Picosecond Dynamics of Confined Excitons and Their Optical Nonlinearities in CuCl Nanocrystals

Optical nonlinearities in confined exciton system were investigated in CuCl nanocrystals embedded in NaCl matrices at 77 K with use of ns and sub-ps laser excitations. Size-dependent excitation photon density necessary for the saturation of the exciton absorption peak under the ns excitation at the exciton resonance showed that the number of excitons per one nanocrystal governs the magnitude of the saturation regardless of the crystal size. Transient absorption change measured under sub-ps band-to-band excitation revealed the strong correlation between the temporal response of the excitonic optical nonlinearities and the formation and decay dynamics of the exciton and biexciton systems in CuCl nanocrystals.