All-optical patterning of Nuclear Polarization in Gallium Arsenide

We employ Stray-Field NMR Imaging for $^{69}$Ga and $^{71}$Ga to monitor the spatially-dependent polarization of nuclear spins in semi-insulating bulk GaAs at 9.4 T. By exploiting two competing mechanism as hyperfine and quadrupolar interaction for optical nuclear polarization at different illumination intensities and wavelengths, we demonstrate all-optical creation of three-dimensional patterns of positive and negative nuclear polarization. We also observe the isotope dependence of the patterning process, where different isotopes ($^{69}$Ga and $^{71}$Ga) have opposite polarization at the same location in the sample. By combining the optical pumping with varied NMR pulse sequences, we demonstrate the control of nuclear polarization.