University of Pennsylvania

Title:All-optical NMR in semiconductors

Abstract: Recent time-resolved optical experiments are able to probe the dynamics of semiconductor electron spins over time scales from femtoseconds to minutes. These studies have shown that circularly-polarized light imparts a magnetic imprint on dilute electron gases that is sensitive to nuclear spin order. We show how electron spins not only serve as a magnetometer of local nuclear fields, but can also be used to generate nuclear polarization and to induce nuclear magnetic resonance. Thus, pulsed lasers can be used to implement a form of NMR that is entirely optical. We discuss how these experiments can exploit localization of the electron wavefunction to restrict the NMR tipping process to small regions of a sample, and demonstrate NMR focusing to a 7.5 nm plane defined by a quantum well.