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 selfstart a dispersion-compensated Ti:sapphire laser, which produces stable time-transform-limited pulses as short as 70 fs in a TEM(00) 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.