Nanoparticle detection in an open-access silicon microcavity

TL;DR

This paper demonstrates the detection of free nanoparticles using a high-finesse, open-access silicon microcavity with a small mode volume, enabling real-time monitoring and strong coupling of nanospheres in high vacuum.

Contribution

It introduces a novel open-access silicon microcavity with high finesse and small mode volume for nanoparticle detection and optomechanical studies.

Findings

Detection of 150 nm silica nanospheres in real time

Strong coupling between particles and cavity field

Potential for cooling and detecting smaller particles

Abstract

We report on the detection of free nanoparticles in a micromachined, open-access Fabry-P\'erot microcavity. With a mirror separation of $130\,\mu$m, a radius of curvature of $1.3\,$mm, and a beam waist of $12\,\mu$m, the mode volume of our symmetric infrared cavity is smaller than $15\,$pL. The small beam waist, together with a finesse exceeding 34,000, enables the detection of nano-scale dielectric particles in high vacuum. This device allows monitoring of the motion of individual $150\,$nm radius silica nanospheres in real time. We observe strong coupling between the particles and the cavity field, a precondition for optomechanical control. We discuss the prospects for optical cooling and detection of dielectric particles smaller than $10\,$nm in radius and $1\times10^7\,$amu in mass.