How accurate is the Fabry-Perot approximation in high-finesse linear variable optical filters for gas absorption spectroscopy?

Abstract

The biggest challenge in the miniaturization of spectrometers is achieving high sensitivity and resolving power at reduced device dimensions. The gas-filled linear variable optical filter (LVOF) enhances the interaction between the light and the sample, thereby improving the sensitivity in a small footprint, by using the resonator cavity of a wideband interference filter also as the gas cell
in a wafer-level implementation. The demanding operating conditions of the gas-filled LVOF renders the conventional approximation of the tapered resonator into an array of Fabry-Perot filters invalid. A novel design method using the Fizeau interferometer approach is
described and demonstrated with measurements.