Linear and nonlinear magneto-optical rotation on the narrow strontium   intercombination line
  In the presence of an external static magnetic field, an atomic gas becomes optically active, showing magneto-optical rotation. In the saturated regime, the coherences among the excited substates give a nonlinear contribution to the rotation of the light polarization. In contrast with the linear magneto-optical rotation, the nonlinear counterpart is insensitive to Doppler broadening. By varying the temperature of a cold strontium gas, we observe both regimes by driving the $J=0\rightarrow J=1$ transition on the intercombination line. For this narrow transition, the sensitivity to the static magnetic field is typically three orders of magnitude larger than for a standard broad alkali transition. 
K. Pandey (1), C. C. Kwong (2), M. S. Pramod (1), D. Wilkowski (1 and   2 and 3) ((1) Centre for Quantum Technologies, Natio...
physics.atom-ph