Crystal growth, EPR and site-selective laser spectroscopy of Gd3+-activated LiCaALF6 single crystals

Ce3+-activated LiCaAlF6 (LiCAF) and LiSrAlF6 (LiSAF) single crystals are the most prospective active media for directly pumped UV solid-state tunable lasers. Due to the geterovalent activation nature of these crystals, crystal spectroscopic properties as well as their laser efficiency strongly depend on the actual crystal growth conditions. In order to establish the growth-related peculiarities of activator center formation in LiCAF, concerted crystal growth, EPR and site-selective laser spectroscopic studies were performed. For EPR and optical spectroscopic studies, the Gd3+-“probe” activation of LiCAF crystal was used here instead of much harder to interpret Ce3+ activation. The obtained results indicate that up to three types of structurally distinct Gd3+ centers are formed in the LiCAF crystals with their relative concentrations changing depending on the crystal growth conditions. The results are being applied for growing Ce3+-activated LiCAF crystals with the desired luminescence and laser performance.