Dynamics of coherent optical phonon generation and decay in GaP

Abstract

Coherent longitudinal optical (LO) phonons are generated through nonlinear excitation by laser light. It is observed that the vibronic sideband structure associated with coherent LO phonons, and that of the acoustic phonons, generated during the dephasing of the LO phonons have an unexpected dependence on the power of the excitation lasers. The effect is traced to the presence of an electron-hole plasma which is shown to influence the phonon generation process. Moreover, it is directly verified that the dephasing of coherent near-zone-center longitudinal optical phonons in GaP is dominated by anharmonic decay into two half-energy longitudinal acoustic phonons.