Nuclear Spin Polarization of Phosphorus Donors in Silicon. Direct Evidence from 31P-Nuclear Magnetic Resonance*

We experimentally demonstrate the optical hyperpolarization and coherent control of $^{31}$P, nuclear spins in single crystal silicon via the inductive readout of the nuclear magnetic resonance (NMR) signal of $^{31}$P at a concentration of 1.5 x 10$^{15}$ cc$^{-1}$. The obtained polarization is sufficient the $^{31}$P spin polarization of 1.17 x 10$^{15}$ in a 10 mm x 10 mm sample, observed in one FID with signal-to-noise ration of 113. The linewidth is 800 Hz. The Hahn echo pulse sequence reveals a $^{31}$P T$_{2}$ time of 0.42 s at 1.6 K, which was extended by the Carr Purcell cycle to 1.2 s at the same temperature. The maximum build-up of the nuclear polarization was achieved within $\sim$577 seconds, at 4.2 K, in 6.7 T, using optical excitations provided by an infra-red laser.