Effect of focusing element-induced aberrations on filamentation and supercontinuum emission in ambient air.

Abstract

Femtosecond laser pulse induced filamentation in atmosphere is susceptible to a number of input laser, focusing optics and medium characteristics. Filamentation of fs pulses in atmosphere is an intense propagation regime where the focusing geometry used to focus the fs laser pulses play an important role influencing the filament intensity and the associated supercontinuum. We identified different optical elements used for focusing the fs laser pulses leading to filamentation in air and classified them according to the induced aberrations. To clearly identify the role of aberrations, all the optical elements were taken to have same focal length. The subsequent filament structure and emissions from the filament were correlated with the aberrations induced by optical element revealed stark differences. The onset of the filamentation, its longitudinal intensity and the associated supercontinuum emission (SCE) have varied drastically with the aberrations induced by the focusing optics. A systematic study directed to choose and identify suitable optical elements according to the usage of the fs pulses for a specific filamentation regime is presented.