Measuring the mode volume of plasmonic nanocavities using coupled optical emitters

TL;DR

This paper experimentally measures the confinement of plasmonic nanocavities by using the cavity modes as probes, demonstrating deep sub-wavelength confinement with mode volumes around rac{}{1000} , confirming their extreme light confinement capabilities.

Contribution

The study introduces a method to measure mode volume in plasmonic nanocavities using dielectric perturbations, providing direct experimental evidence of deep sub-wavelength confinement.

Findings

Mode decay length is less than 5% of .

Mode volume is approximately ^3/1000.

Confirms deep sub-wavelength confinement in metal-based cavities.

Abstract

Metallic optical systems can confine light to deep sub-wavelength dimensions, but verifying the level of confinement at these length scales typically requires specialized techniques and equipment for probing the near-field of the structure. We experimentally measured the confinement of a metal-based optical cavity by using the cavity modes themselves as a sensitive probe of the cavity characteristics. By perturbing the cavity modes with conformal dielectric layers of sub-nm thickness using atomic layer deposition, we find the exponential decay length of the modes to be less than 5% of the free-space wavelength (\lambda) and the mode volume to be of order \lambda^3/1000. These results provide experimental confirmation of the deep sub-wavelength confinement capabilities of metal-based optical cavities.