Noise reduction in optically pumped magnetometer assemblies

Alexandre Stathopulos, Rudy Romain, Sergey I. Mitryukovskiy +1 more

B.S. Mathur

Yifan Yan, Zehua Liu, Yuesong Wu +4 more

Zhang Zhen-yua

In the optically pumped magnetometer,the signal to noise ratio is very low when use the method of detecting Zeeman energy level transition directly.However,the detected signal to noise ratio can be greatly improved by using the technique of magnetic resonances optical detection which can transform the microwave quantum detection to the photon detection,because the energy of photon is much greater than that of microwave quantum.The method of magnetic resonances optical detection in the OPM(Optically Pumped Magnetometer) has been studied,the principles and experimental devices are discussed which includes the method of detection of cells transparency,detection of orthogonal beams,spin exchange collision and the method of pump beam modulation.The characteristics of these methods are analyzed and compared,the application and complexity are considered,and all these will provide the basis for the design of the optically pumped magnetometer.

Morgan W. Mitchell

K. Mouloudakis, V. Koutrouli, Iannis K. Kominis +2 more

Present protocols for obtaining the ultimate magnetic sensitivity of optically pumped magnetometers (OPMs) utilizing alkali-metal ensembles rely on uncorrelated atoms in stretched states. A new approach for calculating the spin projection noise (SPN)-limited signal to noise ratio (SNR) and the magnetic sensitivity of OPMs is proposed. Our model is based solely on the mean-field density matrix dynamics and in contrast to previous models, it applies to both low and high field regimes, it takes into account the degree of spin polarization, the intra- and interhyperfine correlations, the decoherence processes, the atom-light coupling and the effects of the spin dynamics on the spin-noise spectra. Fine tuning of the probe frequency allow us to explore different hyperfine states and ground-state correlations. Especially in the spin-exchange-relaxation-free (SERF) regime, alongside the magnetic resonance narrowing and the increased number density, hallmarks of SERF magnetometers, we report on a new SERF feature; the reduction of spin-projection noise at the spin precession frequency as a consequence of strongly-correlated hyperfine spins that attenuate and redistribute SPN when properly probed.