Cross section of the 4I11/2–4I13/2 laser transition in Er3+ ions in yttrium–erbium–aluminum garnet crystals

Measurements were made of the ratio of the luminescence energies represented by the ⁴I_11/2–⁴I_13/2 and ⁴I_11/2–⁴I_15/2 transitions in Er³⁺ ions in (Y_1–xEr_x)₃Al₅O₁₂ crystals. The Einstein coefficients of these transitions were also determined. The cross section of the ⁴I_11/2–⁴I_13/2 (X₂–Y₆) stimulated emission transition was measured. The concentration dependences of the absolute quantum efficiencies of the luminescence from the ⁴I_11/2 and ⁴I_13/2 levels were obtained.