Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

We demonstrate an all-optical ${}^{133}$Cs scalar magnetometer, operating in nonzero magnetic field,in which the magnetic resonance is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. We achieve a projected shot-noise-limited sensitivity of 1.7 fT/Hz${}^{1\mathrm{/}2}$ and measure a technical noise floor of 40 fT/Hz${}^{1\mathrm{/}2}$. These results are essentially identical to a coil-driven scalar magnetometer using the same setup. This all-optical scheme offers advantages over traditional coil-driven magnetometers for use in arrays and in magnetically sensitive fundamental physics experiments e.g., searches for a permanent electric dipole moment of the neutron.