Dual channel self-oscillating optical magnetometer

TL;DR

This paper introduces a two-channel optical magnetometer capable of high-resolution, unshielded magnetic field measurements with differential detection, suitable for detecting water proton signals and free induction decay.

Contribution

It presents a novel dual-channel magnetometer using nonlinear magneto-optical rotation with wide frequency modulation for differential measurements in unshielded environments.

Findings

Sensitivity of 2 pT/Hz^{1/2} achieved

Able to detect water proton magnetization

Operates effectively in unshielded environments

Abstract

We report on a two-channel magnetometer based on nonlinear magneto-optical rotation in a Cs glass cell with buffer gas. The Cs atoms are optically pumped and probed by free running diode lasers tuned to the D$_2$ line. A wide frequency modulation of the pump laser is used to produce both synchronous Zeeman optical pumping and hyperfine repumping. The magnetometer works in an unshielded environment and spurious signal from distant magnetic sources is rejected by means of differential measurement. In this regime the magnetometer simultaneously gives the magnetic field modulus and the field difference. Rejection of the common-mode noise allows for high-resolution magnetometry with a sensitivity of \pthz{2}. This sensitivity, in conjunction with long-term stability and a large bandwidth, makes possible to detect water proton magnetization and its free induction decay in a measurement volume of 5 cm$^3$