Effect of internal optical pumping on the picosecond kinetics of a laser diode with field-assisted gain control

摘要

Picosecond-range single optical pulses with peak power in the range 10-100 W are fairly attractive for various practical applications. A laser diode structure has lately been suggested which produces powerful (～ 50 W) picosecond (～20 ps) optical pulses near the trailing edge of the current pulse by means of field-assisted gain control. Lasing onset is delayed in this diode by a few nanoseconds due to intendance-reduced pumping efficiency caused by the implementation of internal optical pumping. The ps operating mode is based on a compromise between the dynamics of carrier accumulation and of the transverse electric field, controlled by the efficiency of the internal optical pumping. The pumping efficiency is determined to a large extent by competition between stimulated and spontaneous radiative recombination at the source of optical pumping. An effect of the laser diode switching from the picosecond to the quasi-steady-state (ns) mode was observed when the length of the laser cavity was reduced from 400 μm to 200 μm. This phenomenon is studied and attributed to an increase in the fraction of spontaneous photons due to reduction in the density of the stimulated emission at the source of the optical pumping.