Bright Optical Eigenmode with about 1 nm $^3$ Volume

TL;DR

This paper reports the discovery of extremely localized optical eigenmodes with volumes below 1 nm^3, enabling unprecedented light-matter interaction strength and potential applications in quantum optics and atomic-scale imaging.

Contribution

It introduces a new class of bright, ultra-small optical eigenmodes on metallic nanoparticles with quantum-optical mode volumes under 1 nm^3, surpassing previous size limits.

Findings

Mode volumes below 1 nm^3 achieved

Radiation efficiency up to 30% demonstrated

Intensity enhancement up to 4×10^7 times

Abstract

Concentrating optical field in an eigenmode with a tiny volume is vitally important for light-matter interactions at the fundamental level and underpins new technologies. In the past decades, researchers have investigated various approaches to shrink light and so far managed to reduce the volume of optical eigenmodes, under the quantum-optical definition, down to several ten nm3. Here we report on the discovery, characterization and engineering of a class of extremely localized eigenmodes that are resonances of atomistic protrusions on a metallic host nanoparticle and feature quantum-optical mode volumes of below 1 nm3. We theoretically demonstrate that these extremely localized modes can be made bright with radiation efficiencies reaching 30% and provide up to 4x10^7 times intensity enhancement. The existence of bright eigenmodes with the volume comparable to a photon emitter foresees exciting new optical physics, such as ultrastrong coupling with single optical emitters, angstrom-resolution optical imaging, and atomic-scale single-molecule photochemistry.