Intracavity gain dynamics and their role in mode-locked semiconductor diode lasers

Abstract

In this paper, we present the intracavity gain dynamics of hybrid modelocked external cavity semiconductor lasers. Using the pump-probe method, the optical gain and transmittance of a modelocked external cavity laser diode and saturable absorber were measured, respectively. The pulse shaping processes were measured by investigating the chirp of the optical pulse at the output coupler, before and after the saturable absorber. These measurements were obtained by a spectrally resolved cross correlation technique. In comparison with the previous studies of the single pass dynamics in semiconductor optical amplifiers, the dynamics of the nonlinearities affecting the pulse shaping within the laser cavity is less dramatic owing to the longer intracavity pulse widths. It was also observed that the linear GVD plays an important role in the shaping of the pulse envelop and linearizing the pulse chirp.