Efficient 2 μm stimulated emission in the4F9/2 →4I11/2 channel from monoclinic BaYb2F8: Er3+ crystals

New spectroscopic and laser data on monoclinic Ba(Yb 1-x Er x ) 2 F 8 crystals are obtained. Efficient 2 μm stimulated emission of Er 3+ ions in the 4 F 9/2 → 4 I 11/2 channel and 2 and 3 μm cascade lasing of the sequential 4 F 9/2 → 4 I 11/2 → 4 I 13/2 transitions were excited at room temperature under Xe flashlamp pumping. Intensity characteristics of manifold-to-manifold (JJ' transitions) such as Einstein coefficients A JJ' , line strengths s JJ' , branching ratios β JJ' , and radiative lifetimes τ rad for the initial laser states 4 I 13/2 , 4 I 11/2 , 4 I 9/2 , 4 F 9/2 , 4 S 3/2 , and 2 H(2) 9/2 were analyzed in detail. All observed laser transitions between individual Stark levels were identified. Unlike well-known 2 μm lasers with Ho 3+ , Tm 3+ , Co 2+ , and Ni 2+ ions in many oxide and fluoride compounds. BaYb 2 F 8 :Er 3+ crystals operate on a pure four-level generating scheme.