Study on visible range beam splitter and 1570 nm high reflectivity film in a cem

We focus on a more difficult kind of beam splitter in a cemented cube. The specification is that when the incident angle is 45°, the reflectivity in the visible range is 70%±2%, and the reflectivity at 1570 nm is not less than 90%. The film is thick, so cracking and peeling often occur after coating