Judd-Ofelt analysis and multiphonon relaxations of rare earth ions in fluorohafnate glasses

The optical properties of fluorohafnate glasses doped with Pr³⁺, Nd³⁺, Sm³⁺, Dy³⁺, Ho³⁺, Er³⁺, and Tm³⁺ have been studied. From optical absorption measurements and using Judd-Ofelt theory, JO parameters Ω₂, Ω₄, and Ω₆ have been obtained. The Ω₂ values indicate that fluorohafnate glasses present a less ionic character than fluorozirconates. Multiphonon emission probabilities for several levels of Er³⁺ and Ho³⁺ ions were determined by the difference between the measured rates and the calculated radiative transition probabilities. The results are almost the same as those found in fluorozirconates. Multiphonon emission probabilities are in agreement with the energy-gap law followed by rare-earth ions in crystals and glasses.