Gain and threshold characteristics of long wavelength lasers based on InAs/GaAs quantum dots formed by activated alloy phase separation

Experimental and theoretical study was made of injection lasers based on In As/GaAs quantum dots (QDs) formed by the activated alloy phase separation a nd emitting at about 1.3 mum. Electoluminescence and gain spectra were inve stigated. The maximum modal gain is measured experimentally using two diffe rent techniques. Threshold current densities as low as 22 A cm(-2) per QD s heet were achieved. A step-like switch from ground- to excited-state transi tion lasing was observed with an increasing cavity loss, The characteristic temperatures for a sample with tour cleaved sides and a 2-mm long stripe d evice at 300 K were 140 and 83 K, respectively. Single lateral-mode continu ous-wave (CW) operation with the maximum output power of 210 mW was realize d. Threshold characteristics of a laser were simulated taking into account radiative recombination in QDs, the wetting layer, and the optical confinem ent layer. The dependence of the threshold current density on the cavity le ngth was shown to be extremely sensitive to the QD-array parameters determi ning the maximum gain for ground- and excited-state transitions and to the waveguide design. Our analysis reveals that nonradiative recombination chan nels may play an important role in the laser operation.