Highly sensitive multi-channel atomic magnetometer

We describe a high-sensitivity 16-channel magnetic sensor based on a spin-exchange relaxation-free (SERF) atomic magnetometer, the most sensitive cryogen-free magnetic field sensor. It has been developed in order to accelerate magnetic measurements in various fields, such as neuroscience and biomedical research, and improve the current technologies. The multi-channel operation is based on a single large flat pancake rubidium vapor cell, two broad laser beams (one for optical pumping and the other for optical Faraday effect detection), and a 4 by 4 photodiode matrix. In addition, a nearly parallel configuration of laser beams and multi-mode fibers facilitate the multi-channel design and the coupling of lasers, respectively. We experimentally demonstrate sensitivity in each channel of the sensor of a few tens femtotesla at low frequency. Because of its high sensitivity and parallel multi-channel detection, we anticipate that this sensor will be useful for many applications, such as magnetoencephalography (MEG), magnetocardiography (MCG), and magnetic micro-particle imaging.