Stretched-pulse fiber lasers based on semiconductor saturable absorbers

Stretched-pulse mode-locked erbium-doped fiber lasers based on monolithically grown InGaAsP/InP semiconductor saturable absorber mirrors are described. The saturable absorbers are used to initiate the mode locking, to stabilize the pulse train and to control the cavity dispersion. We obtained reliable operation at the fundamental repetition rate with 1.3 nJ of pulse energy, limited by the maximum available pump power of 175 mW. The amplitude fluctuation was estimated to be less than 1.6×10-3. 135-fs transform-limited pulses were obtained after compression in standard telecommunication fiber. The performance of the stretched-pulse mode-locked fiber laser with near-resonant semiconductor saturable absorber has been studied. A semiconductor dispersive saturable absorber mirror was used for intracavity chirp compensation in the stretched-pulse fiber laser. With the semiconductor mirror combining both negative group-velocity dispersion and saturable absorption, we have demonstrated the production of high-power chirp-free pulses directly from stretched-pulse laser.