A High Sensitivity Laser-Pumped Cesium Magnetometer

An atomic magnetometer based on optically detected magnetic resonance is investigated and demonstrated experimentally. We build an 894 nm external cavity diode laser which is frequency locked to the F=4→F'=3 transition of Cs D₁ line with DAVLL spectroscopy. With the phase-locked loop, the frequency of the rf coils is actively locked to the Larmor frequency and the magnetometer tracks the magnetic field variations in a phase coherent manner. An ultimate sensitivity of 19 fT/Hz^1/2 and an intrinsic sensitivity of 8.6 pT/Hz^1/2 in the magnetic environment which is close to geomagnetic field have been achieved with the spatial resolution smaller than 2 cm.