Abstract

The dephasing of near-zone center longitudinal optical (LO) phonons has recently been measured in high-purity gallium phosphide directly in the time domain. An application of subpicosecond time-resolved coherent anti-Stokes Raman scattering (TR-CARS) has demonstrated that in GaP dephasing occurs through a harmonic decay of the LO phonons into two longitudinal acoustic (LA) phonons. This same technique has also been applied to the dephasing of polaritons of frequency ~350 cm⁻¹ and wave vector k ~ 10³ cm⁴. In the polariton case, however, the dephasing is shown to involve decay through two channels. The temperature dependence of the decay rates leads to the identification of these decay channels.

© 1991 Optical Society of America