Controlling Three-Color Forster Resonance Energy Transfer in an Optical Fabry-Perot Microcavity at Low Mode Order

We study three-color Forster resonance energy transfer (triple FRET) between three spectrally distinct fluorescent dyes, a donor and two acceptors, which are embedded in a single polystyrene nanosphere. The presence of triple FRET energy transfer is confirmed by selective acceptor photobleaching. We show that the fluorescence lifetimes of the three dyes are selectively controlled using the Purcell effect by modulating the radiative rates and relative fluorescence intensities when the nanospheres are embedded in an optical Fabry-Perot microcavity. The strongest fluorescence intensity enhancement for the second acceptor can be observed as a signature of the FRET process by tuning the microcavity mode to suppress the intermediate dye emission and transfer more energy from donor to the second acceptor. Additionally, we show that the triple FRET process can be modeled by coupled rate equations, which allow to estimate the energy transfer rates between donor and acceptors. This fundamental study has the potential to extend the classical FRET approach for investigating complex systems, e.g., optical energy switching, photovoltaic devices, light-harvesting systems, or in general interactions between more than two constituents.

Automated summary

In this study, three-color Forster resonance energy transfer (triple FRET) was achieved between three spectrally distinct fluorescent dyes by selectively controlling their fluorescence lifetimes using the Purcell effect. The presence of triple FRET energy transfer was confirmed by selective acceptor photobleaching. Additionally, the triple FRET process was modeled using coupled rate equations to estimate the energy transfer rates between donor and acceptors. This fundamental study has the potential to expand the application of FRET to investigate complex systems involving interactions between more than two constituents.