We report on an all-optical magnetometric technique based on nonlinear magneto-optical rotation with amplitude-modulated light. The method enables sensitive magnetic field measurements in a broad dynamic range. We demonstrate the sensitivity of at and the magnetic field tracking in a range of . The fundamental limits of the method sensitivity and factors determining current performance of the magnetometer are discussed.
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Note that in an experimental scheme in which phase-sensitive detection of the magneto-optical rotation is used, appearance of NMOR resonances is only possible if light is modulated. For low magnetic fields the modulation is not caused by the Faraday rotation but need to be introduced externally. Since in our experiment the same beam was used for pumping and probing, the light was amplitude modulated and, hence, the lock-in detection of the zero-field resonance was possible. On the contrary, in two-beam experiment, in which separated beams are used form pumping and probing atoms and probe-light intensity is unmodulated, the zero-field resonance is not observed.
