Buildup of steady-state picosecond pulses in an actively mode-locked laser-diode array.

We have studied experimentally the temporal and spectral characteristics of an actively mode-locked laserdiode array in an external cavity as it evolves to the steady state. It is found that the buildup time to steadystate picosecond pulses takes less than 45 round trips. The number of clusters of the longitudinal-mode spectrum reduces during the evolution and finally approaches a steady-state spectral distribution with the pulse energy mainly distributed among a few clusters near the line center.