Optimized deposition and structuring of reactively co-sputtered Al₂O₃:Er waveguide layers with net optical gain

Growth of reactively co-sputtered $Al_2O_3$ layers and micro-structuring using reactive ion etching have been optimized, resulting in channel waveguides in the as-deposited layers with optical propagation losses as low as 0.21 dB/cm. For active functionality, Erdoped $Al_2O_3$ layers have also been deposited by co-sputtering from a metallic Er target. At relevant dopant levels ($~10^{20}$ $cm^{-3})$ lifetimes of the $^{4}I_{13/2}$ level up to 7 ms have been measured and net optical gain of 0.7 dB/cm has been obtained in a 700-nm thick Erdoped $Al_2O_3$ waveguide. Investigation of active devices, such as lasers and amplifiers, exploiting the developed technology is on-going.