Large aperture, highly uniform narrow bandpass Fabry-Perot filter using photosensitive As₂S₃ thin films

We present a thorough study of the use of As₂S₃ thin films for the fabrication of high-performance bandpass filters. We show that these layers can be included inside a multilayer Fabry-Perot structure in order to produce large-aperture narrow bandpass filters. These layers can also exhibit a large local refractive index change up to 0.1 when they are exposed to actinic radiation at 470 nm. Kinetics of photosensitivity are presented. We show that these effects can then be implemented to locally modify the spectral performance of a Fabry-Perot filter after deposition. Highly uniform 65×60  mm² filters with a 4 nm bandpass at 800 nm and ±0.1% fluctuations of the central wavelength are demonstrated using this technique.