“…Optical cooling of solids can overcome the drawbacks of classical mechanical cryocoolers, such as vibration, temperature distribution inhomogeneity, massive additional equipment, to name a few. In the YAB crystals co-doped with Er and Yb ions, pumping near the absorption edge of ytterbium ions may resulted in both laser cycle and cooling cycle [5]. The laser cycle is implemented due to energy transfer from Yb ions to Er ions.…”