Open AccessHelium-4 magnetometers for room-temperature biomedical imaging: toward collective operation and photon-noise limited sensitivity
Author(s) -
William Fourcault,
Rudy Romain,
G. Le Gal,
F. Bertrand,
Vincent Josselin,
Matthieu Le Prado,
Étienne Labyt,
Agustin Palacios-Laloy
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.420031
Subject(s) - magnetometer , optics , magnetic field , materials science , physics , dynamic range , nuclear magnetic resonance , quantum mechanics
Optically-pumped magnetometers constitute a valuable tool for imaging biological magnetic signals without cryogenic cooling. Nowadays, numerous developments are being pursued using alkali-based magnetometers, which have demonstrated excellent sensitivities in the spin-exchange relaxation free (SERF) regime that requires heating to >100 °C. In contrast, metastable helium-4 based magnetometers work at any temperature, which allows a direct contact with the scalp, yielding larger signals and a better patient comfort. However former 4 He magnetometers displayed large noises of >200 fT/Hz 1/2 with 300-Hz bandwidth. We describe here an improved magnetometer reaching a sensitivity better than 50 fT/Hz 1/2 , nearly the photon shot noise limit, with a bandwidth of 2 kHz. Like other zero-field atomic magnetometers, these magnetometers can be operated in closed-loop architecture reaching several hundredths nT of dynamic range. A small array of 4 magnetometers operating in a closed loop has been tested with a successful correction of the cross-talks.