PLANAR ZRO2 WAVE-GUIDES PREPARED BY THE SOL-GEL PROCESS - STRUCTURAL AND OPTICAL-PROPERTIES

ZrO2 waveguides are prepared by the sol-gel process from a solution co ntaining zirconium n-propoxide and acetylacetone in propanol-2. Struct ural characterizations are investigated for different annealing temper atures using suitable techniques including Waveguide Raman Spectroscop y, Electron Microscopy and Atomic Force Microscopy. Films are amorphou s at 300 degrees C and the pure ZrO2 tetragonal crystalline phase appe ars beyond 400 degrees C. Crystallized films present a dense, uniform and polycrystalline structure made up by randomly oriented nanocrystal lites, the diameter of which increases from 38 Angstrom at 400 degrees C to 53 Angstrom at 600 degrees C. Waveguides are at least monomode T E(0) at 632.8 nm. At this wavelength, optical losses are about 0.8 +/- 0.2 dB/cm for amorphous layers and increase up to 2.5 +/- 0.4 dB/cm f or 600 degrees C heat-treated waveguides.