Demonstration of an optical cryocooler

Abstract: 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 fluorescence upcoversion, at a record cooling power of 110 mW. Lowest electronic transition within Yb 3+ 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