Study of Energy Transfer Between Rare Earth Ions and Effect of Al³⁺ in Pr³⁺:Yb³⁺ and Tm³⁺:Yb³⁺ Co‐Doped Sol–Gel Silica Glasses

Silica glass samples co‐doped with Pr 3+ :Yb 3+ as well as Tm 3+ :Yb 3+ were prepared using sol–gel technique and the energy transfer among the rare earth dopants is studied. Judd–Ofelt (JO) parameters Ω 2 , Ω 4 , and Ω 6 are calculated from the absorption spectra. Relatively large values of Ω 2 indicates that the rare earth ions occupy low symmetry sites in the glasses. These parameters are used to estimate branching ratio and radiative lifetime. The measured lifetimes are significantly lower than the calculated lifetimes. Photoluminescence was found to be significantly enhanced with aluminum co‐doping for both Pr 3+ and Tm 3+ emissions. This enhancement is attributed to the reduction in cross‐relaxation. Infrared to visible up‐conversion is also observed under 980 nm excitation as a result of energy transfer from Yb 3+ to Tm 3+ and Pr 3+ ions.