Optical hyperpolarization of nitrogen donor spins in bulk diamond

TL;DR

This paper demonstrates optical hyperpolarization of nitrogen donor spins in bulk diamond, achieving significant polarization enhancement through optical pumping and cross relaxation, with potential applications in diamond-based nuclear polarization technologies.

Contribution

It introduces a method to hyperpolarize nitrogen donor spins in bulk diamond using optical pumping of NV centers and cross relaxation, revealing polarization levels and saturation effects.

Findings

Maximum donor spin polarization of 0.9%

Polarization enhancement factor of 25 over thermal levels

Identification of charge state conversion limiting polarization buildup

Abstract

We report hyperpolarization of the electronic spins associated with substitutional nitrogen defects in bulk diamond crystal. Hyperpolarization is achieved by optical pumping of nitrogen vacancy centers followed by rapid cross relaxation at the energy level matching condition in a 51 mT bias field. The maximum observed donor spin polarization is 0.9 \% corresponding to an enhancement by 25 compared to the thermal Boltzmann polarization. A further accumulation of polarization is impeded by an anomalous optical saturation effect that we attribute to charge state conversion processes. Hyperpolarized nitrogen donors may form a useful resource for increasing the efficiency of diamond-based dynamic nuclear polarization devices.