Emergent Molecular Properties in the Strong Light-Matter Coupling Regime

Can optical environment change the physical or chemical properties of matter? This question arises for molecules in the strong light-matter coupling regime where the particles of light – photons – can no longer be distinguished from a given molecular electronic or vibrational excitation. The resulting hybrid states, known as polaritons, are commonly formed by placing molecules within a microcavity (e.g. a closely-spaced pair of mirrors) and can have different energies, coherence, and vibrational characteristics than the bare molecules do outside of the cavity, raising the possibility of emergent physical/chemical properties for the hybrid system.

In this talk, I will discuss our recent work exploring changes in photoinduced electron transfer and optical nonlinearity that arise upon resonantly exciting molecular polariton modes. In the case of electron transfer, we study photoconductivity that originates from polaron (i.e. charged molecule) absorption and uncover evidence that the underlying photoinduced electron transfer process becomes more efficient when polariton modes are excited as opposed to uncoupled molecules. In the case of optical nonlinearity, we find that the electroabsorption response (a  nonlinearity) of molecular polaritons cannot be understood on the basis of classical electromagnetic modeling, where the applied electric field perturbs the underlying exciton, and is instead consistent with a Hamiltonian description in which the field directly perturbs the polariton states to yield an experimentally distinct outcome. These results support the notion that strong light-matter coupling can be leveraged as a new, non-synthetic means to control molecular properties that are important for organic optoelectronic and photonic devices.

Chris Giebink is an Associate Professor of Electrical Engineering at Penn State University. He received his Ph.D. in Electrical Engineering from Princeton University and holds undergraduate degrees in both Physics and Engineering Science from Trinity University (TX).  His research focuses broadly on optoelectronic and photonic devices based on organic materials, with applications in solar energy conversion, solid-state lighting, lasers, and nonlinear optics. He holds 11 patents and is a senior member of the IEEE, OSA, SPIE, and National Academy of Inventors as well as a recipient of the DARPA YFA, AFOSR YIP, and NSF CAREER awards.