Exceptionally Low Optical Absorption in Aluminum Nitride Thin Films Deposited by Magnetron Sputtering

AlN addresses issues with traditional thin-film waveguides with its wide-bandgap and broad transparency window. This work demonstrates sputter-deposited AlN thin flms with ultra-low optical absorption, optimized via substrate and sputtering conditions. High-temperature deposition reduced oxygen content, improving transparency. Optical-loss measurements on waveguides confirmed record-low losses.