Atomic Magnetometer Based on Chip Scale Rb Atomic Vapour Cell

Abstract

This paper reports the development and characterization of an atomic magnetometer with a microfabricatedRb atomic vapour cell as the sensing element. The measurement principle is based on the Faraday rotation of linearly polarized probe light, which interacts resonantly with atomic spin states in the presence of a magnetic field. In the chip-scale vapour cell (dimensions: 8.0 mm × 12.0 mm × 1.5 mm), the atomic vapour is confined to a micromachined optical cavity of 3.5 µL with an optical path length of 0.5 mm. Optical interrogation is performed using a single laser beam tuned to the D1 absorption resonance of ⁸⁵Rb. The rotation arises due to magnetically induced circular birefringence in the hot atomic vapour. A bench model of the magnetometer is demonstrated over a measurement range of ±50 µT with a maximum uncertainty of 800 nT in an unshielded environment. The magneto-optic rotation (MOR) response in the laboratory was investigated and is observed to vary from 5×10³ rad/T for near zero magnetic field to 3.2×10³ rad/T for ambient geomagnetic field.