Nonlinear optical relaxation times from incoherent and coherent second-harmonic generation

Incoherent second-order nonlinear optical scattering, also known as hyper-Rayleigh scattering (HRS), has become widely accepted as an experimental technique for the determination of the molecular second-order nonlinear optical polarizability (first hyperpolarizability). The generic laser type used for this experiment is a high-power Q-switched nanosecond pulse laser, due to the low quantum efficiency of the HRS process. A femtosecond version of HRS has been developed. This has led to the implementation of high-frequency demodulation techniques for the multi-photon fluorescence contribution in hyper-Rayleigh scattering.