Chalcogenide-Based Ultra-Uniform Narrow Bandpass Filters
(Room Room 104-C)
29 Apr 19
3:00 PM
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3:20 PM
Very large progress has been made within the fabrication method and the complexity of optical thin film filters. Coatings can now be accurate at nanometric scales even for stacks up to hundreds of layers. However, more and more uniform and performant filters are now needed. After filter fabrication the spectral performances of a filter are fixed. To overcome this limitation, materials which refractive index or thickness can be locally changed after exposure with an actinic radiation can be used. In this paper, we present the fabrication of bandpass filters based on photosensitive optical thin films (As2S3). Filters centered at 800 nm, with bandwidth of 1% or below and rejecting the whole silicon detector sensitivity spectral range are demonstrated. These filters are composed with single or multiple Fabry-Perot cavities and have a nominal uniformity of 1% over 100 mm diameter aperture. By using the photosensitive properties of the chalcogenide layers, we show that filters with uniformity below ±0.05% can be achieved. The fabricated filters are shown to have identical performances when used locally or full aperture.