Omnidirectional Narrow Band Pass, Band Pass and Band Blocking IR Filters

In the Phase I SBIR, Lake Shore proved the feasibility of narrow band pass, band pass and band blocking IR filters made from macroporous silicon (MPSi). This type of optical filter consists of a three-dimensional, periodic structure in monocrystalline silicon. Due to the nature of light transmission through such a layer, omnidirectionality of the transmission was demonstrated. Due the construction consisting mostly of a single environmentally stable material, porous silicon filters do not suffer from thermal, mechanical, and environmental instabilities. In Phase II, Lake Shore will optimize the manufacturing process and will evaluate some design changes that should provide viable prototypes for testing by NASA. In particular, different silicon anodization setups will be used to provide uniform silicon anodization across up to 150mm wafers, different pore geometries will be used to maximize the transmittance, CVD pore wall coating will be developed to extend the application range of such filters beyond the transparency window of silicon, antireflection coating of the filter surfaces will be developed to suppress reflection losses and packaging will be developed in order to adapt these filters for different applications. Such filters are expected to impact commercial, military and scientific community in many filter applications.