Designing and Driving Excited State Dynamics in the Condensed Phase: Ultrafast Spectroscopy of Photosynthetic and Semiconducting Systems

Modern day challenges such as energy crisis or rapid increase in demand of high-quality communications cannot be solved without a collaborative effort from researchers in various fields. As physical chemists, we bring in a unique perspective to the issues from the quantum mechanical standpoint, testing hypotheses about dynamic evolutions of the chemical and biological systems with light. In order to tackle synthetic light harvesting, we need to have deep understanding of the nature's ways of evolving the organisms to perform efficient photosynthesis and protect themselves from stress. To address this, we perform non-linear optical spectroscopy on a specific light-harvesting antenna complex called phycobilisome found in cyanobacteria. We seek to identify the photoprotective mechanisms in the organism to understand their response to excess sunlight. Experiments and theory compliment each other in our work on identifying the precise Hamiltonian of the Fenna-Matthews-Olson complex – another important light-harvesting antenna found in green sulfur bacteria. The developed methodology can assist in finding the exact energetic structures of less-studied biological systems. There is a lot of promise in using orbital angular momentum of light to alleviate issues of classical and quantum communications. The potentially infinite amount of OAM supplied to light offers solutions to challenges in information multiplexing in optical communications. We can also use the unique response of the chemical systems to twisted light as a detection mechanism in information encoding. In my work, I take the first step towards understanding the interactions of orbital angular momentum of light with bulk gallium arsenide to identify spectral differences as a function of twist in the light using home-built ultrafast transient absorption spectrometer. While this work is in its early stages, it has shown promising results in establishing the trends governing the electronic transitions induced by twisted light.