Rapidly Enhanced Spin-Polarization Injection in an Optically Pumped Spin Ratchet

Abstract

Rapid injection of spin polarization into an ensemble of nuclear spins is a problem of broad interest, spanning dynamic nuclear polarization (DNP) to quantum information science. We report on a strategy to boost the spin-injection rate by exploiting electrons that can be rapidly polarized via high-power optical pumping. We demonstrate this in a model system of nitrogen-vacancy center electrons injecting polarization into a bath of ${}^{13}\mathrm{C}$ nuclei in diamond. We deliver $>20$ W of continuous, nearly isotropic, optical power to the sample, constituting a substantially higher power than in previous experiments. Through a spin-ratchet polarization transfer mechanism, we show boosts in spin-injection rates by over 2 orders of magnitude. Our experiments elucidate bottlenecks in the DNP process caused by rates of electron polarization, polarization transfer to proximal nuclei, and spin diffusion. This work demonstrates opportunities for rapid spin injection employing nonthermally generated electron polarization, and has relevance to a broad class of experimental systems, including in DNP, quantum sensing, and spin-based MASERs (microwave amplification by stimulated emission of radiation).