Optical refrigeration of payloads to T < 125 K

A modified all-solid-state optical cryocooler prototype based on anti-Stokes fluorescence in a 10%-doped Yb:YLF crystal cooled a payload to temperatures below 125 K starting from room temperature. To achieve this record performance, the optical refrigerator employed a novel, to the best of our knowledge, textured-MgF 2 thermal link to improve the thermal transport and fluorescence escape. Additionally, it used spectrally selective, high-reflection coatings in the pump circulator cavity to suppress parasitic lasing and amplified spontaneous emission.