Nonlinear Ultrafast Optical Spectroscopy

Nonlinear ultrafast optical spectroscopy allows us to track the flow of energy as it moves through the excited states and coherences of a system in real time. Using femtosecond laser pulses we can resolve the vibrational and electronic dynamics of systems ranging from redox-active molecular systems to solid state materials like nitrogen vacancy centers in diamond.

Our group employs a range of experimental techniques to map energy transfer, charge transfer and vibational dynamics. Our current experimental capabilities include transient grating, transient absorption, time correlated single photon counting, fluorescence upconversion, and two dimensional electronic spectroscopy. 

Fluorescence Upconversion and Time Correlated Single Photon Counting

Transient Grating Spectroscopy

Two Dimensional Electronic Spectroscopy

Redox-Activity and Catalysis 

Our group is currently investigating optical controls of redox-activity and catalysis with applications to solar energy capture and biologically relevant synthesis. Recent work involves the ultrafast light-induced dynamics of a new class of tripyrrindione molecules. When bound to metal atoms, these molecular systems are capable of controllable and reversible one-electron redox chemistry localized on the tripyrrindione ligand. The image to the left shows a metal tripyrrindione complex at room temperature (left) and at 77K (right). The color change is due to reversible aggregation.

Solid State Materials for Quantum Information

The optical and material properties of negatively charged nitrogen–vacancy centers in diamond make them attractive for applications ranging from quantum information to electromagnetic sensing. These properties are strongly dependent on the vibrational manifold associated with the center, which determines phenomena associated with decoherence, relaxation and spin–orbit coupling. 

To understand both the role of the vibrational bath surrounding the defect centers and their ultrafast electronic dynamics we use two dimensional ultrafast electronic spectroscopic measurements. These measurements allow us to follow the energy as it moves through the electronic and vibrational states. Through these measurements we have observed picosecond non-radiative relaxation within the phonon sideband and find that strongly coupled local modes dominate the vibrational bath. These findings provide a starting point for new insights into dephasing, spin addressing and relaxation in nitrogen vacancies in diamond with broad implications for magnetometry, quantum information, nanophotonics, sensing and ultrafast spectroscopy.