Kerr-lens mode-locked laser model: role of space-time effects

A spatio-temporal model of a self-mode-locked laser is presented. It uses a full wave-optics approximation of the propagation in the laser resonator and includes dispersion, self-phase modulation, and self-focusing of the intracavity radiation. It is shown that the self-consistent evolution of the pulse toward steady state imposes strong space-time focusing in the crystal, where both the space and time foci are located. This combined focusing is inherent for Kerr-lens mode-locked lasers with linear and ring cavities, and with and without intracavity saturable absorbers. It is considered as a general mechanism for compensation of space-time astigmatism within the nonlinear resonator. The predictions of the model agree very well with the experiment. (C) 1998 Optical Society of America.