Amplified Sensitivity of Nitrogen-Vacancy Spins in Nanodiamonds using All-Optical Charge Readout

TL;DR

This paper demonstrates a fast, high-contrast optical charge readout method for NV centers in nanodiamonds, significantly improving spin measurement speed and contrast for sensing applications.

Contribution

It introduces a novel all-optical charge readout technique that enhances spin readout in nanodiamonds, enabling faster and more sensitive measurements.

Findings

Achieved a fivefold increase in T1 relaxometry measurement speed.

Observed complex charge dynamics involving ionization and recombination.

Demonstrated universal charge-dependent photoluminescence contrast in nanodiamonds.

Abstract

Nanodiamonds containing nitrogen-vacancy (NV) centers offer a versatile platform for sensing applications spanning from nanomagnetism to in-vivo monitoring of cellular processes. In many cases, however, weak optical signals and poor contrast demand long acquisition times that prevent the measurement of environmental dynamics. Here, we demonstrate the ability to perform fast, high-contrast optical measurements of charge distributions in ensembles of NV centers in nanodiamonds and use the technique to improve the spin readout signal-to-noise ratio through spin-to-charge conversion. A study of 38 nanodiamonds, each hosting 10-15 NV centers with an average diameter of 40 nm, uncovers complex, multiple-timescale dynamics due to radiative and non-radiative ionization and recombination processes. Nonetheless, the nanodiamonds universally exhibit charge-dependent photoluminescence contrasts and the potential for enhanced spin readout using spin-to-charge conversion. We use the technique to speed up a $T_1$ relaxometry measurement by a factor of five.