Room-temperature dephasing in InAs quantum dots

The room temperature dephasing in InAs/InGaAs/GaAs self-assembled quantum d ots, embedded in a waveguide for laser applications, is measured using two independent methods: spectral hole burning and four-wave mixing. Without th e application of bias current for electrical carrier injection, a dephasing time of approximate to 260 fs, weakly dependent on the optical excitation density, is found and attributed to phonon interaction. The application of a bias current, leading to population inversion in the dot ground state and optical gain, strongly decreases the dephasing time to less than 50 fs, li kely due to enhanced carrier-carrier scattering in the presence of the elec trically injected carriers.