It does not matter how you fabricate the surface. I only want to have a physical feeling on how big the reflectance can be. Or if someone has a physical equation to show me, well that's even better.
Can I dare to ask you to be even more specific? If we talk about numbers, how much percentage of the initial reflectance (before the coating) is the critical number for a surface to be considered non-reflective? What is the percentage of reflected light of the surface coated with SiN or any other anti-reflective coating (5%, 3%, 1% or less-more?)??