Adjustable ring-mode fiber laser and laser welding stability evaluation method thereof

Abstract

The invention relates to the technical field of optical fiber lasers, provides an adjustable ring-mode optical fiber laser and a laser welding stability evaluation method thereof, and aims to judge whether the adjustable ring-mode optical fiber laser can realize stable industrial processing or not on the basis of Raman light power density and signal light power density of the adjustable ring-mode optical fiber laser. Based on the laser welding stability evaluation method of the adjustable ring mode fiber laser, technicians in the field can be guided to optimize the stimulated Raman scattering effect in the adjustable ring mode fiber laser in a targeted mode, and therefore the good and stable industrial machining effect can be achieved.

Description

Technical Field

[0001] The invention mainly relates to the technical field of optical fiber lasers, in particular to an adjustable ring-mode optical fiber laser and a method for evaluating the laser welding stability thereof. Background Art

[0002] Fiber lasers are easy to integrate, have good conversion efficiency, and have high beam quality. They are widely used in industrial processing fields such as laser welding and laser cutting. As an advanced technology, laser welding has the advantages of fast processing speed, narrow heat-affected zone, high penetration power intensity, etc. It is used in industrial manufacturing fields such as automobile body manufacturing, rail transportation manufacturing, aerospace manufacturing, and shipbuilding.

[0003] However, in the process of laser welding, it is inevitable to come into contact with various materials, especially aluminum alloy and copper materials. Due to the high reflectivity of these materials, it prevents the materials from absorbing laser energy. The emergence of adjustable ring mode fiber lasers further provides a way to deal with this difficulty. It changes the absorption rate of the material by changing the temperature of the material, and achieves a good welding effect through a reasonable ratio of ring laser power to center laser power, thereby improving the quality of the welding surface.

[0004] However, there are various nonlinear effects including stimulated Raman scattering in tunable ring-mode fiber lasers. Currently, there are no relevant reports on the impact of stimulated Raman scattering on laser welding stability, which limits the further optimization direction of tunable ring-mode fiber lasers, which has an adverse impact on the future processing industry. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention proposes an adjustable ring-mode fiber laser and a method for evaluating the laser welding stability thereof.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides an adjustable ring mode fiber laser, comprising a central beam module, an outer ring beam module, a beam combiner and a fiber end cap, wherein the central beam module and the outer ring beam module are beam combined by the beam combiner, and the output fiber of the beam combiner is connected to the fiber end cap to realize beam output, the central beam module is used to output a central signal light and couple the output central signal light into the core of the beam combiner and output it through the core of the output fiber of the beam combiner, and the outer ring beam module is used to output an outer ring signal light and couple the output outer ring signal light into the annular cladding of the outer core of the beam combiner and output it through the annular cladding of the output fiber of the beam combiner. Furthermore, the signal light power density of the adjustable ring mode fiber laser is satisfy W / µm 2 ,Raman optical power density satisfy , such adjustable ring mode fiber laser can achieve stable industrial processing.

[0007] Furthermore, the output optical fiber of the beam combiner includes, from the inside to the outside, a central core, a core cladding, an annular cladding, an outer cladding, and a coating layer; On the other hand, a method for evaluating the welding stability of an adjustable ring mode fiber laser is provided, comprising: Obtaining the Raman optical power, the central signal optical power and the outer ring signal optical power in the output laser of the adjustable ring mode fiber laser; Determine the Raman optical power density according to the Raman optical power, the central core radius of the output optical fiber of the combiner, and the numerical aperture of the central core; Determine the signal light power density according to the central signal light power, the outer ring signal light power, the outer radius of the annular cladding of the output optical fiber of the combiner, the inner radius of the annular cladding, and the numerical aperture of the annular cladding; Determine the signal optical power density Is it satisfied? W / µm 2 , Raman optical power density Is it satisfied? , if met, the adjustable ring mode fiber laser can achieve stable industrial processing.

[0008] Further, the Raman optical power density is calculated by the following formula: :

[0009] in is the core radius of the output fiber of the combiner, is the numerical aperture of the central core of the output fiber of the combiner, is the Raman optical power.

[0010] Furthermore, the signal optical power density is calculated by the following formula: :

[0011] in is the outer radius of the annular cladding of the output fiber of the combiner, is the inner radius of the annular cladding of the output fiber of the combiner, is the numerical aperture of the annular cladding of the output fiber of the combiner, is the center signal optical power, is the outer ring signal optical power.

[0012] On the other hand, the above-mentioned adjustable ring mode fiber laser is applied in industrial processing, such as laser welding.

[0013] Compared with the prior art, the technical effects of the present invention are: The present invention provides an accurate evaluation method by judging the signal light power density of the adjustable ring mode fiber laser. Is it satisfied? W / µm 2 ,Raman optical power density Is it satisfied? , and then judge whether the adjustable ring mode fiber laser can achieve stable industrial processing. Further, under the above relationship, as the output power of the adjustable ring mode fiber laser increases, the welding penetration will increase evenly with the increase of output power. If the above relationship is not satisfied, as the output power of the adjustable ring mode fiber laser increases, the penetration will decrease significantly after reaching a certain value, which indicates that stable industrial processing cannot be achieved.

[0014] The adjustable ring mode fiber laser welding stability evaluation method provided by the present invention can guide technical personnel in the field to optimize the stimulated Raman scattering effect in the adjustable ring mode fiber laser in a targeted manner, thereby achieving a good and stable industrial processing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, 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 invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 Schematic diagram of the structure of an adjustable ring mode fiber laser in one embodiment; Figure 2 is a schematic structural diagram of a central light beam module in one embodiment; Figure 3 A schematic diagram of the block structure of an outer ring beam module in one embodiment; Figure 4 is a schematic diagram of the structure of an output optical fiber of a beam combiner in one embodiment; Figure 5 For a comparative experiment, and dissatisfaction The penetration curve of the adjustable ring mode fiber laser used for copper welding is shown in the figure. Figure 5 (a) To meet The penetration curve of the ring-mode fiber laser used for copper welding. Figure 5 (b) Not satisfied The penetration curve obtained by using the adjustable ring mode fiber laser for copper welding. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4 One embodiment provides an adjustable ring mode fiber laser, including a central beam module 1, an outer ring beam module 2, a beam combiner 26 and a fiber end cap 27. The central beam module 1 and the outer ring beam module 2 are combined by the beam combiner 26. The output fiber of the beam combiner 26 is connected to the fiber end cap 27 to realize beam output. The central beam module 1 is used to output central signal light and couple the output central signal light into the core of the beam combiner and output through the core of the output fiber of the beam combiner 26. The outer ring beam module 2 is used to output outer ring signal light and couple the output outer ring signal light into the annular cladding outside the core of the beam combiner 26 and output through the annular cladding of the output fiber of the beam combiner 26. Furthermore, the signal light power density of the adjustable ring mode fiber laser is satisfy W / µm2, Raman optical power density satisfy .

[0019] Reference Figure 4 The output optical fiber of the combiner 26 includes, from the inside to the outside, a central core 29, a core cladding 30, an annular cladding 31, an outer cladding 32, and a coating 33; The central beam module 1 adopts an integrated oscillation-amplification structure, and the outer ring beam module 2 adopts a conventional oscillation structure. At the same time, both modules use large mode field gain optical fiber to reduce the stimulated Raman scattering effect. Based on the evaluation method for laser welding stability of adjustable ring mode fiber laser provided in the above embodiment, the signal light power density of the adjustable ring mode fiber laser is satisfy W / µm 2 , Raman optical power density satisfy , with lower output Raman, can perform stable industrial processing, such as for laser welding.

[0020] Specifically, the central beam module 1 is composed of a first cladding power stripper 3, a first signal light reflecting fiber Bragg grating 4, a first double-clad ytterbium-doped fiber 5, a first output coupling fiber Bragg grating 6, a second double-clad ytterbium-doped fiber 7, a first (N+1)×1 reverse beam combiner 8, N semiconductor pump sources, and a second cladding power stripper 15, where N=6; The first cladding power stripper 3 is connected to the first signal light reflecting fiber Bragg grating 4, the first double-clad ytterbium-doped fiber 5 is fused between the first signal light reflecting fiber Bragg grating 4 and the first output coupling fiber Bragg grating 6, the other end of the first output coupling fiber Bragg grating 6 is fused to the second double-clad ytterbium-doped fiber 7, the second double-clad ytterbium-doped fiber 7 is connected to the signal input fiber of the first (N+1)×1 reverse beam combiner 8, the N pump input fibers of the first (N+1)×1 reverse beam combiner 8 are respectively connected to a semiconductor pump source, and the six semiconductor pump sources are respectively the first semiconductor pump source 9, the second semiconductor pump source 10, the third semiconductor pump source 11, the fourth semiconductor pump source 12, the fifth semiconductor pump source 13, and the sixth semiconductor pump source 14. The signal output fiber of the first (N+1)×1 reverse beam combiner 8 is connected to one end of the second cladding power stripper 15, and the other end of the second cladding power stripper 15 is connected to the first beam combining arm at the input end of the beam combiner 26. The central beam module 1 can achieve a maximum output power of more than 4 kW.

[0021] The reflectivity of the first signal light reflecting fiber Bragg grating 4 to the signal light in the central light beam module 1 is 99.5%, and the reflectivity of the first output coupling fiber Bragg grating 6 to the signal light in the central light beam module 1 is 6%.

[0022] The outer ring beam module 2 is composed of a third cladding power stripper 16, a second signal light reflecting fiber Bragg grating 17, a third double-cladding ytterbium-doped fiber 18, a second output coupling fiber Bragg grating 19, a second (N+1)×1 reverse beam combiner 20, a semiconductor pump source, and a fourth cladding power stripper 25. The third cladding power stripper 16 is connected to the second signal light reflecting fiber Bragg grating 17, the third double-cladding ytterbium-doped fiber 18 is fused between the second signal light reflecting fiber Bragg grating 17 and the output second output coupling fiber Bragg grating 19, the other end of the second output coupling fiber Bragg grating 19 is connected to the signal input fiber of the second (N+1)×1 reverse beam combiner 20, and the n pump input fibers of the second (N+1)×1 reverse beam combiner 20 are respectively connected to a semiconductor pump source, n is equal to 4, and the four semiconductor pump sources are the seventh semiconductor pump source 21, the eighth semiconductor pump source 22, the ninth semiconductor pump source 23, and the tenth semiconductor pump source 24. The signal output fiber of the second (N+1)×1 reverse beam combiner 20 is connected to one end of the fourth cladding power stripper 25, and the other end of the fourth cladding power stripper 25 is connected to the second beam combining arm of the input end of the beam combiner 26. The reflectivity of the second signal light reflecting fiber grating 17 to the signal light in the outer ring beam module 2 is 99.5%, and the reflectivity of the second output coupling fiber grating 19 to the signal light in the outer ring beam module 2 is 6%. The outer ring beam module 2 can reach a maximum output power of more than 2kW.

[0023] The central beam module 1 and the outer ring beam module 2 are combined by a beam combiner 26, and the output optical fiber of the beam combiner 26 is connected to the optical fiber end cap 27 to realize the beam output, wherein the output optical fiber of the beam combiner 26 includes a central core 29, a core cladding 30, an annular cladding 31, an outer cladding 32, and a coating 33 from the inside to the outside. The maximum output power of the adjustable ring mode fiber laser can reach about 6kW. The laser output power of the adjustable ring mode fiber laser ,in is the Raman optical power, is the center signal optical power, is the outer ring signal optical power.

[0024] The output fiber structure of the combiner 26 is as follows: Figure 4 As shown, from the inside to the outside, it includes a central core 29, a core cladding 30, an annular cladding 31, an outer cladding 32, and a coating layer 33. The diameter of the central core 29 is 25µm, and the numerical aperture is 0.01≤NA 1 ≤0.12, core cladding 30 diameter 50µm, annular cladding 31 diameter 75µm, numerical aperture 0.1≤NA 2 ≤0.3, the outer cladding 32 has a diameter of 280µm, and the coating 33 has a diameter of 480µm.

[0025] The output wavelength of the first semiconductor pump source 9, the second semiconductor pump source 10, the third semiconductor pump source 11, the fourth semiconductor pump source 12, the fifth semiconductor pump source 13, and the sixth semiconductor pump source 14 is 915 nm; the output wavelength of the seventh semiconductor pump source 21, the eighth semiconductor pump source 22, the ninth semiconductor pump source 23, and the tenth semiconductor pump source 24 is 976 nm.

[0026] The first double-clad ytterbium-doped optical fiber 5 and the second double-clad ytterbium-doped optical fiber 7 in the central light beam module 1 and the third double-clad ytterbium-doped optical fiber 18 in the outer ring light beam module 2 are all large mode field ytterbium-doped optical fibers.

[0027] The first signal light reflecting optical fiber Bragg grating 4 and the second signal light reflecting optical fiber Bragg grating 17 have high reflectivity to the signal light of 1080 nm, and the reflectivity is about 99.5%.

[0028] The first output-coupled fiber grating 6 and the second output-coupled fiber grating 19 partially reflect the signal light of 1080 nm, and the reflectivity is about 6%.

[0029] The first (N+1)×1 reverse beam combiner 8 has a very small insertion loss, and its pump efficiency at 915 nm is about 98%.

[0030] The working wavelength of the first cladding power stripper 3 and the third cladding power stripper 16 is 800-1200nm, the stripping power is 100W, and the stripping ratio is 20dB.

[0031] The working wavelength of the second cladding power stripper 15 and the fourth cladding power stripper 25 is 800-1200nm, the maximum withstand power is 600W, and the stripping efficiency is greater than 97%.

[0032] Based on the adjustable ring mode fiber laser provided in the above embodiment, the structure is as follows Figure 1 , 2 , 3 and 4, the device parameter design is the same as above, the maximum output power of the adjustable ring mode fiber laser reaches 5.9kW, and the output Raman light accounts for 0.004%. Up to 0.236W, outer ring signal optical power Reach 2.1kW, center signal optical power The output power reaches 3.799kW. Since the diameter of the central core 29 of the signal output optical fiber of the combiner 26 is 25µm, its numerical aperture NA 1 is 0.06, Raman optical power density =0.1335W / µm 2 The inner diameter of the outer ring of the beam combiner 26 is 50µm, the outer diameter is 75µm, and the numerical aperture NA 2is 0.22, and the signal light power density can be obtained =2319W / µm 2 , Raman optical power density of tunable ring-mode fiber laser , signal light power density satisfy W / µm 2 ,Raman optical power density satisfy , the adjustable ring mode fiber laser that meets the above conditions is applied to the actual industrial processing scene, namely copper welding, and the welding penetration is measured. The results are as follows Figure 5 As shown in (a), Figure 5 (a) It can be seen that the welding penetration increases uniformly with the increase of the output power of the adjustable ring mode fiber laser.

[0033] As Figure 5 (a) The corresponding comparative example of the adjustable ring mode fiber laser, in the adjustable ring mode fiber laser provided in the comparative example, adopts Figure 3 The conventional oscillating structure shown is used as the central beam module and the outer ring beam module, that is, the central beam module and the outer ring beam module are both Figure 3 The conventional oscillating structure shown in the figure, the rest of the settings are the same as Figure 5 (a) The corresponding adjustable ring mode fiber laser has the same settings, the structure and parameters of the beam combiner are the same. The maximum output power P of the adjustable ring mode fiber laser in the comparative example is 6.1kW, the output Raman light accounts for 0.03%, and the output Raman light power is Up to 5.49W, outer ring signal optical power Up to 2.1kW, center signal optical power Raman optical power density up to 3.994kW =3.11W / µm2, signal light power density =2277W / µm2, signal light power density of tunable ring-mode fiber laser satisfy W / µm2, Raman optical power density Dissatisfied , will not be satisfied The adjustable ring mode fiber laser is applied to copper welding and the welding penetration is measured. The results are as follows: Figure 5 As shown in (b), Figure 5 (b) It can be seen that as the power of the adjustable ring-mode fiber laser increases, the welding penetration depth will decrease significantly after reaching a certain value, indicating that stable industrial processing cannot be achieved.

[0034] Another embodiment provides a method for evaluating the laser welding stability of an adjustable ring mode fiber laser, comprising: Obtain the Raman optical power, central signal optical power and outer ring signal optical power in the output laser of the tunable ring mode fiber laser.

[0035] The Raman optical power density is determined based on the Raman optical power, the central core radius of the output optical fiber of the combiner, and the numerical aperture of the central core. :

[0036] in is the core radius of the output fiber of the combiner, is the numerical aperture of the central core of the output fiber of the combiner, is the Raman optical power.

[0037] The signal light power density is determined based on the central signal light power, the outer ring signal light power, the outer radius of the annular cladding of the output fiber of the combiner, the inner radius of the annular cladding, and the numerical aperture of the annular cladding. :

[0038] in is the outer radius of the annular cladding of the output fiber of the combiner, is the inner radius of the annular cladding of the output fiber of the combiner, is the numerical aperture of the annular cladding of the output fiber of the combiner, is the center signal optical power, is the outer ring signal optical power.

[0039] Determine the signal optical power density Is it satisfied? W / µm 2 ,Raman optical power density Is it satisfied? , if met, the adjustable ring mode fiber laser can achieve stable industrial processing.

[0040] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Tunable ring mode fiber laser, characterized in that: The invention comprises a central light beam module (1), an outer ring light beam module (2), a beam combiner (26) and an optical fiber end cap (27); the central light beam module (1) and the outer ring light beam module (2) are beam combined by the beam combiner (26); the output optical fiber of the beam combiner (26) is connected to the optical fiber end cap (27) to realize light beam output; the central light beam module (1) is used to output central signal light and couple the output central signal light into the optical core of the beam combiner and output it through the optical core of the output optical fiber of the beam combiner (26); the outer ring light beam module (2) is used to output outer ring signal light and couple the output outer ring signal light into the annular cladding of the outer core of the beam combiner (26) and output it through the annular cladding of the output optical fiber of the beam combiner (26).

2. The adjustable ring mode fiber laser according to claim 1, characterized in that: The signal light power density of the adjustable ring-mode fiber laser satisfy W / µm 2 , the Raman optical power density satisfies .

3. The adjustable ring mode fiber laser according to claim 1, characterized in that: The output optical fiber of the beam combiner (26) comprises, from the inside to the outside, a central fiber core (29), a fiber core cladding (30), an annular cladding (31), an outer cladding (32), and a coating layer (33).

4. The adjustable ring mode fiber laser according to claim 1 or 3, characterized in that: The central light beam module (1) is composed of a first cladding power stripper (3), a first signal light reflecting fiber Bragg grating (4), a first double-cladding ytterbium-doped fiber (5), a first output coupling fiber Bragg grating (6), a second double-cladding ytterbium-doped fiber (7), a first (N+1)×1 reverse beam combiner (8), N semiconductor pump sources, and a second cladding power stripper (15); The first cladding power stripper (3) is connected to the first signal light reflecting fiber Bragg grating (4), the first double-cladding ytterbium-doped fiber (5) is fused between the first signal light reflecting fiber Bragg grating (4) and the first output coupling fiber Bragg grating (6), the other end of the first output coupling fiber Bragg grating (6) is fused to the second double-cladding ytterbium-doped fiber (7), the second double-cladding ytterbium-doped fiber (7) is connected to the signal input fiber of the first (N+1)×1 reverse beam combiner (8), the N pump input fibers of the first (N+1)×1 reverse beam combiner (8) are respectively connected to a semiconductor pump source, the signal output fiber of the first (N+1)×1 reverse beam combiner (8) is connected to one end of the second cladding power stripper (15), and the other end of the second cladding power stripper (15) is connected to the first beam combining arm of the input end of the beam combiner (26).

5. The adjustable ring mode fiber laser according to claim 4, characterized in that: The reflectivity of the first signal light reflecting fiber Bragg grating (4) to the signal light in the central light beam module (1) is 99.5%, and the reflectivity of the first output coupling fiber Bragg grating (6) to the signal light in the central light beam module (1) is 6%.

6. The adjustable ring mode fiber laser according to claim 4, characterized in that: The outer ring beam module (2) is composed of a third cladding power stripper (16), a second signal light reflecting fiber Bragg grating (17), a third double-cladding ytterbium-doped fiber (18), a second output coupling fiber Bragg grating (19), a second (N+1)×1 reverse beam combiner (20), a semiconductor pump source, and a fourth cladding power stripper (25); The third cladding power stripper (16) is connected to the second signal light reflecting fiber Bragg grating (17), the third double-cladding ytterbium-doped fiber (18) is fused between the second signal light reflecting fiber Bragg grating (17) and the output second output coupling fiber Bragg grating (19), the other end of the second output coupling fiber Bragg grating (19) is connected to the signal input fiber of the second (N+1)×1 reverse beam combiner (20), the n pump input fibers of the second (N+1)×1 reverse beam combiner (20) are respectively connected to a semiconductor pump source, n is less than or equal to N, the signal output fiber of the second (N+1)×1 reverse beam combiner (20) is connected to one end of the fourth cladding power stripper (25), and the other end of the fourth cladding power stripper (25) is connected to the second beam combining arm of the input end of the beam combiner (26).

7. The adjustable ring mode fiber laser according to claim 6, characterized in that: The reflectivity of the second signal light reflecting fiber Bragg grating (17) to the signal light in the outer ring light beam module (2) is 99.5%, and the reflectivity of the second output coupling fiber Bragg grating (19) to the signal light in the outer ring light beam module (2) is 6%.

8. The method for evaluating laser welding stability of an adjustable ring mode fiber laser according to claim 1, 3, 5, 6 or 7, characterized in that: include: Obtaining the Raman optical power, the central signal optical power and the outer ring signal optical power in the output laser of the adjustable ring mode fiber laser; Determine the Raman optical power density according to the Raman optical power, the central core radius of the output optical fiber of the combiner, and the numerical aperture of the central core; Determine the signal light power density according to the central signal light power, the outer ring signal light power, the outer radius of the annular cladding of the output optical fiber of the combiner, the inner radius of the annular cladding, and the numerical aperture of the annular cladding; Determine the signal optical power density Is it satisfied? W / µm 2 ,Raman optical power density Is it satisfied? , if met, the adjustable ring mode fiber laser can achieve stable laser welding.

9. The method according to claim 8, characterized in that The Raman optical power density is calculated by the following formula: : in is the core radius of the output fiber of the combiner, is the numerical aperture of the central core of the output fiber of the combiner, is the Raman optical power.

10. The method according to claim 8, characterized in that The signal optical power density is calculated by the following formula : in is the outer radius of the annular cladding of the output fiber of the combiner, is the inner radius of the annular cladding of the output fiber of the combiner, is the numerical aperture of the annular cladding of the output fiber of the combiner, is the center signal optical power, is the outer ring signal optical power.

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