Joint Time-Frequency Measurements Of Mode-Locked 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 mode-locking 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 intra-cavity 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 mode-locked 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