Terahertz Emission from Quantum Beats in Coupled Quantum Wells

Abstract

We have investigated the terahertz (THz) emission from quantum beats in coupled quantum wells by time-resolved THz spectroscopy. It is found that the intensity of the THz emission exhibits a clear resonance in the excitation wavelength, suggesting that quantum beats in coupled quantum wells are caused by excitons. It is also found that the dephasing time of quantum beats is almost constant (∼6 ps) up to 50 K and decreases rapidly with increasing temperature, indicating that the coherence of quantum beats is broken by impurity and/or roughness scattering at low temperatures and by optical phonon scattering at high temperatures.