Detection of radio-frequency magnetic fields using nonlinear magneto-optical rotation

We describe a room-temperature alkali-metal atomic magnetometer for detection of small, high-frequency magnetic fields. The magnetometer operates by detecting optical rotation due to the precession of an aligned ground state in the presence of a small oscillating magnetic field. The resonance frequency of the magnetometer can be adjusted to any desired value by tuning the bias magnetic field. Based on experimentally measured signal-to-noise ratio, we demonstrate a sensitivity of 1000.3em0expG∕√Hz (rms) in a 3.5-cm-diameter paraffin coated cell. Assuming detection at the photon shot-noise limit, we project a sensitivity as low as 250.3em0expG∕√Hz (rms).