Room-Temperature Dephasing in InAs Quantum Dots

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