Generation of coherent LO phonons in optically driven biased quantum wells

Papenkort T, Kuhn T, Axt VM

Abstract

We present a theoretical analysis and numerical simulations of the resonant generation of coherent LO phonons in an electrically biased quantum well. The system is driven by a laser pulse short enough to simultaneously excite two transitions, which leads to a quantum beat that can resonantly create coherent phonons. The generation of incoherent phonons is also calculated on a quantum kinetic level and found to be dominant in terms of the energy transferred to the lattice. The simulations successfully reproduce the main features found in recent experiments [Mizoguchi et al., Appl. Phys. Lett. 94, 171105 (2009)]. Depending on the excitation conditions different generation mechanisms can be discerned. We discuss their characteristics and their relative efficiency in the special case of the quantum well model under consideration.