title: Characteristics of micro air plasma produced by double femtosecond laser pulses.
abstract: Dynamic characteristics of air plasma generated by focused double collinear femtosecond laser pulses with a time interval of 10 ns are experimentally investigated. The air plasma emission changes significantly when altering the energy ratio between the two laser pulses. Time-resolved shadowgraphic measurements reveal that a small volume of transient vacuum is formed inside the air shock wave produced by the first laser pulse, which causes the second laser pulse induced ionization zone to present as two separate sections in space. Also recorded is strong scattering of the second laser pulse by the ionized air just behind the ionization front of the first laser pulse produced shock wave. Due to the high intensity of the scattered light, coherent Thomson scattering enhanced by plasma instabilities is believed to be the main scattering mechanism in this case.
authors.affiliation: Institute of Modern Optics, Nankai University, Key Laboratory of Optical Information Science and Technology, Ministry of Education, Tianjin 300071, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhang
authors.forename: Zehua
authors.initials: Z
authors.lastname: Wu
authors.forename: Kuanhong
authors.initials: K
authors.lastname: Xu
authors.forename: Xiaonong
authors.initials: X
authors.lastname: Zhu
mesh_terms: D000388:Air / Q000032:analysis*; D007834:Lasers; D008422:Materials Testing; D008904:Miniaturization; D058626:Plasma Gases / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: D058626:Plasma Gases