Optical spectroscopy of erbium-doped fluorohafnate glasses for 2.8 µm lasersSimone Normani, Pavel Loiko, Liudmila Moiseeva, Valeria Vinokurova, Leonid Vaimugin, Elena Dunina, Alexey Kornienko, Alain Braud and Maria BrekhovskikhEPJ Web Conf., 335 (2025) 08015DOI: https://doi.org/10.1051/epjconf/202533508015