The influence of erbium ion concentration on the optical properties of BaF₂:ErF₃ crystals was investigated. Four ErF₃ concentration (0.05, 0.08, 0.15 and 0.5 mol% ErF₃)-doped BaF₂ crystals were obtained using the Bridgman technique. Room temperature optical absorption in the 250–850 nm spectral range was measured, and the photoluminescence (PL) and decay times were also investigated. The Judd–Ofelt (JO) approximation was used, taking into account four absorption peaks (at 377, 519, 653 and 802 nm). The JO intensity parameters, Ω_t (t = 2, 4, 6), were calculated. The influence of the ErF₃ concentration on the JO parameters, branching ratio, radiative transition probability and radiative lifetime were studied. The obtained results were compared with measured values and with those reported in the literature. Under excitation at 380 nm, the well-known green (539 nm) and red (668 nm) emissions were obtained. The calculated and experimental radiative lifetimes were in millisecond range for green and red emissions. The intensity of the PL spectra varied with the Er³⁺ ion concentration. The emission intensity increased linearly or exponentially, depending on the ErF₃ concentration. Under excitation at 290 nm, separate to the green and red emissions, a new UV emission band (at 321 nm) was obtained. Other research has not reported the UV emission or the influence of ErF₃ concentration on emission behavior.

In this study, we report the growth and comprehensive spectroscopic analysis of TmF₃-doped CaF₂ crystals, grown using the vertical Bridgman method. The optical absorption and photoluminescence properties of both trivalent (Tm³⁺) and divalent (Tm²⁺) thulium ions were investigated. Optical absorption spectra in the UV-VIS-NIR range reveal characteristic transitions of Tm³⁺ ions, as well as weaker absorption bands corresponding to Tm²⁺ ions. The Judd–Ofelt (JO) formalism was applied to determine the intensity parameters Ω₂, Ω₄, and Ω₆, which were used to calculate radiative transition probabilities, branching ratios, and radiative lifetimes for the Tm³⁺ ions. The emission spectra showed concentration-dependent quenching effects, with significant emissions observed for the concentration of 0.1 mol% TmF₃ under excitation at 260 nm and 353 nm for Tm³⁺ ions and at 305 nm for Tm²⁺ ions. A new UV emission associated with divalent Thulium is reported. The results indicate that higher TmF₃ 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.

In this paper, we investigate the production of high energy gamma photons at the interaction between an ultra-high intensity laser pulse with an energetic electron beam and with a near-critical density plasma for the laser intensity varying between ${10}^{19}$–${10}^{23}$ W/cm${}^2$. In the case of the interaction with an electron beam, and for the highest laser intensities considered, the electrons lose almost all their energy to emit gamma photons. In the interaction with a near-critical density plasma, the electrons are first accelerated by the laser pulse up to GeV energies and further emit high energy radiation. A maximum laser-to-photons conversion coefficient of $30\%$ is obtained. These results can be used for the preparation of experiments at the Apollon and ELI laser facilities for the investigation of the emission of high energy $\gamma$-photons and to study the electron-positron pair creation in the laboratory.

Tb³⁺-doped CaF₂ single crystals are attractive materials for green photonic applications due to their low phonon energy, high optical transparency, and efficient Tb³⁺ emission. In this work, CaF₂ single crystals doped with different TbF₃ concentrations (1, 5, and 10 mol%) were grown and systematically investigated in order to clarify the concentration-dependent spectroscopic behavior of Tb³⁺ ions in a fluorite host. Optical absorption spectroscopy, Judd–Ofelt analysis, steady-state and time-resolved photoluminescence, colorimetric evaluation, and emission cross-section and gain calculations were employed. Judd–Ofelt intensity parameters typical of fluoride hosts were obtained, enabling the calculation of radiative transition probabilities and lifetimes. The emission spectra are dominated by intense green luminescence from the ⁵D₄ → ⁷F₅ transition, while the absence of ⁵D₃ emission is attributed to efficient cross-relaxation processes. Fluorescence lifetimes in the millisecond range show slight changes with Tb³⁺ concentration. Quantum efficiency increases from low to intermediate concentrations and tends to saturate at higher doping levels. CIE 1931 chromaticity coordinates confirm stable green emission, while emission cross-sections and gain parameters reveal a highest value for orange emission of 10 mol% TbF₃-doped CaF₂ crystal. These results indicate that CaF₂:Tb³⁺ single crystals are promising materials for photonic applications.