Modelocked femtosecond lasers require of luminescent ions with large emission bandwidth and tunability. This requirement is difficult to fulfill with lanthanides due to the inner nature of the 4f orbital. The concept of «disordered single crystals» which is based on multiple (isovalent or heterovalent) cationic substitutions on the same lattice site has gained attention to solve the problem but results are still limited. In our recent publication in Journal of Alloys and Compounds 961 (2023) 171092 (doi 10.1016/j.jallcom.2023.171092) we show that the random orientation of the Bi3+ non-bonded 6s2 lone pair induces a large band broadening of the Yb3+ emission in monoclinic KY1-x-yBixYby(WO4)2 single crystals. The growth of these crystals and their laser capabilities are demonstrated within the activity of our THINLAS project.
