Ultrafast imaging the light-speed propagation of a focused femtosecond laser pulse in air and its ionized electron dynamics and plasma-induced pulse reshaping

作者：Yu, Yanwu; Jiang, Lan^*; Cao, Qiang; Shi, Xueshong; Wang, Qingsong; Wang, Guoyan; Lu, Yongfeng

来源：Applied Physics A, 2016, 122(3): 205.

DOI：10.1007/s00339-016-9773-8

• EMISSION-SPECTRA
• REFRACTIVE-INDEX
• AMBIENT AIR
• TIME
• FILAMENTATION
• GENERATION
• ABLATION
• O-2
• N-2

The light-speed propagation of a focused femtosecond (fs) laser pulse in air was recorded by a pump-probe shadowgraph imaging technique with femtosecond time resolution. The ultrafast dynamics of the laser-ionized electrons were studied, which revealed a strong reshaping of the laser field due to laser-air nonlinear interaction. The influence of laser fluence and focusing conditions on the pulse reshaping was studied, and it was found that: (1) double foci are formed due to the refocusing effect when the laser fluence is higher than 500 J/cm(2) and the focusing numeric aperture (NA) is higher than 0.30; and (2) a higher NA focusing lens can better inhibit the prefocusing effect and nonlinear distortion in the Gaussian beam waist.

• 出版日期2016-3
• 单位北京理工大学