We present temperature-dependent spectroscopy of cubic Yb:KY3F10 and report on its first laser cooling. In comparison with Yb:YLF, Yb:KY3F10 has an intrinsically higher cooling potential at low temperatures so suited for optical refrigerators.
Abstract YAlO 3 (YAP) shows lower phonon energy than Y 3 Al 5 O 12 (YAG), which implies a lower temperature can be obtained in Yb 3+ -doped YAP according to the single-frequency phonon model. Here, a 2% Yb 3+ : YAP crystal was refrigerated by anti-Stokes fluorescence and compared to YAG crystal with the same doping concentration in experiments. Yb 3+ exhibited a broad spectral cooling range in YAP from 1020nm to 1070nm, which was broader than in YAG from 1020 nm to 1055 nm. A minimum achievable temperature (MAT) dropped to ~ 249.7 K at 1040 nm for Yb 3+ : YAP, which was lower than that of ~ 259.3 K obtained in 2% Yb 3+ : YAG. Further analysis predicted that the cooling limit of two crystals can reach ~167 K for Yb 3+ : YAP and ~171 K for Yb 3+ : YAG from room temperature. This work exhibited the excellent cooling properties of Yb 3+ : YAP compared with Yb 3+ : YAG in experiment and provided a unique perspective for the practical application of high-power Radiation balance lasers (RBLs).
We present the first observation of cryogenic operation in an all-solid-state refrigerator. A temperature drop of ~150 K is demonstrated in a 0.2 cm3 rare-earth doped fluoride crystal (Yb:YLF) using anti-Stokes fluorescence, at a record cooling power of 110 mW. Lowest electronic transition within Yb3+ Stark manifold along with cavity enhanced absorption and thermal load management were key in achieving this operation. We show that temperatures down to 100 K are achievable in this arrangement given sufficient absorbed laser power at 1020 nm.