Superradiant Raman laser magnetometer

We demonstrate a proof-of-principle magnetometer that relies on the active oscillation of a cold atom Raman laser to continuously map a field-sensitive atomic phase onto the phase of the radiated light. We demonstrate wideband sensitivity during continuous active oscillation, as well as narrowband sensitivity in passive Ramsey-like mode with translation of the narrowband detection in frequency using spin-echo techniques. The sensor operates with a sensitivity of 190 pT=root Hz p at 1 kHz and effective sensing volume of 2 x 10(-3) mm(3). Fundamental quantum limits on the magnetic field sensitivity of an ideal detector are also considered. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773241]