Observation of Biexciton-Resonant Hyper-Parametric Scattering in SiO2/CuCl Layered Structures

We have prepared SiO2/CuCl layered structures and investigated the structural and optical properties, focusing on the observation of biexciton-resonant hyper-parametric scattering that is a promising process to generate entangled photons. A crystalline CuCl film, which is the active layer, was grown on an Al2O3 substrate by a vacuum deposition method, and then an amorphous SiO2 film as the passivation layer for hygroscopic CuCl was prepared by an rf-magnetron sputtering method. X-ray diffraction patterns and optical spectra of excitons indicate that the growth of the SiO2-passivation layer does not degrade the crystallinity of the underlying CuCl thin film. It has been demonstrated that the biexciton-resonant hyper-parametric scattering is clearly observable in the SiO2/CuCl layered structure.