All-optical atomic magnetometers based on nonlinear magneto-optical   rotation with amplitude modulated light
  We demonstrate a magnetometric technique based on nonlinear magneto-optical rotation using amplitude modulated light. The magnetometers can be operated in either open-loop (typical nonlinear magneto-optical rotation with amplitude-modulated light) or closed-loop (self-oscillating) modes. The latter mode is particularly well suited for conditions where the magnetic field is changing by large amounts over a relatively short timescale. 
S. Pustelny, A. Wojciechowski, M. Kotyrba, K. Sycza, J. Zachorowski,   W. Gawlik, A. Cingoz, N. Leefer, J. M. Higbie, E. Cor...