Second-order optical nonlinearity of TiO2 nanocrystals studied by hyper-Rayleigh scattering

摘要

Incoherent second harmonic generation (SHG) or hyperRayleigh scattering (HRS) technique was used to measure for the first-order hyperpolarizability (β) of TiO2 nanocrystals (10 nm mean diameter)of centrosymmetric materials which are electric dipole forbidden for HRS. Results show per TiO2 particle β value is 1.4x10-27 esu and per TiO2 formula unit β value is 0.09x10-30 esu which is very small compared to that of the nanocrystals of noncentrosymmetric materials reported previously, attributed to the absence of nanoerystal core contribution and resonance enhancement.