Measuring fluorescence into a nanofiber by observing field quadrature noise

TL;DR

This study demonstrates the first measurement of atomic fluorescence into a nanofiber mode using balanced homodyne detection, revealing increased quantum noise and providing insights into atom-light interactions at the nanoscale.

Contribution

It introduces a novel experimental approach to detect and quantify fluorescence in nanofiber systems via field quadrature noise measurement.

Findings

Resonant fluorescence increases quantum noise in the nanofiber mode.

Autocorrelation decay time matches theoretical predictions.

First experimental observation of fluorescence via balanced homodyne detection.

Abstract

We perform balanced homodyne detection of the electromagnetic field in a single-mode tapered optical nanofiber surrounded by rubidium atoms in a magneto-optical trap. Resonant fluorescence of atoms into the nanofiber mode manifests itself as increased quantum noise of the field quadratures. The autocorrelation function of the homodyne detector's output photocurrent exhibits exponential fall-off with a decay time constant of $26.3\pm 0.6$ ns, which is consistent with the theoretical expectation under our experimental conditions. To our knowledge, this is the first experiment in which fluorescence has been observed and measured by balanced optical homodyne detection.