FEMTOSECOND PULSES FROM A CONTINUOUSLY SELF-STARTING PASSIVELY MODE-LOCKED TI-SAPPHIRE LASER

We show that an external coupled cavity containing a nonlinear quantum-well reflector can continuously self-start a dispersion-compensated Ti:sapphire laser, which produces stable time-transform-limited pulses as short as 70 fs in a TEM00 mode. In this mode of operation, the quantum wells do not control the mode-locking process, as in previous research on the resonant passive mode-locked laser. By separating the mode-locking and starting processes, we show that the presence of higher-order spatial modes is not required to start or sustain mode locking.