Rugate filter fabrication using neutral cluster beam deposition

Abstract Neutral cluster beam deposition (NCBD) is shown to be memethod directly applicable to rugate filter fabrication. NCBD provides the necesarry stable low deposition rates and control (±0.1 A s −1 ) required for thin rugate layers (typically 80 A). This paper specifically describes use of NCBD for co-evaporation of ZnS and BaF 2 producing digtal rugate filter structures with a range of effective refractive indices. Automated process control aspects to achieve the necessary tolerances for rugates will be described. This is demonstrated via the excellent agreement between theoretical and experimental rugate performance. Process scalability and production issues are addressed.