LINEAR AND NONLINEAR LIGHT SCATTERING BY EMERGING MATERIALS

摘要

Second-order nonlinear light scattering, or hyper-Rayleigh scattering (HRS) was originally conceived as a simple screening technique for neutral, dipolar second-order nonlinear optical chromophores. It was realized early on that this incoherent scattering technique was, unlike the more conventional coherent electric-field-induced second-harmonic generation (EF1SHG), uniquely suited to address new molecular symmetries. Since the advent of HRS, octopolar design strategies at the molecular and supramolecular level emerged as alternatives to the dipolar paradigm. Also ionic molecules, organometallic complexes and chiral helicenes could be studied at the molecular level. For improved accuracy and precision, HRS has been implemented with high repetition rate femtosecond laser pulses in combination with phase and demodulation measurements. Through rational design of optimized chromophores in the right environment, large first hyperpolarizability values have been obtained in accordance with a limiting theory. Photonic crystals have recently emerged as interesting linear and nonlinear optical materials. We have demonstrated that the natural protein bacteriorhodopsin is, in fact, a nonlinear photonic crystal.