Femtosecond pulse generation in passively mode locked InAs quantum dot lasers

Optical pulse durations of an InAs two-section passively mode-locked quantum dot laser with a proton bombarded absorber section reduce from 8.4 ps at 250 K to 290 fs at 20 K, a factor of 29, with a corresponding increase in optical bandwidth. Rate equation analysis of gain and emission spectra using rate equations suggests this is due to the very low emission rate of carriers to the wetting layer in the low temperature, random population regime which enables dots across the whole inhomogeneous distribution to act as independent oscillators