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Diode-pumped passively Q-switched Nd:YVO_4 laser with GaAs saturable absorber

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Chinese Optics Letters 2004年第8期2卷 462-465页

作者：李桂秋赵圣之杨克建赵宏明 School of Information Science and Engineering Shandong University Ji'nan 250100 School of Information Science and Engineering Shandong University Ji'nan 250100he intracavity photon density is assumed to be of Gaussian spatial distributions and its longitudinal variation is also considered in the rate equations for a laser diode (LD) end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber. These space-dependent rate equations are solved numerically. The dependences of pulse width pulse repetition rate single-pulse energy and peak power on incident pump power are obtained. In the experiment the LD end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber is realized and the experimental results are consistent with the numerical solutions.

The intracavity photon density is assumed to be of Gaussian spatial distributions and its longitudinal variation is also considered in the rate equations for a laser diode (LD) end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber. These space-dependent rate equations are solved numerically. The dependences of pulse width, pulse repetition rate, single-pulse energy, and peak power on incident pump power are obtained. In the experiment, the LD end-pumped passively Q-switched Nd:YVO4 laser with GaAs saturable absorber is realized and the experimental results are consistent with the numerical solutions.

关键词： multiphoton processes Optically pumped lasers Q switched lasers Semiconducting gallium arsenide Semiconductor lasers

Experimental observation of the linewidth narrowing of electromagnetically induced transparency resonance

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Chinese Optics Letters 2005年第8期3卷 486-489页

作者：王波李淑静姚景芹马杰彭枫蒋刚王海 The State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-Electronics Shanxi University Institute of Atomic and Molecular Physics Sichuan University

We report an experimental observation of the variation in linewidth of the electromagnetically induced transparency （EIT） resonance in a three-level A-type system for several laser bandwidths in a Rb vapor cell, with and without a buffer gas. It is found, using narrow bandwidth （about 20 kHz） diode laser for both coupling and probe beams, that the linewidth of the EIT resonance can be significantly narrowed in the Rb vapor cell with the buffer gas. The results are in good qualitative agreement with a simple theoretical calculation.

关键词： multiphoton processes Quantum interference phenomena Quantum optics Quantum theory Semiconductor lasers

A new solid-conversion gas detector for high energy X-ray industrial computed tomography

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Optoelectronics Letters 2011年第5期7卷 337-340页

作者：周日峰陈伟民段晓礁 Key Lab. for Optoelectronic Technology & Systems of Ministry of Education Chongqing University

A new type of solid-conversion gas detector is investigated for high energy X-ray industrial computed tomography (HECT). The conversion efficiency is calculated by using the EGSnrc Monte Carlo code on the Linux platform to simulate the transport process of photons and electrons in the detector. The simulation results show that the conversion efficiency could be more than 65%, if the X-ray beam width is less than about 0.2 mm, and a tungsten slab with 0.2 mm thickness and 30 mm length is employed as a radiation conversion medium. Meanwhile the results indicate that this new detector has higher conversion efficiency as well as less volume. Theoretically this new kind of detector could take place of the traditional scintillation detector for HECT.

关键词： Computer operating systems Computerized tomography Conversion efficiency Gas detectors High energy physics multiphoton processes Tungsten X rays

Angular momentum distribution in strong-field frustrated tunneling ionization

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Chinese Optics Letters 2018年第4期16卷 6-10页

作者： Jintai Liang Ruozhou Zhang Xiaomeng Ma Yueming Zhou and Peixiang Lu School of Physics Huazhong University of Science and Technology Wuhan 430074 China Laboratory of Optical Information Technology Wuhan Institute of Technology Wuhan 430205 China

Using the classical-trajectory Monte Carlo model, we have theoretically studied the angular momentum distribution of frustrated tunneling ionization（FTI） of atoms in strong laser fields. Our results show that the angular momentum distribution of the FTI events exhibits a double-hump structure. With this classical model, we back traced the tunneling coordinates, i.e., the tunneling time and initial transverse momentum at tunneling ionization. It is shown that for the events tunneling ionized at the rising edge of the electric field,the final angular momentum exhibits a strong dependence on the initial transverse momentum at *** for the events ionized at the falling edge, there is a relatively harder recollision between the returning electron and the parent ion, leading to the angular momentum losing the correlation with the initial transverse momentum. Our study suggests that the angular momentum of the FTI events could be manipulated by controlling the initial coordinates of the tunneling ionization.

关键词： 020.2649 Strong field laser physics 020.4180 multiphoton processes 320.7110 Ultrafast nonlinear optics

Femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles

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Chinese Optics Letters 2020年第8期18卷 59-64页

作者： Liping Gong Xiaohe Zhang Zhuqing Zhu Guanghao Rui Jun He Yiping Cui Bing Gu Advanced Photonics Center Southeast UniversityNanjing 210096China Key Laboratory of Optoelectronic Technology of Jiangsu Province School of Physical Science and TechnologyNanjing Normal UniversityNanjing 210023China School of Physics and Electronics Central South UniversityChangsha 410012China Collaborative Innovation Center of Light Manipulations and Applications Shandong Normal UniversityJinan 250358China

We investigate femtosecond laser trapping dynamics of two-photon absorbing hollow-core nanoparticles with different volume fractions and two-photon absorption(TPA)*** simulations show that the hollow-core particles with low and high-volume fractions can easily be trapped and bounced by the tightly focused Gaussian laser pulses,*** studies show that the hollow-core particles with and without TPA can be identified,because the TPA effect enhances the radiation force,and subsequently the longitudinal force destabilizes the trap by pushing the particle away from the focal *** results may find direct applications in particle sorting and characterizing the TPA coefficient of single nanoparticles.

关键词： laser trapping multiphoton processes ultrafast nonlinear optics

Doping transition metal ions as a method for enhancement of ablation rate in femtosecond laser irradiation of silicate glass

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Chinese Optics Letters 2014年第12期12卷 78-82页

作者：房巨强姜澜曹强袁艳萍曲良体段吉安陆永枫 Nano Manufacturing Fundamental Research Joint Laboratory of National Science Foundation of China School of Mechanical EngineeringBeijing Institute of Technology Institute of Laser Engineering Beijing University of Technology Key Laboratory of Cluster Science Ministry of Education School of ChemistryBeijing Institute of Technology State Key Laboratory of High Performance Complex Manufacturing Central South University Department of Electrical Engineering University of Nebraska-LincolnLincoln NE 68588-0511 USA

We present a doping method to improve the femtosecond laser ablation rate and promote ablation selectivity. Doping transition metal ions, Co2＋ or Cu2＋, in silicate glass apparently change absorption spectroscopy and induce resonant absorption at wavelengths of 600 and 800 nm, respectively. Comparing with femtosecond laser processing of the same glass without doping, we find that the threshold fiuenee decreases and the ablation rate increases in resonant absorption in doped silicate glass. Resonant absorption effectively increases multiphoton ionization for seed-free electron generation, which in turn enhances avalanche ionization.

关键词： Absorption spectroscopy Electrons Glass Glass transition Ionization Laser ablation Metal ions multiphoton processes Photoionization Silicates Transition metal compounds Transition metals Ultrashort pulses

The　dissociative　ionization　and　Coulomb　explosion　of　ethane　by　a　femtosecond　laser　field

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Chinese Physics B 2004年第9期13卷 1564-1568页

作者：李霞任海振马日陈建新杨宏龚旗煌 StateKeyLaboratoryforMesoscopicPhysics DepartmentofPhysicsPekingUniversityBeijing100871China

Femtosecond laser-induced dissociation and Coulomb explosion of polyatomic molecule C2H6 were systematically investigated using a time-of-flight mass spectrometer and a chirped pulse amplifier laser. With the laser intensity varying from 2.4× 1015 W/cm2 to 1.2× 1016W/cm2, strong molecular ions C2Hn+ (n=0-6) and atomic ions Cm+ (m=1-3) signals were observed. The double-peak structure of atomic ions indicated the occurrence of Coulomb explosion. Compared with the nearly isotropic distribution of C+, highly charged ions Cm+ (m=2-3) exhibited a sharply anisotropic angular distribution, which was attributed to the geometric alignment.

关键词： field ionization multiphoton processes mass spectra

Compact and high-power broadband terahertz source based on femtosecond photonic crystal fiber amplifier

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Chinese Optics Letters 2011年第11期9卷 26-28页

作者：刘丰胡晓堃李江王昌雷李毅栗岩锋宋有建刘博文胡明列柴路邢岐荣王清月张伟力 Ultrafast Laser Laboratory Center for Terahertz WavesCollege of Precision Instrument and Opto-Electronics EngineeringKey Laboratory of Opto-Electronics Information Technology (Ministry of Education)Tianjin University School of Electrical and Computer Engineering Oklahoma State UniversityStillwater

We present a review of the development of a compact and high-power broadband terahertz （THz） source optically excited by a femtosecond photonic crystal fiber （PCF） *** large mode area of the PCF and the stretcher-free configuration make the pump source compact and very *** THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz.A strong saturation effect is observed,which is attributed to pump pulse absorption;a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm.A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy.

关键词： Broadband amplifiers Crystal whiskers Electromagnetic pulse Fiber amplifiers multiphoton processes Nonlinear optics Optical pumping Photonic crystals Pulse repetition rate Pumps Terahertz spectroscopy

Theoretical and experimental investigations on the threshold of a laser-induced breakdown of air

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Chinese Optics Letters 2016年第4期14卷 6-10页

作者：刘栋陈传松满宝元孙艳娜李菲菲 School of Physics and Electronics Shandong Normal University

The threshold of a laser-induced breakdown of air is determined experimentally and theoretically. We find that the ionization of air has two steps： the first step is a multi-photon ionization process, which provides enough ＂seed electrons＂ to initiate the next step, and the second one is predominated by cascade ionization, which con- tinues to produce free electrons geometrically until the critical free-electron density for breakdown is reached. So a two-step model based on the Morgan ionization model is established to describe the breakdown process. It is found that the time node dividing the two steps is about 9.8 ns in atmospheric air, and the threshold derived from the two-step model proposed here is more consistent with the experimental results than traditional ionization model.

关键词： Atmospheric ionization Electrons Ionization multiphoton processes