FRET Enhancement using Surface Plasmon Modes on Gold Nanogratings*

The plasmonic properties of structured metal surfaces can be engineered to enhance the output of nearby quantum emitters through the manipulation of the local density of optical states (LDOS). Although metal enhanced fluorescence (MEF) has been well understood for decades, the influence of plasmonic modes in Förster resonance energy transfer (FRET) is still a debated issue. Gold nanogratings provide a unique plasmonic substrate to study the effects of altering the LDOS on FRET efficiencies. Gratings support narrow plasmon resonances at a range of wavelengths, allowing for the comparison of FRET efficiencies by increasing the LDOS at donor and acceptor emission wavelengths on a single substrate. In this work, the increase in efficiency was found to be greatest when the surface plasmon modes overlapped the acceptor emission spectrum. Furthering the understanding of the application of MEF to FRET will aid developing methods for the enhancement of FRET, expanding its use in biological systems, photosynthesis, and photovoltaic devices.