CN108462023B - High-power fiber laser amplifier system with high mode instability threshold - Google Patents
High-power fiber laser amplifier system with high mode instability threshold Download PDFInfo
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- CN108462023B CN108462023B CN201810529314.9A CN201810529314A CN108462023B CN 108462023 B CN108462023 B CN 108462023B CN 201810529314 A CN201810529314 A CN 201810529314A CN 108462023 B CN108462023 B CN 108462023B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
- H01S3/06758—Tandem amplifiers
Abstract
The high-power fiber laser amplifier system with the high mode instability threshold comprises a linear polarization master oscillator, a collimating lens group, a lambda/4 glass slide, a lambda/2 glass slide, a focusing lens group, a high-power master amplifier, a beam expanding collimating system, a high-reflection mirror, a power receiver, a beam splitter, a photoelectric signal conversion display module and a beam quality measuring instrument. By introducing the polarization regulation system into the high-power fiber laser amplifier, the proportion of high-order modes longitudinally injected and transmitted along the gain fiber of the high-power fiber laser amplifier is reduced, and the mode instability effect in the high-power fiber laser amplifier can be restrained. The system can effectively improve the mode instability threshold value caused by nonlinear effect and traditional transverse mode interference, and provides a reliable technical means for further power improvement and performance optimization of high-power fiber laser.
Description
Technical Field
The invention belongs to the technical field of strong lasers, and particularly relates to a high-power fiber laser amplifier system with a high mode instability threshold value.
Background
Compared with other types of lasers, the fiber laser has the advantages of high conversion efficiency, good beam quality, convenient thermal management, compact structure, easy maintenance and the like, and is widely focused by a plurality of research units at home and abroad. Since the first fiber laser in 1964, fiber lasers have achieved remarkable development in the development history of more than fifty years, and the application range of fiber lasers has been expanded to various fields such as laser cutting, laser welding, material forming, laser drilling, laser rock breaking and the like. Under the promotion of various application fields, fiber laser is always popular with researchers at home and abroad as an important technical scheme for realizing a high-power light source. After the first breakthrough of the fiber laser in 1999, the fiber laser output power shows very attractive power boosting potential and development prospect in the development history of the last twenty years.
However, the single-path fiber laser power boost has faced serious technical bottlenecks at present, limited by thermal effects of the medium itself, high brightness pumping technology, nonlinear effects, fiber end face damage, mode instability effects, etc.
The current research results show that for gain fibers with cores <100 μm, mode instability is a primary factor limiting the improvement of the laser brightness of the fiber. The mode unstable physical image is as follows: with the increase of the pumping power, when the output power of the fiber laser exceeds a certain threshold power, the output laser mode can be subjected to high-speed dynamic coupling from a fundamental mode to a high-order mode, and the coupling frequency is about 2 kHz; when the output power decreases below the threshold power, the high-speed dynamic coupling between the modes disappears. The output mode of the fiber laser is seriously degraded due to the mode instability effect, so that the output brightness and the beam quality of the fiber amplifier are greatly degraded, and the overall performance of the fiber laser is finally degraded.
At present, although researchers at home and abroad have proposed various inhibition methods such as bending loss, special optical fiber design, changing signal light/pump light wavelength and the like, the mode instability effect is still the most important technical bottleneck for improving the power and brightness of the current high-power fiber laser amplifier. In addition, the latest research results show that the mode instability threshold value is obviously reduced due to nonlinear effects such as stimulated Raman scattering and the like.
Based on the above consideration, focusing on the source and precondition of the mode instability generation, nonlinear effect suppression is comprehensively considered, and the novel scheme suitable for the mode instability suppression of the high-power fiber laser amplifier is of great significance.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a high-power fiber laser amplifier system with a high-mode unstable threshold based on a physical mechanism and basic preconditions generated by mode instability and combined with the dependency relationship between the nonlinear effect threshold characteristics such as stimulated Raman scattering and the polarization characteristics, so as to effectively improve the mode unstable threshold caused by nonlinear effect and traditional transverse mode interference and provide a reliable technical means for further power improvement and performance optimization of high-power fiber laser.
In order to achieve the technical purpose, the technical scheme of the invention is as follows:
the high-power fiber laser amplifier system with the high-mode instability threshold can inhibit the mode instability effect in the high-power fiber laser amplifier by introducing a polarization regulation system into the high-power fiber laser amplifier to reduce the proportion of high-order modes longitudinally injected and transmitted along the gain fiber of the high-power fiber laser amplifier. The polarization regulation system is used for realizing polarization regulation of linearly polarized fiber laser by utilizing a lambda/4 slide and a lambda/2 slide.
Specifically, the high-power fiber laser amplifier system with the high-mode instability threshold comprises a linear polarization master oscillator, a collimating lens group, a lambda/4 glass slide, a lambda/2 glass slide, a focusing lens group, a high-power master amplifier, a beam expanding collimating system, a high-reflection mirror, a power receiver, a beam splitter, a photoelectric signal conversion display module and a beam quality measuring instrument.
The linearly polarized fiber laser output from the linearly polarized master oscillator is collimated and output by the collimating lens group and then sequentially enters the lambda/4 slide and the lambda/2 slide. The laser beams after passing through the lambda/4 slide and the lambda/2 slide are coupled into a high-power main amplifier through a focusing lens group for power amplification. The laser beam amplified by the high-power main amplifier is collimated and output to free space by the beam expanding and collimating system. The light beam output by collimation is incident to the high-reflection mirror, most of the light beam is reflected by the high-reflection mirror, part of the reflected light is received by the power receiver, a small part of the light beam is transmitted by the high-reflection mirror, the part of the transmitted light is divided into two beams by the beam splitter, wherein the reflected light reflected by the beam splitter is incident to the photoelectric signal conversion display module, and the transmitted light transmitted by the beam splitter is injected to the light beam quality measuring instrument. The photoelectric signal conversion display module converts the optical signal into an electrical signal, and displays the time domain and frequency domain signals on the terminal for observing the threshold value of the occurrence of the mode instability effect. The beam quality measuring instrument is used for observing the beam quality change of the high-power fiber laser system before and after the mode instability effect occurs and outputting the detected beam quality measurement value.
In the invention, the following components are added: the polarization regulation and control of the linearly polarized fiber laser are realized by utilizing a lambda/4 slide and a lambda/2 slide; by rotating the angle of the lambda/4 slide and the lambda/2 slide's principal axis, the polarization state of the incident linearly polarized fiber laser can be tailored to the desired polarization distribution.
In the invention, the following components are added: the linear polarization cascade optical fiber pre-amplification system is further included, the linear polarization optical fiber laser output from the linear polarization master oscillator is firstly incident into the linear polarization cascade optical fiber pre-amplification system to be subjected to power pre-amplification, and the linear polarization laser after power pre-amplification is incident into the collimating lens group to achieve collimation output. If the laser power generated by the linear polarization master oscillator can meet the amplification requirement of the high-power master amplifier through the focusing lens group, the linear polarization cascade optical fiber pre-amplification system can be omitted.
In the invention, the following components are added:
the linear polarization master oscillator is unlimited in implementation mode, linewidth, center wavelength and time domain characteristics; in terms of implementation, the fiber-optic resonator can be a traditional fiber-optic oscillator, a super-fluorescent fiber-optic light source, a random fiber-optic laser and the like; the line width can be a narrow line width optical fiber light source or a wide spectrum optical fiber light source; the center wavelength may be any wavelength within a 1-micrometer band (1030-1100 nm), a long-wavelength band (1100-1150 nm), or a 2-micrometer band. From the time domain characteristics, it may be a continuous laser or a pulsed laser.
The linear polarization cascade optical fiber pre-amplification system realizes the pre-amplification of the injection linear polarization optical fiber laser. The number of stages of the linear polarization cascade optical fiber pre-amplification system is not limited, and the linear polarization cascade optical fiber pre-amplification system can be a single-stage linear polarization optical fiber pre-amplifier or a multi-stage linear polarization optical fiber pre-amplifier.
The collimating lens group of the invention collimates and outputs the laser output by the linear polarization cascade optical fiber pre-amplification system to a free space; the collimating lens group is generally composed of one or more optical lenses, the focal length of the optical lenses is not limited, and the collimating lens group is specifically determined according to the fiber core size of the output optical fiber of the linear polarization cascade optical fiber pre-amplification system and the collimated light spot size; the material of the optical lens is not limited, and may be an optical crystal material such as K9 or fused silica.
The lambda/4 glass slide realizes pi/2 phase shift of incident laser in two polarization orthogonal directions (the fast and slow axes of the glass slide), and the constituent materials of the lambda/4 glass slide can have various choices (uniaxial optical crystal materials, liquid crystals and the like);
the lambda/2 glass slide realizes pi phase shift of incident laser in two polarization orthogonal directions (the fast and slow axes of the glass slide), and the constituent materials of the lambda/2 glass slide can have various choices (uniaxial optical crystal materials, liquid crystals and the like);
the focusing lens group focuses the laser passing through the lambda/2 glass slide into the input optical fiber of the high-power main amplifier; the focusing lens group is generally composed of one or more optical lenses, and the focal length of the optical lenses is not limited, and is specifically determined according to the fiber core size and the incident light spot size of the input optical fiber of the high-power main amplifier; the material of the optical lens is not limited, and may be an optical crystal material such as K9 or fused silica.
The high-power main amplifier realizes final amplification of incident laser power, and comprises a pumping source, a signal-pumping beam combiner, a doped optical fiber and the like. The input optical fiber of the main amplifier is generally a signal arm of a signal-pump beam combiner, a pump source is coupled into a doped optical fiber through a pump arm of the signal-pump beam combiner, and the doped optical fiber is pumped to realize high-power optical fiber laser output.
The beam expanding and collimating system of the present invention generally comprises an optical fiber end cap and a collimator; the optical fiber end cap can finish laser beam expansion, so that the laser power density of the output end face is effectively reduced, and optical discharge is prevented; the collimator is used for collimating the laser beam.
The high reflection mirror realizes the high reflection function of output laser, the reflectivity is not limited, and the reflectivity is generally required to be more than 99%; the constituent material of the high reflection mirror is not limited, and may be fused silica, K9, znSe, caF2, or the like.
The power receiver is used for receiving the main laser beam reflected by the high-reflection mirror, and the material of the power receiver is not limited, and can be a fused silica material, a silicon-based material, a copper cone and the like.
The beam splitter has various implementation modes, and can be a white piece (reflectivity is 4%), a wedge-shaped mirror, a beam splitter with a fixed beam splitting ratio and the like, and the beam splitter can be made of materials such as fused quartz, K9, znSe, caF2 and the like without limitation.
The photoelectric signal conversion display module generally consists of a photoelectric detector and an oscilloscope, converts an incident optical signal into an electric signal, and displays the electric signal (a time domain signal and a frequency domain signal of laser) on an external terminal for observing a threshold value of occurrence of a mode instability effect. With the increase of output power, when the mode instability effect occurs, obvious instability and time domain fluctuation can appear in the time domain signal of the output laser, and obvious characteristic frequency can be generated near 2kHz in the frequency domain signal of the output laser.
The beam quality measuring instrument provided by the invention realizes the test and monitoring of the quality of the output laser beam, and observes the beam quality change of the high-power fiber laser system before and after the unstable mode effect occurs. Since dynamic coupling between the fundamental mode and the higher order mode occurs after the mode instability effect occurs, degradation of the beam quality tends to be caused. In addition, by combining the time domain signal and the frequency domain signal output by the photoelectric signal conversion display module and the light beam quality measurement value detected by the light beam quality measurement instrument, the optimal rotation angles of the lambda/4 glass slide 2-4 and the lambda/2 glass slide 2-5 can be selected, and the system optimization is completed.
The principle of the mode instability effect suppression of the invention is as follows:
because the large-mode-field double-cladding gain optical fiber has the capability of supporting a plurality of eigenmodes, a fundamental mode and a small number of high-order modes are inevitably present in the core of the large-mode-field double-cladding gain optical fiber at the same time. Interference occurs between the different transverse modes (i.e., the fundamental and higher order modes) and a non-uniform optical field distribution is formed in the gain fiber core. Furthermore, different heat distribution is generated at different positions of the gain fiber in the longitudinal direction due to different power extraction capacities of the pump light along the gain fiber in the longitudinal direction and quantum defects, so that a temperature gradient is formed. The temperature gradient generates refractive index disturbance under the action of a thermo-optical effect, a long-period refractive index grating is formed in the fiber core, an interference light field is influenced, and finally mutual coupling and closed loop among the interference light field, the temperature field and the refractive index disturbance field are formed, so that a mode instability effect is generated.
The physical mechanism resulting from the above-described mode instability effect is available, and mutual interference between the fundamental mode and the higher-order mode is a fundamental precondition for the generation of mode instability. If no higher order modes are present in the fiber amplifier, mode instability effects will not occur. The fewer higher order modes injected in the fiber amplifier, the weaker the interaction between the fundamental mode and the higher order modes, and the higher the threshold at which mode instability effects occur. Therefore, the mode instability effect can be effectively suppressed by controlling the ratio of the higher-order modes injected into the optical fiber amplifier.
In the multimode optical fiber amplifier, because of the difference of polarization directions among different eigenmodes, the polarization distribution after superposition of each mode has an internal correlation with the integral output mode of the amplifier, and the amplifier itself has a polarization main state, the regulation and control of the injection mode can be realized by adjusting the polarization direction of laser injected into the main amplifier.
Based on the above consideration, by introducing polarization regulation in the high-power fiber laser amplifier, the proportion of the high-order mode in the injection amplifier can be effectively controlled, and effective suppression of the mode instability effect can be realized. In addition, as the power of the optical fiber amplifier increases, nonlinear effects such as stimulated raman scattering occur in the amplifier. Non-linear effects such as stimulated raman scattering effectively reduce the threshold for mode instability. In a high-power fiber laser amplifier, the threshold of nonlinear effects such as stimulated raman scattering is closely related to the polarization direction of the laser light in the amplifier. The threshold of the nonlinear stimulated raman scattering effect is highest when the polarization direction injected into the main amplifier is in a circular polarization state. The threshold of the nonlinear stimulated raman scattering effect is lowest when the polarization direction injected into the main amplifier is in the linear polarization state. Therefore, by introducing polarization regulation in the high-power fiber laser amplifier, nonlinear effects such as stimulated Raman scattering and the like can be effectively inhibited, and the occurrence threshold of the mode instability effect is further improved.
In summary, by introducing a polarization regulation mechanism into the high-power fiber laser amplifier, the proportion of high-order modes injected and transmitted longitudinally along the gain fiber is reduced, and then the nonlinear effect threshold of stimulated raman scattering and the like of the system is reduced, so that the mode instability effect in the high-power fiber laser amplifier can be effectively inhibited.
Compared with the prior art, the invention can produce the following technical effects:
1. the invention is based on the physical mechanism and precondition that the mode instability effect is generated between the basic mode and the higher-order mode, combines the correlation between the polarization and the modes and the dependency relationship between the nonlinear effect such as stimulated Raman scattering and the polarization characteristic, reduces the proportion of the higher-order mode longitudinally transmitted along the gain fiber of the main amplifier by introducing the polarization regulation mechanism into the high-power fiber laser amplifier, improves the nonlinear effect threshold such as stimulated Raman scattering, and finally achieves the aim of inhibiting the mode instability.
2. Compared with the traditional inhibition method, the method can effectively inhibit mode instability caused by the nonlinear effects such as stimulated Raman scattering and the like when the high-power fiber laser amplifier generates the nonlinear effects such as stimulated Raman scattering and the like along with power increase.
3. The invention has universality: in terms of applicable wavelength ranges, the method can be used for any wavelength within a 1 μm band (1030 nm-1100 nm), a long-wave band (1100 nm-1150 nm), and a 2 μm band; the applicable laser time domain characteristics may be continuous laser or different pulse lasers such as nanosecond laser, picosecond laser, femtosecond laser, etc.
4. The linear polarization master oscillator is not limited in implementation mode, and can be a traditional optical fiber oscillator, a super-fluorescent optical fiber light source, a random optical fiber laser and the like; the linear polarization master oscillator is not limited in line width and can be a narrow-line-width optical fiber light source or a wide-spectrum optical fiber light source.
5. The power receiver, the beam splitter and other devices used in the invention have various implementation modes, and the materials of the lenses, the lambda/4 glass slide, the lambda/2 glass slide, the high-reflection mirror and other devices are selected variously.
Drawings
Fig. 1 is a schematic diagram of the system structure of the present invention.
The drawings include:
the device comprises a linear polarization master oscillator 1-1, a linear polarization cascading optical fiber pre-amplification system 1-2, a collimating lens group 1-3, a lambda/4 glass slide 1-4, a lambda/2 glass slide 1-5, a focusing lens group 1-6, a high-power master amplifier 1-7, a beam expanding collimating system 1-8, a high-reflection mirror 1-9, a power receiver 1-10, a beam splitter 1-11, a photoelectric signal conversion display module 1-12 and a beam quality measuring instrument 1-13.
Detailed Description
FIG. 1 is a schematic diagram of a high power fiber laser amplifier system with high mode instability threshold according to an embodiment of the present invention, comprising: the device comprises a linear polarization master oscillator 1-1, a linear polarization cascading optical fiber pre-amplification system 1-2, a collimating lens group 1-3, a lambda/4 glass slide 1-4, a lambda/2 glass slide 1-5, a focusing lens group 1-6, a high-power master amplifier 1-7, a beam expanding collimating system 1-8, a high-reflection mirror 1-9, a power receiver 1-10, a beam splitter 1-11, a photoelectric signal conversion display module 1-12 and a beam quality measuring instrument 1-13.
The laser output from the linear polarization master oscillator 1-1 is first power pre-amplified by the linear polarization cascade fiber pre-amplification system 1-2. The number of stages of the linear polarization cascade optical fiber pre-amplification system 1-2 is not limited, and the linear polarization cascade optical fiber pre-amplification system can be a single-stage linear polarization optical fiber pre-amplifier or a multi-stage linear polarization optical fiber pre-amplifier. The linear polarization laser after being preamplified by the linear polarization cascade optical fiber preamplification system 1-2 is incident to the lambda/4 glass slide 1-4 after passing through the collimating lens group 1-3. The light beam output from the lambda/4 slide 1-4 is injected into the lambda/2 slide 1-5. By rotating the angle of the principal axes of the lambda/4 slide 1-4 and the lambda/2 slide 1-5, the polarization state of the incident ray polarized laser light can be regulated to any polarization distribution. The laser beams after the polarization regulation of the lambda/4 glass slide 1-4 and the lambda/2 glass slide 1-5 are coupled into a high-power main amplifier 1-7 through a focusing lens group 1-6 for final power amplification. If the laser power generated by the linear polarization master oscillator 1-1 can meet the amplification requirement of the high-power master amplifier 1-7 through the focusing lens group 1-6, the linear polarization cascade optical fiber pre-amplification system 1-2 can be omitted. The laser amplified by the high-power main amplifier 1-7 is collimated and output to free space by the beam expanding and collimating system 1-8. After the collimated output light beam passes through the high-reflection mirror 1-9, most of reflected light is received by the power receiver 1-10, and a small part of transmitted light is split into two beams by the beam splitter 1-11. The reflected light after passing through the beam splitters 1 to 11 is incident on the photoelectric signal conversion display modules 1 to 12. The photoelectric signal conversion display modules 1 to 12 are generally composed of a photodetector and an oscilloscope. The photoelectric signal conversion display modules 1 to 12 convert the optical signals into electrical signals and display time domain and frequency domain signals on the output terminals for observing thresholds at which mode instability occurs. With the increase of output power, when the mode instability occurs, obvious instability and time domain fluctuation can appear in the time domain signal of the output laser, and obvious characteristic frequency can be generated near 2kHz in the frequency domain signal of the output laser. The transmitted light after passing through the beam splitters 1-11 is injected into the beam quality measuring instrument 1-13 to observe the beam quality change of the high-power fiber laser system before and after the mode instability occurs. Since dynamic coupling between the fundamental mode and the higher order mode occurs after mode instability occurs, degradation in beam quality tends to be caused. In addition, by combining the time domain signal and the frequency domain signal output by the photoelectric signal conversion display module 1-12 and the light beam quality measurement value detected by the light beam quality measuring instrument 1-13, the optimal rotation angles of the lambda/4 glass slide 1-4 and the lambda/2 glass slide 1-5 can be selected, and the system optimization is completed.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The high-power fiber laser amplifier system with high mode instability threshold is characterized in that: the polarization regulation system is introduced into the high-power fiber laser amplifier, so that the proportion of high-order modes longitudinally injected and transmitted along the gain fiber of the high-power fiber laser amplifier is reduced, and the mode instability effect in the high-power fiber laser amplifier can be restrained, wherein the polarization regulation system is used for realizing the polarization regulation of linearly polarized fiber laser by utilizing a lambda/4 slide and a lambda/2 slide; the high-power fiber laser amplifier system comprises a linear polarization master oscillator, a collimating lens group, a lambda/4 glass slide, a lambda/2 glass slide, a focusing lens group, a high-power master amplifier, a beam expanding collimating system, a high-reflection mirror, a power receiver, a beam splitter, a photoelectric signal conversion display module and a beam quality measuring instrument;
linearly polarized fiber laser output from the linear polarization master oscillator is collimated and output by a collimating lens group and then sequentially enters a lambda/4 slide and a lambda/2 slide; the laser beams after passing through the lambda/4 glass slide and the lambda/2 glass slide are coupled into a high-power main amplifier through a focusing lens group to carry out power amplification; the laser beam amplified by the high-power main amplifier is collimated and output to a free space by a beam expanding and collimating system; the collimated output light beam is incident to the high-reflection mirror, most of the light beam is reflected by the high-reflection mirror, and the reflected light is received by the power receiver; a small part of light beam is transmitted out through the high reflection mirror, the part of transmitted light is divided into two beams by the beam splitter, wherein the reflected light reflected by the beam splitter is incident on the photoelectric signal conversion display module, and the transmitted light transmitted by the beam splitter is injected into the light beam quality measuring instrument; the photoelectric signal conversion display module converts the optical signal into an electric signal, and displays the time domain and frequency domain signals on the terminal so as to observe a threshold value of occurrence of a mode instability effect; with the increase of output power, when the mode instability effect occurs, obvious instability and time domain fluctuation can appear in the time domain signal of the output laser, and obvious characteristic frequency can be generated near 2kHz in the frequency domain signal of the output laser.
2. The high power fiber laser amplifier system with high mode instability threshold according to claim 1, wherein: by rotating the angle of the λ/4 slide and the angle of the principal axis of the λ/2 slide, the polarization state of the incident linearly polarized fiber laser light can be adjusted to a desired polarization distribution.
3. The high power fiber laser amplifier system with high mode instability threshold according to claim 2, wherein: the linear polarization cascade optical fiber pre-amplification system is further included, the linear polarization optical fiber laser output from the linear polarization master oscillator is firstly incident into the linear polarization cascade optical fiber pre-amplification system to be subjected to power pre-amplification, and the linear polarization laser after power pre-amplification is incident into the collimating lens group to achieve collimation output.
4. A high power fiber laser amplifier system with high mode instability threshold according to claim 1 or 2 or 3, wherein: the beam quality measuring instrument is used for observing the beam quality change of the high-power fiber laser system before and after the mode instability effect occurs and outputting the detected beam quality measurement value, and the optimal rotation angles of the lambda/4 slide and the lambda/2 slide can be selected by combining the time domain signal and the frequency domain signal output by the photoelectric signal conversion display module and the beam quality measurement value detected by the beam quality measuring instrument, so that the system optimization is completed.
5. The high power fiber laser amplifier system with high mode instability threshold of claim 4, wherein: the linear polarization master oscillator is a fiber oscillator, a super-fluorescent fiber light source or a random fiber laser.
6. The high power fiber laser amplifier system with high mode instability threshold of claim 4, wherein: the center wavelength of the linear polarization master oscillator is any one wavelength of a 1 micron wave band of 1030 nm-1100 nm, a long wave band of 1100 nm-1150 nm or a 2 micron wave band.
7. The high power fiber laser amplifier system with high mode instability threshold of claim 5 or 6, wherein: the linear polarization cascade optical fiber pre-amplification system is a single-stage linear polarization optical fiber pre-amplifier or a multi-stage linear polarization optical fiber pre-amplifier.
8. The high power fiber laser amplifier system with high mode instability threshold of claim 7, wherein: the lambda/4 slide realizes pi/2 phase shift of the two polarization orthogonal directions of the incident laser.
9. The high power fiber laser amplifier system with high mode instability threshold of claim 7, wherein: the lambda/2 slide realizes pi phase shift of the incident laser in the orthogonal direction of two polarizations.
10. The high power fiber laser amplifier system with high mode instability threshold according to claim 1 or 2 or 3 or 5 or 6 or 8, wherein: the reflectivity of the high-reflectivity mirror is more than 99 percent, and the high-reflectivity mirror is made of fused quartz, K9, znSe or CaF2.
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| CN111969400B (en) * | 2020-08-27 | 2022-02-15 | 中国人民解放军国防科技大学 | High power fiber laser system |
| CN112345208B (en) * | 2020-10-29 | 2021-12-24 | 长沙大科激光科技有限公司 | Method and device for measuring mode instability threshold of single-mode fiber oscillator based on high-reflectivity grating leakage light |
| CN115566519B (en) * | 2022-12-07 | 2023-03-07 | 中国航天三江集团有限公司 | High-power high-beam-quality narrow-linewidth optical fiber laser amplification system |
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