Abstract

Vertical-external-cavity surface-emitting semiconductor lasers (VECSELs) in passively mode-locked operation can emit trains of transform-limited pulses in diffraction-limited circular beams with high average power [1] from which, moreover, pulse durations as short as 60 fs have been demonstrated [2]. The VECSEL uses an active-mirror gain structure containing quantum wells grown above a quarter-wave stack. The shortest pulses to date have been achieved using InGaAs/GaAs quantum wells emitting around 1 µm. The gain structure is pumped optically into the quantum well barriers by a fibre-coupled diode. A quantum well intracavity semiconductor saturable absorber mirror (SESAM) initiates spontaneous mode-locking at a repetition rate typically between 1 and some 10s of GHz, consistent with the nanosecond lifetime of the optically excited carriers.

© 2011 Optical Society of America