Optically-patterned nuclear doughnuts in GaAs/MnAs heterostructures
  We demonstrate a scheme for optically patterning nuclear spin polarization in semiconductor/ferromagnet heterostructures. A scanning time-resolved Kerr rotation microscope is used to image the nuclear spin polarization that results when GaAs/MnAs epilayers are illuminated with a focused laser having a Gaussian profile. Rather than tracking the intensity profile of the laser spot, these images reveal that the nuclear polarization forms an annular lateral structure having circular symmetry with a dip rather than a peak at its center. 
J. Stephens, J. Berezovsky, R. K. Kawakami, A. C. Gossard, and D. D.   Awschalom