High power quantum dot lasers at 1160 nm

Improved device characteristics of high-power InGaAs/GaAs quantum dot (QD) lasers are presented. An ideal internal quantum efficiency close to 100%, v ery low transparency current density of 18 A/cm(2) and a peak power close t o 4 W at 1155 nm lasing wavelength in pulsed operation at room temperature are demonstrated. The improvement of the devices is mainly due to the reduc tion of non-radiactive recombination centres in the GaAs matrix around the dots. The lasing spectra for different driving currents are presented and c ompared to theoretical calculations based on master equations for the micro -states (MEM) coupled to the rate equations for the: photon density. From t he maximum width of the lasing spectra under high driving currents (18 nm) the fraction of QDs that contribute to the lasing, emission is deduced. For different lasers the maximum ground (excited) state gain is found to be 13 .6 cm(-1) (34 cm(-1)), respectively, via a fit of the QD gain-cur rent depe ndence according to the MEM theory.