Multi-witness glass monitoring strategy for two-cavity thin-film Fabry-Perot filter

Narrow bandpass thin-film filters are frequently used for many applications that require frequency filtering. Although various designs and approaches have been studied in past decades, they still present serious challenges regarding deposition. Especially, as the required passband of the designs becomes narrower, the accuracy needed on layer thicknesses increases involving more difficulty to control the layers during deposition. This paper presents a multi-witness glass monitoring strategy for narrow thin film Fabry-Perot filter deposition.