Spectral Asymmetry of Atoms in the van der Waals Potential of an Optical Nanofiber

TL;DR

This study investigates how van der Waals interactions modify the transmission spectra of cold rubidium atoms near an optical nanofiber, revealing asymmetric spectral features that inform about atomic spatial distribution and potential trapping near surfaces.

Contribution

It introduces a semi-classical model for thermal excitation of atoms in van der Waals bound states near nanofibers, linking spectral asymmetry to atom-surface interactions.

Findings

Van der Waals interactions cause spectral asymmetry near nanofibers.

Thermal excitation affects atomic distribution and spectra.

Potential for trapping atoms at nanometer distances from surfaces.

Abstract

We measure the modification of the transmission spectra of cold $^{87}$Rb atoms in the proximity of an optical nanofiber (ONF). Van der Waals interactions between the atoms an the ONF surface decrease the resonance frequency of atoms closer to the surface. An asymmetric spectra of the atoms holds information of their spatial distribution around the ONF. We use a far-detuned laser beam coupled to the ONF to thermally excite atoms at the ONF surface. We study the change of transmission spectrum of these atoms as a function of heating laser power. A semi-classical phenomenological model for the thermal excitation of atoms in the atom-surface van der Waals bound states is in good agreement with the measurements. This result suggests that van der Waals potentials could be used to trap and probe atoms at few nanometers from a dielectric surfaces, a key tool for hybrid photonic-atomic quantum systems.