Low-frequency characterization of MEMS-based portable atomic magnetometer

Atomic magnetometers based on absorption or polarization rotation of light in an alkali vapor have recently demonstrated sensitivities rivaling those of superconducting quantum interference devices (SQUIDs). Miniaturization of such devices containing vapor cells fabricated with micro-electro-mechanical (MEMS) technology has been the focus of development for the better part of the last decade. In this paper, we describe a portable magnetometry system with a sensitivity below 50 fT/√Hz at 100 Hz. The atomic magnetometer consists of a microfabricated sensor head that is fiber coupled to a control module consisting of a laser and electronics. We describe the construction of this system and present the results of sensitivity measurements with an emphasis on identifying and characterizing the source of 1/f (flicker) noise. This portable magnetometer system was developed to measure magnetocardiograms (MCG) of human subjects inside a shielded environment.