All-optical hyperpolarization of electron and nuclear spins in diamond

TL;DR

This paper demonstrates a method for optically inducing high levels of nuclear spin polarization in diamond, significantly enhancing NMR signals without microwaves, enabling sensitive biological sample analysis at room temperature.

Contribution

It introduces a microwave-free optical technique to hyperpolarize nuclear spins in diamond, achieving large polarization enhancements for $^{13} ext{C}$ and $^{15} ext{N}$.

Findings

Achieved $-2000$ polarization enhancement of $^{15} ext{N}$ in diamond.

Observed NMR enhancements of $-200$ at room temperature.

Demonstrated polarization diffusion to bulk $^{13} ext{C}$ enabling ambient-condition NMR.

Abstract

Low thermal polarization of nuclear spins is a primary sensitivity limitation for nuclear magnetic resonance. Here we demonstrate optically pumped (microwave-free) nuclear spin polarization of $^{13}\mathrm{C}$ and $^{15}\mathrm{N}$ in $^{15}\mathrm{N}$-doped diamond. $^{15}\mathrm{N}$ polarization enhancements up to $-2000$ above thermal equilibrium are observed in the paramagnetic system $\mathrm{N_s}^{0}$. Nuclear spin polarization is shown to diffuse to bulk $^{13}\mathrm{C}$ with NMR enhancements of $-200$ at room temperature and $-500$ at $\mathrm{240~K}$, enabling a route to microwave-free high-sensitivity NMR study of biological samples in ambient conditions.