  Nonstationary pulse regimes associated with self modulation of a Kerr-lens
modelocked Ti:sapphire laser have been studied experimentally and
theoretically. Such laser regimes occur at an intracavity group delay
dispersion that is smaller or larger than what is required for stable
modelocking and exhibit modulation in pulse amplitude and spectra at
frequencies of several hundred kHz. Stabilization of such modulations, leading
to an increase in the pulse peak power by a factor of ten, were accomplished by
weakly modulating the pump laser with the self-modulation frequency. The main
experimental observations can be explained with a round trip model of the fs
laser taking into account gain saturation, Kerr lensing, and second- and
third-order dispersion.
