The polarization and the fundamental sensitivity of $^{39}$K ($^{133}$Cs)-$^{85}$Rb-$^{4}$He hybrid optical pumping spin exchange relaxation free atomic magnetometers

摘要

The hybrid optical pumping spin exchange relaxation free (SERF) atomicmagnetometers can realize ultrahigh sensitivity measurement of magnetic fieldand inertia. We have studied the $^{\text{85}}$Rb polarization of two types ofhybrid optical pumping SERF magnetometers based on$^{\text{39}}$K-$^{\text{85}}$Rb-$^{\text{4}}$He and$^{\text{133}}$Cs-$^{\text{85}}$Rb-$^{\text{4}}$He respectively. Then we foundthat $^{\text{85}}$Rb polarization varies with the number density of buffer gas$^{\text{4}}$He and quench gas N$_{\text{2}}$, pumping rate of pump beam andcell temperature respectively, which will provide an experimental guide for thedesign of the magnetometer. We obtain a general formula on the fundamentalsensitivity of the hybrid optical pumping SERF magnetometer due to shot-noise.The formula describes that the fundamental sensitivity of the magnetometervaries with the number density of buffer gas and quench gas, the pumping rateof pump beam, external magnetic field, cell effective radius, measurementvolume, cell temperature and measurement time. We obtain a highest fundamentalsensitivity of $1.5073$ $aT/Hz^{1/2}$ ($1$ $aT=10^{-18}$ $T$) with$^{\text{39}}$K-$^{\text{85}}$Rb-$^{\text{4}}$He magnetometer between above twotypes of magnetometers when $^{\text{85}}$Rb polarization is $0.1116$. Weestimate the fundamental sensitivity limit of the hybrid optical pumping SERFmagnetometer to be superior to $1.8359\times10^{-2}$ $aT/Hz^{1/2}$, which ishigher than the shot-noise-limited sensitivity of $1$ $aT/Hz^{1/2}$ of K SERFatomic magnetometer.