A spiro ring laser beam combiner based on a spiro ring fiber

Abstract

The utility model discloses a kind of annular light beam laser beam combiner based on spindling annular optical fiber, annular light beam laser beam combiner uses (N+1)*1 combiner, the input end of annular light beam laser beam combiner includes a center optical fiber and N root side fiber, and the output fiber of annular light beam laser beam combiner is 1 spindling annular optical fiber.

Description

Technical Field

[0001] This utility model relates to a ring beam laser combiner based on a spindle-shaped annular fiber, used to bundle and transmit a high-power adjustable fiber annular spot with high brightness characteristics at the center. Background Technology

[0002] With the rapid development of laser welding technology, the field of welding has high requirements for laser energy output. The higher the energy output of the laser, the more welding fields it can be applied to. In particular, welding of aerospace and certain special materials requires very high laser energy density. However, when high-energy laser beams are output from optical fibers, nonlinear effects are easily induced, which limits the output energy. Currently, the main method for suppressing nonlinear effects in fiber lasers is to use chirped tilt gratings. However, this scheme is mainly used for fiber lasers with a core diameter ≤30 micrometers. For fibers with larger mode fields, the increase in mode field area leads to an increase in fiber modes, making the fabrication of chirped tilt gratings complex and difficult to achieve good results, thus limiting its application range. Furthermore, the reflection effect of chirped gratings can couple nonlinear laser components to the cladding, amplifying the nonlinear laser within the cladding.

[0003] Existing technologies have developed techniques to address fiber nonlinearity effects using spindle-shaped optical fibers. Xi Xiaoming from the National University of Defense Technology designed an integrated oscillation amplification laser using spindle-shaped optical fibers, and Shi Jianhong from Huazhong University of Science and Technology designed a fiber laser that utilizes spindle-shaped optical fibers to enhance the Raman threshold. However, these spindle-shaped optical fiber designs are relatively simple, only capable of outputting extremely simple spot light fields, and cannot be applied to specific laser welding fields or complex beam application scenarios. Currently, there is a strong demand in the welding field for low-nonlinearity, high-power output of special spot light fields. For example, annular tunable spot laser welding technology, which can achieve deep welding depth and low spatter effect, has emerged and is now widely used in deep penetration welding. Improving the output power of annular lasers is particularly important; however, the high-power output of annular fiber lasers (core or annular region) is severely limited by nonlinear effects. Therefore, the inventors hope to develop a device based on spindle-shaped optical fibers that can output a high-power annular tunable laser spot with a high nonlinear threshold.

[0004] Based on this, the engineers of this utility model creatively conceived of designing a new ring beam laser combiner based on a spindle-shaped ring fiber, which can achieve high-power ring laser output with a high nonlinear threshold. Utility Model Content

[0005] The purpose of this invention is to propose a ring beam laser combiner based on a spindle-shaped fiber, which overcomes the problem that the existing spindle-shaped fiber can only output a simple spot light field, and obtains a high-power ring fiber tunable laser spot with improved nonlinear threshold, without reducing beam quality.

[0006] To address the aforementioned problems, this invention provides a ring beam laser combiner based on a spindle-shaped annular fiber. The ring beam laser combiner employs an (N+1)*1 combiner. The input end of the ring beam laser combiner includes a central fiber and N side fibers. The output fiber of the ring beam laser combiner is a single spindle-shaped annular fiber. The spindle-shaped annular fiber includes a first non-conical region, a first conical region, a second non-conical region, a second conical region, and a third non-conical region, sequentially connected from the incident end towards the output end. The diameter of the first conical region extends along the output... The light direction gradually increases, and the diameter of the second conical region gradually decreases along the light output direction; the center of the spindle ring fiber is the central core, and a first cladding is set immediately outside the central core, covering the central core; a second cladding is set immediately outside the first cladding, covering the first cladding; a third cladding is set immediately outside the second cladding, covering the second cladding; a fourth cladding is set immediately outside the third cladding, covering the third cladding; a coating layer is set immediately outside the fourth cladding, covering the fourth cladding; N is a positive integer greater than 1.

[0007] Preferably, the core of the central fiber is fused with the core of the first non-conical region of the spindle ring fiber, and the central laser is injected into the core of the central fiber of the spindle ring fiber. The cores of N side fiber fibers are fused with the cores of the annular cladding of the first non-conical region of the spindle ring fiber, and the annular laser is injected into the annular cladding of the spindle ring fiber, where N is greater than or equal to 3.

[0008] Preferably, in the spindle ring fiber, the refractive index of the first cladding is less than the refractive index of the central core, and the refractive index of the first cladding is less than the refractive index of the second cladding; the refractive index of the third cladding is less than the refractive index of the second cladding; the refractive index of the third cladding is less than the refractive index of the fourth cladding; the central fiber core is fused to the central core of the first non-conical region of the spindle ring fiber, and N side fiber cores are fused to the second cladding of the first non-conical region of the spindle ring fiber; N is greater than 3.

[0009] Preferably, the central core, the second cladding, and the fourth cladding are composed of pure quartz material, while the first cladding and the third cladding are composed of fluorine-doped quartz material with low refractive index.

[0010] Preferably, both the first and second cone regions are uniformly tapered, with the same cone length and tapering ratio, and opposite tapering directions. The first and second cone regions have a symmetrical conical structure. The mode field diameter of the second non-conical region is larger than the mode field diameter of the light in the first and second cone regions, and the second non-conical region is a large mode field transmission region.

[0011] Preferably, both the first and second conical regions meet the thermal tapering condition, the length of the first conical region is greater than 3m, the length of the second conical region is greater than 3m, and the fiber length of the second non-conical region is greater than or equal to 10m.

[0012] Preferably, the lasers output from the central region laser module and the ring region laser module are combined by a ring beam laser combiner and output through a spindle ring fiber. The ring region laser module includes N ring region laser units, which respectively input lasers into N side fibers. The output power of the central region laser module is greater than 3kW, the output power of a single ring region laser unit is greater than 2kW, and N is greater than or equal to 6.

[0013] Preferably, a cladding stripper is provided on the third non-conical region to strip the cladding light. A CO2 laser is used to etch the cladding diameter with an etching depth greater than or equal to 25 μm and a roughened region length greater than or equal to 5 cm, generating a regular groove structure on the cladding surface. The output end of the third non-conical region can be fused with a quartz end cap.

[0014] Preferably, the fiber parameters in the first non-conical region and the third non-conical region are the same. In the first non-conical region and the third non-conical region, the fiber core diameter is 10-40 μm; the diameter of the first cladding is 15-50 μm, the diameter of the second cladding is 50-130 μm, the diameter of the third cladding is 60-150 μm, the diameter of the fourth cladding is 150-280 μm, and the diameter of the coating layer is 170-300 μm; the numerical aperture of the core is 0.06-0.22, the numerical aperture of the second cladding is 0.1-0.24, and the fiber length in the first non-conical region or the third non-conical region is 0.3m-10m.

[0015] Preferably, in the second non-conical region, the diameter of the central core is 20-80 μm, the diameter of the first cladding layer is 30-100 μm, the diameter of the second cladding layer is 100-260 μm, the diameter of the third cladding layer is 120-300 μm, the diameter of the fourth cladding layer is 300-560 μm, the diameter of the coating layer is 340-600 μm, the numerical aperture of the central core is 0.06-0.22, and the numerical aperture of the second cladding layer is 0.1-0.24. The length of the second non-conical region is ≥10 m.

[0016] The beneficial effects of this invention lie in the design of a ring beam laser combiner based on a spindle-shaped annular fiber. A specially designed combiner structure allows for excellent beam combining of the central optical module and the annular optical module into the spindle-shaped annular fiber, overcoming the limitation of existing spindle-shaped fibers that can only output simple optical fields. This results in a high-power annular fiber laser with an improved nonlinear threshold, without compromising beam quality. The ring beam laser combiner utilizes a double-grooved structure to output the fiber, suppressing the nonlinear effects of specific high-power annular optical fields and effectively confining the cladding annular light. This improves light extraction efficiency and increases the output power of the annular fiber laser while ensuring that the output fiber quality does not deteriorate. The spindle-shaped design based on the special double-grooved annular fiber significantly increases the power density of the annular laser in the core and annular region within the transmission annular fiber, suppressing the nonlinear effects caused by high peak power density and increasing the upper limit of the system output power. Furthermore, it increases the length of the special annular fiber laser transmission cable while effectively confining and transmitting the annular light, expanding the welding workspace supported by the special annular fiber. Meanwhile, the combination of its side fiber, central fiber, and spindle-shaped double-groove ring fiber also enables the adjustment of the ring spot. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the application scenario of this utility model.

[0018] Figure 2 This is a schematic diagram of the structure of the ring beam laser combiner of this utility model.

[0019] Figure 3 This is a schematic diagram of the structure of the spindle-shaped optical fiber of this utility model.

[0020] Figure 4 This is the optical transmission diagram of the first cone region of this utility model.

[0021] Figure 5 This is a light distribution diagram within the spindle-shaped annular optical fiber of this utility model. Detailed Implementation

[0022] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, this utility model discloses a ring beam laser combiner based on a spindle-shaped ring fiber. The ring beam laser combiner 3 preferably employs an (N+1)*1 combiner. See [link to relevant documentation]. Figure 2The input end of the ring beam laser combiner includes a fiber bundle formed by a central fiber and N side fibers (preferably, N is a positive integer greater than 1, preferably, N is a positive integer greater than or equal to 3, preferably, N is greater than or equal to 6, preferably, N is 6). Preferably, it can be prepared using a sleeve tapering technique. The output end of the ring beam laser combiner is a single spindle-shaped ring fiber 8. The core of the central fiber is fused together with the core of the spindle-shaped ring fiber, and the central laser is injected into the core of the spindle-shaped ring fiber. After the fiber bundle is tapered, the cores of the N side fibers are fused together with the annular cladding of the spindle-shaped ring fiber, and the annular laser is injected into the annular cladding of the spindle-shaped ring fiber.

[0024] See Figure 3 The transverse cross-sectional structure of the spindle-shaped ring optical fiber 8 preferably consists of a central core, first, second, third, and fourth cladding layers, and a coating layer, all of which are ring-shaped. Preferably, the total length of the spindle-shaped ring optical fiber is ≥22m. Its longitudinal structure includes three non-conical regions and two conical regions. That is, the spindle-shaped ring optical fiber 8 includes a first non-conical region 81, a first conical region 82, a second non-conical region 83, a second conical region 84, and a third non-conical region 85, which are sequentially connected from the incident end towards the emission end. The diameter of the first conical region gradually increases along the light emission direction, and the diameter of the second conical region gradually decreases along the light emission direction. The spindle-shaped ring optical fiber has a central core 61 at its center. A first cladding 62 is immediately surrounding the central core 61, covering it. A second cladding 63 is immediately surrounding the first cladding 62, covering it. A third cladding 64 is immediately surrounding the second cladding 63, covering it. A fourth cladding 65 is immediately surrounding the third cladding 64, covering it. A coating layer 66 is immediately surrounding the fourth cladding 65, covering it. The refractive index of the first cladding 62 is less than that of the central core 61. The refractive index of the first cladding 62 is less than that of the second cladding 63. The refractive index of the third cladding is less than that of the second cladding. The refractive index of the third cladding is less than that of the fourth cladding, thus forming a double-groove ring structure.

[0025] See Figure 1 The optical system in which the ring beam laser combiner based on spindle ring fiber is used generally requires the following additional optical components, such as a central region laser module 1, a ring region laser module 2, a cladding stripper 4, and an output device 5.

[0026] The central region laser module 1 preferably includes at least one high-power fiber laser built based on a MOPA or resonant cavity structure, preferably with an output power ≥ 3kW; the output fiber parameters are preferably 14 / 250 / 0.07 (the parameters adopt the common expression method of the prior art, and their format is "core diameter μm / cladding diameter μm / numerical aperture", and the fiber parameters in the following text are also expressed in the same format). The central region laser module 1 is used to inject into the central core of the ring fiber to provide the central spot laser power for the tunable spot. The central region laser module preferably includes an independent driver, which can independently control its output power.

[0027] The ring-region laser module 2 comprises N high-power fiber lasers (preferably N ≥ 3, more preferably N ≥ 6) built using a MOPA or resonant cavity structure. The output power of a single high-power fiber laser in the ring-region laser module 2 is preferably ≥ 2kW. Each high-power fiber laser can be referred to as a ring-region laser unit, meaning the ring-region laser module comprises N ring-region laser units. The ring-region laser module 2 includes N output fibers for outputting the laser beams from the N high-power fiber lasers built using MOPA or resonant cavity structures. The output fiber type used in the ring-region laser module 2 is preferably 20 / 250 / 0.07. The ring-region laser module 2 is used to inject laser beams into the annular cladding region of the annular fiber to provide an adjustable annular laser beam power. The ring-region laser module preferably includes an independent driver, allowing independent control of its output power.

[0028] The ring-beam laser combiner 3 is used to combine the laser beams output from the central region laser module and the ring region laser module, and output them through the spindle-shaped ring fiber 8. See also... Figure 2 For example, when the number N of high-power fiber lasers in the ring region laser module 2 is 6, the ring beam laser combiner is a 7*1 combiner. The input fiber consists of 7 fibers, fabricated using a sleeve tapering technique. The 7 fibers in the input fiber include one central fiber and 6 side fibers. The preferred parameters of the central fiber are 14 / 250 / 0.07. The core of this central fiber is fused with the central core (preferably with a diameter d = 15 μm) of the first non-tapered region 81 of the spindle ring fiber, and the central laser is injected into the central core of the spindle ring fiber. The preferred type of the 6 side fibers is 20 / 250 / 0.07. After tapering, the cores of these 6 side fibers are fused with the annular cladding (preferably with a diameter d = 100 μm) of the first non-tapered region of the spindle ring fiber, and the annular laser is injected into the annular cladding of the spindle ring fiber.

[0029] Preferably, the core of the central optical fiber is fused together with the core of the first non-conical region 81 of the spindle ring optical fiber, and the cores of the N side fibers are fused together with the second cladding of the first non-conical region 81 of the spindle ring optical fiber.

[0030] The fiber parameters in the first and third non-conical regions are identical. The diameter of the fiber core can be 10-40 μm, preferably 15 μm; the diameter of the first cladding can be 15-50 μm, preferably 30 μm; the diameter of the second cladding can be 50-130 μm, preferably 100 μm; the diameter of the third cladding can be 60-150 μm, preferably 115 μm; the diameter of the fourth cladding can be 150-280 μm, preferably 200 μm; and the diameter of the coating layer can be 170-300 μm, preferably 250 μm. The core, second cladding, and fourth cladding are composed of pure quartz material, while the first and third cladding are composed of low-refractive-index fluorine-doped quartz material (i.e., the refractive indices of the first and third cladding are significantly lower than those of the core, second cladding, and fourth cladding, used to form a double-groove ring structure). For numerical aperture, for example, the numerical aperture of the central core can be 0.06-0.22, preferably 0.1, and the numerical aperture of the second cladding (annular cladding) can be 0.1-0.24, preferably 0.22. For example, the fiber length of the first or third non-conical region can be 0.3-10m, preferably 1m.

[0031] The second non-conical region is a large mode field transmission region, mainly used to reduce the power density of the transmitted laser to suppress and reduce the nonlinear effect of the transmitted laser. For the fiber parameters of the second non-conical region, for example, preferably, the central core diameter can be 20-80μm, preferably 30μm; the first cladding diameter can be 30-100μm, preferably 60μm; the second cladding diameter can be 100-260μm, preferably 200μm; the third cladding diameter can be 120-300μm, preferably 230μm; the fourth cladding diameter can be 300-560μm, preferably 400μm; and the coating diameter can be 340-600μm, preferably 500μm. For the numerical aperture of the second non-conical region, the central core numerical aperture can be 0.06-0.22, preferably 0.1; and the second cladding (annular cladding) numerical aperture can be 0.1-0.24, preferably 0.22. Preferably, the fiber length of the second non-conical region is ≥10m.

[0032] For the first and second conical regions, preferably, both the first and second conical regions are uniformly tapered. Preferably, the first and second conical regions have the same length and tapering ratio, but opposite tapering directions. The lengths of the first and second conical regions can range from 3m to 10m, generally greater than 3m, and preferably greater than 6m. Due to the existence of the symmetrical double conical regions, the transmission angle of the laser in the fiber core gradually decreases when the transmitted laser passes through the first conical region (see appendix). Figure 4 When the laser passes through the second non-conical region and is transmitted to the second conical region, it has the opposite effect to passing through the first conical region, which causes the transmission angle of the laser to gradually increase. The inventor discovered that due to the symmetrical structure of the two conical regions, the quality of the injected laser beam will not deteriorate during the transmission of the laser beam through the spindle fiber, thus having the effect of maintaining the quality of the laser beam transmission.

[0033] Preferably, both the first and second conical regions meet the adiabatic tapering condition. Under this condition, the mode field matches during the transmission of the laser throughout the entire conical region, thereby reducing insertion loss. This entire spindle-shaped fiber is obtained by controlling the different drawing speeds during the preform drawing process. The injected laser is bundled using a spindle-shaped annular fiber combiner. Through electronic control design, the laser power of the central spot (≥3kW) and the annular cladding laser power (≥12kW) can be individually adjusted for different spot laser outputs.

[0034] Preferably, a cladding stripper 4 can be installed in the third non-conical region to effectively remove the cladding light and ensure the quality of the output laser beam. For its manufacturing process, preferably, a CO2 laser can be used to etch a 200μm cladding diameter with an etching depth greater than or equal to 25μm and a roughened region length greater than or equal to 5cm, creating a regular groove structure on the cladding surface.

[0035] The output device 5 is located at the output end of the third non-conical region. Preferably, by increasing the effective cross-sectional area of ​​the laser output end face, the power density of the output end face is effectively reduced. A CO2 fusion splicer is used to fuse the output optical fiber to the quartz end cap to increase the upper limit of the output power.

[0036] The technical principles of this utility model have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of this utility model and should not be construed as limiting the scope of protection of this utility model in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of this utility model without any inventive effort, and these embodiments will all fall within the scope of protection of this utility model.

Claims

1. A ring beam laser combiner based on a spindle-shaped annular fiber, wherein the ring beam laser combiner employs an (N+1)*1 combiner, characterized in that: The input end of the ring beam laser combiner includes a central fiber and N side fibers. The output fiber of the ring beam laser combiner is a single spindle-shaped fiber. The spindle-shaped fiber includes a first non-conical region, a first conical region, a second non-conical region, a second conical region, and a third non-conical region connected sequentially from the incident end towards the output end. The diameter of the first conical region gradually increases along the light output direction, and the diameter of the second conical region gradually decreases along the light output direction. The center of the spindle-shaped fiber is the central core. A first cladding is immediately placed outside the central core, covering the central core. A second cladding is immediately placed outside the first cladding, covering the first cladding. A third cladding is immediately placed outside the second cladding, covering the second cladding. A fourth cladding is immediately placed outside the third cladding, covering the third cladding. A coating layer is immediately placed outside the fourth cladding, covering the fourth cladding. N is a positive integer greater than 1.

2. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 1, characterized in that: The core of the central fiber is fused with the core of the first non-conical region of the spindle ring fiber, and the central laser is injected into the core of the central fiber of the spindle ring fiber. The cores of N side fibers are fused with the cores of the annular cladding of the first non-conical region of the spindle ring fiber, and the annular laser is injected into the annular cladding of the spindle ring fiber; N is greater than or equal to 3.

3. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 2, characterized in that: In a spindle-shaped optical fiber, the refractive index of the first cladding is less than that of the central core, and the refractive index of the first cladding is less than that of the second cladding; the refractive index of the third cladding is less than that of the second cladding; the refractive index of the third cladding is less than that of the fourth cladding; the central fiber core is fused to the central core of the first non-conical region of the spindle-shaped optical fiber, and N side fiber cores are fused to the second cladding of the first non-conical region of the spindle-shaped optical fiber; N is greater than 3.

4. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 3, characterized in that: The central core, second cladding, and fourth cladding are composed of pure quartz material, while the first and third cladding are composed of fluorine-doped quartz material with low refractive index.

5. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 3, characterized in that: Both the first and second cone regions are uniformly tapered. The first and second cone regions have the same cone length and tapering ratio, but opposite tapering directions. The first and second cone regions have symmetrical cone structures. The mode field diameter of the second non-cone region is larger than the mode field diameter of the first and second cone regions. The second non-cone region is a large mode field transmission region.

6. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 2, characterized in that: Both the first and second conical regions meet the thermal tapering conditions, with the length of the first conical region being greater than 3m and the length of the second conical region being greater than 3m; the length of the optical fiber in the second non-conical region is greater than or equal to 10m.

7. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 2, characterized in that: The lasers output from the central region laser module and the ring region laser module are combined by a ring beam laser combiner and output through a spindle ring fiber. The ring region laser module includes N ring region laser units, which respectively input the laser into N side fibers. The output power of the central region laser module is greater than 3kW, the output power of a single ring region laser unit is greater than 2kW, and N is greater than or equal to 6.

8. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 2, characterized in that: A cladding stripper is installed on the third non-conical region to remove the cladding light. A CO2 laser is used to etch the cladding diameter with an etching depth greater than or equal to 25 μm and a roughened region length greater than or equal to 5 cm, generating a regular groove structure on the cladding surface. The output end of the third non-conical region can be fused with a quartz end cap.

9. The ring beam laser combiner based on spindle-shaped annular fiber according to claim 2, characterized in that: The fiber parameters are the same in the first and third non-conical regions. In both regions, the fiber core diameter is 10-40 μm; the first cladding diameter is 15-50 μm, the second cladding diameter is 50-130 μm, the third cladding diameter is 60-150 μm, the fourth cladding diameter is 150-280 μm, and the coating diameter is 170-300 μm. The numerical aperture of the core is 0.06-0.22, and the numerical aperture of the second cladding is 0.1-0.

24. The fiber length in either the first or third non-conical region is 0.3 m-10 m.

10. The ring beam laser combiner based on a spindle-shaped annular fiber according to claim 9, characterized in that: In the second non-conical region, the diameter of the central core is 20-80 μm, the diameter of the first cladding is 30-100 μm, the diameter of the second cladding is 100-260 μm, the diameter of the third cladding is 120-300 μm, the diameter of the fourth cladding is 300-560 μm, the diameter of the coating layer is 340-600 μm, the numerical aperture of the central core is 0.06-0.22, the numerical aperture of the second cladding is 0.1-0.24, and the length of the second non-conical region is ≥10 m.

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