ABSTRACT
All materials possess odd order nonlinear optical susceptibility; however even-order nonlinear susceptibility terms only exist in crystals that have non-centrosymmetric atomic geometry. Development of the laser that provides an intense source of monochromatic, coherent light, stimulated research and applications in the field of nonlinear optics. Nonlinear optical excitations are widely used in nonlinear optical microscopy that is extensively used for decades to study inorganic, organic and biological materials. The chapter addresses nonlinear optical response in quantum confined nanostructured materials. Nonlinear optical response from the surfaces and interfaces is substantially different from the bulk. Realistic modelling of optical functions of solid surfaces and interfaces remains challenging for the first principle theories. The nonlinear electro-optical effect has been used in modulation optical spectroscopy to increase its sensitivity to the fine structure of the electron energy spectrum of materials. Electronic processes at the nanocrystal boundaries lead to the reduction of k-vector symmetry and modifications of optical selection rules.
