The Experts below are selected from a list of 19257 Experts worldwide ranked by ideXlab platform
X C Zhang - One of the best experts on this subject based on the ideXlab platform.
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enhancement of terahertz wave generation from Laser Induced Plasma
Applied Physics Letters, 2007Co-Authors: Xu Xie, Jianming Dai, X C ZhangAbstract:It is well known that air Plasma Induced by ultrashort Laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the Laser Induced Plasma where there is a preexisting Plasma background. When a Laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another Laser beam creating a Plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.
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detection of broadband terahertz waves with a Laser Induced Plasma in gases
Physical Review Letters, 2006Co-Authors: Jianming Dai, Xu Xie, X C ZhangAbstract:We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) waves via electric-field-Induced second-harmonic generation in Laser-Induced air Plasma with ultrashort Laser pulses. By introducing the second-harmonic component of the white light in the Laser-Induced Plasma as a local oscillator, coherent detection of broadband THz waves with ambient air is demonstrated for the first time. Our results show that, depending on the probe intensity, detection of THz waves in air can be categorized as incoherent, hybrid, and coherent detection. Coherent detection is achieved only when the tunnel ionization process dominates in gases.
Xu Xie - One of the best experts on this subject based on the ideXlab platform.
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enhancement of terahertz wave generation from Laser Induced Plasma
Applied Physics Letters, 2007Co-Authors: Xu Xie, Jianming Dai, X C ZhangAbstract:It is well known that air Plasma Induced by ultrashort Laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the Laser Induced Plasma where there is a preexisting Plasma background. When a Laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another Laser beam creating a Plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.
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detection of broadband terahertz waves with a Laser Induced Plasma in gases
Physical Review Letters, 2006Co-Authors: Jianming Dai, Xu Xie, X C ZhangAbstract:We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) waves via electric-field-Induced second-harmonic generation in Laser-Induced air Plasma with ultrashort Laser pulses. By introducing the second-harmonic component of the white light in the Laser-Induced Plasma as a local oscillator, coherent detection of broadband THz waves with ambient air is demonstrated for the first time. Our results show that, depending on the probe intensity, detection of THz waves in air can be categorized as incoherent, hybrid, and coherent detection. Coherent detection is achieved only when the tunnel ionization process dominates in gases.
Jianming Dai - One of the best experts on this subject based on the ideXlab platform.
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enhancement of terahertz wave generation from Laser Induced Plasma
Applied Physics Letters, 2007Co-Authors: Xu Xie, Jianming Dai, X C ZhangAbstract:It is well known that air Plasma Induced by ultrashort Laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the Laser Induced Plasma where there is a preexisting Plasma background. When a Laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another Laser beam creating a Plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.
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detection of broadband terahertz waves with a Laser Induced Plasma in gases
Physical Review Letters, 2006Co-Authors: Jianming Dai, Xu Xie, X C ZhangAbstract:We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) waves via electric-field-Induced second-harmonic generation in Laser-Induced air Plasma with ultrashort Laser pulses. By introducing the second-harmonic component of the white light in the Laser-Induced Plasma as a local oscillator, coherent detection of broadband THz waves with ambient air is demonstrated for the first time. Our results show that, depending on the probe intensity, detection of THz waves in air can be categorized as incoherent, hybrid, and coherent detection. Coherent detection is achieved only when the tunnel ionization process dominates in gases.
Wenqi Lei - One of the best experts on this subject based on the ideXlab platform.
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Generation and expansion of Laser-Induced Plasma as a spectroscopic emission source
Frontiers of Physics, 2012Co-Authors: Vincent Motto-ros, Wenqi Lei, Xiaochun Wang, Xueshi BaiAbstract:Laser-Induced Plasma represents today a widespread spectroscopic emission source. It can be easily generated using compact and reliable nanosecond pulsed Laser on a large variety of materials. Its application for spectrochemical analysis for example with Laser-Induced breakdown spectroscopy (LIBS) has become so popular that one tends to forget the complex physical and chemical processes leading to its generation and governing its evolution. The purpose of this review article is to summarize the backgrounds necessary to understand and describe the Laser-Induced Plasma from its generation to its expansion into the ambient gas. The objective is not to go into the details of each process; there are numerous specialized papers and books for that in the literature. The goal here is to gather in a same paper the essential understanding elements needed to describe Laser-Induced Plasma as results from a complex process. These elements can be dispersed in several related but independent fields such as Laser-matter interaction, Laser ablation of material, optical and thermodynamic properties of hot and ionized gas, or Plasma propagation in a background gas. We believe that presenting the ensemble of understanding elements of Laser-Induced Plasma in a comprehensive way and in limited pages of this paper will be helpful for further development and optimized use of the LIBS technique. Experimental results obtained in our laboratory are used to illustrate the studied physical processes each time such illustration becomes possible and helpful.
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time resolved characterization of Laser Induced Plasma from fresh potatoes
Spectrochimica Acta Part B: Atomic Spectroscopy, 2009Co-Authors: Wenqi Lei, Vincent Mottoros, Myriam Boueri, Dacheng Zhang, Lijuan Zheng, Heping ZengAbstract:Abstract Optical emission of Laser-Induced Plasma on the surface of fresh vegetables provides sensitive analysis of trace elements for in situ or online detection of these materials. This emergent technique promises applications with expected outcomes in food security or nutrition quality, as well as environment pollution detection. Characterization of the Plasma Induced on such soft and humid materials represents the first step towards quantitative measurement using this technique. In this paper, we present the experimental setup and protocol that optimize the Plasma generation on fresh vegetables, potatoes for instance. The temporal evolution of the Plasma properties are investigated using time-resolved Laser-Induced breakdown spectroscopy (LIBS). In particular, the electron density and the temperatures of the Plasma are reported as functions of its decay time. The temperatures are evaluated from the well known Boltzmann and Saha-Boltzmann plot methods. These temperatures are further compared to that of the typical molecular species, CN, for Laser-Induced Plasma from plant materials. This comparison validates the local thermodynamic equilibrium (LTE) in the specific case of fresh vegetables ablated in the typical LIBS conditions. A study of the temporal evolution of the signal to noise ratio also provides practical indications for an optimized detection of trace elements. We demonstrate finally that, under certain conditions, the calibration-free LIBS procedure can be applied to determine the concentrations of trace elements in fresh vegetables.
Michael N R Ashfold - One of the best experts on this subject based on the ideXlab platform.
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position and time resolved stark broadening diagnostics of a non thermal Laser Induced Plasma
Plasma Sources Science and Technology, 2016Co-Authors: Benjamin S Truscott, Michael N R AshfoldAbstract:We present an analysis of the Stark-broadened line shapes of silicon ions in a Laser-Induced Plasma using a model constructed, without assuming local thermodynamic equilibrium (LTE), using a Druyvesteyn electron energy distribution function (EEDF). The method is applied to temporally and spatially resolved measurements of Si2+ and Si3+ emissions from a transient Plasma expanding into vacuum, produced by 1064 nm, nanosecond pulsed Laser ablation of a Si (1 0 0) target. The best-fitting simulated line shapes and the corresponding electron number densities and temperatures (or equivalently, Druyvesteyn average energies) are compared with those returned assuming LTE (i.e. for a Maxwellian EEDF). Non-thermal behavior is found to dominate at all but the very earliest stages of expansion close to the target surface, consistent with McWhirter's criterion for the establishment of LTE. The Druyvesteyn EEDF always yields an equivalent or better model of the experimental measurements, and the observed increasingly strong departure from the Maxwellian case with time and distance from the ablation event highlights the essential invalidity of the LTE assumption for moderate-power, nanosecond Laser-Induced Plasma expanding in vacuo.
