Stimulated emission from Er3+ ions in yttrium aluminum garnet crystals at λ = 2.94 μ

Stimulated emission due to the ⁴I_11/2–⁴I_13/2 transition (λ = 2.936 μ) in yttrium aluminum garnet (Y₃Al₅O₁₂) doped with Er³⁺ ions (30 wt%) was observed for the first time at 300°K. The output energy from crystals of 50×3 mm dimensions was 0.3 J under free-oscillation conditions and 0.05 J in the case of Q switching. The lifetime of the ⁴I_11/2 level was determined for crystals with 3–30 wt% Er³⁺. The energy from the higher Er³⁺ levels relaxed in a cascade manner through ⁴I_11/2 to ⁴I_13/2.