Ultrafast solid-state mode-locked lasers using resonant nonlinearities

The authors discuss recent experiments in which resonant nonlinearities are used in order to directly mode lock solid-state lasers or to initiate self-focusing mode locking. Three configurations using resonant nonlinearities are considered. They are coupled cavity mode locking using a semiconductor nonlinear mirror, a further extension of this including self-focusing mode locking, and the closely related case of an intracavity saturable absorber dye. In the last two cases, the resonant nonlinearity only starts the self-focusing mode locking. Passive mode-locking techniques using resonant nonlinearities have the advantage that they self-start mode locking. The focus is on the Ti:sapphire laser, for which the techniques were first demonstrated