Metal-Dielectric-Enhanced Upconversion: Going "Meso"

TL;DR

This paper introduces a mesocavity design using metal nanoparticles coated with thick high-index dielectric shells, achieving record upconversion enhancement levels of over 10^8 through combined plasmonic and whispering gallery-mode resonances.

Contribution

It presents a novel mesocavity concept with thick dielectric shells that significantly boosts upconversion efficiency beyond previous limits.

Findings

Achieved upconversion enhancement of over 10^6 on the cavity surface.

Enhanced UC of over 10^8 when emitter is inside the dielectric shell with Lorentz correction.

Synergistic use of plasmonic and whispering gallery modes in mesocavities.

Abstract

A novel concept of a \textit{mesocavity}, based on a simple yet counter-intuitive idea of covering metal nanoparticles with unusually thick ($\gtrsim 100$ nm) high-index dielectric shells, is demonstrated in technologically relevant and largely sought-after case of an upconversion (UC) enhancement. For readily available combinations of materials and geometrical parameters of metal-dielectric core-shell mesocavity, record high values of UC enhancement of $\gtrsim 10^6$ can be achieved on the cavity surface. For emitter inside the high-index dielectric shell with refractive index $n=2.7$, the Lorentz local-field correction can provide an additional enhancement factor for UC of $\approx 92$, resulting in UC enhancement of $\gtrsim 10^8$, which is three orders of magnitude larger than it has ever been reported for individual particles. Our mesocavity concept facilitates a beneficial synergy of plasmonic and whispering gallery-mode resonance functionalities within an intermediary region between nanoscale ($\lesssim 100$ nm) and microscale ($\gtrsim 1$ $\mu$m).