Joint time-frequency measurements of mode-locked semiconductor diode lasers and dynamics using fuequency-resolved optical gating

Joint time-frequency ultrafast measurements using frequency-resolved optica l gating (FROG) have been used to provide a fundamental understanding of: 1 ) ultrashort pulse propagation in semiconductor optical amplifiers; 2) the mode-locking dynamics in external cavity semiconductor diode lasers; and 3) correlated multiple-wavelength generation from mode-locked semiconductor l asers, The pulse shaping and chirping effects measured by FROG are shown to be attributed to intracavity gain and saturable absorbing dynamics, as wel l as group velocity dispersion. In addition, the intracavity gain dynamics show a regime of transient unsaturated gain, which can be exploited to allo w phase-correlated multiple-wavelength mode-locked operation from a single- stripe external-cavity semiconductor diode laser. In this case, FROG techni ques are used to understand the underlying mechanisms involved in the phase correlation process.