Parametric modulation of an atomic magnetometer (original) (raw)

2006, Applied Physics Letters

The authors report on a rubidium atomic magnetometer designed for use in a shielded environment. Operating in the spin-exchange relaxation-free regime, the magnetometer utilizes parametric modulation of the z-magnetic field to suppress noise associated with airflow through the oven and to simultaneously detect xand y-field components, using a single probe beam, with minimal loss of sensitivity and bandwidth. A white noise level of 60 fT/(Hz) 1/2 was achieved. Measurement of extremely weak magnetic fields is essential in several important areas of physics and medicine, such as fundamental symmetry tests 1,2 and magnetoencephalography. 3 Due to their high sensitivity, superconducting quantum interference devices (SQUIDs) traditionally have been the detectors of choice; however, recent advances in atomic magnetometers 4,5 have made them an attractive alternative due to the lack of helium cryogenics and the potential for cost reduction and increased sensitivity. Among the atomic magnetometers developed to date, the spin-exchange relaxation-free (SERF) magnetometer of Kominis et al. has achieved the highest magnetic field sensitivity, rivaling that of SQUIDs. 5 Using a longitudinally spin-polarized alkali vapor, the SERF magnetometer detects the transverse spin polarization induced by weak magnetic fields. For highest sensitivity, the SERF magnetometer requires careful nulling of external magnetic fields, which can be achieved with magnetic shielding; 5 however, operation in an unshielded environment has also been reported. 6

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