A Sub-$\rm \lambda^{3}$-Volume Cantilever-based Fabry-P\'erot Cavity

TL;DR

This paper demonstrates a novel open plane-concave Fabry-Pérot microcavity with a sub-wavelength mode volume, enabling detection of single nanoparticles and offering broadband tunability for optomechanical applications.

Contribution

It introduces a new microcavity design with ultra-small mode volume below λ³, combining broadband operation, tunability, and mechanical scanning capabilities.

Findings

Achieved mode volume below λ³ at optical frequencies.

Detected resonance shifts from single nanoparticles at low Q factors.

Provided a tunable, broadband cavity with optomechanical potential.

Abstract

We report on the realization of an open plane-concave Fabry-P\'erot resonator with a mode volume below $\lambda^3$ at optical frequencies. We discuss some of the less common features of this new microcavity regime and show that the ultrasmall mode volume allows us to detect cavity resonance shifts induced by single nanoparticles even at quality factors as low as $100$. Being based on low-reflectivity micromirrors fabricated on a silicon cantilever, our experimental arrangement provides broadband operation, tunability of the cavity resonance, lateral scanning and promise for optomechanical studies.