A high-bandwidth atomic magnetometer

We have studied the bandwidth of atomic magnetometers based on nonlinear magneto-optical rotation (NMOR). We demonstrated broadband, high-bandwidth magnetic field measurements from DC up to 100kHz with two different techniques. The first technique measures the instantaneous phase evolution of the optical polarisation rotation in the temporal domain which enabled quantitative measurements of modulated magnetic fields up to 100kHz for a carrier frequency of 30kHz, while the second method employs active feedback techniques to track magnetic field fluctuations up to 100kHz, approximately 2800-fold greater than the passive bandwidth. For the latter case, a slew rate of 91.4nT/μs and a sensitivity of 200fT/Hz1/2 around 8Hz have been achieved at a bias field of 50μT.