A microfabricated optically-pumped magnetic gradiometer
Abigail R. Perry, Sean P. Krzyzewski, John E. Kitching, S. Geller, Sheng D., Svenja A. Knappe
We report on the development of a microfabricated atomic magnetic gradiometer based on optical spectroscopy of alkali atoms in the vapor phase. The gradiometer, with a length of 60 mm and a cross section diameter of 12 mm, is made of two chip-scale atomic magnetometers, which are interrogated by light from a common laser and operate in the spin-exchange relaxation free regime. The sensor can measure differences in magnetic field over a 2 cm baseline of 10 fT/Hz^1/2 at frequencies above 20 Hz. The maximum rejection of magnetic field noise is 1000 at 10 Hz. By use of a set of compensation coils wrapped around the sensor, we also measure the sensor sensitivity at several external bias field strengths up to 150 mG. This device is useful for applications that require both sensitive gradient field information and high common-mode noise cancellation.