Optical-beat-frequency measurement of strong magnetic field using a Cs micron-thick cell

Measuring strong magnetic fields with atoms holds promise for various scientific applications, yet enhancing measurement resolution remains a challenge. This paper demonstrates strong magnetic-field measurement using the saturated absorption spectrum of a cesium micron-thick cell (MC), where the magnetic-field strength is indicated by the Zeeman shift of spectral lines and assessed via beat-frequency measurements with two stabilized lasers. Theoretical calculations have been refined to better interpret the clear splitting of experimental saturated absorption spectra of the MC in inhomogeneous strong magnetic fields with suppressed crossover spectral lines, which facilitates the magnetic-field measurements. Our approach achieves a measurement resolution of 0.36 G in an ambient magnetic field of 610 G and can effectively track time-varying magnetic fields. The measurement scheme provides high measurement resolution, which is valuable for remotely monitoring nuclear reactors, characterizing particle accelerator magnets, and mapping the magnetic fields of sunspots.