Femtotesla atomic magnetometry in a microfabricated vapor cell.

We describe an optically pumped 87Rb magnetometer with 5 fT/Hz(1/2) sensitivity when operated in the spin-exchange relaxation free (SERF) regime. The magnetometer uses a microfabricated vapor cell consisting of a cavity etched in a 1 mm thick silicon wafer with anodically bonded Pyrex windows. The measurement volume of the magnetometer is 1 mm3, defined by the overlap region of a circularly polarized pump laser and a linearly polarized probe laser, both operated near 795 nm. Sensitivity limitations unique to the use of microfabricated cells are discussed.

Conversion of laser-frequency noise to optical-rotation noise in cesium vapor.

We have studied the noise in the optical rotation of a linearly polarized laser beam transmitted through a spin-polarized (133)Cs vapor as a function of its frequency detuning from the optical resonance. Our measurements demonstrate the direct conversion of the laser-frequency noise into optical rotation noise by the dispersive response of the atomic vapor. We describe this noise-conversion process in terms of a simple model that can be used to optimize the performance of atomic devices, such as atomic magnetometers, that use optical rotation as their operational signal.