Elliptically polarized laser-pumped $M_x$ magnetometer towards applications at room temperature

An atomic magnetometer operated with elliptically polarized light is investigated theoretically and experimentally. To explore the potential of this magnetometric configuration, the analytical form of the outgoing signal is derived. Parameters that significantly influence the performance are optimized, which lead to a sensitivity of 300 $\rm fT/\sqrt{Hz}$ at 45 $^{\circ}$C with a 2$\times$2$\times2$ cm uncoated Rb vapor cell. It is remarkable that a sensitivity of 690 $\rm fT/\sqrt{Hz}$ is achieved at room temperature of 24 $^{\circ}$C, which is improved by an order of magnitude compared with the conventional $M_x$ magnetometer under its own optimized condition. The elliptically polarized approach offers attractive features for developing compact, low-power magnetometers, which are available without heating the uncoated vapor cell.