Three dimensional confinement of vapor in nanostructures for sub-Doppler optical resolution

TL;DR

This paper demonstrates sub-Doppler optical spectral features by confining Cs vapor in a 3D nanostructured glass opal, revealing potential for compact optical frequency references.

Contribution

It introduces a novel method of 3D vapor confinement in nanostructures to achieve sub-Doppler resolution in optical spectroscopy.

Findings

Observation of sub-Doppler structures in vapor confined within nanostructures.

Evidence of Dicke narrowing due to 3D confinement.

Potential application in micron-scale optical frequency clocks.

Abstract

We confine a Cs thermal vapor in the interstitial regions of a glass opal. We perform linear reflection spectroscopy on a cell whose window is covered with a thin film (10 or 20 layers) of ~ 1000 nm (or 400 nm) diameter glass spheres, we observe sub-Doppler structures in the optical spectrum for a large range of oblique incidences. This original feature associated with the inner (3-dimension) confinement of the vapor in the interstitial regions of the opal, evokes a Dicke narrowing. We finally consider possible micron-size references for optical frequency clocks based on weak, hard to saturate, molecular lines.