Materials for Optical Cryocoolers

Abstract

Vibration-free cooling of detectors to cryogenic temperatures is critical for many terrestrial, airborne, and space-based instruments. Cooling of solids by anti-Stokes fluorescence is an emerging refrigeration technology that is inherently vibration-free and compact, and enables cooling of small loads to cryogenic temperatures. In this Highlight, advances in laser-cooling of solids are discussed with a particular focus on the recent breakthrough laser cooling of Yb³⁺-doped YLiF₄ crystals to 114 K. The importance of the material structure, composition, and purity of laser-cooling materials and their influence on the optical refrigerator device performance is emphasized.