Aluminum Oxide Waveguides for Improved Transmission in the Visible and Near-Infrared Spectrum

Planar waveguides were fabricated from amorphous aluminum oxide (AlO
_x
) for the visible and near-infrared spectra. AlO
_x
films with the nominal thickness of 1 μm were deposited on glass substrates using pulsed-dc magnetron sputtering with RF substrate bias without substrate heating. Films were deposited using various combinations of pulsed-dc power and RF substrate bias to study the dependence of optical properties under a range of controlled ion energy and ion-to-neutral ratio. To observe changes in waveguide performance, samples were further annealed at 550 °C for 1 h in air. Optical properties of the waveguides were assessed using spectroscopic ellipsometry and lateral transmission measurements with prism coupling. Results show that by using high pulsed-dc power at the target, it is possible to achieve 1.5-dB/cm transmission loss without postdeposition annealing, enabling the deposition of AlO
_x
films at high deposition rates with low transmission loss in applications with a low thermal budget.