Joint time-frequency measurements of modelocked semiconductor diode lasers and dynamics using frequency-resolved optical gating

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