Low-loss Al2O3 waveguides produced by pulsed laser deposition at room temperature

Al2O3 waveguides have been produced at room temperature by pulsed laser deposition on Si Substrates covered by a SiO2 buffer layer. The dependence of the refractive index and the losses on both the laser energy density and the gas used during deposition (either reactive (O-2) or inert (Ar)) are discussed in terms of densification processes, surface roughness, and oxygen-related defects. Amorphous waveguides with refractive indices > 1.66 and losses below 10 dB cm(-1) were produced under a wide range of experimental conditions, the best results being achieved with low laser energy densities and gas oxygen pressures. Losses as low as approximate to 2.5 dB cm(-1), which are close to the resolution limit, were achieved under optimized conditions, even when the waveguide had a thickness inhomogeneity along the propagation direction of at least 10%.