Microfabricated Optically Pumped Gradiometer with Uniform Buffer Gases

This paper reports on the development of a microfabricated gradiometer that permits uniform buffer gas content in both magnetometers. This improves the common mode noise rejection of the gradiometer by ensuring the broadening and shift of the Rb optical absorption line are uniform. The reported fabrication process permits micro-channels connecting the two magnetometers allowing for uniform buffer gas pressure. We discuss two methods of characterizing the common mode rejection ratio (CMRR), before and after measuring the frequency response of the individual magnetometers. The average uncalibrated and calibrated CMRR achieved in a table-top setup was 72.7 and 85.0 respectively over a bandwidth 3-200Hz.