Dual channel self-oscillating optical magnetometer

We report on a two-channel magnetometer based on non-linear magneto optical rotation in Cs buffered glass cell. The Cs atoms are optically pumped and probed by free running diode lasers tuned to the D2 line. A wide frequency modulation of the pump laser is used to produce both synchronous Zeeman optical pumping and hyperfine repumping. The magnetometer works in an unshielded environment and spurious signal from far located magnetic sources is rejected by means of differential measurement. In this regime the magnetometer gives simultaneously the magnetic field modulus and the field difference. The rejection of the common mode noise allows for high-resolution magnetometry with a sensitivity of 2 pT/ √ Hz. This sensitivity in conjunction with long-term stability and large bandwidth makes possible to detect water proton magnetization and its free induction decay in a measurement volume of 5 cm. c © 2009 Optical Society of America