Large fluorescence enhancement via lossless all-dielectric spherical mesocavities

TL;DR

This paper demonstrates that lossless all-dielectric spherical mesocavities can significantly enhance fluorescence signals, up to 10,000 times, offering a promising alternative to plasmonic particles for various optical applications.

Contribution

It introduces the concept that homogeneous, lossless dielectric spheres in the mesoscale range can achieve large fluorescence enhancements, expanding the design space for optical signal amplification.

Findings

Fluorescence enhancement up to 10^4 times achieved.

Enhancement depends on the intrinsic quantum yield and decay rates.

Flexibility in fluorophore placement inside or outside the sphere.

Abstract

Nano- and microparticles are popular media to enhance optical signals, including fluorescence from a dye proximal to the particle. Here we show that homogeneous, lossless, all-dielectric spheres with diameters in the mesoscale range, between nano- ($\lesssim 100$~nm) and micro- ($\gtrsim 1$ $\mu$m) scales, can offer surprisingly large fluorescence enhancements, up to $F\sim 10^4$. With the absence of nonradiative Ohmic losses inherent to plasmonic particles, we show that $F$ can increase, decrease or even stay the same with increasing intrinsic quantum yield $q_0$, for suppressed, enhanced or intact radiative decay rates of a fluorophore, respectively. Further, the fluorophore may be located inside or outside the particle, providing additional flexibility and opportunities to design fit for purpose particles. The presented analysis with simple dielectric spheres should spur further interest in this less-explored scale of particles and experimental investigations to realize their potential for applications in imaging, molecular sensing, light coupling, and quantum information processing.