Optical properties of erbium-doped xerogels embedded in porous anodic alumina

Structures comprising erbium-doped titanium oxide xerogel/porous anodic alumina show strong photoluminescence at 1.54 μm originating from 4I13/2 → 4I15/2 transitions of Er3+ ions in the xerogel. Depending on the annealing conditions, two phases of erbium-doped titanium oxide xerogel, anatase and rutile, mesoscopically confined in porous anodic alumina, were detected by X-ray analysis. Photoluminescence excitation spectra for 1.54 μm emission line are characterized by 10 bands of intra-shell transitions of Er ions, where the dominating band at 524 nm coincides with the 4I15/2 → 2H11/2 transitions. The photoluminescence lifetime of the 1.54 μm emission line is 1.8 ms. The influence of the shape of the porous anodic alumina film grown on an aluminium foil or silicon wafer, as well as the role of chemical content of xerogel matrix on light emission at 1.54 μm, is discussed.