Picosecond internal Q-switching mode correlates with laser diode breakdown voltage

Abstract

The record picosecond power density recently achieved with a current-pumped laser diode turned our attention to a still unexplained 50-year-old phenomenon termed “internal Q-switching”. The correlation found experimentally here between the relatively high breakdown voltage (∼5–11 V) in a heavily doped single-heterostructure laser diode and its high-power picosecond lasing provides a means for solving the puzzle. Together with the experimental fact that picosecond lasing occurs from the p-n junction, this implies that internal Q-switching is determined by the compensated layer rather than by “traditional” single-heterostructure waveguide. This finding is valid for various growth technologies independently of whether the high break-down voltage and picosecond lasing are achieved by exact compensation of shallow donors by shallow acceptors, or by doping profile gradients.