Control of the direction and rate of nuclear spin flips in InAs quantum dots using detuned optical pulse trains

School of Computational Sciences, George Mason University, Fairfax, VA 22030, USA(Dated: January 16, 2009)We find that detuning an optical pulse train from electronic transitions in quantum dots controlsthe direction of nuclear spin flips. The optical pulse train generates electron spins that precess aboutan applied magnetic field, with a spin component parallel to the field only for detuned pulses. Thiscomponent leads to asymmetry in the nuclear spin flips, providing a way to produce a stable andprecise value of the nuclear spin polarization. This effect is observed using two-color, time-resolvedFaraday rotation and ellipticity.