Interrogation of Polar Structural Modification on the Atomic Length Scale by Radiative Nonlinear Optical Phenomena

Abstract

This dissertation investigates the interaction of (ultrashort) laser pulses with polar oxide single and nanocrystals, with a focus on light-induced polar structural modification studied by nonlinear optical phenomena. Central to this work are self-localization processes such as self-trapped excitons (STEs) and small polarons, which govern the optical and electronic properties of these materials. Using temperature-dependent and time-resolved spectroscopic techniques, it is demonstrated that STEs dominate the photoluminescence in lithium niobate tantalate systems and persist in nanocrystalline form as sensitive probes of dynamic polarization processes. Complementary nonlinear optical measurements establish a direct link between microscopic lattice distortions and macroscopic optical response. Additional studies on potassium niobate nanocrystals and novel polar sulfido-vanadate systems further expand the understanding of polar structural dynamics and multifunctional material properties. The results provide new insights into ultrafast light-matter interaction and contribute to the development of advanced photonic and optoelectronic applications