Theoretical treatment of the first-order hyper-Raman scattering in semiconductors

Abstract

ABSTRACT The hyper-Raman scattering by LO phonon s is theoretically investigated, taking into account the Wannier excitons as intermediate virtual states. The different scattering mechanisms are considered. The hyper-Raman efficiency as a function of the energy of incident photons is calculated for ZnSe, ZnO, CdS and GaN. Keywords: hyper-Raman scattering, exciton, phonon 1. INTRODUCTION The hyper-Raman scattering (HRS) is a non linear optical process where an emission of a quantum of scattered light and a creation of a phonon occur under simultaneous absorption of two quanta of exciting radiation. The increase of a number of photons participating in the elementary event of the HRS in comparison with the Raman scattering (RS) leads to the wider selection rules and enables one to obta in information which is inaccessible to RS methods. The HRS of light under two-photon excitation near the energy gap is of special interest because in this case the hyper-Raman signal sharply grows. Besides, in the hyper-Raman scattering process the doubled frequency of incident radiation can be in resonance with transitions to the two-photon allowed states. Thus, the HRS can be the powerful technique for characterizing such states. The resonant HRS of light was experimentally investigated in CdS