The control of nuclear spin polarization is important to the design of materials and algorithms for spin-based quantum computing and spintronics. Towards that end, it would be convenient to control the sign and magnitude of nuclear polarization as a function of position within the host lattice. Here we show that, by exploiting different mechanisms for electron–nuclear interaction in the optical pumping process, we are able to control and image the sign of the nuclear polarization as a function of distance from an irradiated GaAs surface. This control is achieved using a crafted combination of light helicity, intensity and wavelength, and is further tuned via use of NMR pulse sequences. These results demonstrate all-optical creation of micron scale, rewritable patterns of positive and negative nuclear polarization in a bulk semiconductor without the need for ferromagnets, lithographic patterning techniques, or quantum-confined structures.. ? 2012 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
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