Numerical studies of the modification of photodynamic processes by film-coupled plasmonic nanoparticles

The local plasmon resonances of metallic nanostructures are commonly associated with massive local field enhancements, capable of increasing the photoexcitation of nearby quantum emitters by orders of magnitude. However, these same plasmonic structures support high densities of bound and dissipative states, often quenching the nearby emitter or at least offering competitive nonradiative channels. Thus, finding a plasmonic platform that supports massive field enhancements and a high proportion of radiating to nonradiating states remains an active and promising area of research. In this paper, we outline a simple method for numerically studying plasmonic enhancements in fluorescence and apply it to several variants of the film-coupled nanoparticle platform. Filmcoupled nanoparticles make excellent candidates for these investigations since the gap dimension between nanoparticle and film-key to the enhancement mechanism-can be precisely controlled in experimental realizations. By correlating the properties of embedded fluorophores with the resonances of the film-coupled nanoparticles, we show quantum yield engineering that is nearly independent of the fluorophore's intrinsic quantum yield, yielding overall fluorescence enhancements of over four orders of magnitude.