CN212810845U - High power fiber laser amplifier system - Google Patents
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- CN212810845U CN212810845U CN202022199072.7U CN202022199072U CN212810845U CN 212810845 U CN212810845 U CN 212810845U CN 202022199072 U CN202022199072 U CN 202022199072U CN 212810845 U CN212810845 U CN 212810845U
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Abstract
A high-power fiber laser amplifier system comprises an oscillator and an amplifier, wherein a high-reflection grating and a low-reflection grating in the oscillator are respectively and directly inscribed on an oscillator input energy transmission fiber and an oscillator output energy transmission fiber, one end of an oscillator gain fiber is welded with the oscillator input energy transmission fiber, the other end of the oscillator gain fiber is welded with the oscillator output energy transmission fiber, a first grating for inhibiting the stimulated Raman effect in a cavity is directly inscribed on the oscillator gain grating, and a second grating for inhibiting the pump dumping effect and the SRS effect is inscribed on the oscillator output energy transmission fiber; the oscillator output energy transmission fiber is welded with the amplifier input energy transmission fiber, the amplifier input energy transmission fiber is welded with one end of the amplifier gain fiber, a third grating for inhibiting the stimulated Raman effect in the cavity and a high-order mode filter are directly inscribed on the amplifier gain fiber, and a fourth grating for inhibiting the SRS effect is inscribed on the amplifier output energy transmission fiber. The utility model discloses restrain SRS effect and TMI effect when reducing the melting point.
Description
Technical Field
The utility model relates to a high power fiber laser technical field, concretely relates to can restrain optical fiber amplifier system of stimulated raman scattering and transverse mode instability simultaneously.
Background
The fiber laser has the advantages of compact structure, high efficiency, good beam quality and the like, and plays an increasingly important role in industrial processing and defense industry. The amplifier structure can effectively amplify the input seed light. The maximum output power of the reported near-single mode amplifier reaches 20kW, which is far greater than that of the near-single mode oscillator structure. Stimulated Raman Scattering (SRS) is one of the limiting factors limiting further increases in amplifier power, in order to improve the SRS effectThreshold value, the effective mode field area of the optical fiber needs to be properly increased, namely the diameter of the fiber core needs to be increased, at the moment, the single-mode transmission condition cannot be ensured, and two modes (LP) can be transmitted simultaneously in the fiber core01And LP11) The two modes interfere with each other to form a strong and weak alternating optical field along the axial direction of the optical fiber, because the photothermal effect can form a refractive index long period grating with the period of interference beat length, when noise exists in the system, the thermotropic long period grating and the interference field are not synchronous any more, the thermotropic long period grating moves to cause a transverse mode instability effect (TMI), the quality of a laser beam is sharply reduced due to the TMI effect, the pumping power is continuously improved, and the output power is not increased or decreased reversely.
In order to further increase the output power of the amplifier, it is necessary to suppress both SRS and TMI effects.
SUMMERY OF THE UTILITY MODEL
To the defect that prior art exists, the utility model provides a high power optic fibre laser amplifier system.
In order to achieve the technical purpose, the utility model discloses a specific technical scheme as follows:
a high-power fiber laser amplifier system comprises an oscillator and an amplifier, wherein a high-reflection grating and a low-reflection grating in the oscillator are respectively and directly inscribed on an input energy transmission fiber of the oscillator and an output energy transmission fiber of the oscillator, the input energy transmission fiber of the oscillator is welded with one end of a gain fiber of the oscillator, a first grating for inhibiting the stimulated Raman effect in a cavity is directly inscribed on the gain grating of the oscillator, the other end of the gain fiber of the oscillator is welded with the output energy transmission fiber of the oscillator, and a second grating for inhibiting the pump dumping and the SRS effect is inscribed on the output energy transmission fiber of the oscillator; the oscillator output energy transmission fiber is welded with the amplifier input energy transmission fiber, the amplifier input energy transmission fiber is welded with one end of the amplifier gain fiber, a third grating for inhibiting the stimulated Raman effect in the cavity and a high-order mode filter are directly inscribed on the amplifier gain fiber, and a fourth grating for inhibiting the SRS effect is inscribed on the amplifier output energy transmission fiber.
Furthermore, the oscillator and the pump fibers of the pump light sources in the pump units in the amplifier form a side-pumped beam combiner in a mode of tapering and fusing to the energy transmission fiber. Or the side pumping beam combiner can be replaced by an end pumping beam combiner according to the actual situation.
Further, the oscillator of the present invention may be a forward pump fiber laser oscillator, a backward pump fiber laser oscillator, or a bidirectional pump fiber laser oscillator. The pump unit in the forward pump fiber laser oscillator is a forward pump unit, and the pump fibers of the pump light sources in the forward pump unit form a side pump beam combiner in a mode of tapering and fusing on the input energy-transmitting fibers. The pump unit in the backward pump fiber laser oscillator is a backward pump unit, and the pump fibers of the pump light sources in the backward pump unit form a side pump beam combiner in a mode of tapering and fusing to the output energy-transmitting fibers. The pump unit in the bidirectional pump fiber laser oscillator comprises a forward pump unit and a backward pump unit, the pump fibers of all pump light sources in the forward pump unit form a side pump beam combiner in a mode of tapering and fusing on the input energy-transmitting fibers, and the pump fibers of all pump light sources in the backward pump unit form a side pump beam combiner in a mode of tapering and fusing on the output energy-transmitting fibers.
Further, the amplifier includes amplifier forward pumping unit and amplifier backward pumping unit, and the side pumping beam combiner is constituteed with the mode that the amplifier input can the optic fibre to the pumping optic fibre of each pump light source among the amplifier forward pumping unit fuses with the broach to the amplifier, and the side pumping beam combiner is constituteed with the mode that the amplifier output can the optic fibre to the pumping optic fibre of each pump light source among the amplifier backward pumping unit fuses with the broach.
Furthermore, the high reflection grating of the present invention is a high reflection fiber bragg grating directly written on the oscillator input energy transmission fiber by an ultraviolet exposure method or a femtosecond laser phase template method; the low reflection grating is a low reflection fiber Bragg grating directly written on the output energy transfer fiber of the oscillator by an ultraviolet exposure method or a femtosecond laser phase template method.
Furthermore, the utility model disclosesThe fiber cores of the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating are provided with circular refractive index modulation regions concentric with the fiber cores, the radius of the refractive index modulation regions is smaller than that of the fiber cores, the refractive index modulation regions and the fiber vector mode are circularly symmetrical, and the LP01Mold and LP11Modes do not couple with each other, and LP11The self-coupling coefficient of the mode is lower than LP01Self-coupling coefficient of mode, LP11Reflectivity of the mode lower than LP01The reflectivity of the mode.
Preferably, the first grating is a chirped tilted fiber bragg grating written directly on the oscillator gain fiber by a femtosecond laser. The plurality of chirped and inclined fiber Bragg gratings on the oscillator gain fiber can be distributed, and the plurality of chirped and inclined fiber Bragg gratings on the oscillator gain fiber form a cascaded chirped and inclined fiber Bragg grating. Or, the whole oscillator gain fiber is engraved with the chirped inclined fiber Bragg grating to form the distributed chirped inclined fiber Bragg grating.
Preferably, the second grating is a chirped tilted fiber bragg grating written on the oscillator output energy transfer fiber by an ultraviolet exposure method or a femtosecond laser phase template method. The chirped inclined fiber Bragg gratings on the oscillator output energy transmission fiber are distributed in a plurality, and the plurality of chirped inclined fiber Bragg gratings on the oscillator output energy transmission fiber form a cascade chirped inclined fiber Bragg grating.
Preferably, the third grating and the higher-order mode filter are directly written on different positions on the gain fiber of the amplifier by femtosecond laser. The chirped inclined fiber Bragg gratings on the amplifier gain fiber are distributed in a plurality, and the plurality of chirped inclined fiber Bragg gratings on the amplifier gain fiber form a cascaded chirped inclined fiber Bragg grating. The cladding waveguide is etched in the cladding outside the fiber core of the optical fiber at the position of the high-order mode filter by femtosecond laser, the cladding waveguide has a certain length, the length direction of the cladding waveguide is consistent with the length direction of the optical fiber, and mode coupling is realized by energy overlapping between respective evanescent fields of the fiber core and the cladding waveguide. A certain distance is arranged between the fiber core and the cladding waveguideAnd the space is within 20 mu m. Furthermore, cladding waveguides with certain lengths are engraved in the outer claddings in the x direction and the y direction of the optical fiber core of the high-order mode filter, and LP in the core11aMode coupling to fundamental mode of cladding waveguide in x-direction, LP in core11bThe mode couples with the fundamental mode of the cladding waveguide in the y-direction. High-order mode filter capable of realizing LP in fiber core11Fundamental mode coupling in mode-to-cladding waveguides reduces LP in the core11And the mode inhibits the formation of the thermotropic grating and improves the threshold value of the TMI effect.
Preferably, the fourth grating is a chirped tilted fiber bragg grating written on the output energy transmission fiber of the amplifier by an ultraviolet exposure method or a femtosecond laser phase template method. The chirped inclined fiber Bragg gratings on the amplifier output energy transmission fiber are distributed in a plurality, and the plurality of chirped inclined fiber Bragg gratings on the amplifier output energy transmission fiber form a cascaded chirped inclined fiber Bragg grating. Or the chirped inclined fiber Bragg gratings are engraved on the output energy transmission fibers of the whole amplifier to form the distributed chirped inclined fiber Bragg gratings.
Preferably, the first grating and the third grating in the present invention may also be long period fiber gratings written on the oscillator gain fiber by femtosecond.
Preferably, the second grating and the fourth grating in the present invention may also be formed by femtosecond laser or ultraviolet exposure or CO2Laser-written long-period fiber grating.
Preferably, the oscillator gain fiber and the amplifier gain fiber of the present invention both use ytterbium-doped fibers.
The utility model has the advantages of as follows:
the utility model discloses a femto second laser inscribes the suppression that chirp slope optic fibre bragg grating realized the SRS effect in the fibre core of doping ytterbium optic fibre and biography ability optic fibre. In addition, a high-order mode filtering device is etched in the ytterbium-doped optical fiber through the femtosecond direct writing technology, so that LP is realized11The mode is filtered out, thereby increasing the threshold of the TMI effect.
The utility model provides an oscillator has the inhibit function of SRS effect and TMI effect simultaneously, and output can obtain promoting.
The utility model provides an all devices can all process through femto second laser in the amplifier, have avoided optic fibre to carry hydrogen and can directly process on gain optic fibre, and quantity that can effectual reduction melting point has avoided generating heat of melting point. Specifically, the chirped and tilted fiber bragg grating and the high-order mode filter are processed by a femtosecond laser. A high-order mode filter capable of realizing LP in the fiber core11Fundamental mode coupling in mode-to-cladding waveguides reduces LP in the core11And the mode inhibits the formation of the thermotropic grating and improves the threshold value of the TMI effect.
The utility model provides an all pumping beam combiners all adopt the mode of side pump, can further promote system's efficiency.
To sum up, the utility model discloses have advantages such as the integrated level is high, the melting point is few, can reduce SRS effect and TMI effect to the influence of system, avoided extra melting point to generate heat to the output of booster amplifier.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a light path diagram of example 1.
FIG. 2 is a schematic diagram of the transverse cross-sectional refractive index profiles of a high reflection fiber Bragg grating and a low reflection fiber Bragg grating;
FIG. 3 is a schematic diagram of a lateral in-plane refractive index profile of a high order mode filter.
Figure 4 is a schematic diagram of a cascaded chirped tilted fiber bragg grating.
Figure 5 is a schematic diagram of a distributed chirped tilted fiber bragg grating.
Figure 6 is a schematic diagram of a series chirped tilted fiber bragg grating.
The reference numbers in the figures illustrate:
Rcore: the core radius of the double-clad optical fiber; rgrating: the radius of the refractive index modulation region of the fiber Bragg grating; c1: a core of a double-clad ytterbium-doped fiber; c2: a cladding waveguide; r is1: the radius of the inner cladding of the double-clad ytterbium-doped fiber; r is2: the core radius of the double-clad ytterbium-doped fiber; r is3: a cladding waveguide radius; d: the spacing between the core and the cladding waveguide;
1: pumping beam combiner on the side of oscillator; 2: high reflection fiber bragg gratings; 3: a first grating; 4: an oscillator ytterbium-doped fiber; 5: a low reflection fiber Bragg grating; 6: pouring a pump; 7. a second grating; 8: the positive side of the amplifier pumps the beam combiner; 9: a third grating; 10: a high order mode filter; 11: an amplifier ytterbium-doped fiber; 12: the amplifier reverse side pumps the beam combiner; 13: a fourth grating; 14: and (4) welding points.
Detailed Description
In order to make the technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.
Example 1:
the embodiment provides a high-power fiber laser amplifier system which comprises an oscillator and an amplifier.
The oscillator comprises an oscillator pumping unit, a high reflection optical fiber Bragg grating 2, a first grating 3, an oscillator ytterbium-doped optical fiber 4, a low reflection optical fiber Bragg grating 5, a pumping dump 6 and a second grating 7. The amplifier comprises an amplifier forward pumping unit, a third grating 9, a high-order mode filter 10, an amplifier ytterbium-doped fiber 11, an amplifier backward pumping unit and a fourth grating 13.
The pumping fibers of the pumping light sources in the oscillator pumping unit form an oscillator side pumping beam combiner 1 in a mode of tapering and fusing the pumping fibers to the input energy transmission fibers of the oscillator. The 976nm pump light enters the resonator of the oscillator through the side pumping beam combiner 1 of the oscillator, and the pump fiber of each pump light source is 105/125 fiber. The high reflection optical fiber Bragg grating 2 is directly inscribed on the input energy transmission optical fiber. The input optical energy fiber is fused to one end of the ytterbium-doped fiber 4 of the oscillator to form a fusion point 14. The oscillator ytterbium-doped fiber 4 is inscribed with a first grating 3 for inhibiting the stimulated Raman effect in the cavity. The first grating 3 is a chirped tilted fibre bragg grating. The chirped and tilted fiber bragg grating is written on the ytterbium-doped fiber 4 of the oscillator by femtosecond laser lithography, the first grating 3 can inhibit the SRS effect in the cavity of the oscillator,
the other end of the ytterbium-doped oscillator fiber 4 is welded with the oscillator output energy transmission fiber to form a welding point 14. The low reflection fiber Bragg grating 5 and the second grating 7 are arranged on the same optical fiber, namely on the output energy transmission optical fiber, and a pump pouring 6 exists between the low reflection fiber Bragg grating 5 and the second grating 7. The second grating 7 is a chirped and tilted fiber bragg grating, which can play a role in suppressing the SRS and prevent the light of the SRS from entering the amplifier. The high reflection fiber Bragg grating 2, the low reflection fiber Bragg grating 5 and the second grating 7 can be written by an ultraviolet exposure method or a femtosecond laser phase template method, and the optical fibers of the oscillator part can be 10/125, 15/130 and 20/400.
The pumping fibers of the pumping light sources in the forward pumping unit of the amplifier form a forward side pumping beam combiner 8 of the amplifier in a mode that a tapering is fused on the input energy transmission fiber of the amplifier. The pump fibers of the pump light sources in the amplifier back pumping unit form an amplifier back side pumping beam combiner 12 in a mode that the tapering is fused on the output energy transmission fiber of the amplifier.
The laser output from the oscillator is used as a seed source and input into the amplifier through the amplifier forward side pumping beam combiner 8. The third grating 9 and the high-order mode filter 10 are written on the amplifier ytterbium-doped fiber 11 by femtosecond laser. The third grating 9 is a chirped tilted fiber bragg grating. The third grating 9 and the higher order mode filter 10 act to suppress the SRS and TMI effects, respectively. The amplified laser light is output through an amplifier reverse side pump combiner 12. A fourth grating 13 is engraved on the amplifier output energy-transmitting optical fiber by an ultraviolet exposure method or a femtosecond laser phase template method, the fourth grating 13 is a chirped inclined fiber Bragg grating array, and the fourth grating is used for SRS filtering. The optical fibers used by the amplifier can be 20/400, 25/400, 30/400, 30/600 and the like, the used pump optical fibers are different according to different input powers, if the output power is 5kW, the pump optical fibers are 20/400 and the like, if the output power is more than 10kW, the pump optical fibers are 220/242 and the like, the number of pump arms can be properly increased according to needs to improve the pump power, and a side pump beam combiner in the system can be replaced by an end pump beam combiner according to actual situations.
Referring to fig. 2, the transverse cross-sectional refractive index profiles of the high reflection fiber bragg grating and the low reflection fiber bragg grating are illustrated. Wherein R iscoreThe radius of the double-clad optical fiber core; rgratingThe radius of the refractive index modulation region of the fiber Bragg grating. The fiber cores of the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating are provided with circular refractive index modulation regions concentric with the fiber cores, the radius of the refractive index modulation regions is smaller than that of the fiber cores, the refractive index modulation regions and the fiber vector mode are circularly symmetrical, and the LP01Mold and LP11Modes do not couple with each other, and LP11The self-coupling coefficient of the mode is lower than LP01Self-coupling coefficient of mode, LP11Reflectivity of the mode lower than LP01The reflectivity of the mode.
In order to suppress the TMI effect, the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating as the cavity mirror need to be aligned to LP01The mold has high reflection to LP11The reflectivity of the mode is low due to LP11The center of the mode is a phase singularity, the intensity distribution near this point is close to 0, and LP01The mode presents Gaussian-like distribution, the intensity near the center is maximum, therefore, the transverse refractive index distribution of the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating is a circle concentric with the fiber core, and LP can be ensured01Reflectivity of the mode higher than LP11Reflectivity of the mode, and at such index profile, no mutual coupling between the two core modes can occur to avoid LP01Axial LP11Conversion of the mode by which the LP in the oscillation chamber is lifted11Threshold value of oscillation is started, and LP is ensured01The threshold of the mode is low, causing LP01The modes dominate in the transverse mode competition, suppressing the occurrence of TMI effects.
FIG. 3 is a high order mode filter transverse plane optical path. Fiber core C of double-cladding ytterbium-doped fiber at high-order mode filter inscribing position1A cladding waveguide C is inscribed in the outer cladding by femtosecond laser2Said clad waveguide C2Having a length, said clad waveguide C2The length direction of the double-clad ytterbium-doped fiber is consistent with that of the double-clad ytterbium-doped fiber, and the fiber core C of the double-clad ytterbium-doped fiber1And a clad waveguide C2Mode coupling is achieved by energy overlap between the respective evanescent fields. Core C of the double-cladding ytterbium-doped optical fiber1And a clad waveguide C2With a certain distance between them, the distance is within 20 μm. The radius of the inner cladding of the double-clad ytterbium-doped fiber is r1. The core radius of the double-clad ytterbium-doped fiber is r2. Radius of cladding waveguide is r3。
Directly writing cladding waveguide in the cladding outside the fiber core by femtosecond laser, wherein the cladding waveguide only supports fundamental mode transmission, and when the refractive index n of the cladding waveguide31.46017, the phase matching condition is satisfied, i.e. the core LP11The effective refractive index of the mode is the same as the effective refractive index of the cladding waveguide fundamental mode. When the distance D between the fiber core and the cladding waveguide is 15 μm, and the length of the cladding waveguide is 1.967mm, LP in the fiber core can be realized to the maximum extent11The mode is coupled to the waveguide, and the energy in the waveguide is finally transmitted to the cladding and filtered by the cladding light filter.
Figure 4 is a schematic diagram of a cascaded chirped tilted fiber bragg grating. The first grating 3 and the third grating 9 in fig. 1 may be formed by a plurality of chirped tilted fiber bragg gratings distributed on the corresponding ytterbium-doped fiber, so as to form a cascaded chirped tilted fiber bragg grating. Similarly, the second grating and the fourth grating in fig. 1 may be formed by a plurality of chirped tilted fiber bragg gratings distributed on the corresponding output energy-transmitting fibers, so as to form a cascaded chirped tilted fiber bragg grating.
The resonant wavelengths of the chirped and inclined fiber Bragg gratings can be the same so as to increase the depth of SRS inhibition, a certain interval can exist between the resonant wavelengths of the chirped and inclined fiber Bragg gratings so as to increase the inhibition bandwidth, the number of the cascaded chirped and inclined fiber Bragg gratings can be two, three or even more, the cascaded chirped and inclined fiber Bragg gratings on the ytterbium-doped fiber are inscribed through femtosecond laser, and the cascaded chirped and inclined fiber Bragg gratings on the output energy-transfer fiber are inscribed through femtosecond laser inscription or ultraviolet exposure.
Fig. 5 is a schematic diagram of a distributed chirped tilted fiber bragg grating, and the first grating 3 in fig. 1 may be a chirped tilted fiber bragg grating distributed on the entire ytterbium-doped fiber to form the distributed chirped tilted fiber bragg grating. Similarly, the fourth grating 13 in fig. 1 may be a chirped tilted fiber bragg grating distributed on the entire output energy-transmitting fiber, so as to form a distributed chirped tilted fiber bragg grating.
Because the SRS effect can occur at any position of the oscillator, the distributed chirped inclined fiber Bragg grating is engraved on the ytterbium-doped fiber or the energy transmission fiber through the femtosecond laser, and the SRS effect can be effectively inhibited at any position of the fiber.
Fig. 6 is a schematic diagram of a series chirped tilted fiber bragg grating, where unlike the cascaded chirped tilted fiber bragg grating in fig. 4, a certain distance may exist between any two chirped tilted fiber bragg gratings in a series structure. The resonant wavelength of each chirped tilted fiber bragg grating may be the same to increase the depth of suppression for SRS. Certain intervals can exist among the resonant wavelengths of the chirped and inclined fiber Bragg gratings to increase the suppression bandwidth, and the number of the chirped and inclined fiber Bragg gratings connected in series can be two, three or even more. The chirped and inclined fiber Bragg grating connected in series on the ytterbium-doped fiber is inscribed through femtosecond laser, and the chirped and inclined fiber Bragg grating connected in series on the output energy-transfer fiber is inscribed through femtosecond laser inscription or an ultraviolet exposure method.
In summary, although the present invention has been described with reference to the preferred embodiments, it should be understood that the present invention is not limited thereto, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention.
Claims (10)
1. High power fiber laser amplifier system, including oscillator and amplifier, its characterized in that: a high-reflection grating and a low-reflection grating in an oscillator are directly inscribed on an oscillator input energy transmission optical fiber and an oscillator output energy transmission optical fiber respectively, the oscillator input energy transmission optical fiber is welded with one end of an oscillator gain optical fiber, a first grating for inhibiting the stimulated Raman effect in a cavity is directly inscribed on the oscillator gain grating, the other end of the oscillator gain optical fiber is welded with an oscillator output energy transmission optical fiber, and a second grating for inhibiting the pump dumping and the SRS effect is inscribed on the oscillator output energy transmission optical fiber; the oscillator output energy transmission fiber is welded with the amplifier input energy transmission fiber, the amplifier input energy transmission fiber is welded with one end of the amplifier gain fiber, a third grating for inhibiting the stimulated Raman effect in the cavity and a high-order mode filter are directly inscribed on the amplifier gain fiber, and a fourth grating for inhibiting the SRS effect is inscribed on the amplifier output energy transmission fiber.
2. The high power fiber laser amplifier system of claim 1, wherein: the side pumping beam combiner is formed by the mode that the pumping fibers of the pumping light sources in the pumping units in the oscillator and the amplifier are fused to the energy transmission fiber in a tapering manner.
3. The high power fiber laser amplifier system of claim 2, wherein: the oscillator is a forward pumping fiber laser oscillator, a backward pumping fiber laser oscillator or a bidirectional pumping fiber laser oscillator; the pump unit in the forward pump fiber laser oscillator is a forward pump unit, and pump fibers of all pump light sources in the forward pump unit form a side pump beam combiner in a mode of tapering and fusing the pump fibers to input energy-transmitting fibers; the pump unit in the backward pump fiber laser oscillator is a backward pump unit, and the pump fibers of all pump light sources in the backward pump unit form a side pump beam combiner in a mode of tapering and fusing on the output energy-transfer fibers; the pump unit in the bidirectional pump fiber laser oscillator comprises a forward pump unit and a backward pump unit, the pump fibers of all pump light sources in the forward pump unit form a side pump beam combiner in a mode of tapering and fusing on the input energy-transmitting fibers, and the pump fibers of all pump light sources in the backward pump unit form a side pump beam combiner in a mode of tapering and fusing on the output energy-transmitting fibers.
4. The high power fiber laser amplifier system of claim 2, wherein: the amplifier comprises an amplifier forward pumping unit and an amplifier backward pumping unit, wherein pumping fibers of all pumping light sources in the amplifier forward pumping unit form a side pumping beam combiner in a mode that a taper is fused on an input energy-transmitting fiber of the amplifier, and pumping fibers of all pumping light sources in the amplifier backward pumping unit form the side pumping beam combiner in a mode that the taper is fused on an output energy-transmitting fiber of the amplifier.
5. The high power fiber laser amplifier system according to any of claims 1 to 4, wherein: the high reflection grating is a high reflection fiber Bragg grating directly written on the energy transmission fiber input by the oscillator by an ultraviolet exposure method or a femtosecond laser phase template method; the low reflection grating is a low reflection fiber Bragg grating directly written on the output energy transfer fiber of the oscillator by an ultraviolet exposure method or a femtosecond laser phase template method.
6. The high power fiber laser amplifier system of claim 5, wherein: the fiber cores of the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating are internally provided with circular refractive index modulation regions concentric with the fiber cores, the radius of the refractive index modulation regions is smaller than that of the fiber cores, the refractive index modulation regions and the fiber vector modes are circularly symmetrical, the LP01 mode and the LP11 mode cannot be mutually coupled, the self-coupling coefficient of the LP11 mode is lower than that of the LP01 mode, and the reflectivity of the LP11 mode is lower than that of the LP01 mode.
7. The high power fiber laser amplifier system of claim 5, wherein: the first grating is a chirped inclined fiber Bragg grating directly written on the gain fiber of the oscillator through femtosecond laser;
a plurality of chirped inclined fiber Bragg gratings are distributed on the oscillator gain fiber, and the plurality of chirped inclined fiber Bragg gratings on the oscillator gain fiber form a cascaded chirped inclined fiber Bragg grating; or, the whole oscillator gain fiber is engraved with the chirped inclined fiber Bragg grating to form the distributed chirped inclined fiber Bragg grating.
8. The high power fiber laser amplifier system of claim 5, wherein: the second grating is a chirped inclined fiber Bragg grating which is written on the energy transmission fiber output by the oscillator by an ultraviolet exposure method or a femtosecond laser phase template method; the chirped inclined fiber Bragg gratings on the oscillator output energy transmission fiber are distributed in a plurality, and the plurality of chirped inclined fiber Bragg gratings on the oscillator output energy transmission fiber form a cascade chirped inclined fiber Bragg grating.
9. The high power fiber laser amplifier system of claim 5, wherein: the third grating and the high-order mode filter are directly inscribed on different positions on the gain fiber of the amplifier through femtosecond laser;
a plurality of chirped inclined fiber Bragg gratings are distributed on the amplifier gain fiber, and the plurality of chirped inclined fiber Bragg gratings on the amplifier gain fiber form a cascaded chirped inclined fiber Bragg grating;
the cladding waveguide is etched in the cladding outside the fiber core of the optical fiber at the position of the high-order mode filter by femtosecond laser, the cladding waveguide has a certain length, the length direction of the cladding waveguide is consistent with the length direction of the optical fiber, and mode coupling is realized by energy overlapping between respective evanescent fields of the fiber core and the cladding waveguide.
10. The high power fiber laser amplifier system of claim 5, wherein: the fourth grating is a chirped inclined fiber Bragg grating which is written on the output energy transmission fiber of the amplifier by an ultraviolet exposure method or a femtosecond laser phase template method;
a plurality of chirped inclined fiber Bragg gratings are distributed on the amplifier output energy transmission fiber, and the plurality of chirped inclined fiber Bragg gratings on the amplifier output energy transmission fiber form a cascade chirped inclined fiber Bragg grating; or the chirped inclined fiber Bragg gratings are engraved on the output energy transmission fibers of the whole amplifier to form the distributed chirped inclined fiber Bragg gratings.
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| CN114204389A (en) * | 2021-11-24 | 2022-03-18 | 四川橙科通信技术研究院有限责任公司 | Fiber grating string structure and preparation method thereof |
| CN116316001A (en) * | 2022-12-30 | 2023-06-23 | 长沙大科光剑科技有限公司 | Few-mode fiber Bragg grating capable of filtering high-order modes and fiber oscillator |
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| CN113296185A (en) * | 2021-06-28 | 2021-08-24 | 中国工程物理研究院激光聚变研究中心 | Optical fiber with cascade structure grating and preparation method thereof |
| CN114204389A (en) * | 2021-11-24 | 2022-03-18 | 四川橙科通信技术研究院有限责任公司 | Fiber grating string structure and preparation method thereof |
| CN116316001A (en) * | 2022-12-30 | 2023-06-23 | 长沙大科光剑科技有限公司 | Few-mode fiber Bragg grating capable of filtering high-order modes and fiber oscillator |
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