Just before the deposition of your Er:Al2O3 active content, the coupling circuit, i.e., the strip waveguides, the method changeover tapers and also the method converters ended up included using a 800 nm thick layer of hydrogen silsesquioxane (HSQ, n ~1.45) to avoid their coating with the active product, as shown https://ignacyf296zhn3.bimmwiki.com/user