Second-order optical nonlinearity study of CdS nanoparticles via hyper-Rayleigh scattering

The second-order nonlinear optical (NLO) properties of the CdS colloid were experimentally studied in water by the newly developed hyper-Rayleigh scat tering (HRS) technique. The 'per particle' first-order hyperpolarizability beta value was found to fall in the range of 10(-26) esu, which is among th e largest values reported for solution species. It was also found that the beta value of CdS nanoparticles decreases with increasing aging time, attri buted to the change in the surface chemical structure of nanoparticles in s olution as a result of their high surface activity. In addition, the strong two-photon fluorescence (2PF) of CdS nanoparticles implies that two-photon absorption (2PA)-induced resonance enhancement may contribute to the HRS s ignal of CdS nanoparticles. (C) 2001 Elsevier Science Ltd. All rights reser ved.