Dispersive Optical Interface Based on Nanofiber-Trapped Atoms

TL;DR

This paper demonstrates a dispersive optical interface using nanofiber-trapped atoms, enabling significant birefringence and dispersion effects, and allows non-destructive atom number measurement.

Contribution

It introduces a novel dispersive interface based on nanofiber-trapped atoms and exploits azimuthally-asymmetric coupling for non-destructive atom counting.

Findings

Phase shift per atom of ~1 mrad at specific detuning

Effective resonant optical density per atom of 0.027

Strong dispersion enables non-destructive atom number measurement

Abstract

We dispersively interface an ensemble of one thousand atoms trapped in the evanescent field surrounding a tapered optical nanofiber. This method relies on the azimuthally-asymmetric coupling of the ensemble with the evanescent field of an off-resonant probe beam, transmitted through the nanofiber. The resulting birefringence and dispersion are significant; we observe a phase shift per atom of $\sim$\,1\,mrad at a detuning of six times the natural linewidth, corresponding to an effective resonant optical density per atom of 0.027. Moreover, we utilize this strong dispersion to non-destructively determine the number of atoms.