Self-starting mode locking of a cw Nd:YAG laser using cascaded second-order nonlinearities

The nonlinear mode variations induced by the equivalent third-order susceptibility resulting from cascaded secondorder nonlinearities in an intracavity lithium triborate crystal are exploited for mode locking of a cw Nd:YAG laser. The loss modulations are provided by a slit, as in the Kerr-lens mode-locking scheme. The mode-locking process is self-starting and produces nearly transform-limited pulses of 14-ps duration with 0.5-W average power.