We propose a fiber-solid hybrid system which consists of a semiconductor saturable absorber mirror(SESAM)modelocked fiber seed with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz,a two-level fiber pre-ampl...We propose a fiber-solid hybrid system which consists of a semiconductor saturable absorber mirror(SESAM)modelocked fiber seed with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz,a two-level fiber pre-amplifier and a double-passing end-pumped Nd:YVO4 amplifier.In the solid-state amplifier,to enhance the gain and the extraction efficiency,a specially designed structure in which the seed light passes through the gain medium four times and makes full use of population inversion is used as the double-passing amplifier.Besides,the beam filling factor(the ratio of the seed light diameter to the pump light diameter)and the thermal lens effect of the double-passing amplifier are considered and its optical-to-optical conversion efficiency is further improved.To preserve the beam quality of the double-passing amplifier,a new method of spherical-aberration self-compensation based on the principles of geometrical optics is used and discussed.Our system achieves a maximum average power of 9.5Wat the pump power of 28W,corresponding to an optical-to-optical efficiency of 27%.And the beam quality factor M^2 reaches 1.3 at the maximum output power.展开更多
A high-energy 100-Hz optical parametric oscillator(OPO)based on a confocal unstable resonator with a Gaussian reflectivity mirror was demonstrated.A KTA-based OPO with a good beam quality was obtained when the magnifi...A high-energy 100-Hz optical parametric oscillator(OPO)based on a confocal unstable resonator with a Gaussian reflectivity mirror was demonstrated.A KTA-based OPO with a good beam quality was obtained when the magnification factor was 1.5,corresponding to the maximum signal(1.53μm)energy of 56 m J and idler(3.47μm)energy of 20 m J,respectively.The beam quality factors(M^(2))were measured to be M^(2)_(x)=5.7,M^(2)_(y)=5.9 for signal and M^(2)_(x)=8.4,M^(2)_(y)=8.1 for idler accordingly.The experimental results indicated that the beam quality positively changed with the increase of magnification factors,accompanied by an acceptable loss of pulse energy.展开更多
In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate ga...In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate gas deposition technique,and subsequently applied in a tandem-pumped fiber amplifier for high-power operation and transverse mode instability(TMI)mitigation.Notably,the impacts of the seed laser power and mode purity are preliminarily investigated through comparative experiments.It is found that the TMI threshold could be significantly affected by the seed laser mode purity.The possible mechanism behind this phenomenon is proposed and revealed through comprehensive comparative experiments and theoretical analysis.Finally,a maximum output power of 7.49 kW is obtained with the beam quality factor of approximately 1.83,which is the highest output power ever reported in a forward tandem-pumped confined-doped fiber amplifier.This work could provide a good reference and practical solution to improve the TMI threshold and realize high-power high-brightness fiber lasers.展开更多
Beam quality improvements by a large margin for signal and idler beams of a high energy 100 Hz KTiOAsO_(4)(KTA)non-critical phase matching(NCPM)optical parametric oscillator(OPO)were demonstrated using an unstable res...Beam quality improvements by a large margin for signal and idler beams of a high energy 100 Hz KTiOAsO_(4)(KTA)non-critical phase matching(NCPM)optical parametric oscillator(OPO)were demonstrated using an unstable resonator configuration instead of a plane-parallel one.Theoretically,influences of cavity lengths and transmission of an output coupler on the OPO conversion efficiency for both were numerically simulated.For OPO based on an unstable resonator with a Gaussian reflectivity mirror,the maximum pulse energies at the signal(1.53μm)and idler(3.47μm)were about 75 mJ and 26 mJ,respectively.The corresponding beam quality factors of the signal were M_(x)^(2)=9.8 and M_(y)^(2)=9.9,and M_(x)^(2)=11.2 and M_(y)^(2)=11.5 for the idler.As a comparison,128 mJ of signal and 48 mJ of idler were obtained with the plane-parallel resonator,and the M~2 factors of the signal were M_(x)^(2)=39.8 and M_(y)^(2)=38.4,and M_(x)^(2)=32.1 and M_(y)^(2)=31.4 for the idler.Compared with a plane-parallel cavity,over eight times and three times brightness improvements were realized for the signal and idler light,respectively.展开更多
We report on the performance of a continuous-wave Nd:Gd VO_4 laser in-band diode-pumped at 912 nm with high output power and excellent beam quality. The laser produced an output power of 19.8 W at 1063 nm with an opti...We report on the performance of a continuous-wave Nd:Gd VO_4 laser in-band diode-pumped at 912 nm with high output power and excellent beam quality. The laser produced an output power of 19.8 W at 1063 nm with an optical efficiency of 59.3% and slope efficiency of 62.7%. The laser threshold was ~2.04 W of the absorbed pump power, and the laser output beam quality was ≤ 1.2 in the horizontal and vertical directions. The strength of thermal lensing at full output power(33.4 W of absorbed power) was measured to be an average of 8.6 diopters.It is shown that thermal lensing is reduced by a factor of 2 with respect to the Nd:YVO_4 lasers, thus opening a way for further output-power scaling.展开更多
The degradation of beam quality in large-core fiber is investigated experimentally. It is found that the output beam quality factor M2 is a compound tanh function of the fiber lengths and misalignment launch results t...The degradation of beam quality in large-core fiber is investigated experimentally. It is found that the output beam quality factor M2 is a compound tanh function of the fiber lengths and misalignment launch results that the beam quality degraded faster.展开更多
Based on space-charge wave theory,the formulae of the beam-wave coupling coefficient and the beam-loaded conductance are given for the beam-wave interaction in an N-gap Hughes-type coupled cavity chain.The ratio of th...Based on space-charge wave theory,the formulae of the beam-wave coupling coefficient and the beam-loaded conductance are given for the beam-wave interaction in an N-gap Hughes-type coupled cavity chain.The ratio of the nonbeam-loaded quality factor of the coupled cavity chain to the beam quality factor is used to determine the stability of the beam-wave interaction.As an example,the stabilities of the beam-wave interaction in a three-gap Hughes-type coupled cavity chain are discussed with the formulae and the CST code for the operations of the 2π,π,and π/2 modes,respectively.The results show that stable operation of the 2π,π,and π/2 modes may all be realized in an extended-interaction klystron with the three-gap Hughes-type coupled cavity chain.展开更多
Stimulated Raman-scattering-based lasers provide an effective way to achieve wavelength conversion.However,thermally induced beam degradation is a notorious obstacle to power scaling and it also limits the applicable ...Stimulated Raman-scattering-based lasers provide an effective way to achieve wavelength conversion.However,thermally induced beam degradation is a notorious obstacle to power scaling and it also limits the applicable range where high output beam quality is needed.Considerable research efforts have been devoted to developing Raman materials,with diamond being a promising candidate to acquire wavelength-versatile,high-power,and high-quality output beam owing to its excellent thermal properties,high Raman gain coefficient,and wide transmission range.The diamond Raman resonator is usually designed as an external-cavity pumped structure,which can easily eliminate the negative thermal effects of intracavity laser crystals.Diamond Raman converters also provide an approach to improve the beam quality owing to the Raman cleanup effect.This review outlines the research status of diamond Raman lasers,including beam quality optimization,Raman conversion,thermal effects,and prospects for future development directions.展开更多
The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtaine...The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtained by the RWGs.And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A,after that,a kink will appear.The slow axis(SA)far-field divergence angle of the unit is 13.65.The beam quality factor M;of the units determined by the second-order moment(SOM)method,is 1.2.This single-mode emission laser array can be used for laser processing.展开更多
In order to reach the highest intensities,modern laser systems use adaptive optics to control their beam quality.Ideally,the focal spot is optimized after the compression stage of the system in order to avoid spatio-t...In order to reach the highest intensities,modern laser systems use adaptive optics to control their beam quality.Ideally,the focal spot is optimized after the compression stage of the system in order to avoid spatio-temporal couplings.This also requires a wavefront sensor after the compressor,which should be able to measure the wavefront on-shot.At PHELIX,we have developed an ultra-compact post-compressor beam diagnostic due to strict space constraints,measuring the wavefront over the full aperture of 28 cm.This system features all-reflective imaging beam transport and a high dynamic range in order to measure the wavefront in alignment mode as well as on shot.展开更多
We found the beam quality factor M^(2)of the fundamental mode as a function of wavelength is U-shaped in the working photonic bandgap(PBG) of an all-solid PBG fiber(AS-PBGF) for the first time,to the best of our knowl...We found the beam quality factor M^(2)of the fundamental mode as a function of wavelength is U-shaped in the working photonic bandgap(PBG) of an all-solid PBG fiber(AS-PBGF) for the first time,to the best of our knowledge,and our simulation results also match well with the phenomenon.The normal band that is near the high-frequency edge of the third PBG integrates the lowest M^(2)and single-mode operation simultaneously,while the other two edge regions suffer from anomalous variation of M^(2)versus wavelength.The general applicability of this finding can be further extended to other PBGs and also other representative structures in the AS-PBGF field.展开更多
Based on the moiré effect and the Fresnel diffraction theory, a novel technique for diagnosing the beam properties is presented and analyzed, which is especially suitable for X-ray lasers. The method makes it pos...Based on the moiré effect and the Fresnel diffraction theory, a novel technique for diagnosing the beam properties is presented and analyzed, which is especially suitable for X-ray lasers. The method makes it possible, in a one-shot experimental measurement, to determine the beam quality factor M2, the effective radius of curvature, the beam width, the far-field divergence, and the waist location and radius as well as the spatial coherence and its evolution. Numerical simulation proves the validity of the method. Note that the novel moiré technique opens an efficient road, for the first time, to fully diagnose the spatial properties of X-ray lasers.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61675009 and 61325021)Key Program of Beijing Municipal Natural Science Foundation,China(Grant No.KZ201910005006).
文摘We propose a fiber-solid hybrid system which consists of a semiconductor saturable absorber mirror(SESAM)modelocked fiber seed with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz,a two-level fiber pre-amplifier and a double-passing end-pumped Nd:YVO4 amplifier.In the solid-state amplifier,to enhance the gain and the extraction efficiency,a specially designed structure in which the seed light passes through the gain medium four times and makes full use of population inversion is used as the double-passing amplifier.Besides,the beam filling factor(the ratio of the seed light diameter to the pump light diameter)and the thermal lens effect of the double-passing amplifier are considered and its optical-to-optical conversion efficiency is further improved.To preserve the beam quality of the double-passing amplifier,a new method of spherical-aberration self-compensation based on the principles of geometrical optics is used and discussed.Our system achieves a maximum average power of 9.5Wat the pump power of 28W,corresponding to an optical-to-optical efficiency of 27%.And the beam quality factor M^2 reaches 1.3 at the maximum output power.
基金supported by the National Natural Science Foundation of China(Nos.62075116 and 62075117)Key Research Program of Shandong Province(No.2020JMRH0302)+2 种基金Natural Science Foundation of Shandong Province(Nos.ZR2019MF039,ZR2020MF114,and ZR2022QF087)Founding for Qilu Young Scholars from Shandong UniversityChina Postdoctoral Science Foundation(No.2021TQ0190)。
文摘A high-energy 100-Hz optical parametric oscillator(OPO)based on a confocal unstable resonator with a Gaussian reflectivity mirror was demonstrated.A KTA-based OPO with a good beam quality was obtained when the magnification factor was 1.5,corresponding to the maximum signal(1.53μm)energy of 56 m J and idler(3.47μm)energy of 20 m J,respectively.The beam quality factors(M^(2))were measured to be M^(2)_(x)=5.7,M^(2)_(y)=5.9 for signal and M^(2)_(x)=8.4,M^(2)_(y)=8.1 for idler accordingly.The experimental results indicated that the beam quality positively changed with the increase of magnification factors,accompanied by an acceptable loss of pulse energy.
基金supported by the National Natural Science Foundation of China(62035015)the Innovative Research Groups of Hunan Province(2019JJ10005)the Hunan Provincial Innovation Construct Project(2019RS3018).
文摘In this work,a confined-doped fiber with the core/inner-cladding diameter of 40/250μm and a relative doping ratio of 0.75 is fabricated through a modified chemical vapor deposition method combined with the chelate gas deposition technique,and subsequently applied in a tandem-pumped fiber amplifier for high-power operation and transverse mode instability(TMI)mitigation.Notably,the impacts of the seed laser power and mode purity are preliminarily investigated through comparative experiments.It is found that the TMI threshold could be significantly affected by the seed laser mode purity.The possible mechanism behind this phenomenon is proposed and revealed through comprehensive comparative experiments and theoretical analysis.Finally,a maximum output power of 7.49 kW is obtained with the beam quality factor of approximately 1.83,which is the highest output power ever reported in a forward tandem-pumped confined-doped fiber amplifier.This work could provide a good reference and practical solution to improve the TMI threshold and realize high-power high-brightness fiber lasers.
基金supported in part by the National Natural Science Foundation of China(Nos.62075116 and 62075117)Key Research Program of Shandong Province(No.2019JMRH0111)+2 种基金Natural Science Foundation of Shandong Province(Nos.ZR2019MF039 and ZR2020MF114)Founding for Qilu Young Scholars from Shandong UniversityChina Postdoctoral Science Foundation(No.2021TQ0190)。
文摘Beam quality improvements by a large margin for signal and idler beams of a high energy 100 Hz KTiOAsO_(4)(KTA)non-critical phase matching(NCPM)optical parametric oscillator(OPO)were demonstrated using an unstable resonator configuration instead of a plane-parallel one.Theoretically,influences of cavity lengths and transmission of an output coupler on the OPO conversion efficiency for both were numerically simulated.For OPO based on an unstable resonator with a Gaussian reflectivity mirror,the maximum pulse energies at the signal(1.53μm)and idler(3.47μm)were about 75 mJ and 26 mJ,respectively.The corresponding beam quality factors of the signal were M_(x)^(2)=9.8 and M_(y)^(2)=9.9,and M_(x)^(2)=11.2 and M_(y)^(2)=11.5 for the idler.As a comparison,128 mJ of signal and 48 mJ of idler were obtained with the plane-parallel resonator,and the M~2 factors of the signal were M_(x)^(2)=39.8 and M_(y)^(2)=38.4,and M_(x)^(2)=32.1 and M_(y)^(2)=31.4 for the idler.Compared with a plane-parallel cavity,over eight times and three times brightness improvements were realized for the signal and idler light,respectively.
基金Natural Sciences and Engineering Research Council of Canada(NSERC)University of Manitoba(U of M)
文摘We report on the performance of a continuous-wave Nd:Gd VO_4 laser in-band diode-pumped at 912 nm with high output power and excellent beam quality. The laser produced an output power of 19.8 W at 1063 nm with an optical efficiency of 59.3% and slope efficiency of 62.7%. The laser threshold was ~2.04 W of the absorbed pump power, and the laser output beam quality was ≤ 1.2 in the horizontal and vertical directions. The strength of thermal lensing at full output power(33.4 W of absorbed power) was measured to be an average of 8.6 diopters.It is shown that thermal lensing is reduced by a factor of 2 with respect to the Nd:YVO_4 lasers, thus opening a way for further output-power scaling.
文摘The degradation of beam quality in large-core fiber is investigated experimentally. It is found that the output beam quality factor M2 is a compound tanh function of the fiber lengths and misalignment launch results that the beam quality degraded faster.
基金supported by the National Natural Science Foundation of China (Grant No. 11205162)
文摘Based on space-charge wave theory,the formulae of the beam-wave coupling coefficient and the beam-loaded conductance are given for the beam-wave interaction in an N-gap Hughes-type coupled cavity chain.The ratio of the nonbeam-loaded quality factor of the coupled cavity chain to the beam quality factor is used to determine the stability of the beam-wave interaction.As an example,the stabilities of the beam-wave interaction in a three-gap Hughes-type coupled cavity chain are discussed with the formulae and the CST code for the operations of the 2π,π,and π/2 modes,respectively.The results show that stable operation of the 2π,π,and π/2 modes may all be realized in an extended-interaction klystron with the three-gap Hughes-type coupled cavity chain.
基金supported by the National Natural Science Foundation of China(Nos.62005075,61927815,and 61905061)Hebei Science and Technology Research Project(No.QN2020182)Hebei Natural Science Foundation(Nos.F2020202029 and F2020202026)。
文摘Stimulated Raman-scattering-based lasers provide an effective way to achieve wavelength conversion.However,thermally induced beam degradation is a notorious obstacle to power scaling and it also limits the applicable range where high output beam quality is needed.Considerable research efforts have been devoted to developing Raman materials,with diamond being a promising candidate to acquire wavelength-versatile,high-power,and high-quality output beam owing to its excellent thermal properties,high Raman gain coefficient,and wide transmission range.The diamond Raman resonator is usually designed as an external-cavity pumped structure,which can easily eliminate the negative thermal effects of intracavity laser crystals.Diamond Raman converters also provide an approach to improve the beam quality owing to the Raman cleanup effect.This review outlines the research status of diamond Raman lasers,including beam quality optimization,Raman conversion,thermal effects,and prospects for future development directions.
基金Project supported by the National Science and Technology Major Project of China(Grant Nos.2018YFB0504600and 2017YFB0405102)the Frontier Science Key Program of the President of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC006)+7 种基金the Pilot Project of the Chinese Academy of Sciences(Grant No.XDB43030302)the National Natural Science Foundation of China(Grant Nos.62090051,62090052,62090054,11874353,61935009,61934003,61904179,61727822,61805236,62004194,and 61991433)the Science and Technology Development Project of Jilin Province,China(Grant Nos.20200401062GX,202001069GX,20200501006GX,20200501007GX,20200501008GX,and 20190302042GX)the Key Research and Development Project of Guangdong Province,China(Grant No.2020B090922003)the Equipment Pre-researchChina(Grant No.2006ZYGG0304)the Special Scientific Research Project of the Academician Innovation Platform in Hainan Province,China(Grant No.YSPTZX202034)the Dawn Talent Training Program of CIOMP,China。
文摘The semiconductor laser array with single-mode emission is presented in this paper.The 6-μm-wide ridge waveguides(RWGs)are fabricated to select the lateral mode.Thus the fundamental mode of laser array can be obtained by the RWGs.And the maximum output power of single-mode emission can reach 36 W at an injection current of 43 A,after that,a kink will appear.The slow axis(SA)far-field divergence angle of the unit is 13.65.The beam quality factor M;of the units determined by the second-order moment(SOM)method,is 1.2.This single-mode emission laser array can be used for laser processing.
基金This work has received partial funding from the EUROfusion Consortium,funded by the European Union via the Euratom Research and Training Programme(Grant Agreement No.101052200—EUROfusion).
文摘In order to reach the highest intensities,modern laser systems use adaptive optics to control their beam quality.Ideally,the focal spot is optimized after the compression stage of the system in order to avoid spatio-temporal couplings.This also requires a wavefront sensor after the compressor,which should be able to measure the wavefront on-shot.At PHELIX,we have developed an ultra-compact post-compressor beam diagnostic due to strict space constraints,measuring the wavefront over the full aperture of 28 cm.This system features all-reflective imaging beam transport and a high dynamic range in order to measure the wavefront in alignment mode as well as on shot.
基金financially supported by the National Natural Science Foundation of China (Nos. 62035015 and 61805280)the Innovation Group of Hunan Province, China (No. 2019JJ10005)+1 种基金the Research Plan of National University of Defense Technology (No. ZK19-07)the Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology (No. SKL2020ZR07)
文摘We found the beam quality factor M^(2)of the fundamental mode as a function of wavelength is U-shaped in the working photonic bandgap(PBG) of an all-solid PBG fiber(AS-PBGF) for the first time,to the best of our knowledge,and our simulation results also match well with the phenomenon.The normal band that is near the high-frequency edge of the third PBG integrates the lowest M^(2)and single-mode operation simultaneously,while the other two edge regions suffer from anomalous variation of M^(2)versus wavelength.The general applicability of this finding can be further extended to other PBGs and also other representative structures in the AS-PBGF field.
基金supported by the National High Technology Research and Development Program of China.
文摘Based on the moiré effect and the Fresnel diffraction theory, a novel technique for diagnosing the beam properties is presented and analyzed, which is especially suitable for X-ray lasers. The method makes it possible, in a one-shot experimental measurement, to determine the beam quality factor M2, the effective radius of curvature, the beam width, the far-field divergence, and the waist location and radius as well as the spatial coherence and its evolution. Numerical simulation proves the validity of the method. Note that the novel moiré technique opens an efficient road, for the first time, to fully diagnose the spatial properties of X-ray lasers.
