Sensitization of the Er3+ luminescence in (YЕr)3Аl5O12Сr3+ crystals and lasing at the 2.7 μm wavelength

An investigation was made of the spectroscopic properties of YAG:Cr³⁺ and YAG:Cr³⁺:Er³⁺ crystals. The decay kinetics of the Cr³⁺ ions was also studied. Efficient nonradiative transfer of energy from the Cr³⁺ to the Er³⁺ ions was observed at room temperature. In YAG:Cr³⁺:Er³⁺ crystals (⁴I_11/2→⁴I_13/2 transition) free-running stimulated emission was obtained at the 2.698 μm wavelength at room temperature. The mechanism for filling of the active levels of the Er³⁺ ions in these crystals is discussed.