Spin-exchange relaxation free magnetometry with Cs vapor

TL;DR

This paper presents a Cs-based SERF atomic magnetometer achieving high sensitivity and narrow resonance widths, with potential for further improvements and applications at lower operating temperatures.

Contribution

It demonstrates a Cs vapor SERF magnetometer with record sensitivity and analyzes its theoretical limits, highlighting advantages of Cs for low-temperature applications.

Findings

Achieved a sensitivity of 400 pG/√Hz experimentally.

Projected sensitivity of 40 pG/√Hz based on photon shot noise.

Theoretically optimized sensitivity of 2 pG/√Hz in a 1 cm^3 volume.

Abstract

We describe a Cs atomic magnetometer operating in the spin-exchange relaxation-free (SERF) regime. With a vapor cell temperature of $103^\circ\rm{C}$ we achieve intrinsic magnetic resonance widths $\Delta B=17 {\rm \mu G}$ corresponding to an electron spin-relaxation rate of $300 {\rm s^{-1}}$ when the spin-exchange rate is $\Gamma_{SE}=14000 {\rm s^{-1}}$. We also observe an interesting narrowing effect due to diffusion. Signal-to-noise measurements yield a sensitivity of about $400\thinspace{\rm pG/\sqrt{Hz}}$. Based on photon shot noise, we project a sensitivity of $40 {\rm pG/\sqrt{Hz}}$. A theoretical optimization of the magnetometer indicates sensitivities on the order of $2 {\rm pG/\sqrt{Hz}}$ should be achievable in a $1 {\rm cm^3}$ volume. Because Cs has a higher saturated vapor pressure than other alkali metals, SERF magnetometers using Cs atoms are particularly attractive in applications requiring lower temperatures.