Progress in a multi-pass, all-optical single beam atomic magnetometer in small cubic vapor cell

Atomic magnetometers are based on the principle of atom-light interaction such as optical pumping, spin precession, Faraday rotation in an external magnetic field. When applied in industrial fields, the atomic magnetometers have several advantages: high sensitivity, room temperature operation and miniaturization. For miniaturization, we apply a single beam-single pass configuration and a sub-cm size atomic vapor cell to our magnetometer. However, the short interaction length, due to a single pass in a sub-cm sized atomic cell, limits the sensitivity to a few hundred fT/Hz^1/2, which is mainly determined by photon-shot-noise. This sensitivity limit can be overcame by adopting a multi-pass. Here, we will present our research in the progress all-optical single beam atomic magnetometer with multi-pass interaction in a small cubic vapor cell with 5x5x5 mm³(inner).