# Optical Cryocooling of Diamond

## TL;DR

This paper investigates optical cryocooling in diamond with NV or SiV defects, demonstrating potential for cooling microdiamonds by over 10 Kelvin at low power, with observable effects in vacuum and water environments.

## Contribution

It reveals diamond's potential for optical cryocooling using NV defects, providing experimental and theoretical insights into cooling microdiamonds at low power levels.

## Key findings

- NV-doped diamond microcrystals can be cooled below room temperature by over 10 Kelvin.
- Cooling effects are observable via changes in diffusion constants or spectroscopic signatures.
- Low irradiation powers (<100 mW) are sufficient for significant cooling in vacuum conditions.

## Abstract

The cooling of solids by optical means only using anti-Stokes emission has a long history of research and achievements. Such cooling methods have many advantages ranging from no-moving parts or fluids through to operation in vacuum and may have applications to cryosurgery. However achieving large optical cryocooling powers has been difficult to achieve except in certain rare-earth crystals. Through study of the emission and absorption cross sections we find that diamond, containing either NV or SiV (Nitrogen or Silicon vacancy), defects shows potential for optical cryocooling and in particular, NV doping shows promise for optical refrigeration. We study the optical cooling of doped diamond microcrystals ranging 10-250 microns in diameter trapped either in vacuum or in water. For the vacuum case we find NV-doped microdiamond optical cooling below room temperature could exceed 10 Kelvin, for irradiation powers of P< 100 mW. We predict that such temperature changes should be easily observed via large alterations in the diffusion constant for optically cryocooled microdiamonds trapped in water in an optical tweezer or via spectroscopic signatures such as the ZPL width or Raman line.