Solid-state laser refrigeration of nanoscale quantum sensors

Photothermal heating remains a major challenge during the optical excitation of nanoscale quantum sensors [C. Bradac, S. F. Lim, H. C. Chang, I. Aharonovich, Adv. Opt. Mater. 8, 2000183 (2020)]. At low laser powers, heating of the sensor leads to the thermal drift of quantum electronic transition energies. At high laser powers, sensors degrade due to thermally induced phase transitions, including melting. Here, we report a general approach for mitigating the photothermal heating of nanoscale quantum sensors through solid-state laser refrigeration of the sensors' underlying substrate. Experimentally, both nanodiamonds and gold nanocrystals are attached separately to a ceramic laser-cooling substrate through van der Waals interaction. A combination of Debye-Waller factor thermometry and optically detected magnetic resonance spectroscopy of nitrogen vacancy centers is used to demonstrate that solid-state laser refrigeration of the substrate can reduce the temperature of attached nanodiamond payloads by 25 ± 3 K below steady-state operating temperatures. Stokes/anti-Stokes Raman spectroscopy is used to demonstrate reduced photothermal heating of plasmonic gold nanocrystals by 8.8 ± 2.7 K during surface-enhanced Raman spectroscopy sensing of rhodamine-6G molecules. These results suggest that solid-state laser cooling could open up experimental possibilities for rapid feedback-controlled cooling of a wide range of nanoscale quantum resources.