Spectral responses of phonon optical generation and detection in superlattices

M. F. PASCUAL-WINTER, A. FAINSTEIN, B. JUSSERAND, B. PERRIN, AND A. LEMAÎTRE

PHYSICAL REVIEW B - SOLID STATE

APS

Lugar: Nueva York; Año: 2012 vol. 85 p. 235443 - 235443

0556-2805

We present a thorough theoretical and experimental analysis of the generation and detection of coherent phonons in superlattices by optical femtosecond pulses. We focus on the spectral responses of both phenomena in pump-probe experiments. The samples consist of two GaAs/AlAs superlattices separated by an intermediate layer through which phonons can propagate. The spatial decoupling of the generation and detection stages in one and the other supperlattice enables the individualization of each phenomenon. We clearly verify experimentally the selection rules for the generation and detection processes, which translate into well-defined maxima at specific frequencies in the corresponding spectral responses. A thickness gradient in one of the superlattices adds a degree of freedom that permits the variation of the spectral detuning between the maxima in the generation and in the detection spectral responses. The zero-detuning case is investigated. In the analysis of both spectral responses, the full size of the sample is found to play a significant role. Thin (similar to 3 mu m) and thick (similar to 350 mu m) samples are compared. Backreflection of light at sample outer surfaces and inner interfaces induces important alterations to the spectral responses as well.