All-Optical Cryogenic Thermometry Based on Nitrogen-Vacancy Centers in Nanodiamonds

The nitrogen-vacancy center in diamond offers a platform for high-sensitivity temperature sensing at the nanoscale. Extension of such thermometry to low temperatures has been limited, though, as techniques based on spin resonances lose sensitivity. The authors show that an alternative, all-optical technique works from room temperature down to liquid-nitrogen temperature, with no deterioration in thermal sensitivity. Using an array of diamond nanoparticles embedded in a polymer membrane, they measure a temperature gradient on the surface of yttrium iron garnet under local heating, which suggests that this technique could reveal crucial spatiothermal details in spin-caloritronic systems.