Solid-state laser cooling properties of a 7 mol% Yb3+-doped LiLuF4 single crystal grown by the Bridgman technique

The development of vibration-free, solid-state, optical cryocoolers is rapidly approaching application-relevant technological readiness. The optimization of their purity and doping concentration is an important and ongoing area of research necessary for realizing practical optical cryocoolers. We present spectroscopic studies of a Bridgman-grown 7 mol% Yb3+-doped LiLuF4 (LLF:7%Yb) crystal, a doping concentration that is set between previously studied LLF:5%Yb and LLF:10%Yb crystals. We evaluate the wavelength-dependent cooling efficiency and background absorption as well as perform targeted high-power laser pumping at 1020 nm to assess the bulk cooling performance. These results will help to explore the potential for an optimum in laser-cooling performance between these two doping concentrations.