Persistent optical nuclear spin narrowing in a singly charged InAs quantum dot

We review the investigation of the hole-assisted dynamical nuclear spin polarization mechanism in a singly charged InAs quantum dot. Using coherent dark state spectroscopy, we measure the locking of the Overhauser field to a value determined only by the laser frequencies. Importantly, we review data that the locking effect can suppress nuclear spin fluctuations. We determine the onset time of the nuclear spin narrowing effect and its persistence absent laser interactions by directly measuring the enhancement of the electron spin coherence. This nuclear field locking effect can be explained in terms of an anisotropic hyperfine coupling between the hole spin and the nuclear spins. (C) 2012 Optical Society of America