Sensitive magnetometry based on nonlinear magneto-optical rotation

Application of nonlinear magneto-optical (Faraday) rotation to magnetometry is investigated. Our experimental setup consists of a modulation polarimeter that measures rotation of the polarization plane of a laser beam resonant with transitions in Rb. Rb vapor is contained in an evacuated cell with antirelaxation coating that enables atomic ground-state polarization to survive many thousand wall collisions. This leads to ultranarrow features (similar to 10(-6) G) in the magnetic-field dependence of optical rotation. The potential sensitivity of this scheme to sub-mu G magnetic fields as a function of atomic density, light intensity, and light frequency is investigated near the D1 and D2 lines of Rb-85. It is shown that through an appropriate choice of parameters the shot-noise-limited sensitivity to small magnetic fields can reach 3x10(-12) G/root Hz.