Precise determination of minimum achievable temperature for solid-state optical refrigeration

► Laser cooling model for optical refrigeration is reviewed in this article. ► Importance of crystalline host for cryogenic operation is explained and verified. ► Novel differential spectroscopy is used for sensitive temperature measurements. ► Minimum achievable temperature of 110 K in Yb:YLF is measured at E4-E5 transition. ► Measurements and model predictions are in excellent agreement.