Study of erbium doped ZrO2 waveguides elaborated by a sol-gel process

Er3+ doped ZrO2 thin films (1 mol%) are prepared by sol-gel process and dip-coating technique. After annealing the films exhibit good optical quality and waveguiding properties. The observed fluorescence of Er3+ ions, especially at 1.53 mu m, is used by Waveguide Fluorescence Spectroscopy (WFS). It is shown that the band shape of the I-4(13/2) --> I-4(15/2) transition depends on the annealing temperature. Waveguide Raman Spectroscopy (WRS) is used at room temperature in order to analyse the films structure. Such study was conducted for different annealing temperatures at an excitation wavelength where erbium absorption is low (i.e. 676.4 nm). An amorphous waveguide is obtained below 400 degrees C. Up to 800 degrees C, the tetragonal phase mainly appears, although both monoclinic and tetragonal phases are simultaneously detected in undoped waveguides at this temperature. High Resolution Transmission Electron Microscopy (HRTEM) observations provide the mean diameter of ZrO2 crystallites which increases up to 15 nm after a 800 degrees C heat-treatment. This large size explains in part the high attenuation measured on this film at 676.4 nm (around 20 dB/cm). (C) 1999 Elsevier Science B.V. All rights reserved.