Spectroscopic Properties of TmF-Doped CaF Crystals.

In this study, we report the growth and comprehensive spectroscopic analysis of TmF-doped CaF crystals, grown using the vertical Bridgman method. The optical absorption and photoluminescence properties of both trivalent (Tm) and divalent (Tm) thulium ions were investigated. Optical absorption spectra in the UV-VIS-NIR range reveal characteristic transitions of Tm ions, as well as weaker absorption bands corresponding to Tm ions. The Judd-Ofelt (JO) formalism was applied to determine the intensity parameters Ω, Ω, and Ω, which were used to calculate radiative transition probabilities, branching ratios, and radiative lifetimes for the Tm ions. The emission spectra showed concentration-dependent quenching effects, with significant emissions observed for the concentration of 0.1 mol% TmF under excitation at 260 nm and 353 nm for Tm ions and at 305 nm for Tm ions. A new UV emission associated with divalent Thulium is reported. The results indicate that higher TmF 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.