Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient gratin...Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient grating. Two major compo- nents are resolved in the dynamics of Rh6G＋. The first component, with a lifetime τTPIET = 140 fs-260 fs, is attributed to PIET from the phenyl ring to the xanthene plane. The IVR process occurring in the range ZIVR = 3.3 ps-5.2 ps is much slower than the first component. The PIET and IVR processes occurring in the excited state of Rh6G＋ are quantitatively determined, and a better understanding of the relationship between these processes is obtained.展开更多
Spectral modulation and supercontinuum generation of a probe pulse is investigated by using the plasma grating induced by the interference of two infrared femtosecond laser pulses. The dependences of the supercontinuu...Spectral modulation and supercontinuum generation of a probe pulse is investigated by using the plasma grating induced by the interference of two infrared femtosecond laser pulses. The dependences of the supercontinuum generation from the probe pulse on the time delay, the relative polarization angle between the probe pulse and the two-pump pulses, and the input probe pulse energy are investigated. The far-field spatial profiles of the three pulses are measured with different time delays and relative polarization angle, and the core energy of the probe pulse as functions of the time delay and relative polarization angle are also shown.展开更多
The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond （130 fs） Ti...The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond （130 fs） Ti： sapphire laser （λp=790 rim）. The refractive index modifications with diameters ranging from 400 nm to 4 gm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1 ×10^13 W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change （An） was estimated to be 1.5x10 2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.展开更多
The simple surface current model is extended to study the generation of high-order harmonics for a relativistic circularly polarized laser pulse interacting with a plasma grating surface. Both exact relativistic elect...The simple surface current model is extended to study the generation of high-order harmonics for a relativistic circularly polarized laser pulse interacting with a plasma grating surface. Both exact relativistic electron dynamics and optical interference of surface periodic structure are considered. It is found that high order harmonics in the specular direction are obviously suppressed whereas the harmonics of the grating periodicity are strongly enhanced and folded into small solid angles with respect to the surface direction. The conversion efficiency of certain harmonics is five orders of magnitude higher than that of the planar target cases. It provides an effective approach to generate a coherent radiation within the so-called ＇water window＇ while maintaining high conversion efficiency and narrow angle spread.展开更多
Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial str...Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial strength distribution of magnetic fields can be accurately predicted by calculating the net flow caused by the superposition of source flow and return flow of hot electrons.The theoretical model established shows good agreement with the simulation results,indicating that the magnetic-field strength scales positively to the temperature of hot electrons.This provides us a way to improve the magnetic-field generation by using a micro-structured plasma grating in front of the solid target.Compared with that for a common flat target,hot electrons can be effectively heated with the well-designed grating size,leading to a stronger magnetic field.The spatial distribution of magnetic fields can be modulated by optimizing the grating period and height as well as the incident angle of the laser pulse.展开更多
The fabrication of an internal diffraction grating with photoinduced refractive index modification in planar hybrid germanium-silica plates was demonstrated using low-density plasma formation excited by a high-intensi...The fabrication of an internal diffraction grating with photoinduced refractive index modification in planar hybrid germanium-silica plates was demonstrated using low-density plasma formation excited by a high-intensity femtosecond (150 fs) Ti:sapphire laser (λp=790 nm).The refractive index modifications with diameters ranging from 400 nm to 3 μm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 2×1013 W/cm2.The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which low-density plasma occurred.展开更多
For atmospheric pressure plasma jets(APPJ),the gas temperature is essential for their applications.A spectral diagnosis of APPJ’s gas temperature is conducted in this work.The optical emission spectra of helium APPJ ...For atmospheric pressure plasma jets(APPJ),the gas temperature is essential for their applications.A spectral diagnosis of APPJ’s gas temperature is conducted in this work.The optical emission spectra of helium APPJ are captured by using an optical spectrometer system.Then,the grating secondary spectrum of OH(A2∑+(ν=0)→X2П(ν=0))are used to diagnose the gas temperature of plasmas because the spectrum has excellent resolution.Meanwhile,the vibrational temperatures are estimated by using the vibration sequence of N2band(SPS,the second positive system).On the basis of the method,some important conclusions were obtained.First,the spectral identifying indicates that the grating primary spectrum covers a whole wavelength range from 200 nm to 900 nm,and that the grating secondary spectrum overlaps with the primary spectrum from 400 nm to 900 nm.Second,the gas temperature(about 320 K)is close to the room temperature,while the vibrational temperature of the N2(SPS)is about 5 000 K.The trend of the two temperatures changing with the applied voltage is discussed in the end.展开更多
Filament-and plasma-grating-induced breakdown spectroscopy(F-GIBS)was demonstrated as an efficient technique for sensitive detection of metals in water,where plasma gratings were established through synchronized nonli...Filament-and plasma-grating-induced breakdown spectroscopy(F-GIBS)was demonstrated as an efficient technique for sensitive detection of metals in water,where plasma gratings were established through synchronized nonlinear interaction of two noncollinear filaments and an additional filament was generated with another fs laser beam propagating along their bisector.A water jet was constructed vertically to the three coplanar filaments,overcoming side effects from violent plasma explosion and bubble generation.Three distinct regimes of different mechanisms were validated for nonlinear couplings of the third filament with plasma gratings.As the third filament was temporally overlapped with the two noncollinear filaments in the interaction zone,all the three filaments participated in synchronous nonlinear interaction and plasma grating structures were altered by the addition of the third filament.As the third filament was positively or negatively delayed,the as-formed plasma gratings were elongated by the delayed third filament,or plasma gratings were formed in the presence of plasma expansion of the ahead third filament,respectively.Using F-GIBS for trace metal detection in water,significant spectral line enhancements were observed.展开更多
As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the pl...As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the plasma density grating driven by two intersecting driver laser pulses is not only nonuniform in space but also varies over time.Consequently,the probe laser pulse that passes through such a dynamic plasma density grating will be depolarized,that is,its polarization becomes spatially and temporally variable.More importantly,the laser depolarization may spontaneously take place for crossed laser beams if their polarization angles are arranged properly.The laser depolarization by a dynamic plasma density grating may find application in mitigating parametric instabilities in laser-driven inertial confinement fusion.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21003033 and 21203047)the Guangxi Provincial Natural Science Foundation,China(Grant Nos.2012GXNSFBA053012 and 2014GXNSFAA118019)the Research Foundation of Education Bureau of Guangxi Zhuang Autonomous Region,China(Grant No.ZD2014127)
文摘Photo-induced intramolecular electron transfer （PIET） and intramolecular vibrational relaxation （IVR） dynamics of the excited state of rhodamine 6G （Rh6G＋） in DMSO are investigated by multiplex transient grating. Two major compo- nents are resolved in the dynamics of Rh6G＋. The first component, with a lifetime τTPIET = 140 fs-260 fs, is attributed to PIET from the phenyl ring to the xanthene plane. The IVR process occurring in the range ZIVR = 3.3 ps-5.2 ps is much slower than the first component. The PIET and IVR processes occurring in the excited state of Rh6G＋ are quantitatively determined, and a better understanding of the relationship between these processes is obtained.
基金the National Natural Science Foundation of China(Grant Nos.11135002,11075069,91026021,and 11075068)the Scholarship Award for Excellent Doctoral Student of Ministry of Education,China
文摘Spectral modulation and supercontinuum generation of a probe pulse is investigated by using the plasma grating induced by the interference of two infrared femtosecond laser pulses. The dependences of the supercontinuum generation from the probe pulse on the time delay, the relative polarization angle between the probe pulse and the two-pump pulses, and the input probe pulse energy are investigated. The far-field spatial profiles of the three pulses are measured with different time delays and relative polarization angle, and the core energy of the probe pulse as functions of the time delay and relative polarization angle are also shown.
基金Projects(2010-0001-226, 2010-0008-277) supported by NCRC(National Core Research Center) Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology
文摘The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond （130 fs） Ti： sapphire laser （λp=790 rim）. The refractive index modifications with diameters ranging from 400 nm to 4 gm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1 ×10^13 W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change （An） was estimated to be 1.5x10 2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11375265,11475259 and 11675264the National Basic Research Program of China under Grant No 2013CBA01504the Science Challenge Project under Grant No JCKY2016212A505
文摘The simple surface current model is extended to study the generation of high-order harmonics for a relativistic circularly polarized laser pulse interacting with a plasma grating surface. Both exact relativistic electron dynamics and optical interference of surface periodic structure are considered. It is found that high order harmonics in the specular direction are obviously suppressed whereas the harmonics of the grating periodicity are strongly enhanced and folded into small solid angles with respect to the surface direction. The conversion efficiency of certain harmonics is five orders of magnitude higher than that of the planar target cases. It provides an effective approach to generate a coherent radiation within the so-called ＇water window＇ while maintaining high conversion efficiency and narrow angle spread.
基金supported by the National Natural Science Foundation of China(Grant Nos.12175310,12305268,and U2241281)the Natural Science Foundation of Hunan Province(Grant Nos.2024JJ6184,2022JJ20042,and 2021JJ40653)the Scientific Research Foundation of Hunan Provincial Education Department(Grant Nos.22B0655 and 22A0435)。
文摘Generation of self-generated annular magnetic fields at the rear side of a solid target driven by relativistic laser pulse is investigated by using theoretical analysis and particle-in-cell simulations.The spatial strength distribution of magnetic fields can be accurately predicted by calculating the net flow caused by the superposition of source flow and return flow of hot electrons.The theoretical model established shows good agreement with the simulation results,indicating that the magnetic-field strength scales positively to the temperature of hot electrons.This provides us a way to improve the magnetic-field generation by using a micro-structured plasma grating in front of the solid target.Compared with that for a common flat target,hot electrons can be effectively heated with the well-designed grating size,leading to a stronger magnetic field.The spatial distribution of magnetic fields can be modulated by optimizing the grating period and height as well as the incident angle of the laser pulse.
文摘为解决半导体激光器的偏振问题,提出了一种利用泰尔博特位移光刻曝光技术在Ga As衬底上制作周期光栅的方法,并系统研究了工艺参数和抗反射层对制备的周期光栅质量的影响。利用二次光刻工艺和反应离子蚀刻工艺在Ga As衬底上制备圆孔阵列周期光栅;通过电感耦合等离子体蚀刻设备制造均匀光栅。实验结果表明,该工艺流程可制备深度为20~150 nm的动态可调圆孔阵列周期光栅;当曝光剂量为30 m J·cm^(-2),曝光光强度为2 m W·cm^(-2),显影时间为1 min时,所曝光出的周期光栅符合实验要求;重复实验证明了利用泰尔伯特位移光刻技术制备光栅工艺的可行性及稳定性。
基金Project(2010-0008-277)supported by NCRC(National Core Research Center)Program through the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology
文摘The fabrication of an internal diffraction grating with photoinduced refractive index modification in planar hybrid germanium-silica plates was demonstrated using low-density plasma formation excited by a high-intensity femtosecond (150 fs) Ti:sapphire laser (λp=790 nm).The refractive index modifications with diameters ranging from 400 nm to 3 μm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 2×1013 W/cm2.The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which low-density plasma occurred.
基金Project supported by China National Fund for Distinguished Young Scientists （51125029）, China Foundation for the Author of National Excellent Doctoral Dissertation （200338）, Intersection Subject Program of Xi＇an Jiaotong University （xjj2012132）, Fundamental Research Fund for the Central Universities （xjj2010160）, China National Science Foundation for Young Scientists （51307133）.
文摘For atmospheric pressure plasma jets(APPJ),the gas temperature is essential for their applications.A spectral diagnosis of APPJ’s gas temperature is conducted in this work.The optical emission spectra of helium APPJ are captured by using an optical spectrometer system.Then,the grating secondary spectrum of OH(A2∑+(ν=0)→X2П(ν=0))are used to diagnose the gas temperature of plasmas because the spectrum has excellent resolution.Meanwhile,the vibrational temperatures are estimated by using the vibration sequence of N2band(SPS,the second positive system).On the basis of the method,some important conclusions were obtained.First,the spectral identifying indicates that the grating primary spectrum covers a whole wavelength range from 200 nm to 900 nm,and that the grating secondary spectrum overlaps with the primary spectrum from 400 nm to 900 nm.Second,the gas temperature(about 320 K)is close to the room temperature,while the vibrational temperature of the N2(SPS)is about 5 000 K.The trend of the two temperatures changing with the applied voltage is discussed in the end.
基金sponsored by Shanghai Rising-Star Program(Grant No.22QC1401000)the National Defense Administration of Science,Technology and Industry(Grant No.HTKJ2021KL504014)+2 种基金the National Key Research and Development Program(Grant No.2018YFB0504400)the National Natural Science Foundation of China(Grant Nos.11621404,11727812,and 62035005)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01-ZX05).
文摘Filament-and plasma-grating-induced breakdown spectroscopy(F-GIBS)was demonstrated as an efficient technique for sensitive detection of metals in water,where plasma gratings were established through synchronized nonlinear interaction of two noncollinear filaments and an additional filament was generated with another fs laser beam propagating along their bisector.A water jet was constructed vertically to the three coplanar filaments,overcoming side effects from violent plasma explosion and bubble generation.Three distinct regimes of different mechanisms were validated for nonlinear couplings of the third filament with plasma gratings.As the third filament was temporally overlapped with the two noncollinear filaments in the interaction zone,all the three filaments participated in synchronous nonlinear interaction and plasma grating structures were altered by the addition of the third filament.As the third filament was positively or negatively delayed,the as-formed plasma gratings were elongated by the delayed third filament,or plasma gratings were formed in the presence of plasma expansion of the ahead third filament,respectively.Using F-GIBS for trace metal detection in water,significant spectral line enhancements were observed.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975154,11991074,12005287 and 12135009)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA25050100 and XDA25010100)+1 种基金the Presidential Foundation of the China Academy of Engineering Physics(Grant No.YZJJLX2016008)the Science Challenge Project(Grant No.TZ2018005).
文摘As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the plasma density grating driven by two intersecting driver laser pulses is not only nonuniform in space but also varies over time.Consequently,the probe laser pulse that passes through such a dynamic plasma density grating will be depolarized,that is,its polarization becomes spatially and temporally variable.More importantly,the laser depolarization may spontaneously take place for crossed laser beams if their polarization angles are arranged properly.The laser depolarization by a dynamic plasma density grating may find application in mitigating parametric instabilities in laser-driven inertial confinement fusion.
