Ahead of the deposition of the Er:Al2O3 Lively product, the coupling circuit, i.e., the strip waveguides, the mode transition tapers along with the manner converters were being covered using a 800 nm thick layer of hydrogen silsesquioxane (HSQ, n ~1.45) to avoid their coating with the active materials, as proven https://hectornvbhn.jts-blog.com/27458007/the-slot432-diaries