Ultrahigh-power fiber laser module with low nonlinear effect and laser

Abstract

The utility model relates to the technical field of lasers, in particular to an ultra-high power fiber laser module with a low nonlinear effect and a laser. The laser module comprises an active optical fiber, two output gratings connected to the two ends of the active optical fiber respectively, at least one pumping source, a pumping signal beam combiner corresponding to the pumping source, two cladding light stripping devices used for filtering residual pumping light in signal light and in a high-order mode, and two output heads arranged at the output ends of the cladding light stripping devices respectively. The reflectivity of the output grating is lt; 5%, transmittance gt; 95%. The laser comprises one or more laser modules, a laser beam combiner, a mode stripper and a third output head, and the laser modules, the laser beam combiner, the mode stripper and the third output head are sequentially connected through optical fiber fusion. By reducing the reflectivity of the output grating, the power density in the cavity is reduced, so that the interaction strength of laser and the optical fiber is reduced, the influence of a nonlinear effect is weakened, and the stability of the optical fiber laser is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lasers, in particular to an ultra-high power fiber laser module and a laser with low nonlinear effect. Background Technique

[0002] Nonlinear effect is an important factor restricting the performance of high-power fiber lasers, and its suppression or utilization has always been an important topic for major fiber laser manufacturers and research institutions.

[0003] In high-power fiber lasers, common nonlinear effects include stimulated Raman scattering (SRS), four-wave mixing (FWM), self-phase modulation (SPM), etc. Among them, FWM and SPM will significantly broaden the spectrum of the laser, seriously deteriorating the performance of laser processing; while SRS not only affects laser processing, but also affects the stability of the laser itself - it will induce mode instability (TMI) and cause strong backlight damage to the laser during the processing. In addition, SRS in fiber lasers also limits the power upper limit of multimode combined fiber lasers, making it extremely difficult to obtain the expected brightness.

[0004] The nonlinear effect stems from the too high laser energy density in the fiber. Therefore, the conventional methods to suppress the nonlinear effect are to increase the effective mode field area of the fiber, shorten the fiber length, etc. Among them, increasing the effective mode field area of the fiber will reduce the threshold of transverse mode instability of the laser system and deteriorate the beam quality; while shortening the fiber length is likely to cause insufficient total absorption of the pump light and reduce the optical-to-optical conversion efficiency of the fiber laser.

[0005] Therefore, without changing the total conversion efficiency of the system, directly reducing the energy density in the fiber is an effective and balanced solution.

[0006] In the Chinese patent literature database, a patent with the application number 2018216446463 discloses a linear cavity all-fiber laser oscillator with dual-end output. The reflectivity range of the limiting grating is 5%-95%, and the transmittance is 95%-5%. The cases of lower reflectivity and higher transmittance are not considered, which restricts the potential for improving the efficiency of fiber lasers and the further suppression and optimization of nonlinear effects. A patent with the application number 2018216446162 discloses a linear cavity all-fiber laser oscillator with adjustable dual-end output power. By tuning the central wavelengths of the forward grating and the subsequent grating, the reflectivity of the corresponding grating at the corresponding central wavelength is changed, so as to achieve wavelength tunability within a certain range and laser output with different power ratios in both directions. However, the uncertainty of the central wavelength of the grating makes the system extremely vulnerable to the influence of the environment (such as temperature), resulting in uncontrollable output, which is not conducive to industrial applications. At the same time, to meet the technical requirements of its wavelength and power tunability, the implementation difficulty of industrialization is increased. The above patents all require that the series-connected devices be energy-transmitting fibers of the same specification, which will not be able to diversely control the output laser mode according to actual needs, greatly reducing the application scenarios of the laser. The above patents and the prior art all require that the series-connected devices be energy-transmitting fibers of the same specification, which will not be able to diversely control the output laser mode according to actual needs, greatly reducing the application scenarios of the laser. Summary of the Invention

[0007] The purpose of the present invention is to provide a high-power fiber laser module and a laser with low nonlinear effects to solve the problems raised in the above background technology.

[0008] To achieve the above purpose, the present invention provides the following technical solution: A high-power fiber laser module with low nonlinear effects includes an active fiber, two output gratings respectively connected to both ends of the active fiber, at least one pump source and a pump signal combiner corresponding to the pump source, two cladding light strippers for filtering out the residual pump light and high-order mode in the signal light, and two output heads respectively arranged at the output ends of the cladding light strippers. The reflectivity of the output grating is <5%, and the transmittance is >95%.

[0009] Further, the active fiber, the output grating, the pump source, the pump signal combiner, the cladding light stripper, and the output head are fused together by optical fibers.

[0010] Further, the pump signal combiner includes one or more pump input arms, and one or more pump input arms are connected to one or more output ends of the pump source through optical fibers.

[0011] Further, the pump signal combiner is arranged between the output grating and the cladding light stripper.

[0012] Further, the pump signal combiner is disposed between the active fiber and the output grating.

[0013] Further, the center wavelengths of the two output gratings match, and the center wavelength is immutable.

[0014] Further, the active fiber is a double-clad fiber or a triple-clad fiber, and rare earth ions are doped in the core for absorbing pump light and generating laser, and no rare earth ions are doped in the cladding for transmitting pump light.

[0015] A laser includes one or more laser modules, a laser combiner, a mode stripper, and a third output head, and the laser modules, the laser combiner, the mode stripper, and the third output head are sequentially connected by fiber fusion splicing.

[0016] Further, the number of optical fibers at the fiber bundle end of the laser combiner is more than twice the number of laser modules.

[0017] Compared with the prior art, the beneficial effects of the present utility model are as follows: The active fiber in the ultra-high power fiber laser module with low non-linear effect cooperates with two output gratings to form a single oscillation cavity; since the reflectivity of the output grating is <5% and the transmittance is >95%, according to the relationship between the intracavity power density of a solid-state laser and the reflectivity of the output cavity mirror - the lower the reflectivity of the output mirror, the lower the intracavity power and the lower the energy density.

[0018] By reducing the reflectivity of the output grating, the intracavity power density is reduced, thereby reducing the interaction intensity between the laser and the fiber, weakening the influence of the non-linear effect, and significantly suppressing FWM, SPM, SRS, etc., and improving the spectral broadening situation - through actual verification, adopting the solution of the present utility model, the line width of the output 3500W laser is 84% of the line width of the output 3500W laser in the conventional solution. And no obvious non-linear effect appears.

[0019] When consuming the same total pump power, the power during the output of the conventional solution is P0, and when adopting the solution of the present utility model, the powers output by the two output heads of the laser module are P1 and P2 respectively; through experimental verification, P1 + P2 > P0, and the optical efficiency is significantly higher. At the same time, P1 < P0 and P2 < P0, and the power values at the two output heads are farther from the mode instability threshold of the active fiber than the power value during the conventional output, and also weaken the influence of photon darkening. Obviously, this also reduces the action of the output laser on the energy transfer fiber outside the cavity, is far from the non-linear effect threshold of the energy transfer fiber, and greatly improves the stability of the fiber laser.

[0020] The high-power fiber laser obtained by combining the laser modules with low non-linear effects also has excellent non-linear effect suppression performance. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the laser module in Embodiment 1 of the present utility model;

[0022] Figure 2 It is a schematic structural diagram of the laser of the present utility model;

[0023] Figure 3 It is a schematic structural diagram of the laser module in Embodiment 2 of the present utility model;

[0024] Figure 4 It is a schematic structural diagram of the laser module in Embodiment 3 of the present utility model;

[0025] Figure 5 It is a schematic structural diagram of the laser module in Embodiment 4 of the present utility model;

[0026] Figure 6 It is a schematic structural diagram of the laser module in Embodiment 5 of the present utility model;

[0027] Figure 7 It is a schematic structural diagram of the laser module in Embodiment 6 of the present utility model;

[0028] In the figure: 10, laser module; 11, first pump source; 12, second pump source; 13, first pump signal combiner; 14, second pump signal combiner; 15, first output grating; 16, second output grating; 17, active optical fiber; 18, first cladding light stripper; 19, second cladding light stripper; 20, laser combiner; 30, mode stripper; 40, third output head; 50, first output head; 60, second output head. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0030] In the description of the present utility model, it should be noted that the descriptions of terms such as "first" and "second" are only for descriptive purposes, and do not particularly refer to the order or sequence. Nor are they used to limit the present utility model. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0031] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", "linkage", and "setting" should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances. In addition, in the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present utility model.

[0032] Example 1, please refer to Figure 1 , an embodiment provided by the present utility model: a high-power fiber laser module with low non-linear effect, including an active fiber 17, a first output grating 15 and a second output grating 16 respectively fiber-fused at both ends of the active fiber 17, a first pump source 11 and a second pump source 12, and a first pump signal combiner 13 and a second pump signal combiner 14 corresponding to the first pump source 11 and the second pump source 12 respectively, a first cladding light stripper 18 and a second cladding light stripper 19 for filtering out the residual pump light and high-order modes in the signal light, and two first output heads 50 and second output heads 60 respectively arranged at the output ends of the first cladding light stripper 18 and the second cladding light stripper 19.

[0033] The first pump source 11 and the second pump source 12 are fiber output semiconductor laser modules or combinations, and their central wavelengths can be all wavelengths that can be used as the pump source of the fiber laser. The specific wavelengths can be any one or a combination of multiple of 915 nm and 976 nm.

[0034] The first pump signal combiner 13 and the second pump signal combiner 14 ensure that the signal light can be transmitted with low loss when transmitting from a single fiber to a multi-fiber bundle direction in the signal fiber, and ensure that the pump light can be transmitted with low loss when transmitting to the single-end direction. The pump signal combiner includes one or more pump input arms, and one or more pump input arms are connected to one or more output ends of the pump source through optical fibers. In this embodiment, the first pump signal combiner 13 is arranged between the first output grating 15 and the first cladding light stripper 18, and the second pump signal combiner 14 is arranged between the second output grating 16 and the second cladding light stripper 19. Each device is connected by fiber fusion.

[0035] A first output grating 15 and a second output grating 16, whose central wavelengths match. For a specific laser module embodiment, the central wavelength is immutable, and the central wavelength value can be any value achievable by a fiber laser at the corresponding pump wavelength, avoiding output instability caused by environmental changes and reducing the implementation difficulty of the laser; an active fiber 17, which cooperates with the first output grating 15 and the second output grating 16 to form a single oscillation cavity. The first output grating 15 and the second output grating 16 both satisfy a reflectivity <5% and a transmittance >95% in the central wavelength band, having low reflectivity and high transmittance, which can reduce the energy density of the fiber in the cavity participating in oscillation and enhance the suppression of nonlinear effects.

[0036] The active fiber 17 is a double-clad fiber or a triple-clad fiber, with rare earth ions doped in the core for absorbing pump light and generating laser, and no rare earth ions doped in the cladding for transmitting pump light.

[0037] A first cladding light stripper 18 and a second cladding light stripper 19 are used to filter out the residual pump light and high-order modes in the signal light, and are respectively fiber spliced at the output ends of the first pump signal combiner 13 and the second pump signal combiner 14. The fiber specifications thereof should ensure that the required components of the signal light output from the first pump signal combiner 13 and the second pump signal combiner 14 can be transmitted with low loss.

[0038] A first output head 50 and a second output head 60 are respectively fiber spliced at the output ends of the first cladding light stripper 18 and the second cladding light stripper 19, and are used to expand and antireflect the signal light in the output fibers of the first cladding light stripper 18 and the second cladding light stripper 19, reducing the power density and reflection at the output end face and improving the reliability of the laser.

[0039] The energy transfer fibers between all devices only need to ensure low-loss transmission of the signal light in the direction of the first output head 50 and the second output head 60, and low-loss transmission of the pump light in the direction of the active fiber 17, and no clear restrictions are imposed on the structural size specifications of the energy transfer fibers. This can further actively adjust the mode of the output laser according to actual needs, suppress nonlinear effects, meet a wider range of processing requirements, and also reduce the implementation difficulty of laser industrialization.

[0040] A laser, please refer to Figure 2 , including one or more laser modules 10, a laser combiner 20, a mode stripper 30, and a third output head 40, which are sequentially connected by fiber splicing.

[0041] The laser beam combiner 20 is a device that combines the signal light output by one or more laser modules 10 into the same optical fiber. When connecting the laser module 10 to the laser beam combiner 20, the first output head 50 and the second output head 60 need to be removed, and the first cladding light stripper 18 and the second cladding light stripper 19 are fusion spliced with the input optical fiber of the laser beam combiner 20. The number of optical fibers at the fiber bundle end is greater than twice the number of laser modules 10. The optical fiber specifications before and after beam combination need to meet the low-loss transmission of the signal light output by the laser module 10.

[0042] The mode stripper 30 is a device that filters out the unwanted components in the signal light output from the laser beam combiner 20. The optical fiber specifications ensure the low-loss transmission of the signal light components within the desired range.

[0043] The third output head 40 is used to expand and antireflect the signal light in the output optical fiber of the mode stripper 30, reduce the power density and reflectivity of the output end face, and improve the reliability of the laser.

[0044] Using a single-cavity fiber laser with low nonlinear effect as the laser module 10, the high-power fiber laser obtained by beam combination also has excellent nonlinear effect suppression performance. At the same time, the spectral linewidth is narrower than that obtained by combining conventional laser modules. Without the influence of nonlinear effects, the brightness of the fiber laser can be further improved (the power and beam quality are optimized synchronously); the narrower the spectrum, the more efficient the absorption of the laser by the processed material. With the same power laser, the processing efficiency is higher and the effect is better.

[0045] Using the first output grating 15 and the second output grating 16, both of which satisfy a reflectivity <5% and a transmittance >95% in the central wavelength band, to form a single-cavity oscillation structure fiber laser. While saving optical fiber materials and maintaining a small volume of the laser, it further releases the conversion efficiency potential of the single-module fiber laser to obtain higher power; reduces the power density in the laser cavity, optimizes the nonlinear characteristics, and avoids unstable situations caused by nonlinear effects.

[0046] Example 2, please refer to Figure 3 , the difference between this embodiment and Embodiment 1 is that there is only one set of pump source and the corresponding pump signal combiner, that is, only the first pump source 11 and the first pump signal combiner 13 are provided, and the input end of the second cladding light stripper 19 is fusion spliced with the output end of the second output grating 16 through an optical fiber.

[0047] Example 3, please refer to Figure 4, the difference between this embodiment and Embodiment 1 is that only one set of pump source and the pump signal combiner corresponding to the pump source is provided, that is, only the second pump source 12 and the second pump signal combiner 14 are provided. The input end of the first cladding light stripper 18 is fiber-optically spliced to the output end of the first output grating 15.

[0048] Embodiment 4. On the premise of ensuring low-loss transmission of the signal light and the pump light, the positions of the first output grating 15 and the second output grating 16 can be adjusted and moved on the signal optical fibers of the first pump signal combiner 13 and the second pump signal combiner 14. Please refer to Figure 5 , the difference between this embodiment and Embodiment 1 is that the pump signal combiner is arranged between the active optical fiber 17 and the output grating, that is, the first pump signal combiner 13 is fiber-optically spliced between the active optical fiber 17 and the first output grating 15, and the second pump signal combiner 14 is fiber-optically spliced between the active optical fiber 17 and the second output grating 16.

[0049] Embodiment 5. Please refer to Figure 6 , the difference between this embodiment and Embodiment 2 is that the first pump signal combiner 13 is fiber-optically spliced between the active optical fiber 17 and the first output grating 15.

[0050] Embodiment 6. Please refer to Figure 7 , the difference between this embodiment and Embodiment 3 is that the second pump signal combiner 14 is fiber-optically spliced between the active optical fiber 17 and the second output grating 16.

[0051] For those skilled in the art, it is obvious that the present utility model is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present utility model, the present utility model can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present utility model. Any reference signs in the claims should not be regarded as limiting the claimed rights.

Claims

1. A high-power fiber laser module with low nonlinear effect, characterized in that: The invention comprises an active optical fiber, two output gratings respectively connected to two ends of the active optical fiber, at least one pump source and a pump signal combiner corresponding to the pump source, two cladding light strippers for filtering residual pump light and high-order modes in the signal light, and two output heads respectively arranged at the output ends of the cladding light strippers, wherein the output grating has a reflectivity of <5% and a transmittance of >95%.

2. The high-power fiber laser module with low nonlinear effect according to claim 1, characterized in that: The source optical fiber, the output grating, the pump source, the pump signal combiner, the cladding light stripper and the output head are connected by optical fiber fusion.

3. The high-power fiber laser module with low nonlinear effect according to claim 1, characterized in that: The pump signal combiner comprises one or more pump input arms, and the one or more pump input arms are connected to one or more output ends of a pump source through optical fibers.

4. The high-power fiber laser module with low nonlinear effect according to claim 1, characterized in that: The pump signal combiner is arranged between the output grating and the cladding light stripper.

5. The high-power fiber laser module with low nonlinear effect according to claim 1, characterized in that: The pump signal combiner is arranged between the active optical fiber and the output grating.

6. The high-power fiber laser module with low nonlinear effect according to claim 1, characterized in that: The central wavelengths of the two output gratings are matched and cannot be changed.

7. The high-power fiber laser module with low nonlinear effect according to claim 1, characterized in that: The active optical fiber is a double-clad optical fiber or a triple-clad optical fiber, the core of which is doped with rare earth ions for absorbing pump light and generating laser light, and the cladding is not doped with rare earth ions for transmitting pump light.

8. A laser, characterized in that: It comprises one or more high-power fiber laser modules with low nonlinear effects, a laser beam combiner, a mode stripper and a third output head as described in any one of claims 1 to 7, wherein the laser module, the laser beam combiner, the mode stripper and the third output head are sequentially connected by fiber fusion splicing.

9. The laser according to claim 8, characterized in that: The number of optical fibers at the optical fiber bundle end of the laser beam combiner is greater than twice the number of laser modules.

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