Spectroscopic ellipsometry of a-Si/SiO 2 large waveband coating for the JWST-FGS-TFI etalon plates fabrication

Previous publications for the JWST-FGS-TFI instrument described the design and fabrication of mirror coatings for scanning Fabry-Perot etalons. Since that time, we have extended the fabrication process using ellipsometry analysis over the full operational bandwidth from 1.0 to 5.0 microns for both mirror and anti-reflection coatings. This paper will present single and multiple layer ellipsometry analysis of the a-Si/SiO₂ optical properties. Analysis improvement came from a-Si/SiO₂ interface consideration and simultaneous use of ellipsometric data from Woollam V-VASE and IRVASE instruments. Simulations of reflectance and transmittance based on the ellipsometric analysis results will also be compared to spectrophotometric measurements for witness pieces.