Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and ran...Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and random number generation.However,due to their high threshold and phase instability,the production of picosecond random lasers has still been a challenge.In this work,we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers.Notably,stable picosecond random laser emission lasting600 ps is observed at a low pump energy of 50μJ,indicating the gain-switching mechanism.Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level.When the intensity of the continuously pumped light reaches a specific value,the number of inversion populations in the“scattering cavity”surpasses the threshold rapidly.Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon.This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.展开更多
The high-pressure structure and elastic properties of calcium azide(Ca(N_(3))_(2))were investigated using in-situ highpressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa,respectively.The compressib...The high-pressure structure and elastic properties of calcium azide(Ca(N_(3))_(2))were investigated using in-situ highpressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa,respectively.The compressibility of Ca(N_(3))_(2)changed as the pressure increased,and no phase transition occurred within the pressure from ambient pressure up to 54 GPa.The measured zero-pressure bulk modulus of Ca(N_(3))_(2)is higher than that of other alkali metal azides,due to differences in the ionic character of their metal-azide bonds.Using CASTEP,all vibration modes of Ca(N_(3))_(2)were accurately identified in the vibrational spectrum at ambient pressure.In the high-pressure vibration study,several external modes(ext.)and internal bending modes(ν_(2))of azide anions(N_(3)^(-))softened up to~7 GPa and then hardened beyond that pressure.This evidence is consistent with the variation observed in the F_(E)–f_(E)data analyzed from the XRD result,where the slope of the curve changes at 7.1 GPa.The main behaviors under pressure are the alternating compression,rotation,and bending of N_(3)^(-)ions.The bending behavior makes the structure of Ca(N_(3))_(2)more stable under pressure.展开更多
探讨甲酸和蔗糖两种添加剂对红麻青贮的影响。以刈割后的红麻为青贮原料,添加不同计量的蔗糖(10 g/kg,15 g/kg和20 g/kg)和甲酸(3 m L/kg,6 m L/kg和9 m L/kg),并分别设空白对照,密封青贮60 d后分析。结果显示,添加蔗糖或者甲酸能够显...探讨甲酸和蔗糖两种添加剂对红麻青贮的影响。以刈割后的红麻为青贮原料,添加不同计量的蔗糖(10 g/kg,15 g/kg和20 g/kg)和甲酸(3 m L/kg,6 m L/kg和9 m L/kg),并分别设空白对照,密封青贮60 d后分析。结果显示,添加蔗糖或者甲酸能够显著提高粗蛋白含量(P<0.05)和可溶性碳水化合物含量(P<0.05)降低红麻青贮饲料的PH值,实验组p H均小于4.0,乳酸含量显著增加(P<0.05),氨态氮含量显著降低(P<0.05),实验组均没有检测到丁酸含量,青贮发酵品质良好;且在本实验研究范围内认为,添加20 g/kg的蔗糖得到的红麻青贮饲料的品质优于其他实验组,添加9 m L/kg的甲酸得到的红麻青贮饲料的品质优于其他实验组。展开更多
基金supported by the National Natural Science Foundation of China(Nos.12174002,11874012,11874126,and 51771186)the Excellent Scientific Research and Innovation Team of Anhui Province(No.2022AH010003)+3 种基金the Key Research and Development Plan of Anhui Province(No.202104a05020059)the Innovation Project for the ReturnedOverseasScholarsofAnhuiProvince(No.2021LCX011)the University Synergy Innovation Program of Anhui Province(No.GXXT-2020-052)the Anhui Young Wanjiang Scholars Talent Project(No.Z010118167)。
文摘Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and random number generation.However,due to their high threshold and phase instability,the production of picosecond random lasers has still been a challenge.In this work,we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers.Notably,stable picosecond random laser emission lasting600 ps is observed at a low pump energy of 50μJ,indicating the gain-switching mechanism.Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level.When the intensity of the continuously pumped light reaches a specific value,the number of inversion populations in the“scattering cavity”surpasses the threshold rapidly.Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon.This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.
基金Project supported financially by the Program for the Development of Science and Technology of Jilin Province,China(Grant Nos.YDZJ202301ZYTS382,YDZJ202201ZYTS316,and 20230101285JC)the National Natural Science Foundation of China(Grant No.11904128)+1 种基金the Program for Science and Technology of Education Department of Jilin Province,China(Grant Nos.JJKH20220438KJ and JJKH20220423KJ)the Program for the Jilin Provincial Development and Reform Commission Project(Grant No.2022C040-6)。
文摘The high-pressure structure and elastic properties of calcium azide(Ca(N_(3))_(2))were investigated using in-situ highpressure x-ray diffraction and Raman scattering up to 54 GPa and 19 GPa,respectively.The compressibility of Ca(N_(3))_(2)changed as the pressure increased,and no phase transition occurred within the pressure from ambient pressure up to 54 GPa.The measured zero-pressure bulk modulus of Ca(N_(3))_(2)is higher than that of other alkali metal azides,due to differences in the ionic character of their metal-azide bonds.Using CASTEP,all vibration modes of Ca(N_(3))_(2)were accurately identified in the vibrational spectrum at ambient pressure.In the high-pressure vibration study,several external modes(ext.)and internal bending modes(ν_(2))of azide anions(N_(3)^(-))softened up to~7 GPa and then hardened beyond that pressure.This evidence is consistent with the variation observed in the F_(E)–f_(E)data analyzed from the XRD result,where the slope of the curve changes at 7.1 GPa.The main behaviors under pressure are the alternating compression,rotation,and bending of N_(3)^(-)ions.The bending behavior makes the structure of Ca(N_(3))_(2)more stable under pressure.
文摘探讨甲酸和蔗糖两种添加剂对红麻青贮的影响。以刈割后的红麻为青贮原料,添加不同计量的蔗糖(10 g/kg,15 g/kg和20 g/kg)和甲酸(3 m L/kg,6 m L/kg和9 m L/kg),并分别设空白对照,密封青贮60 d后分析。结果显示,添加蔗糖或者甲酸能够显著提高粗蛋白含量(P<0.05)和可溶性碳水化合物含量(P<0.05)降低红麻青贮饲料的PH值,实验组p H均小于4.0,乳酸含量显著增加(P<0.05),氨态氮含量显著降低(P<0.05),实验组均没有检测到丁酸含量,青贮发酵品质良好;且在本实验研究范围内认为,添加20 g/kg的蔗糖得到的红麻青贮饲料的品质优于其他实验组,添加9 m L/kg的甲酸得到的红麻青贮饲料的品质优于其他实验组。
