Preparation and characterization of sol-gel derived Er3+: Al2O3-SiO2 planar waveguides

Er 3+ doped aluminosilicate thin films were prepared on silica and silica Si substrates by the sol-gel method. The Er ion concentration was varied from 0.25% to 1%. Fluorescences of Er ions in the visible and infrared regions were characterized. Green and red up-conversion fluorescences centered at 548 and 655 nm for, respectively, the (2H11/2+4S3/2)→4I15/2 and 2F9/2→4I15/2 were observed. A broadband peak was observed at 1531 nm corresponding to the 4I13/2 → 4I15/2 transition, with the full width at half-maximum of 47 nm comparable to those prepared by other methods. The fluorescence lifetime of the 4I13/2 excited state was found to be constant and equal to 3.5 ms until a high Er doping of 0.5 at. %.