Fluorescence enhancement via lossless all-dielectric spherical mesocavities

Abstract

Metal nanoparticles have traditionally been used to enhance optical signals, including fluorescence from a dye proximal to the particle. Here, we sought to examine whether appreciable enhancement was possible using relatively simple all-dielectric particles. Using rapid numerical simulations, we deduce that lossless all-dielectric spherical particles with mesoscale sizes, between nanoscale ( 100 nm) and microscale ( 1 µm), are surprisingly suitable for fluorescence enhancement demonstrating up to F ∼ 10 4 enhancement factors. We discuss both the enhancement possible as well as limiting losses, which are distinct from those observed in metal particles. For a given sphere of a specific refractive index size matters: much larger fluorescence enhancement can be achieved with meso-sized particles than with particles of smaller size. The enhancement originates from multipolar ( 410) resonances which induce much stronger electric field enhancement within spheres. The order, , of these resonances is larger than conventionally utilized dipolar or quadrupolar Mie resonances in nanoparticles 1