LAUSR

We report on the experimental investigation of femtosecond laser filament guided negative coronas. When the coupling between the filament and negative corona was weak, the side fluorescence spectral analysis confirmed the existence of impact ionization although less effect on the filament length was observed. When the coupling was strong so that the negative corona was well connected with the filament, the filament guided coronas at the ends of laser filaments were observed. The newly generated negative coronas were confined around the filament axis, and no streamer-type of coronas guided by the filament was observed under conditions similar to those reported in the work of Wang et al. [Sci. Rep. 5, 18681 (2015)] although both could give rise to an elongation of the filament. A physical picture was proposed to understand the processes of the laser filament guided coronas.