Powerful femtosecond laser pulse propagation in the atmosphere and applications

High-power ultra-short laser pulses can propagate through a significant distance in air after self-focusing and filamentation.. Upon self-focusing, the pulse undergoes self-phase modulation turning into a broadband pulse spectrally ranging from the UV to IR, yet of strong spectral coherence, hence a white light laser pulse. Molecules in the filament will be ionized, fragmented and the resulting particles will fluoresce with well resolved molecular spectra without the interference of a plasma continuum even at atmospheric pressure. This talk gives a summary of some of our recent findings on the above mentioned phenomena as well as on ring formation, etc.