Donor-Acceptor Energy Transfer involving Classical and Quantum Light in the Presence of Photonic and Plasmonic Structures

George C. Schatz of Northwestern University is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry to develop theory and models that describe the transfer of energy between molecules that is mediated by metal nanoparticles (typically silver, gold or aluminum) that show strong optical absorption properties known as plasmon excitation.

The theory builds from the past history of research on energy transfer, but here is adapted to problems at the leading edge of science, in which energy transfer can extend over distances from 10s of nm to mm, involves strong coupling where traditional perturbation theory approaches can break down, and where quantum effects provide opportunities for making fundamental changes to the energy transfer process. Energy transfer involving metal nanoparticles is important in emerging optical technologies, including topics related to optical switching, in the development of new types of optical devices, in single photon emitters, and in secure communications.

Schatz will also study energy transfer and other properties associated with quantum light including the emission, absorption and energy transfer involving two entangled photons. The students and postdocs who work on this project include a significant number of women and minorities, and they will acquire unique skills that they can use to launch their own careers.

In addition, there will be outreach to K-12 groups, undergraduate training, numerous seminars and workshops, and interactions with the public.

The proposed work on energy transfer mediated by metal nanoparticles is a relatively new field where analytical theory based on quantum mechanics is essential. In addition to analytical theory, the research will pursue computational algorithms for using the theory, and applications of the theory to describe experiments done by experimental collaborators.

The theory includes the description of: (1) donor-acceptor energy transfer near arrays of plasmonic nanoparticles where energy transfer can be mediated by optical modes of the lattice, and where issues of coherence and strong light-matter interactions can be tuned by controlling array structural parameters and emitter/absorber concentrations; (2) energy transfer mediated by individual or a few nanoparticles where Schatz will develop a full quantum electrodynamics formalism that incorporates plasmonic, excitonic and electromagnetic states on equal footing and which will provide the capability of describing quantum effects under circumstances where perturbation-theory based energy transfer theory breaks down; (3) energy transfer associated with quantum light that is coupled to entangled plasmons, including donor-acceptor energy transfer in which interference between the entangled photons modulates the rate. In addition, (4) Schatz will collaborate with several experimentalists in the field who are studying problems related to plasmon-mediated donor-acceptor energy transfer involving structures where the donor, acceptor and nanoparticles are organized via DNA structures, or that involve arrays with unique optical cavity features.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.