Influences of astigmatic focusing geometry on femtosecond filamentation and supercontinuum generation in fused silica

The influences of focal lens tilting on the filamentation of femtosecond laser pulses in fused silica were studied experimentally. The length of filamentation, output beam profile and supercontinuum generation were found to be close related with the tilt angle of the focusing element. When the focusing lens is rotated, the filament breaks into two parts along the propagation axis. The distance between the two parts was calculated and well matched with the predicted results. It is also found that the supercontinuum spectrum becomes narrower and its conversion efficiency becomes lower by rotating the focal lens.