Black aperture coating with an anti-reflective clear aperture: Developed and qualified for space-based applications

The monitoring of anthropogenic CO2 by satellites (part of Copernicus, the European Union's Earth Observation and Monitoring program) requires a special dispersive spectrometer. As a highly efficient light dispersing element, a Prism-Grating Prism (PG-P) optical element will operate in the program, mentioned above. Anti-reflection (AR) coatings and light blocking apertures are requested to suppress optical losses, to reduce stray light and to shape the beam. Beside the AR-coatings, deposition of "black" aperture as a coating directly on the PG-P element, allows to abstain a mechanical aperture. Thereby, reduced number of elements in the optical setup and therefore reduced payload of the satellite can be achieved. For this purpose, an antireflective coating inside a clear aperture combined with a light blocking and absorbing aperture-coating outside the clear aperture was realized. The developments shown in this contribution were performed for the application wavelength of 1590-1675 nm.