Fiber laser and laser treatment device

Abstract

The utility model discloses a fiber laser and a laser treatment device, and the fiber laser comprises a pumping source which is used for outputting pumping light; the beam combiner is connected with the pumping source; the first reflection device is connected with the beam combiner; the active optical fiber is connected with the first reflection device and is used for providing an upper energy level particle number; the second reflection device is connected with the active optical fiber and is used for outputting laser; the cladding light stripper is connected with the second reflecting device and is used for stripping the residual pump light and the return light entering the cladding; wherein a resonant cavity is formed between the first reflection device and the second reflection device, the beam combiner is used for coupling the pump light into the active optical fiber, and the laser is generated through pumping of the pump light and oscillation of the resonant cavity. Through the mode, the structure of the fiber laser is simplified, the manufacturing cost is reduced, the return light resistance is improved, the conversion efficiency of the pump light to the laser is improved, the beam combiner and other optical assemblies are protected, and optical damage and performance reduction caused by the return light are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to a fiber laser and a laser treatment device. BACKGROUND

[0002] The working wavelength of continuous or quasi-continuous thulium-doped fiber laser is near 2μm, which belongs to the eye-safe wavelength band, and has good absorption spectrum for NO, H2O, CO2, etc., and can be applied to laser radar, space communication, biological medicine, material processing and other fields. Due to the high absorption peak of water molecules in this wavelength band, precise and efficient ablation and cutting of biological tissues can be achieved, and it can be used as a laser scalpel. In addition, 2μm fiber laser has good application effect in urinary system and is often used for stone crushing in clinical medicine.

[0003] At present, the technical scheme of quasi-continuous laser capable of achieving a peak power of 600W mainly adopts a master oscillator power amplifier mode. This scheme uses a fiber grating as an oscillator to generate a seed source, and amplifies the power to 600W through a single-stage amplifier structure. Although this mode has low technical difficulty and good pulse time-domain stability, it has limitations such as high cost, poor anti-backlight capability, and easy damage to the amplification light path. CONTENT OF THE INVENTION

[0004] The present application mainly provides a fiber laser and a laser treatment device to solve the problems of high cost, poor anti-backlight capability and easy damage to the amplification light path of quasi-continuous laser.

[0005] The present application provides a fiber laser, comprising:

[0006] a pump source for outputting pump light;

[0007] a combiner connected with the pump source;

[0008] a first reflecting device connected with the combiner;

[0009] an active optical fiber connected with the first reflecting device for providing upper energy level particle number;

[0010] a second reflecting device connected with the active optical fiber for outputting laser;

[0011] a cladding light stripper connected with the second reflecting device for stripping residual pump light and back-reflected light entering the cladding;

[0012] Wherein, the first reflecting device and the second reflecting device form a resonant cavity, and the combiner is used to couple the pump light into the active optical fiber, and the laser is generated by pump light pumping and resonant cavity oscillation.

[0013] The fiber laser further comprises a photodetector connected with the combiner, for monitoring laser power and controlling current of the pump source based on power of the back light.

[0014] The fiber laser further comprises an output head connected with the cladding light stripper, for outputting the laser.

[0015] The reflectivity of the first reflecting device is higher than that of the second reflecting device.

[0016] The first reflecting device is a high-reflectivity grating, and the second reflecting device is a low-reflectivity grating.

[0017] The pump source generates pump light in a wavelength range of 0.75-3 μm.

[0018] The pump source comprises a plurality of laser diodes, and power of the laser diodes ranges from 150 W to 200 W.

[0019] The combiner comprises one signal fiber and a plurality of pump fibers, for coupling the pump light of the plurality of pump fibers and signal light of one signal fiber into one output fiber.

[0020] The core diameter of the active fiber ranges from 20 μm to 25 μm.

[0021] The application further provides a laser treatment device comprising the fiber laser as described above.

[0022] The fiber laser comprises a pump source, a combiner, a first reflecting device, an active fiber, a second reflecting device and a cladding light stripper, wherein a resonant cavity is formed between the first reflecting device and the second reflecting device, the combiner is used for coupling pump light into the active fiber, and laser is generated through storage and transportation of the pump light and oscillation of the resonant cavity. All optical paths of the application are completed in optical fibers, and pump light is directly coupled into the active fiber from outside of the resonant cavity, i.e. a single-cavity all-fiber structure and a forward cavity-outside pumping mode are adopted, thereby avoiding complex optical lenses and spatial optical path elements, and multiple reflections of pump light in the resonant cavity and damage of the combiner by back light. Through the single-cavity all-fiber structure, the structure of the fiber laser is simplified, the manufacturing cost is reduced, and the back light resistance is improved. Through the forward cavity-outside pumping mode, the conversion efficiency of pump light to laser is improved, the combiner and other optical components are protected, and optical damage and performance degradation caused by back light are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort. Among them:

[0024] Figure 1 FIG. 1 is a structural schematic diagram of an embodiment of the optical fiber laser provided by the present application. DETAILED DESCRIPTION

[0025] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0027] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0028] In this document, the term "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean that the same embodiment is referred to, nor does it mean that independent or alternative embodiments are mutually exclusive or alternative to each other. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0029] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this document generally represents a "or" relationship between the front and rear associated objects.

[0030] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0031] In the description of the embodiments of the present application, the orientation or positional relationship indicated by the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0032] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be connected between them, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0033] The working wavelength band of continuous or quasi-continuous thulium-doped fiber laser is near 2 μm, which belongs to the eye-safe wavelength band, has good absorption spectrum lines for NO, H2O, CO2, etc., and can be applied to laser radar, space communication, biological medicine, material processing and other directions. Due to the high absorption peak of water molecules in this wavelength band, precise and efficient ablation and cutting of biological tissues can be achieved, which can be used as a laser scalpel. In addition, 2 μm fiber laser has good application effect in urinary system, and is often used for stone crushing in clinical medicine.

[0034] There are mainly four kinds of laser schemes, which are single-cavity all-fiber structure, master oscillator power amplifier, same-band pumping and spatial coupling pumping. Among them, the master oscillator power amplifier scheme generally uses a thin fiber core to build a resonant cavity to generate a seed source, uses a mode field adapter, an isolator, a large-core active optical fiber and a high-power pump source to amplify the seed source signal light single or multiple times, or the seed source is divided into several beams which are amplified and then combined, and finally a 600W peak power laser is generated. The master oscillator power amplifier scheme has unstable power and poor anti-backlight capability. The high-power same-band pumping scheme has high requirements for the manufacture of active optical fiber, generally needs three cladding optical fibers for heat management, requires high doping concentration, and has high cost of pump source manufacturing. The pump source of the spatial coupling pumping is coupled into the active optical fiber through a spatial light path, and after oscillation in the resonant cavity, a high peak power laser is generated. The spatial coupling pumping scheme has poor anti-interference capability and poor stability, and is not easy to industrial production. The single-cavity all-fiber structure scheme has low manufacturing cost, low manufacturing difficulty, strong anti-backlight capability and good power stability.

[0035] At present, the technical scheme of a quasi-continuous laser capable of achieving a peak power of 600W mainly adopts a master oscillator power amplifier mode. This scheme uses a fiber grating as an oscillator to generate a seed source, and amplifies the power to 600W through a single-stage amplification structure. Although this mode has lower technical difficulty and better pulse time-domain stability, it has limitations such as high cost, poor anti-backlight capability, and easy damage to the amplification optical path.

[0036] For example, the laser adopts a 790nm waveband as pump light, a high-reflection grating and a low-reflection grating as a resonant cavity, and a single-mode fiber as a gain medium to generate a high-brightness seed source. The seed source passes through a thin-layer pump light stripper, a mode field adapter and an isolator and enters an amplification stage, which further amplifies the seed light until a peak power of 600W is reached. This mode mainly has poor anti-backlight capability. When a part of the reflected light from the surface of an object enters the amplification stage, the optical path device is damaged after being amplified again, resulting in that the laser cannot work normally.

[0037] The present application provides a kind of fiber laser, please see Figure 1 As shown in the figure, Figure 1 It is the structure schematic diagram of an embodiment of the fiber laser provided by the present application. The fiber laser 10 of the embodiment includes a pump source 11, a beam combiner 12, a first reflecting device 13, an active optical fiber 14, a second reflecting device 15 and a cladding light stripper 16.

[0038] The pump source 11 is used to output pump light, i.e. the pump source 11 provides pump light for the fiber laser 10. Pump light refers to light used to excite particles in a laser gain medium to reach an excited state, thereby achieving particle number inversion.

[0039] Optionally, the pump source 11 includes but is not limited to a semiconductor laser pump source, a solid laser pump source or an electric pump source.

[0040] The beam combiner 12 is connected with the pump source 11, and the pump light output by the pump source 11 is transmitted to the beam combiner 12, i.e. the beam combiner 12 receives the pump light. The beam combiner 12 is used to combine the pump light and a signal light into an output optical fiber.

[0041] In some embodiments, the pump light of the pump source 11 is transmitted to the beam combiner 12 through an optical fiber, so that the beam combiner 12 combines the pump light.

[0042] The first reflecting device 13 is connected with the beam combiner 12, the active optical fiber 14 is connected with the first reflecting device 13, and the second reflecting device 15 is connected with the active optical fiber 14.

[0043] The active optical fiber 14 is a gain medium of the fiber laser 10, and is usually doped with rare earth elements such as ytterbium, thulium, etc. for providing upper level particle number. For example, the active optical fiber 14 is a double-clad thulium-doped optical fiber. In other embodiments, the active optical fiber 14 is a single-clad thulium-doped optical fiber or a triple-clad thulium-doped optical fiber.

[0044] The first reflecting device 13 and the second reflecting device 15 include, but are not limited to, fiber gratings or mirrors, and the second reflecting device 15 is configured to output the laser.

[0045] The cladding light stripper 16 is connected to the second reflecting device 15 and is configured to strip the residual pump light and the back-incoming light into the cladding.

[0046] The residual pump light refers to the pump light that is not completely absorbed in the active optical fiber 14, and the pump light decays exponentially during transmission, but part of the light remains in the cladding of the optical fiber. The back-incoming light refers to the signal light that leaks into the cladding due to the bending and fusion of the optical fiber during the transmission of the optical fiber, forming back-incoming light.

[0047] In some embodiments, the second reflecting device 15 outputs the laser, and the cladding light stripper 16 connected to the second reflecting device 15 strips the residual pump light in the optical fiber and the back-incoming light into the cladding, so as to reduce the influence of the back-incoming light on the stability of the resonant cavity and improve the anti-back-incoming light capability of the fiber laser 10.

[0048] The first reflecting device 13 and the second reflecting device 15 form a resonant cavity, and the combiner 12 is configured to couple the pump light into the active optical fiber 14, and the pump light pumping and the resonant cavity oscillation generate the laser.

[0049] In some embodiments, the first reflecting device 13 is a high-reflectivity fiber grating, and the second reflecting device 15 is a partially-reflective fiber grating, so that the first reflecting device 13 and the second reflecting device 15 form a resonant cavity. At this time, the first reflecting device 13 forms one end of the resonant cavity, the second reflecting device 15 forms the other end of the resonant cavity, and the active optical fiber 14 is located in the resonant cavity. The pump light of the pump source 11 is coupled into the active optical fiber 14 in the resonant cavity through the combiner 12, excites the doped ions of the active optical fiber 14, and makes the doped ions transition from the ground state to the excited state, forming particle number inversion; and the light repeatedly goes back and forth in the resonant cavity, and is effectively amplified, and finally forms high-power laser output. That is, the combiner 12 couples the pump light of the pump source 11 into the active optical fiber 14 in the resonant cavity, and the pump light pumping and the resonant cavity oscillation generate the laser.

[0050] Since the second reflecting device 15 is a partially reflecting fiber grating, it allows part of the signal light to output, forming a laser output. In other embodiments, the first reflecting device 13 and the second reflecting device 15 are mirrors.

[0051] Optionally, the pump source 11, the combiner 12, the first reflecting device 13, the active fiber 14, the second reflecting device 15, and the cladding light stripper 16 in the fiber laser 10 are connected by optical fibers.

[0052] All the optical paths in the embodiment are completed in optical fibers, and the pump light is directly coupled into the active fiber 14 from outside the resonant cavity, i.e., a single-cavity all-fiber structure and a forward extracavity pumping mode are adopted, avoiding complex optical lenses and spatial optical path elements, as well as multiple reflections of the pump light in the resonant cavity and the damage of the combiner by the back-reflected light; by using the single-cavity all-fiber structure, the structure of the fiber laser 10 is simplified, the manufacturing cost is reduced, and the back-reflected light resistance is improved; by using the forward extracavity pumping mode, the conversion efficiency of the pump light to the laser is improved, the combiner 12 and other optical components are protected, and the optical damage and performance degradation caused by the back-reflected light are reduced.

[0053] According to some embodiments of the present application, the fiber laser 10 further comprises a photodetector 17 connected with the combiner 12, for monitoring the laser power and controlling the current of the pump source 11 based on the power of the back-reflected light.

[0054] Here, the laser power refers to the laser power output by the fiber laser 10; and the power of the back-reflected light refers to the power of part of the laser beam returning to the inside of the fiber laser 10 due to material surface reflection or other reasons during the operation of the fiber laser 10.

[0055] In some embodiments, the fiber laser 10 outputs laser, the photodetector 17 monitors the laser power output by the fiber laser 10 to ensure that the fiber laser 10 operates at a preset power level; and the photodetector 17 monitors the power of the back-reflected light, and when the power of the back-reflected light exceeds a preset threshold, the current of the pump source 11 is adjusted by a control circuit to reduce the influence of the back-reflected light on the fiber laser 10.

[0056] The embodiment can monitor the laser power and the power of the back-reflected light by connecting the photodetector 17 with the combiner 12, to improve the stability and safety of the fiber laser 10 during operation.

[0057] According to some embodiments of the present application, the fiber laser 10 further comprises an output head 18 connected with the cladding light stripper 16, for outputting laser.

[0058] In some embodiments, the cladding light stripper 16 outputs the laser light through the output head 18 after stripping the residual pump light and the back-return light entering the cladding. The output head 18 is the final output component of the fiber laser 10, which is used to guide the laser light out of the fiber and transmit to the application end.

[0059] The output head 18 includes but is not limited to a fiber connector, a collimating lens or a focusing lens. For example, the output head 18 is a collimator or an SMA905 connector. The output head 18 is selected according to different application scenarios to meet specific optical requirements.

[0060] According to the setting of the output head 18, the embodiment can be configured as required to meet the application requirements of different scenarios.

[0061] According to some embodiments of the present application, the reflectivity of the first reflective device 13 is higher than the reflectivity of the second reflective device 15.

[0062] In some embodiments, the reflectivity of the first reflective device 13 is 99%, and the reflectivity of the second reflective device 15 is 10%, so that the reflectivity of the first reflective device 13 is higher than the reflectivity of the second reflective device 15.

[0063] According to some embodiments of the present application, the first reflective device 13 is a high-reflectivity grating, and the second reflective device 15 is a low-reflectivity grating.

[0064] In some embodiments, the first reflective device 13 is a fiber grating with a reflectivity of 99%, i.e., a high-reflectivity grating, which is used for the composition of the laser resonant cavity and the selection of the laser longitudinal mode; the second reflective device 15 is a fiber grating with a reflectivity of 10%, i.e., a low-reflectivity grating, which is used for the composition of the resonant cavity, the selection of the laser longitudinal mode and the laser output.

[0065] The reflectivity of the second reflective device 15 is lower than the reflectivity of the first reflective device 13, which prevents the laser light located far from the center wavelength from being transmitted from the first reflective device 13 and damaging the photodetector 17.

[0066] According to some embodiments of the present application, the pump source 11 generates pump light in the 0.75-3 μm wavelength band.

[0067] In some embodiments, the pump source 11 generates pump light in the 790 nm wavelength band.

[0068] According to some embodiments of the present application, the pump source 11 includes a plurality of laser diodes, and the power range of the laser diodes is between 150-200 W.

[0069] In some embodiments, the pump source 11 is 8 laser diodes of 180 W.

[0070] In some embodiments, the fiber laser 10 is more convenient to use by using air cooling to dissipate heat; since the thulium-doped fiber has a narrow absorption bandwidth at 790 nm, in order to reduce the influence of laser diode temperature drift on laser power, a heat pipe is used to dissipate heat to reduce the temperature variation of the laser diode, further improving the laser time domain stability.

[0071] According to some embodiments of the present application, the combiner 12 includes one signal fiber and multiple pump fibers for combining the pump light of the multiple pump fibers and the signal light of the one signal fiber into one output fiber.

[0072] In some embodiments, the combiner 12 includes one signal fiber and eight pump fibers, i.e. the combiner 12 is a (8+1)*1 combiner; when the pump source 11 is eight 1980W laser diodes, the combiner 12 combines the pump light of the eight pump fibers and the signal light of the one signal fiber into one output fiber.

[0073] According to some embodiments of the present application, the core diameter of the active fiber 14 ranges from 20-25μm. For example, the active fiber 14 is a double-clad thulium-doped fiber with a core diameter of 25μm and an inner cladding diameter of 400μm.

[0074] In some embodiments, the fiber laser 10 has two working modes, one is continuous light output with a power of 60W, and the other is quasi-continuous light output with a peak power of 600W and an average power of 60W. Specifically, the two working modes are realized by controlling the current of the pump source 11, which increases the application range of the fiber laser 10.

[0075] Another embodiment of the present application also provides a laser treatment device including the fiber laser 10 of the above-described embodiments.

[0076] In summary, all optical paths of the present application are completed in the fiber, and the pump light is directly coupled into the active fiber 14 from the outside of the resonant cavity, i.e. a single-cavity all-fiber structure and a forward cavity-outside pumping mode are used, which avoids complex optical lenses and spatial optical path elements, as well as multiple reflections of the pump light in the resonant cavity and the damage of the combiner by the back light; by using the single-cavity all-fiber structure, the structure of the fiber laser 10 is simplified, the manufacturing cost is reduced, and the anti-back light capability is improved; by using the forward cavity-outside pumping mode, the conversion efficiency of the pump light to laser is improved, the combiner 12 and other optical components are protected, and the optical damage and performance degradation caused by the back light are reduced; by monitoring with the photodetector, the laser time domain stability and the anti-back light capability are strengthened; air cooling and heat pipe heat dissipation make the fiber laser 10 more convenient to use, strengthen the temperature management of the laser diode, and reduce the influence of the laser diode temperature drift on the laser power variation; the continuous and quasi-continuous dual modes increase the application range of the laser.

[0077] The above merely describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is made according to the content of the present application specification and drawings, is also included in the patent protection scope of the present application.

Claims

1. A fiber laser, characterized by, The fiber laser comprises: a pump source for outputting pump light; a combiner connected with the pump source; a first reflecting device connected with the combiner; an active fiber connected with the first reflecting device for providing upper level particle number; a second reflecting device connected with the active fiber for outputting laser light; a cladding light stripper connected with the second reflecting device for stripping residual pump light and back light into cladding; wherein the first reflecting device and the second reflecting device form a resonant cavity, and the combiner is used for coupling the pump light into the active fiber, and the laser light is generated by pump light pumping and resonant cavity oscillation.

2. The fiber laser of claim 1, wherein, The fiber laser further comprises a photodetector connected with the combiner for monitoring laser power and controlling current of the pump source based on power of the back light.

3. The fiber laser of claim 1, wherein, The fiber laser further comprises an output head connected with the cladding light stripper for outputting the laser light.

4. The fiber laser of claim 1, wherein, Reflectivity of the first reflecting device is higher than that of the second reflecting device.

5. The fiber laser of claim 4, wherein, The first reflecting device is a high reflection grating, and the second reflecting device is a low reflection grating.

6. The fiber laser of claim 1, wherein, The pump source generates pump light in a wave band of 0.75-3 μm.

7. The fiber laser of claim 1, wherein, The pump source comprises a plurality of laser diodes, and power of the laser diodes ranges from 150 W to 200 W.

8. The fiber laser of claim 1, wherein, The combiner comprises one signal fiber and a plurality of pump fibers, and is used for combining the pump light of the plurality of pump fibers and signal light of one signal fiber into one output fiber.

9. The fiber laser of claim 1, wherein, A core diameter of the active fiber ranges from 20 μm to 25 μm.

10. A laser treatment device, characterized in that, The fiber laser comprises any one of claims 1-9. The fiber laser comprises any one of claims 1-9.

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