Second-Order Nonlinear Optical Properties of Metal Based Molecular Switches, Bridging Theory and Experiment.

Optics, the science of the interaction of light with matter, has become ubiquitous in our society. Light is propagating in the form of photons over optical fibers, very much as electricity in the form of electrons, is transported over electrical conductors. Indeed, photonics is the technology platform that relies on the manipulation of photons, rather than electrons in electronics. Nonlinear optics (NLO) is a sub-field describing all optical processes that depend in a nonlinear manner on the applied optical field. In this project we will focus on second-order effects, meaning they are quadratically dependent on the strength of the field. This interaction is only present in materials where loosely bound electrons are available that can feel the detailed electromagnetic properties of light. Organic molecules with lots of such electrons have been synthesized and tested for their NLO properties. More elaborated molecules, such as those with a transition metal ion incorporated, exhibit different electronic properties based on the oxidation state of the metal. Because these molecules can also be reversibly switched between these two forms, their optical properties can be altered. We envisage the detailed, both experimental and theoretical, study of such molecular switches for a better fundamental understanding of their electronic and optical phenomena. This involves the determination of their second-order NLO properties both with highly accurate quantum chemical methods as well as measurements with a unique laser setup.