Absorption and emission cross sections of Er3+ in Al2O3 slab waveguides

Al₂O₃ slab waveguide films were doped with erbium using ion implantation to a peak concentration of 1.5 at. %. Prism coupling measurements show absorption caused by ⁴I_15/2 → ⁴I_13/2 intra-4f transitions in Er³⁺ with a maximum at 1.530 µm of 8 dB/cm. The Er³⁺ absorption cross section is determined as a function of wavelength. We used the McCumber theory to derive the emission cross section spectrum from the absorption results, which we then compared with the Er³⁺ photoluminescence spectrum. The peak absorption and emission cross sections are found to be 6 x 10^­21cm^-2. The results are used to predict the optical gain performance of an Er-doped Al₂O₃ optical amplifier that operates around 1.5 µm.