The control of nuclear spin polarization is important to the design of materials and algorithmsfor spin-based quantum computing and spintronics. Towards that end, it would be convenientto control the sign and magnitude of nuclear polarization as a function of position within thehost lattice. Here we show that, by exploiting different mechanisms for electron – nuclearinteraction in the optical pumping process, we are able to control and image the sign of thenuclear polarization as a function of distance from an irradiated GaAs surface. This control isachieved using a crafted combination of light helicity, intensity and wavelength, and is furthertuned via use of NMR pulse sequences. These results demonstrate all-optical creation of micronscale, rewritable patterns of positive and negative nuclear polarization in a bulk semiconductorwithout the need for ferromagnets, lithographic patterning techniques, or quantum-confinedstructures.
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