Optical selection rule for hyper-Rayleigh scattering in resonance with exciton states in ZnSe

We report on the polarization dependence for hyper-Rayleigh scattering (HRS) in two-photon resonance with exciton states in ZnSe. The HRS signal is enhanced drastically when twice the incident photon energy is resonant with the excitation energy of the 2P excitons in ZnSe/GaAs thin films. The selection rules for the HRS in two-photon resonance with the 2P excitons are different from those for nonlinear susceptibility determined by crystal symmetry. Further, we report a study of the symmetries of the 2P excitonic wave function with linearly- and circularly-polarized incident beams. The heavy and light hole 2P excitons belong to different symmetries of the base functions