Optical waveguiding characteristics of amorphous TeO2-x films deposited by reactive sputtering under different O-2:Ar gas mixtures are investigated on fused quartz and Corning glass substrates. Infra-red absorption band in the range 641-658 cm(-1) confirmed the formation of a Te-O bond, and a 20:80 O-2:Ar gas mixture ratio is found to be optimum for achieving highly uniform and transparent films at a high deposition rate. As grown amorphous films exhibited a large band gap (3.76 eV); a high refractive index value (2.042-2.052) with low dispersion over a wide wavelength range of 500-2000 rim. Optical waveguiding with low propagation loss of 0.26 dB/cm at 633 nm is observed on films subjected to a post-deposition annealing treatment at 200 degreesC. Packing density and etch rates have been determined and correlated with the lowering of optical propagation loss in the annealed films. (C) 2003 Elsevier Science B.V. All rights reserved.