Eur. Phys. J. D (2015) 69: 135
https://doi.org/10.1140/epjd/e2015-50875-3

Regular Article

A sensitive and accurate atomic magnetometer based on free spin precession

¹ Physics Department, University of Fribourg, 1700 Fribourg, Switzerland
² Paul Scherrer Institute, 5232 Villigen, Switzerland

^a e-mail: zoran.grujic@unifr.ch
^b Present address: Instituut voor Kern- en Stralingsfysica, Katholieke Universiteit Leuven, B3001 Leuven, Belgium.

Received: 5 December 2014
Received in final form: 17 March 2015
Published online: 21 May 2015

Abstract

We present a laser-based atomic magnetometer that allows inferring the modulus of a magnetic field from the free Larmor precession of spin-oriented Cs vapour atoms. The detection of free spin precession (FSP) is not subject to systematic readout errors that occur in phase feedback-controlled magnetometers in which the spin precession is actively driven by an oscillating field or a modulation of light parameters, such as frequency, amplitude, or polarization. We demonstrate that an FSP-magnetometer can achieve a ~200 fT/ $\sqrt{\mathrm{Hz}}$ sensitivity ( <100 fT/ $\sqrt{\mathrm{Hz}}$ in the shotnoise limit) and an absolute accuracy at the same level.