Role of emitter position and orientation on silicon nanoparticle-enhanced fluorescence

Abstract

High-index spherical dielectric nanoparticles are explored as templates for tailoring the fluorescence of nearby electric point-dipole-like emitters. The role of emitter orientation and position around the nanosphere on the modification of both its excitation and its emission rate is studied rigorously through derivation of appropriate analytic solutions. It is shown that dielectric nanoparticles, which support a richness of optical modes of electric or magnetic character and thus a variety of mechanisms for near-field enhancement, provide moderate fluorescence enhancement factors—as compared, e.g., to their plasmonic counterparts—which survive, however, for a wide range of emitter positions and orientations. Understanding the physical mechanisms governing this behaviour, which offers a promising route towards efficient control of the emission properties of randomly arranged emitters, is widely facilitated by the existence of analytic expressions such as the ones derived here. Further enhancement can be achieved by designing nanoparticle-aggregate antennas, or by combining dielectric and plasmonic components.