Double-resonance magnetometry in arbitrarily oriented fields

Ingleby, Stuart and Riis, Erling and Arnold, Aidan and Griffin, Paul and O'Dwyer, Carolyn and Chalmers, Iain (2017) Double-resonance magnetometry in arbitrarily oriented fields. In: Workshop on Optically Pumped Magnetometers 2017, 2017-08-21 - 2017-08-22, University of Fribourg.

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Our magnetometry development is focussed on compact, portable sensors for geophysical field measurements. In order to develop practical sensors with minimised size and power requirements, single-beam double-resonance magnetometry is used, avoiding any requirement for extensive optical hardware or full-field compensation. Magnetic resonance in atomic polarisation is detected using a polarimeter to measure optical rotation in transmitted pump light, allowing rejection of common-mode optical noise. The application of this technique to unshielded geophysical field measurements requires detailed understanding of systematic effects arising in arbitrary orientations of the static field B0. We report the development and calibration of a test system for double resonance measurements in generated static fields of well-controlled magnitude and orientation, including systems for automated B0 control and software generated modulation/demodulation [1]. The sensitivity of these devices depends on signal amplitude, phase and RF broadening, all of which vary with B0 orientation. By working in a low-field, weak-pumping regime, we obtain experimental measurements of anisotropy in these parameters, in agreement with theoretically derived distributions [2]. We comment on the importance of measurement mode and signal demodulation in optimising double-resonance sensitivity and bandwidth, and the suitability of these techniques for compact, portable magnetometers. This work is supported by the UK Quantum Technology Hub in Sensors and Metrology [3].