Alignment-Based Optically Pumped Magnetometer Using a Buffer-Gas Cell

Abstract

Alignment-based optically pumped magnetometers (OPMs) are capable of measuring oscillating magnetic fields with high sensitivity in the $\mathrm{fT}/\sqrt{\mathrm{Hz}}$ range. Until now, alignment-based magnetometers have only used paraffin-coated vapour cells to extend the spin relaxation lifetimes of the alkali vapour. The drawback of these cells is that they are hand blown and are therefore time intensive, and somewhat unreliable, to produce. Buffer-gas cells, on the other hand, can be manufactured on a mass scale using microfabrication techniques. In this work we use hand-blown cells, but our methods also apply to microfabricated buffer-gas cells. We present the first demonstration of an alignment-based magnetometer using a buffer-gas vapour cell containing caesium (Cs) alkali vapour and nitrogen (${\mathrm{N}}_{2}$) buffer gas. The OPM is operated at $55{\phantom{\rule{0.1em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ and we achieve a $325\phantom{\rule{0.2em}{0ex}}\mathrm{fT}/\sqrt{\mathrm{Hz}}$ sensitivity to 10 kHz oscillating magnetic fields with an 800 Hz bandwidth. The alignment-based magnetometer uses a single low-power laser beam for optical pumping and probing and could potentially allow for more rapid commercialization of radio-frequency OPMs, due to the robustness of the one-beam geometry.