Extended filamentation of temporally chirped femtosecond Bessel beam in fused silica

Abstract

We reported experimental results on extending the filamentaion in fused silica with the temporally chirped femtosecond Bessel beams. The effect of the pulse chirp on the femtosecond filamentation with different pulse energies has been studied. The results show that the filamentation length is strongly influenced by the pulse energy and the chirp. Under our experiment condition, low enough pulse energies were used to avoid the damage of the fused silica. It is demonstrated that the filamentation length increases first and then reduces with the increase of the absolute value of the negative pulse chirp. There exists a negative chirp range where the filamentation length reaches a maximum and is relative stable for all cases of pulse energies under our experiment condition. However, when the positive chirp is applied, both the intensity and length of filamentation decrease with the increase of the positive chirp. In addition, both the negative and positive chirps do not affect the onset of the filamentation. On the other hand, we find that the greater the laser energy is, the longer the filamentation is. Furthermore, the extent of the filamentation extension is more obvious when a lower pulse energy is used. For higher energies, the filamentation has a more uniform intensity distribution. Therefore, the extension of the filamentation in fused silica with uniform intensity can be realized by adjusting the energy and temporally chirp of the laser pulse.