Second-order nonlinear optics in isotropic liquids: Hyper-Rayleigh scattering in solution.

The incoherent second-order nonlinear light scattering in a macroscopically isotropic molecular liquid has emerged as a simple and widely applicable technique for the experimental determination of the first hyperpolarizability of nonlinear optical molecules in solution. The technique has become widely known as hyper-Rayleigh scattering. Until recently, electric-field-induced second-harmonic generation was the only solution technique to determine molecular hyperpolarizabilities. Apart from being more complex a technique, the applied field also limits its applicability to neutral and dipolar solutions. In this paper, we present the specific advantages of the new hyper-Rayleigh scattering technique and exemplify its wider scope with results from three different kinds of molecular materials: octopoles, biological chromophores, and quantum colloids.