Abstract: A crystalline material for optically pumped solid state lasers has the chemical composition of M3RE1−xYbx(BO3)3, where M is selected from the group Mg, Ca, Sr, Ba, and Ra, optionally replaced at least partially with another element from this group, RE is selected from the group Sc, Y, Lu, and Y partially replaced with Lu, and x is greater than or equal to 0 and less than or equal to 1. The material is useful for preparing lasers having high average initial power and short pulse duration, and has flat amplification and fluorescence spectra, high thermal conductivity and a large emission cross-section.