Spectroscopy and 2.8 µm laser operation of disordered Er:CLNGG crystals

We report on the first, to the best of our knowledge, laser operation on the ⁴I_11/2 → ⁴I_13/2 transition of erbium-doped disordered calcium lithium niobium gallium garnet (CLNGG) crystals with broadband mid-infrared emission properties. A 41.4 at.% Er:CLNGG continuous-wave laser generated 292 mW at 2.80 µm with 23.3% slope efficiency and a laser threshold of 209 mW. Er³⁺ ions in CLNGG feature inhomogeneously broadened spectral bands (σ_SE = 1.79 × 10^-21 cm² at 2.79 µm; emission bandwidth, 27.5 nm), a large luminescence branching ratio for the ⁴I_11/2 → ⁴I_13/2 transition of 17.9%, and a favorable ratio of the ⁴I_11/2 and ⁴I_13/2 lifetimes, exhibiting values of 0.34 ms and 1.17 ms (for 41.4 at.% Er³⁺), respectively.