A mathematical model was constructed in order to evaluate line of sight thin film deposition geometries for uncooled annular resonator optics that have very low absorption high reflectance coatings. Model inputs include thin film source distribution profiles, source offset location and orientation, substrate surface profile and dimensions, substrate height and rotation, and radially varying masks if required. The model calculates the uniformity of the resulting films as well as other parameters that affect film quality such as deposition angles and relative deposition rates. This paper presents the results of the analysis for the Alpha laser beam compactor and rear cone. The use of tilted deposition sources promises to improve film quality, uniformity, and producibility. The model is readily revised to include additional constraints of concern to vendors and end-users. A mask concept is proposed to minimize film quality degradation due to intermittency effects.
Robert A. Field,
"Evaluation of coating deposition geometries for annular resonator optics", Proc. SPIE 2262, Optical Thin Films IV: New Developments, (7 September 1994); doi: 10.1117/12.185790; https://doi.org/10.1117/12.185790