Measurement Techniques of Optical Nonlinearities—Two-Photon Absorption/Fluorescence and Hyper-Rayleigh Scattering

Abstract

There is considerable interest in finding nanomaterials exhibiting large optical nonlinearities. Thus, there is a need to develop methods to determine nonlinear coefficients discussed throughout this book. The Z-scan technique is a method able to measure both nonlinear absorption (NLA) and nonlinear refraction (NLR) in solids, liquids, and liquid solutions. In this chapter, we first present a brief review of this technique. Also the “P-scan” technique developed in our experimental laboratory will be described along with the photon detection set-up which permits to measure two-photon-excited fluorescence cross sections. We will also describe the physical principles that allow the realization of Hyper-Rayleigh scattering. We will compare the incoherent Hyper-Rayleigh scattering (HRS) technique with a coherent experimental technique: electric-field-induced second harmonic generation (EFISHG). Hyper-Rayleigh technique can be employed to characterize the first hyperpolarizability of nanoclusters in solution.