Pulse Self-Compression in the Nonlinear Propagation of Intense Femtosecond Laser Pulse in Normally Dispersive Solids

Abstract

Summary. The self-compression phenomena of intense femtosecond pulses in normally dispersive solids were investigated experimentally. Both un-chirped and negatively chirped laser pulses were used as input pulses. It is demonstrated that intense femtosecond laser pulses can be compressed by the nonlinear propagation in the transparent solids, and the temporal and spectral characteristics of output pulses were found to be significantly affected by the input laser intensity, with higher intensity corresponding to shorter compressed pulses. By the propagation in a 3 mm thick BK7 glass plate with the laser power of GW level, a self-compression from 50 fs to 20 fs was achieved, with a compression factor of about 2.5. However, the output laser pulse was observed to split into two peaks when the input laser intensity is high enough to generate super-continuum and conical emission. When the input laser pulse is negatively chirped, the spectra of the pulse are reshaped and narrowed due to strong self-action effects, and the temporal pulse duration is found to be self-shortening. With the increase in the input pulse intensity, the resulted self-compressed pulses became even shorter than the input laser pulse, and also shorter than sech 2 transform-limited pulse according to the corresponding spectra.

Femtosecond filamentation in transparent media

“…From Tzortzakis et al (2001d). filaments in BaF 2 and have interpreted the white light spectral distribution as resulting from plasma induced self-phase modulation. Chen et al (2006bChen et al ( , 2005 and Li et al (2006) have shown experimentally that high-power femtosecond pulses undergoing filamentation in a piece of BK7 glass lead to a self-compression from 50 to 20 fs, with a compression factor of about 2.5. However, the output pulse was observed to be split into two peaks when the input intensity is high enough to generate supercontinuum and conical emission as shown by Tzortzakis et al (2001d).…”