title: Simple method of measuring laser peak intensity inside femtosecond laser filament in air.
abstract: Measurement of laser intensity inside a femtosecond laser filament is a challenging task. In this work, we suggest a simple way to characterize laser peak intensity inside the filament in air. It is based on the signal ratio measurement of two nitrogen fluorescence lines, namely, 391 nm and 337 nm. Because of distinct excitation mechanisms, the signals of the two fluorescence lines increase with the laser intensity at different orders of nonlinearity. An empirical formula has been deduced according to which laser peak intensity could be simply determined by the fluorescence ratio.
authors.affiliation: Institute of Modern Optics, Nankai University, Key Laboratory of Optical Information Science and Technology, Ministry of Education, Tianjin, 300071 China.
authors.forename: Shengqi
authors.initials: S
authors.lastname: Xu
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Sun
authors.forename: Bin
authors.initials: B
authors.lastname: Zeng
authors.forename: Wei
authors.initials: W
authors.lastname: Chu
authors.forename: Jiayu
authors.initials: J
authors.lastname: Zhao
authors.forename: Weiwei
authors.initials: W
authors.lastname: Liu
authors.forename: Ya
authors.initials: Y
authors.lastname: Cheng
authors.forename: Zhizhan
authors.initials: Z
authors.lastname: Xu
authors.forename: See Leang
authors.initials: SL
authors.lastname: Chin
mesh_terms: D000388:Air; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007834:Lasers; D055096:Optical Devices; D010783:Photometry / Q000295:instrumentation*