Faraday spectroscopy of atoms confined in a dark optical trap

TL;DR

This paper demonstrates high-speed Faraday spectroscopy using atoms confined in a dark optical trap, enabling precise measurement and compensation of transient magnetic fields with high duty cycle and sampling rate.

Contribution

The authors introduce a novel dark optical trap setup for Faraday spectroscopy, achieving high duty cycle and sampling rate for transient magnetic field measurements.

Findings

Measured magnetic fields with ~10 nT precision.

Achieved nearly 100% duty cycle at 500 Hz sampling rate.

Demonstrated effective magnetic field compensation.

Abstract

We demonstrate Faraday spectroscopy with high duty cycle and sampling rate using atoms confined to a blue-detuned optical trap. Our trap consists of a crossed pair of high-charge-number hollow laser beams, which forms a dark, box-like potential. We have used this to measure transient magnetic fields in a 500-micron-diameter spot over a 400 ms time window with nearly unit duty cycle at a 500 Hz sampling rate. We use these measurements to quantify and compensate time-varying magnetic fields to ~10 nT per time sample.