Theory for coherent control of longitudinal optical phonons in GaAs using polarized optical pulses with relative phase locking

Abstract

A theoretical model for the coherent control of longitudinal optical phonons in GaAs (001) by double-pulse excitation was derived using a simplified band model and the allowed and forbidden Raman scattering. The time evolution of the electron-phonon states was calculated with the density-matrix formalism and second-order perturbation. The amplitude of the longitudinal optical phonons controlled by the two pulses was obtained as a function of the delay between the pulses for several polarization conditions. For parallel-polarized pulses, electronic and phonon interference fringes were predicted, which were independent of the crystal orientation and the ratio between the allowed and forbidden Raman scattering intensities. For orthogonally polarized pulses, only phonon interference fringes were obtained at an angle of $\ensuremath{\pi}/4$ from the [100] direction. When one of the pulses was along the [100] direction, electronic interference fringes were induced by the allowed Raman scattering, although the pump pulses do not interfere themselves.