Optimizations of a parametric-modulation atomic magnetometer in a nuclear magnetic resonance gyroscope

Abstract

Atomic magnetometers are emerging as the most sensitive sensors for magnetic field detections, and have found applications in various fields. In nuclear magnetic resonance gyroscopes (NMRG), researchers usually use an embedded atomic magnetometer to sense the transverse magnetic fields generated by the precessing nuclear spins. The additional spin-exchange and spin-destruction collisions between alkali-metal and inert gas atoms reduce the coherence time τ of the alkali-metal atom spins. In addition, in order to achieve an NMRG of high sensitivity, a relatively small bias magnetic field needs to be applied, thus giving a low Larmor frequency ω0 of the alkali-metal atom spins. These two factors violate the condition . In this paper, we systematically study the performance of this embedded atomic magnetometer when the product ζ = ω0τ is on the order of unity. We demonstrate that the sensitivity of the magnetometer depends on two dimensionless parameters ζ and the modulation depth η when the system is on resonance. We then find the key factor for achieving the best sensitivity of the magnetometer is to choose an optimized η value. As an application of our results, we consider the demodulation phase in NMRG, where the Larmor frequency of the nuclear spins is to be determined by the magnetometer. We give an analytical expression of the demodulation phase, with which one can obtain maximal nuclear magnetic resonance signals.