CN112886374A - Fiber laser for inhibiting stimulated Raman scattering effect and manufacturing method thereof - Google Patents
Fiber laser for inhibiting stimulated Raman scattering effect and manufacturing method thereof Download PDFInfo
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Abstract
The utility model provides a fiber laser of suppression stimulated raman scattering effect includes semiconductor pump source, active fiber, the semiconductor pump source with active fiber is connected, fiber laser still include at least a pair of setting respectively the first grating of active fiber input side and output side, and set up at least one slope grating of active fiber output side, first grating with at least one in the slope grating sets up through carving the mode active fiber is last. The fiber laser method for inhibiting the stimulated Raman scattering effect adjusts the laser source according to the preset laser power and the irradiation time, and at least one grating in the pair of first gratings and the at least one inclined grating is etched at the position of the active fiber where the grating is to be etched. This application is based on the fiber grating of active optical fiber inscription different functions, not only can further reduce the splice point of laser instrument, reduces the butt fusion loss, makes the laser instrument compacter, improves laser instrument efficiency, can also restrain stimulated raman scattering effect simultaneously.
Description
Technical Field
The present disclosure relates to laser devices, and particularly to a fiber laser for suppressing stimulated raman scattering effect and a method for manufacturing the same.
Background
Compared with the traditional solid laser, the optical fiber laser has the advantages of high optical-to-optical conversion efficiency, good beam quality, compact structure, good heat dissipation performance and the like. With the development of fiber laser technology and the maturity of matched fiber devices, the output power of fiber lasers is higher and higher. High-power fiber lasers have been widely used in the fields of metal cutting, welding, cladding, national defense, scientific research, and the like. The stimulated raman scattering effect is one of the main factors that currently limit the further increase of the power of the fiber laser. Therefore, in the field of high-power fiber lasers, it is one of the hot topics of research at present to improve the efficiency of the laser and suppress the stimulated raman scattering effect.
In the fiber laser, the threshold value of the continuous wave stimulated raman scattering can be calculated by the following formula:
wherein A iseffIs the effective mode field area, g, of the optical fiberR(omega) is the Raman gain coefficient of the fiber, LeffIs the effective length of the optical fiber. As can be seen from the above formula, the effective mode field area A of the optical fiber is increasedeffOr reducing the effective length L of the optical fibreeffThe threshold value of the stimulated Raman scattering effect can be effectively improved, so that the purpose of inhibiting the stimulated Raman scattering effect is achieved. Increasing the effective mode field area A of the optical fibereffThere are two general approaches: firstly, the diameter of the fiber core of the optical fiber is directly increased. However, as the core diameter increases, it becomes difficult for the laser to maintain single mode output, and the beam quality gradually deteriorates. And secondly, adopting the optical fiber with a special structure. Such as a Photonic Crystal Fiber (PCF). Reducing the effective length L of the optical fibereffThe commonly used method is as follows: properly improve the doping concentration of the active optical fiber, ensure that the active optical fiber fully absorbs the pump light and simultaneously shorten the active timeThe length of the optical fiber.
In addition to the above method of directly increasing the threshold of stimulated raman scattering, the stimulated raman scattering spectrum can also be filtered out by using a spectrum control technique. For example, the spectral filtering is performed using a Tilted Fiber Bragg Grating (TFBG). The current common scheme is as follows: and the grating pair is welded at two ends of the active optical fiber to form a resonant cavity, and the inclined grating TFBG is welded in the resonant cavity or outside the resonant cavity to filter the stimulated Raman scattering spectrum. Each device is connected with the other device through a welding mode. However, the more fusion points of the optical fiber in the optical fiber laser, the higher fusion loss of the optical fiber is introduced, and the output efficiency of the entire laser is also affected. In addition, the more optical fiber devices are introduced, the longer the tail fiber of the device is, and the stimulated Raman scattering threshold of the laser is also reduced.
Based on the problems and limitations existing at present, it is necessary to provide a fiber laser which can effectively improve the threshold value of the stimulated raman scattering effect and inhibit the stimulated raman scattering effect.
Disclosure of Invention
The application aims to provide a fiber laser and a manufacturing method thereof, wherein the threshold value of the stimulated Raman scattering effect can be effectively improved, and the stimulated Raman scattering effect can be inhibited.
To achieve the above object, the present application provides a fiber laser suppressing a stimulated raman scattering effect, comprising: the optical fiber laser comprises a semiconductor pumping source LD and an active optical fiber, wherein the semiconductor pumping source LD is connected with the active optical fiber, the optical fiber laser further comprises at least one pair of first gratings respectively arranged at the input side and the output side of the active optical fiber, and at least one inclined grating arranged at the output side of the active optical fiber, and at least one of the first gratings and the inclined gratings is arranged on the active optical fiber in a writing mode.
The application provides a fiber laser, active fiber wherein on carve write with the grating, can carve write one or more grating on the active fiber, reduced the splice point, simultaneously fiber laser be equipped with slope grating TFBG, restrain common stimulated Raman scattering effect among the high power laser when reducing laser instrument splice point loss. The grating inscribed on the active fiber can be a common grating, and the inclined grating can also be inscribed on the active fiber.
The semiconductor pump source is connected with the active optical fiber, and may be directly connected, or the output end of the semiconductor pump source is connected with the active optical fiber through a passive optical fiber. Specifically, in some embodiments, a plurality of pump sources are provided, and after the plurality of pump sources pass through the beam combiner, the output end of the beam combiner is fusion-spliced with the active optical fiber by a passive optical fiber.
In some embodiments, the at least one pair of first gratings comprises a high-reflectivity grating HR-FBG and a low-reflectivity grating LR-FBG, the high-reflectivity grating and the low-reflectivity grating form a grating pair serving as an input cavity mirror and an output cavity mirror of the resonant cavity, and the high-reflectivity grating and/or the low-reflectivity grating are/is written on the active fiber, that is, either one of the high-reflectivity grating and the low-reflectivity grating is/are written on the active fiber, or the high-reflectivity grating and the low-reflectivity grating are written on the active fiber. In these embodiments, the tilted gratings may be written on the active fiber simultaneously, or may be connected by fusion. In a specific embodiment, the high reflective grating is written on the input side of the active optical fiber, and/or the low reflective grating is written on the output side of the active optical fiber.
In some specific embodiments, the high reflective grating is etched at a position 5-30 cm away from the input end of the active optical fiber, and/or the low reflective grating is etched at a position 5-30 m away from the output end of the active optical fiber. The specific writing position can be adjusted according to actual needs and is not limited to the numerical range.
In some embodiments, the high-reflectivity grating and the low-reflectivity grating are written on the active fiber while at least one tilted grating is also written on the active fiber. Specifically, a plurality of the slanted gratings may be written on the active fiber as needed. In some specific embodiments, the high reflective grating is etched at a position 5-30 cm away from the input end of the active optical fiber, the low reflective grating is etched at a position 10-30 cm away from the output end of the active optical fiber, and the inclined grating is etched at a position 5-20 cm away from the output end of the active optical fiber. The specific writing position can be adjusted according to actual needs, and is not limited to the numerical range.
In a specific embodiment, the number of the semiconductor pump sources LD is plural, the optical fiber laser further includes a beam combiner, and output lasers of the plural semiconductor pump sources are combined together by the beam combiner.
In a specific embodiment, the active optical fiber output end is further connected with a transmission optical fiber or an optical fiber end cap. The semiconductor pump source LD, the active optical fiber engraved with the grating, the transmission optical fiber or the optical fiber end cap are connected together by an optical fiber fusion method.
In some embodiments, the active fiber is any one of an ytterbium-doped fiber, a praseodymium-doped fiber, an erbium-doped fiber, a thulium-doped fiber, and a holmium-doped fiber.
The present application further provides a method for manufacturing a fiber laser for suppressing the stimulated raman scattering effect, which includes:
providing a semiconductor pump source and an active optical fiber connected,
a pair of first gratings is arranged at the input side and the output side of the active optical fiber, at least one inclined grating is arranged at the output side of the active optical fiber,
after passing through a plano-convex cylindrical lens and a phase mask plate, the collimated laser is focused to the position of the active optical fiber where a grating is to be etched;
and adjusting a laser source according to preset laser power and irradiation time, and writing at least one grating in the pair of first gratings and the at least one inclined grating at the position of the grating to be written of the active optical fiber.
The laser source can adopt a femtosecond laser or an excimer laser and the like for writing a fiber grating.
In some embodiments, the writing method further includes: connecting a test light source with an input end of an active optical fiber, and connecting a spectrometer with an output end of the active optical fiber; and in the grating writing process, online monitoring is carried out through a test light source, and the laser is adjusted by matching with a spectrometer.
In some embodiments, the diffraction spot is coincident with the active fiber by adjusting the multi-dimensional fiber alignment jig.
In some embodiments, a high-reflection grating, and/or a low-reflection grating, and/or a tilted grating is written on the active fiber. In some specific embodiments, a high-reflectivity grating is written on the input side of the active optical fiber, and/or a low-reflectivity grating is written on the output side of the active optical fiber, and/or a tilted grating is written on the output side of the active grating. Specifically, in addition to the grating disposed by writing, other gratings in specific embodiments may also be disposed on the active fiber by writing or fusing.
Has the advantages that: be different from prior art's condition, this application not only can further reduce the splice point of laser instrument based on active optical fiber inscription fiber grating, reduces the butt fusion loss, makes the laser instrument compacter, improves laser instrument efficiency, can also restrain stimulated raman scattering effect simultaneously.
One or more gratings can be inscribed on the active optical fiber, so that the number of welding points is reduced, meanwhile, the fiber laser is provided with the inclined grating TFBG, and the common stimulated Raman scattering effect in a high-power laser is inhibited while the loss of the welding points of the laser is reduced. The grating inscribed on the active fiber can be a common grating, and the inclined grating can also be inscribed on the active fiber.
Drawings
FIG. 1 is a schematic diagram of an embodiment of a fiber laser for suppressing stimulated Raman scattering (SSSD) effect according to the present application;
FIG. 2 is a schematic diagram of a second embodiment of a fiber laser for suppressing stimulated Raman scattering effect according to the present application;
FIG. 3 is a schematic diagram of an embodiment of a fiber laser for suppressing stimulated Raman scattering effect according to the present application;
fig. 4 is a schematic diagram of grating writing in the present application.
Detailed Description
In order to make the technical solutions of the present application better understood by those skilled in the art, the present application is described in further detail below with reference to the accompanying drawings and the detailed description.
Referring to fig. 1 to 3, the fiber laser for suppressing the stimulated raman scattering effect of the present application includes: the optical fiber laser comprises a semiconductor pumping source LD, an active optical fiber, a transmission optical fiber or an optical fiber end cap, wherein the semiconductor pumping source LD, the active optical fiber, the transmission optical fiber or the optical fiber end cap are sequentially connected to form the optical fiber laser, the optical fiber laser comprises at least one pair of first gratings and at least one inclined grating TFBG, the first gratings and the inclined gratings are arranged on the active optical fiber in a writing mode. The at least one pair of first gratings comprises a high anti-grating HR-FBG and a low reflective grating LR-FBG, namely, at least one of the high anti-grating HR-FBG, the low reflective grating LR-FBG and the inclined grating is inscribed on the active optical fiber.
The fiber laser for inhibiting the stimulated Raman scattering effect has various embodiments, wherein one or more gratings can be inscribed on the active fiber, so that the number of welding points is reduced, meanwhile, the fiber laser is provided with the inclined gratings, and the common stimulated Raman scattering effect in the high-power laser is inhibited while the loss of the welding points of the laser is reduced. The grating inscribed on the active fiber can be a common grating, and the inclined grating can also be inscribed on the active fiber.
The fiber laser may include a plurality of semiconductor pump sources LD, and further include a beam combiner, by which output lasers of the plurality of semiconductor pump sources LD are combined together.
In the embodiment of the application, the high-reflection grating and the low-reflection grating form a grating pair serving as an input cavity mirror and an output cavity mirror of a resonant cavity, the high-reflection grating is highly reflective to signal light, and the low-reflection grating is lowly reflective to the signal light. The tilted grating TFBG can filter out stimulated Raman scattering spectra.
As shown in fig. 1, in the first embodiment, the semiconductor pumping sources 101 are combined together through a beam combiner 201, an output end of the beam combiner is connected to an input end of a source optical fiber 401, a high reflective grating 301 is inscribed at a position, close to the input end, of the source optical fiber 401, an output end of the source optical fiber 401 is sequentially connected to a low reflective grating 501 and an inclined grating 601, and the low reflective grating 501 and the inclined grating 601 are inscribed on a passive optical fiber.
Specifically, the semiconductor pump source 101 is connected to the active fiber through a passive fiber after being combined by the beam combiner 201. Specifically, the input end and the output end of the active optical fiber are respectively the welding point positions of the input side and the output side of the active optical fiber and the passive optical fiber. The input and output refer to the input and output of the pump light.
In a specific embodiment, the high-reflectivity grating 301 is written on the active fiber 401 10cm away from the input end. The distance between the writing position and the input end is determined according to specific conditions, and the optional range is approximately 5-30 cm away from the input end.
In this embodiment, the active fiber is an ytterbium-doped double-clad fiber.
As an alternative embodiment, the low reflectivity grating 601 may also be written on the active fiber 401 near the output end.
Referring to fig. 4 in combination, a method for manufacturing a fiber laser for suppressing stimulated raman scattering effect according to the present application includes:
providing a semiconductor pump source 101 and an active optical fiber 401, wherein the semiconductor pump source is fused with the active optical fiber 401 through a passive optical fiber after being combined by a beam combiner 201;
a high reflecting grating 301 is engraved on the input side of the active optical fiber, and a low reflecting grating 501 and an inclined grating 601 are sequentially connected on the output side of the active optical fiber and can be connected in a fusion mode;
the method for writing the high-reflectivity grating comprises the following steps:
after passing through a plano-convex cylindrical lens and a phase mask plate, the collimated laser is focused to the position of the active optical fiber where a grating is to be etched;
and adjusting a laser source according to preset laser power and irradiation time, and writing the high-reflection grating 301 at the position of the active optical fiber grating to be written.
Specifically, the laser used for writing may be a femtosecond laser. Specifically, the fiber grating writing platform may be first set up before writing the optical fiber: and welding an output tail fiber of the test light source with the input end of the ytterbium-doped double-clad fiber, and welding the spectrometer with the output end of the ytterbium-doped double-clad fiber. And focusing the collimated femtosecond laser to a fiber core at the position of about 10cm away from the input end of the ytterbium-doped double-clad fiber through a plano-convex cylindrical lens, and adjusting a multi-dimensional fiber adjusting frame to keep the phase mask plate and the active fiber parallel and tightly attached.
Then, writing a grating on line: and turning on the test light source and setting power. The power and the irradiation time of the femtosecond light source are adjusted by matching with the spectrometer. And writing a high-return grating HR-FBG with the signal light reflectivity of more than or equal to 99% into the fiber core at the position of about 10cm away from the input end of the ytterbium-doped double-clad fiber. Or writing a low-return grating LR-FBG with the signal light reflectivity less than or equal to 10% into the fiber core at the position of about 10cm away from the output end of the ytterbium-doped double-clad fiber. The distance range is determined according to specific conditions, and the selectable range is about 5-30 cm.
After the active optical fiber is well engraved, the laser is built: as shown in fig. 1, a pump light source LD, a Combiner, an ytterbium-doped double-clad fiber with an HR-FBG for high return of signal light, an LR-FBG for low return of signal light, and a tilted grating TFBG for filtering a stimulated raman scattering spectrum are connected in sequence by a fusion method. The scheme is characterized in that a grating is engraved on the ytterbium-doped double-clad optical fiber, and 1 welding point can be reduced compared with the traditional scheme.
For a common fiber bragg grating FBG, coupling occurs between a forward-transmission core mode and a backward-transmission core mode of the grating, so that energy of the forward-transmission core mode is transferred to the backward-transmission core mode, thereby forming reflection of an incident wave. The reflection wavelength is the Bragg wavelength and can be calculated by the following formula:
wherein λ isBIn the form of a bragg wavelength, and,
is the effective refractive index of the fiber core model, and the lambda is the grating period.
For the tilted fiber bragg grating TFBG, the common fiber bragg grating FBG is similar, and the fiber core in the grating region exhibits periodic refractive index modulation along the axial direction of the optical fiber, except that a certain tilt angle exists between the grating plane of the tilted fiber bragg grating TFBG and the axial direction of the optical fiber. The bragg wavelength can be calculated by the following formula:
and theta is an axial included angle between the grating plane in the fiber core and the optical fiber. Under the action of the inclination angle, part of forward-transmitted core mode energy is coupled into backward-transmitted cladding mode, and the corresponding wavelengths are as follows:
wherein,
the effective refractive index of the ith cladding mode. And the fiber bragg grating TFBG is inclined by selecting a proper included angle, so that the stimulated Raman scattering light transmitted backwards can be coupled to the cladding and consumed, and the stimulated Raman scattering effect is filtered. Therefore, the tilted fiber grating TFBG can be used as a Raman filter to filter out Raman components in the output laser spectrum.
As shown in fig. 2, in the second embodiment, the semiconductor pump sources 102 are combined together by the beam combiner 202, the output end of the beam combiner is connected to the input end of the active optical fiber 402, the high reflective grating 302 is engraved at the position, close to the input end, of the active optical fiber 402, the low reflective grating 502 is engraved at the position, close to the input end, of the active optical fiber 402, the output end of the active optical fiber 402 is connected to the tilted grating 602, and the tilted grating 602 is engraved on the passive optical fiber.
In a specific embodiment, the high-reflectivity grating 302 is written on the active fiber 402 at a distance of 10cm from the input end, the writing position of the high-reflectivity grating may be determined according to specific situations, and the selectable range may be 5-30 cm from the input end of the active fiber. The low reflective grating 502 is etched on the active optical fiber 402 10cm away from the output end, the etching position of the low reflective grating can be determined according to specific conditions, and the optional range can be 5-30 cm away from the output end of the active optical fiber.
Referring to fig. 4 in combination, a method for manufacturing a fiber laser for suppressing stimulated raman scattering effect according to the present application includes:
providing a semiconductor pump source 102 and an active optical fiber 402, wherein the semiconductor pump source is fused with the active optical fiber 402 through a passive optical fiber after being combined by a beam combiner 202;
a high reflecting grating 302 is engraved on the input side of the active optical fiber, a low reflecting grating 502 is engraved on the output side of the active optical fiber, and the output end of the active optical fiber is connected with an inclined grating 602 and can be connected in a fusion mode;
the writing mode of the high-reflection grating and the low-reflection grating comprises the following steps:
after passing through a plano-convex cylindrical lens and a phase mask plate, the collimated laser is focused to the position of the active optical fiber where a grating is to be etched;
and adjusting the laser source according to preset laser power and irradiation time, and writing the grating at the position of the active optical fiber where the grating is to be written.
Specifically, the laser used for writing may be a femtosecond laser. Specifically, the fiber grating writing platform may be first set up before writing the optical fiber: and welding an output tail fiber of the test light source with the input end of the ytterbium-doped double-clad fiber, and welding the spectrometer with the output end of the ytterbium-doped double-clad fiber. The collimated femtosecond laser is respectively focused to fiber cores at the input end and the output end of the ytterbium-doped double-clad optical fiber by a plano-convex cylindrical lens, and the phase mask plate and the active optical fiber are kept parallel and tightly attached to the active optical fiber by adjusting the multidimensional optical fiber adjusting frame.
Then, writing a grating on line: and turning on the test light source and setting power. The power and the irradiation time of the femtosecond light source are adjusted by matching with the spectrometer. And writing a low-return grating LR-FBG with the signal light reflectivity less than or equal to 10% into the fiber core at the position of about 10cm away from the output end of the ytterbium-doped double-clad fiber. And then writing the grating to the fiber core at the position of about 10cm away from the input end of the ytterbium-doped double-clad fiber according to the writing parameters of the signal light high-return HR-FBG.
After the active optical fiber is well engraved, the laser is built: as shown in fig. 2, the pump light source LD, the Combiner, the ytterbium-doped double-clad fiber with the grating pair and the tilted grating TFBG for filtering the stimulated raman scattering spectrum are connected in sequence by a fusion method. According to the scheme, two gratings are inscribed on the ytterbium-doped double-clad optical fiber, and 2 welding points can be reduced compared with the traditional scheme.
In the third embodiment shown in fig. 3, the semiconductor pump sources 103 are combined together by the beam combiner 203, the output end of the beam combiner is connected to the input end of the active optical fiber 403, the high reflective grating 303 is engraved at the position, close to the input end, of the active optical fiber 403, and the low reflective grating 503 and the tilted grating 603 are engraved at the position, close to the output end, of the active optical fiber 403.
In a specific embodiment, the high-reflectivity grating inscription 303 is written at a position 10cm away from the input end of the active optical fiber 403, the writing position of the high-reflectivity grating may be determined according to specific situations, and the selectable range may be 5-30 cm away from the input end of the active optical fiber. The low-reflection grating 503 is etched on the active optical fiber 403 10cm away from the output end, the etching position of the low-reflection grating can be determined according to specific conditions, and the optional range can be 10-30 cm away from the output end of the active optical fiber. The inclined grating 603 is etched on the active optical fiber 403 5cm away from the output end, the etching position of the inclined grating can be determined according to specific conditions, and the optional range can be 5-20 cm away from the output end of the active optical fiber.
Referring to fig. 4 in combination, a method for manufacturing a fiber laser for suppressing stimulated raman scattering effect according to the present application includes:
providing a semiconductor pump source 103 and an active optical fiber 403, wherein the semiconductor pump source is fused with the active optical fiber 403 through a passive optical fiber after being combined by a beam combiner 203;
a high reflecting grating 303 is engraved on the input side of the active optical fiber, and a low reflecting grating 503 and an inclined grating 603 are engraved on the output side of the active optical fiber;
the writing method of the high reflecting grating 303, the low reflecting grating 503 and the inclined grating 603 comprises the following steps:
after passing through a plano-convex cylindrical lens and a phase mask plate, the collimated laser is focused to the position of the active optical fiber where a grating is to be etched;
and adjusting the laser source according to preset laser power and irradiation time, and writing the grating at the position of the active optical fiber where the grating is to be written.
Specifically, the laser used for writing may be a femtosecond laser. Specifically, the fiber grating writing platform may be first set up before writing the optical fiber:
and welding an output tail fiber of the test light source with the input end of the ytterbium-doped double-clad fiber, and welding the spectrometer with the output end of the ytterbium-doped double-clad fiber. The collimated femtosecond laser is respectively focused to fiber cores at the positions of about 10cm of the input end and about 10cm and 5cm of the output end surface of the ytterbium-doped double-clad optical fiber through a plano-convex cylindrical lens, and the phase mask plate is kept to be tightly attached to the active optical fiber by adjusting the multi-dimensional optical fiber adjusting frame.
Then, writing a grating on line: and turning on the test light source and setting power. The power and the irradiation time of the femtosecond light source are adjusted by matching with the spectrometer. And rotating the phase mask plate to enable the phase mask plate and the ytterbium-doped double-clad optical fiber to have a certain inclination angle and to be kept close to each other. And writing inclined grating on the fiber core at the position of about 5cm away from the output end of the ytterbium-doped double-clad fiber to serve as a Raman filter. And rotating the phase mask plate to enable the phase mask plate to be parallel to the active optical fiber and cling to the active optical fiber, and respectively writing the grating to the input end of the ytterbium-doped double-clad optical fiber and the fiber core at the position of outputting about 10cm according to the writing parameters of writing to the high return HR-FBG and the low return LR-FBG of the signal light. Alternatively, to further filter the stimulated raman scattering spectrum, multiple TFBGs may be written to further improve the stimulated raman scattering suppression ratio.
After the active optical fiber is well engraved, the laser is built: as shown in fig. 3, the pump light source LD, the Combiner, and the ytterbium-doped double-clad fiber with the grating group are connected in sequence by a fusion method. According to the scheme, three gratings are inscribed on the ytterbium-doped double-clad optical fiber, and 3 welding points can be reduced compared with the traditional scheme.
The above embodiments are merely examples and are not intended to limit the scope of the present disclosure, and all modifications, equivalents, and flow charts using the contents of the specification and drawings are included in the scope of the present disclosure.
Claims (10)
1. A fiber laser for suppressing stimulated raman scattering effects, comprising: the optical fiber laser comprises a semiconductor pumping source and an active optical fiber, wherein the semiconductor pumping source is connected with the active optical fiber, the optical fiber laser further comprises at least one pair of first gratings respectively arranged at the input side and the output side of the active optical fiber, and at least one inclined grating arranged at the output side of the active optical fiber, and at least one of the first gratings and the inclined gratings is arranged on the active optical fiber in a writing mode.
2. The fiber laser of claim 1, wherein the at least one pair of first gratings comprises a high-reflectivity grating and a low-reflectivity grating, the high-reflectivity grating and the low-reflectivity grating forming a grating pair serving as an input and output cavity mirror of a resonant cavity, the high-reflectivity grating and/or the low-reflectivity grating and/or the tilted grating being written on the active fiber.
3. The fiber laser of claim 2, wherein the high reflectivity grating is written on the input side of the active fiber and/or the low reflectivity grating is written on the output side of the active fiber.
4. The fiber laser of claim 3, wherein the high reflective grating is written 5-30 cm from the input end of the active fiber and/or the low reflective grating is written 5-30 cm from the output end of the active fiber.
5. The fiber laser of claim 3, wherein the high-reflectivity grating is written 5-30 cm from the input end of the active fiber, the low-reflectivity grating is written 10-30 cm from the output end of the active fiber, and the tilted grating is written 5-20 cm from the output end of the active fiber.
6. The fiber laser of any of claims 1 to 5, wherein the number of the semiconductor pump sources is plural, the fiber laser further comprises a beam combiner, and output lasers of the plural semiconductor pump sources are combined together by the beam combiner.
7. The fiber laser of any of claims 1 to 5, wherein a transmission fiber or a fiber end cap is further connected to the active fiber output end.
8. A method for manufacturing a fiber laser for suppressing stimulated Raman scattering effect according to any one of claims 1 to 7,
providing a semiconductor pump source and an active optical fiber connected,
a pair of first gratings is arranged at the input side and the output side of the active optical fiber, at least one inclined grating is arranged at the output side of the active optical fiber,
after passing through a plano-convex cylindrical lens and a phase mask plate, the collimated laser is focused to the position of the active optical fiber where a grating is to be etched;
and adjusting a laser source according to preset laser power and irradiation time, and writing at least one grating in the pair of first gratings and the at least one inclined grating at the position of the grating to be written of the active optical fiber.
9. The fiber laser manufacturing method according to claim 8, wherein the writing method further includes: connecting a test light source with an input end of an active optical fiber, and connecting a spectrometer with an output end of the active optical fiber; and in the grating writing process, online monitoring is carried out through a test light source, and the laser is adjusted by matching with a spectrometer.
10. The fiber laser manufacturing method according to claim 9, wherein a high-reflectivity grating is written on the input side of the active fiber, and/or a low-reflectivity grating is written on the output side of the active fiber, and/or a tilted grating is written on the output side of the active grating.
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