Antireflection and absorbing coatings for TROPOMI SWIR immersed grating

CILAS is involved in a scientific project for SRON Netherlands Institute for Space Research, on the development of multilayer coatings for the silicon immersed grating prism, which is a key component of the short-wave-infrared (SWIR) channel of the TROPOMI imaging spectrometer. For the project, two specific coatings have been implemented and qualified by CILAS: first, an antireflection coating deposited on the entrance and exit facets of the immersed grating prism, which reaches a very low value of reflectivity in the infrared [2305nm; 2385nm] spectral range and for a wide angular range [0° to 47°] of incidence of the transmitted light, and second, a metal-dielectric absorbing coating for the third facet of the prism to eliminate parasitic light inside the silicon prism.