The pulsed laser deposition technique was used to grow silicon oxynitride (SiOxNy) thin films at low temperatures (25-300 degrees C). The thin films were found to be smooth in surface morphology, extremely inert in HF/H2O solution, and highly transparent in the optical range from 0.3 mu m to 5 mu m. The refractive index is tunable between 1.4 and 2.1 by the addition of oxygen in substitution for nitrogen in the thin films.