Spectroscopic studies and downconversion luminescence in OH ^--free Pr³⁺-Yb³⁺ co-doped low-silica calcium aluminosilicate glasses

We report on spectroscopic studies and downconversion luminescence in OH^--free Pr³⁺-Yb³⁺ co-doped low-silica calcium aluminosilicate glasses (LSCAS). The dependencies of the visible to near-infrared emissions, photoacoustic signals, luminescence decay times and energy transfer efficiencies from Pr³⁺→Yb³⁺ on the doped Yb₂O₃ concentration were investigated. The results confirmed the occurrence of downconversion processes in the examined samples, followed by a back-energy transfer mechanism from the Yb³⁺: ²F_5/2 level to the Pr³⁺:¹G ₄ level, from where the multiphonon relaxations through the ¹G₄,³F₄→³H ₄ transitions occurred. The photoacoustic data provided evidence of the energy transfer that resulted in heat generation in the sample, confirming the observations provided by the luminescence data. The energy transfer mechanisms that are involved in the Pr³⁺:Yb³⁺ co-doped LSCAS glasses are discussed.