Ultrafast dissociation dynamics of chloroiodomethane (CH2ICl) in the B band is studied by femtosecond time- resolved time-of-flight (TOF) mass spectrometry. Time-resolved TOF mass signal of parent ion (CH2ICl+)...Ultrafast dissociation dynamics of chloroiodomethane (CH2ICl) in the B band is studied by femtosecond time- resolved time-of-flight (TOF) mass spectrometry. Time-resolved TOF mass signal of parent ion (CH2ICl+) and main daughter ion (CH2Cl+) are obtained. The curve for the transient signal of CH2ICl+ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function. The decay constant determined to be less than 35 fs reflects the lifetime of the B band. Significant substituent effects on photodissociation dynamics of CH2IC1 compared with CH3I are discussed. The dissociation time from the parent ion CH2IC1+ to the daughter ion CH2Cl+ is determined in the experiment. The optimized geometry of the ionic state of CH2ICl and the ionization energy are calculated for further analysis of the measurements. In addition, compared with the parent ion, a new decay component with time constant of -596 fs is observed for CH2Cl+, and reasonable mechanisms are proposed for the explanation.展开更多
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
We propose a metalens for coaxial double wavelength focusing.One focusing spot is a circular solid spot,and the other focusing spot is a doughnut-shaped spot that is circling the solid spot.The designed metalens was c...We propose a metalens for coaxial double wavelength focusing.One focusing spot is a circular solid spot,and the other focusing spot is a doughnut-shaped spot that is circling the solid spot.The designed metalens was composed of a met a-molecular nanostructured cell array.Each meta-molecular nanostructured cell was divided into four squares.Two slots with exactly the same shape,but usually with the rotation angle measured clockwise from the positive x axis,are etched into the gold film in two diagonally connected squares.Another two slots with the same shape but with the rotation angle measured counter-clockwise from the positive x axis are etched into another two diagonally connected squares in the same cell.The lasers with two different wavelengths are trans?formed into right-handed and left-handed circularly polarized beams,respectively.The two sets of slots with different azimuthal rotations modulated the phases of incident right-handed and left-handed circularly polarized beams independently.The numerical simulation with finite-difference time-domain(FDTD)software was carried out,and the experimental verification was also implemented.Both the experimental result and the numerical simulation agree well with the theoretical design.展开更多
We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthall...We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthally polarized beam, and a linearly polarized beam with three different weighting factors, respectively. A specially designed adjustable amplitude angular selector is also inserted at the back aperture of the objective for tuning the polarization azimuthally. It is shown that any desired overall polarization orientation can be obtained. We calculated the overall polarization orientation in the focal volume. It is found that the polar angle of the overall polarization orientation can be arbitrarily tuned by the combination of a radially polarized beam and a linearly polarized beam with different weighting factors, and the azimuthal angle can be tuned by rotating the orientation of the linearly polarized beam azimuthally.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 11304157,21303255 and 11475229the‘Six Talent Peaks’Project in Jiangsu Province under Grant No 2015-JNHB-011the College Students Practice Innovative Training Program of Nuist under Grant No 201610300042
文摘Ultrafast dissociation dynamics of chloroiodomethane (CH2ICl) in the B band is studied by femtosecond time- resolved time-of-flight (TOF) mass spectrometry. Time-resolved TOF mass signal of parent ion (CH2ICl+) and main daughter ion (CH2Cl+) are obtained. The curve for the transient signal of CH2ICl+ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function. The decay constant determined to be less than 35 fs reflects the lifetime of the B band. Significant substituent effects on photodissociation dynamics of CH2IC1 compared with CH3I are discussed. The dissociation time from the parent ion CH2IC1+ to the daughter ion CH2Cl+ is determined in the experiment. The optimized geometry of the ionic state of CH2ICl and the ionization energy are calculated for further analysis of the measurements. In addition, compared with the parent ion, a new decay component with time constant of -596 fs is observed for CH2Cl+, and reasonable mechanisms are proposed for the explanation.
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supported by the National Natural Science Foundation of China(Nos.61675093,61775140,and 61905106)the Natural Science Foundation of Shandong Province(Nos.ZR2017MA035 and ZR2019PF013)。
文摘We propose a metalens for coaxial double wavelength focusing.One focusing spot is a circular solid spot,and the other focusing spot is a doughnut-shaped spot that is circling the solid spot.The designed metalens was composed of a met a-molecular nanostructured cell array.Each meta-molecular nanostructured cell was divided into four squares.Two slots with exactly the same shape,but usually with the rotation angle measured clockwise from the positive x axis,are etched into the gold film in two diagonally connected squares.Another two slots with the same shape but with the rotation angle measured counter-clockwise from the positive x axis are etched into another two diagonally connected squares in the same cell.The lasers with two different wavelengths are trans?formed into right-handed and left-handed circularly polarized beams,respectively.The two sets of slots with different azimuthal rotations modulated the phases of incident right-handed and left-handed circularly polarized beams independently.The numerical simulation with finite-difference time-domain(FDTD)software was carried out,and the experimental verification was also implemented.Both the experimental result and the numerical simulation agree well with the theoretical design.
基金supported by the National Natural Science Foundation of China(Nos.61675093 and 61775140)the Shandong Natural Science Foundation(No.ZR2017MA035)
文摘We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthally polarized beam, and a linearly polarized beam with three different weighting factors, respectively. A specially designed adjustable amplitude angular selector is also inserted at the back aperture of the objective for tuning the polarization azimuthally. It is shown that any desired overall polarization orientation can be obtained. We calculated the overall polarization orientation in the focal volume. It is found that the polar angle of the overall polarization orientation can be arbitrarily tuned by the combination of a radially polarized beam and a linearly polarized beam with different weighting factors, and the azimuthal angle can be tuned by rotating the orientation of the linearly polarized beam azimuthally.