation optical fiber 43 includes a core 431, a cladding 432 covering the core 431, and a coating (not shown) covering the cladding 432. The refractive index of the cladding 432 is lower than that of the core 431. Therefore, the interior of the core 431 of the rear excitation optical fiber 43 serves as an optical waveguide for propagating the excitation light from the rear excitation light source 40.

[0026] The rear optical combiner 41 includes a core 411, an inner cladding 412 covering the core 411, an outer cladding 413 covering the inner cladding 412, and a cover 414 covering the outer cladding 413. The refractive index of the inner cladding 412 is lower than that of the core 411, and the interior of the core 411 serves as an optical waveguide for propagating signal light. In addition, the refractive index of the outer cladding 413 is lower than that of the inner cladding 412, and the interiors of the core 411 and the inner cladding 412 serve as optical waveguides for propagating excitation light. Each rear excitation optical fiber 43 is fusion-connected to the rear optical combiner 41 in such a manner that the core 431 of the rear excitation optical fiber 43 is located within the region of the inner cladding 412 of the rear optical combiner 41. The coating of the rear excitation optical fiber 43 and the coating 414 of the rear optical combiner 41 are removed near the fusion connection portion between the rear excitation optical fiber 43 and the rear optical combiner 41. Alternatively, an air layer may be formed around the inner cladding 412 of the rear optical combiner 41 and used as the outer cladding 413.

[0027] The low reflection part 22 of this embodiment is composed of a double-clad optical fiber formed with a fiber Bragg grating. That is, the low reflection part 22 has: a core, an inner cladding covering the periphery of the core, and an outer cladding covering the periphery of the inner cladding. Figure 1 ), the core 411 of the rear optical combiner 41 (refer to Figure 4 ) is optically coupled to the core of the low-reflection portion 22, and the inner cladding 412 of the rear optical combiner 41 is optically coupled to the inner cladding of the low-reflection portion 22. Figure 1 ), the core 201 of the amplification optical fiber 20 (refer to Figure 2 ) is optically coupled to the core of the low reflection portion 22, and the inner cladding 202 (refer to Figure 2 ) is optically coupled to the inner cladding of the low-reflection portion 22.

[0028] like Figure 4 As shown, an output optical fiber 60 is connected to the central part of the end face of the rear optical combiner 41. The output optical fiber 60 includes: a core 601 (first core), and a cladding 602 (first cladding) covering the core 601. The refractive index of the cladding 602 is lower than the refractive index of the core 601, and the interior of the core 601 becomes an optical waveguide for propagating signal light. For example, the outer diameter of the core 601 of the output optical fiber 60 is 40μm, and the outer diameter of the cladding 602 is 125μm. The output optical fiber 60 is fusion-connected to the rear optical combiner 41 in such a way that the core 411 of the rear optical combiner 41 is located within the region of the core 601 of the output optical fiber 60. The output optical fiber 60 is housed in the housing unit 12 (see Figure 1 ).

[0029] like Figure 4 As shown, a transmission optical fiber 70 is connected to the end of the output optical fiber 60. The transmission optical fiber 70 has a core 701 (second core), a cladding 702 (second cladding) covering the periphery of the core 701, and a coating 703 covering the periphery of the cladding 702. The refractive index of the cladding 702 is lower than that of the core 701, and the interior of the core 701 serves as an optical waveguide for propagating signal light. For example, the outer diameter of the core 701 of the transmission optical fiber 70 is 40 μm, and the outer diameter of the cladding 702 is 400 μm. The transmission optical fiber 70 is fusion-connected to the output optical fiber 60 in such a manner that the core 601 of the output optical fiber 60 is located within the region of the core 701 of the transmission optical fiber 70. The coating 703 of the transmission optical fiber 70 is removed near the fusion-connected portion between the output optical fiber 60 and the transmission optical fiber 70.

[0030] The end of the transmission optical fiber 70 on the output optical fiber 60 side is stored in the storage unit 12 (first storage unit), and the transmission optical fiber 70 extends to the outside from the storage unit 12, and is introduced into the storage unit 11 (second storage unit) after being arranged in a predetermined path. In addition, in order to reduce damage to the transmission optical fiber 70, it is preferred that the portion of the transmission optical fiber 70 extending to the outside from the storage units 11, 12 has a coating 703.

[0031] The storage unit 11 stores a cladding mode remover 80 as a cladding mode removal unit for removing cladding mode light, and the end of the transmission optical fiber 70 introduced into the storage unit 11 is connected to the cladding mode remover 80 at a fusion splice 81. As the cladding mode remover 80, various known cladding mode removal structures can be adopted, and the cladding mode remover 80 is used to remove unnecessary cladding mode light propagating in the cladding 702 of the transmission optical fiber 70. The cladding mode remover 80 in the storage unit 11 is connected to an optical fiber 83 at a fusion splice 82. The optical fiber 83 extends to the beam output end 50.

[0032] In such a structure, the excitation light generated by each front excitation light source 30 propagates in the core 331 of the front excitation optical fiber 33 and is introduced into the core 311 of the front optical combiner 31. The excitation light introduced into the core 311 of the front optical combiner 31 is introduced into the inner cladding 202 of the amplification optical fiber 20 through the high reflection portion 21. In addition, the excitation light generated by each rear excitation light source 40 propagates in the core 431 of the rear excitation optical fiber 43 and is introduced into the inner cladding 412 of the rear optical combiner 41. The excitation light introduced into the inner cladding 412 of the rear optical combiner 41 is introduced into the inner cladding 202 of the amplification optical fiber 20 through the low reflection portion 22.

[0033] like Figure 2As shown, the excitation light P introduced into the amplification optical fiber 20 from the front excitation light source 30 and the rear excitation light source 40 propagates inside the inner cladding 202 and the core 201 of the amplification optical fiber 20. The excitation light P is absorbed by the rare earth element ions when passing through the core 201, so that the rare earth element ions are excited to generate spontaneous emission light. The spontaneous emission light is cyclically reflected between the high reflection part 21 and the low reflection part 22, so that the light of a specific wavelength (for example, 1064nm) is amplified to generate laser oscillation. The laser light (signal light) amplified in this way propagates inside the core 201 of the amplification optical fiber 20, and a part of it passes through the low reflection part 22. The signal light that has passed through the low reflection part 22 propagates in the core 411 of the rear optical combiner 41, and is introduced into the core 701 of the transmission optical fiber 70 through the core 601 of the output optical fiber 60. The signal light propagates in the core 701 of the transmission optical fiber 70 and reaches the cladding mode remover 80 in the storage unit 11, where unnecessary cladding mode light is removed, and then the signal light is emitted from the beam output end 50, for example, toward the object to be processed.

[0034] Here, in order to reduce the loss of signal light, it is preferred that the outer diameter of the core 701 of the transmission optical fiber 70 (e.g., 40 μm) is equal to the outer diameter of the core 601 of the output optical fiber 60 (e.g., 40 μm). On the other hand, the outer diameter of the cladding 702 of the transmission optical fiber 70 (e.g., 400 μm) is larger than the outer diameter of the cladding 602 of the output optical fiber 60 (e.g., 125 μm). The outer diameter of the cladding 702 is preferably 4 times or more and 25 times or less, more preferably 5 times or more and 14 times or less, and further preferably about 10 times the outer diameter of the core 701 of the transmission optical fiber 70. In addition, considering the arrangement of the transmission optical fiber 70, the outer diameter of the cladding 702 of the transmission optical fiber 70 is preferably 1 mm or less.

[0035] Generally, the larger the outer diameter of the cladding of the optical fiber, the smaller the degree of beam quality degradation with respect to bending of the optical fiber. In this embodiment, the outer diameter of the cladding 702 of the transmission optical fiber 70 is larger than the outer diameter of the cladding 602 of the output optical fiber 60. Therefore, even if the transmission optical fiber 70 is arranged in a bent state outside the storage unit 12, the degradation of the beam quality of the laser light propagating in the core 701 of the transmission optical fiber 70 can be suppressed and the beam quality can be stabilized.

[0036] In particular, the fiber laser device 1 of the present embodiment has a rear optical combiner 41 to which a plurality of rear excitation optical fibers 43 are connected in addition to the output optical fiber 60. Therefore, the outer diameter of the cladding 602 of the output optical fiber 60 is smaller than the inner cladding 412 of the rear optical combiner 41. Therefore, by connecting the output optical fiber 60 to the transmission optical fiber 70 having the cladding 702 having a larger outer diameter as described above, it is possible to effectively suppress the deterioration of the beam quality of the laser light propagating in the core 701 of the transmission optical fiber 70.

[0037] In addition, in the present embodiment, the transmission optical fiber 70 extends from the storage unit 12 toward the storage unit 11, so the transmission optical fiber 70 is often bent between the storage unit 12 and the storage unit 11. In particular, when the storage unit 11 and the storage unit 12 are stacked in the vertical direction as in the present embodiment, the transmission optical fiber 70 needs to be bent and arranged. Even if the transmission optical fiber 70 is arranged in a state of being bent between the storage unit 12 and the storage unit 11, as described above, the outer diameter of the cladding 702 of the transmission optical fiber 70 is larger than the outer diameter of the cladding 602 of the output optical fiber 60, so that the deterioration of the beam quality of the laser propagating in the core 701 of the transmission optical fiber 70 can be suppressed. In addition, even if a disturbance such as vibration is generated due to maintenance or movement of the device, the outer diameter of the cladding 702 of the transmission optical fiber 70 is larger than the outer diameter of the cladding 602 of the output optical fiber 60, so that the beam quality is not easily changed, and a structure with strong anti-interference performance is obtained.

[0038] In addition, by arranging the storage units 11 to 14 adjacent to each other in the vertical direction as in the present embodiment, the space occupied by the storage units 11 to 14 can be reduced. Furthermore, since the storage units 11 to 14 are arranged adjacent to each other in the vertical direction, it is possible to easily maintain the storage units 11 to 14 by, for example, arranging the storage units 11 to 14 in a pull-out manner in the frame. Furthermore, it is known that stimulated Raman scattering can be reduced by shortening the length of the optical fiber. By arranging the storage unit 11 and the storage unit 12 adjacent to each other as in the present embodiment, the length of the optical fiber from the output optical fiber 60 to the cladding mode remover 80 can be shortened, thereby reducing stimulated Raman scattering.

[0039] The storage units 11 to 14 may also be cooled by a separate cooling system. Thus, the components stored in the storage units 11 to 14 can be cooled independently of each other. Therefore, the change in optical characteristics caused by the temperature change of these components can be effectively reduced, and the efficiency of the fiber laser device is improved.

[0040] The fiber laser device 1 of this embodiment includes a plurality of rear excitation light sources 40 and rear light combiners 41, but the rear excitation light sources 40 and rear light combiners 41 may be omitted. In this case, the low reflection unit 22 and the output optical fiber 60 are connected to each other.

[0041] In the example shown in the drawings, the storage units 11 to 14 are stacked in the vertical direction, but the storage units 11 to 14 may be stacked in the horizontal direction.

[0042] As a fiber laser device, a MOPA fiber laser device is also known that amplifies seed light from a seed light source using pumping light from an pumping light source. The present invention can also be applied to such a MOPA fiber laser device.

[0043] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can of course be implemented in various different forms within the scope of the technical concept.

[0044] As described above, according to one aspect of the present invention, there is provided a fiber laser device that suppresses the deterioration of the beam quality of the output laser and can obtain a stable beam quality. The fiber laser device includes: an amplification optical fiber that can amplify the laser; at least one excitation light source that can generate excitation light supplied to the amplification optical fiber; an output optical fiber that includes a first core that propagates the laser amplified by the amplification optical fiber; and a first cladding that has a lower refractive index than the first core and covers the periphery of the first core; a transmission optical fiber that includes a second core that is optically coupled to the first core of the output optical fiber, and a second cladding that has a lower refractive index than the second core and covers the periphery of the second core; and a first storage unit that stores the amplification optical fiber and the output optical fiber inside. The outer diameter of the second cladding of the transmission optical fiber is larger than the outer diameter of the first cladding of the output optical fiber. The transmission optical fiber extends from the inside of the first storage unit to the outside of the first storage unit.

[0045] According to one embodiment of the present invention, the outer diameter of the second cladding of the transmission optical fiber is larger than the outer diameter of the first cladding of the output optical fiber. Therefore, even if the transmission optical fiber is configured in a bent state outside the first storage unit, the deterioration of the beam quality of the laser propagating in the second core of the transmission optical fiber can be suppressed and the beam quality can be stabilized.

[0046] The above-mentioned optical fiber laser device may be further provided with a second storage unit, the second storage unit internally storing a cladding mode removal portion that removes cladding mode light. The second storage unit is independent of the above-mentioned first storage unit. The above-mentioned transmission optical fiber may extend from the inside of the above-mentioned first storage unit to the outside of the above-mentioned first storage unit, and be connected to the above-mentioned cladding mode removal portion of the above-mentioned second storage unit. In such a structure, the transmission optical fiber is more likely to be bent between the first storage unit and the second storage unit, but as described above, even if the transmission optical fiber is arranged in a bent state between the first storage unit and the second storage unit, it is possible to suppress the deterioration of the beam quality of the laser propagating in the second core of the transmission optical fiber and stabilize the beam quality.

[0047] In this case, the first storage unit and the second storage unit may be disposed adjacent to each other. It is known that stimulated Raman scattering can be reduced by shortening the length of the optical fiber, and by arranging the first storage unit and the second storage unit adjacent to each other, the length of the optical fiber from the output optical fiber to the cladding mode removal portion can be shortened, thereby reducing stimulated Raman scattering.

[0048] Alternatively, the second storage unit may be disposed adjacent to the first storage unit above or below the first storage unit. If the first storage unit and the second storage unit are disposed adjacent to each other in the vertical direction, the storage units can be easily maintained by, for example, disposing the storage units in a pull-out manner within the frame.

[0049] It may be that the at least one excitation light source includes a plurality of rear excitation light sources arranged on the downstream side of the amplification optical fiber. It may be that the fiber laser device further comprises: a plurality of rear excitation optical fibers that propagate the excitation light generated by the plurality of rear excitation light sources; and a rear optical combiner that couples the excitation light generated by the plurality of rear excitation light sources and introduces it into the amplification optical fiber. The rear optical combiner has an end face that optically couples the plurality of rear excitation optical fibers with the output optical fiber. According to such a structure, a plurality of rear excitation optical fibers are connected to the rear optical combiner in addition to the output optical fiber, so the outer diameter of the first cladding of the output optical fiber is smaller than that of the optical fiber on the upstream side of the rear optical combiner. Therefore, by connecting the output optical fiber to the transmission optical fiber having the second cladding having a larger outer diameter as described above, it is possible to effectively suppress the deterioration of the beam quality of the laser propagating in the second core of the transmission optical fiber.

[0050] The above-mentioned fiber laser device may further include a third storage unit, which stores the above-mentioned at least one excitation light source inside. The third storage unit is independent of the above-mentioned first storage unit. The first storage unit and the above-mentioned third storage unit may also be arranged adjacent to each other. In addition, the third storage unit may also be independent of the above-mentioned second storage unit. According to such a structure, the cooling systems of the first storage unit and the third storage unit can be made independent of each other, so that the amplification optical fiber and the output optical fiber stored in the first storage unit and the excitation light source stored in the third storage unit can be cooled independently of each other. Therefore, the change of optical characteristics caused by the temperature change of these components can be reduced, and the efficiency of the fiber laser device is improved.

[0051] According to one embodiment of the present invention, the outer diameter of the second cladding of the transmission optical fiber is larger than the outer diameter of the first cladding of the output optical fiber. Therefore, even if the transmission optical fiber is configured in a bent state outside the first storage unit, the deterioration of the beam quality of the laser propagating in the second core of the transmission optical fiber can be suppressed.

[0052] This application claims priority based on Japanese Patent Application No. 2020-041303 filed on March 10, 2020. The entire contents disclosed in the application are incorporated herein by reference.

[0053] Industrial Applicability

[0054] The present invention is applicable to a fiber laser device that generates high-output laser light using excitation light.

[0055] Description of Reference Numerals

[0056] 1-fiber laser device; 11-(second) storage unit; 12-(first) storage unit; 13-(third) storage unit; 14-(third) storage unit; 20-amplification optical fiber; 21-high reflection unit; 22-low reflection unit; 30-front excitation light source; 31-front light combiner; 33-front excitation optical fiber; 40-rear excitation light source; 41-rear light combiner; 43-rear excitation optical fiber; 50-light Beam output end; 60-output optical fiber; 70-transmission optical fiber; 80-cladding mode remover (cladding mode removal unit); 201, 311, 331, 411, 431-core; 202, 412-inner cladding; 203, 413-outer cladding; 312, 332, 432-cladding; 601-(first) core; 602-(first) cladding; 701-(second) core; 702-(second) cladding.

Claims

1. A fiber laser device comprising: Amplifying optical fiber, which can amplify the laser; at least one excitation light source capable of generating excitation light supplied to the amplification optical fiber; an output optical fiber including a first core for propagating the laser light amplified by the amplification optical fiber, and a first cladding having a lower refractive index than the first core and covering the periphery of the first core; a transmission optical fiber comprising a second core optically coupled to the first core of the output optical fiber by fusion splicing, and a second cladding having a lower refractive index than the second core and covering a periphery of the second core; and a first storage unit that stores the amplification optical fiber and the output optical fiber inside; The outer diameter of the second cladding of the transmission optical fiber is larger than the outer diameter of the first cladding of the output optical fiber, The transmission optical fiber is bent and extends from the inside of the first storage unit to the outside of the first storage unit.

2. The optical fiber laser device according to claim 1, characterized in that: A second storage unit is further provided, the second storage unit internally storing a cladding mode removal unit for removing cladding mode light, and the second storage unit is independent of the first storage unit. The transmission optical fiber extends from the inside of the first housing unit to the outside of the first housing unit and is connected to the cladding mode removal portion of the second housing unit.

3. The optical fiber laser device according to claim 2, characterized in that: The first storage unit is arranged adjacent to the second storage unit.

4. The optical fiber laser device according to claim 3, characterized in that: The second storage unit is disposed adjacent to or above the first storage unit.

5. The optical fiber laser device according to any one of claims 1 to 4, characterized in that: The at least one excitation light source includes a plurality of rear excitation light sources arranged on the downstream side of the amplification optical fiber, The fiber laser device also has: a plurality of rear excitation optical fibers that propagate the excitation light generated by the plurality of rear excitation light sources; and A rear optical combiner couples the excitation light generated by the plurality of rear excitation light sources and introduces the excitation light into the amplification optical fiber, and has an end face for optically coupling the plurality of rear excitation optical fibers with the output optical fiber.

6. The optical fiber laser device according to any one of claims 1 to 4, characterized in that: A third storage unit is further provided, the third storage unit storing the at least one excitation light source therein, and the third storage unit is independent of the first storage unit.

7. The optical fiber laser device according to claim 6, characterized in that The first storage unit is arranged adjacent to the third storage unit.

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