Laser cooling of Yb³⁺-doped LuLiF₄ crystal

In order to meet the demands for applications of optical refrigerators in the fields of spaceflight, aviation, space science, and detection, a 2 wt. % Yb3+-doped LuLiF4 crystal, as a new laser cooling material, was prepared and demonstrated by using a 178 mW diode laser centered at 1015 nm and a resonant extra-cavity scheme with an enhancement factor of 12.8. Cooling efficiency of 1.27% and a temperature drop of 14.3 K/W are obtained with 79% of the incident laser power being absorbed. Based on our results, a sample with background absorption of α=4.2×10(-4)  cm(-1) can be potentially cooled down to ∼145 K. Our investigation shows that Yb3+-doped LuLiF4 crystal is potentially a promising candidate for solid-state refrigeration.