Efficiency of population of the 4I13/2 level of the Er3+ ion and the possibility of lasing at 1.5 μm in Yb, Er:YAG at high temperatures

It is shown that, as the temperature of an Yb, Er:YAG crystal is increased from room temperature to 400–600°C, the efficiency of energy accumulation on the ⁴I_13/2 level of the Er³⁺ ion increases by several times upon optical pumping through Yb³⁺ ions. Under these conditions, up to 60% of erbium ions can be excited, which gives promise that lasing at a wavelength of 1.54 μm can be achieved in the Yb, Er:YAG crystal in the three-level scheme.