Spectroscopic Properties of TmF 3 -Doped CaF 2 Crystals.

In this study, we report the growth and comprehensive spectroscopic analysis of TmF ₃ -doped CaF ₂ crystals, grown using the vertical Bridgman method. The optical absorption and photoluminescence properties of both trivalent (Tm ³⁺ ) and divalent (Tm ²⁺ ) thulium ions were investigated. Optical absorption spectra in the UV-VIS-NIR range reveal characteristic transitions of Tm ³⁺ ions, as well as weaker absorption bands corresponding to Tm ²⁺ ions. The Judd-Ofelt (JO) formalism was applied to determine the intensity parameters Ω ₂ , Ω ₄ , and Ω ₆ , which were used to calculate radiative transition probabilities, branching ratios, and radiative lifetimes for the Tm ³⁺ ions. The emission spectra showed concentration-dependent quenching effects, with significant emissions observed for the concentration of 0.1 mol% TmF ₃ under excitation at 260 nm and 353 nm for Tm ^{3 +} ions and at 305 nm for Tm ²⁺ ions. A new UV emission associated with divalent Thulium is reported. The results indicate that higher TmF ₃ concentrations lead to increased non-radiative energy transfer, which reduces luminescence efficiency. These findings contribute to the understanding of the optical behavior of Tm-doped fluoride crystals, with implications for their application in laser technologies and radiation dosimetry.