Resonant Optical Excitation for NV-Based Magnetometry at Cryogenic Temperatures

Color centers in wide bandgap semiconductors, such as the nitrogen-vacancy (NV) center in diamond, have gained popularity in the last decade due to their ability to perform nanoscale resolved magnetic imaging. Unfortunately, the traditional readout method, achieved via a non-resonant 532nm excitation, is inefficient at low temperatures due to a decrease in spin contrast and reduction of photoluminescence (PL) intensity, therefore increasing measurement times. Here, we introduce a novel approach to NV sensing that benefits from the atom-like, spin-state-resolved optical transitions shown by NVs at low temperatures. Specifically, we leverage the singular mechanisms of intersystem crossing under resonant, narrow-band optical excitation to develop spin-contrast-enhanced forms of scanning magnetometry. Building on proof-of-principle demonstrations, we show this alternative route to NV readout ultimately increases magnetic and electric field sensitivity, hence facilitating the investigation of a broader sample class.