A stardust resonant filter is a type of optical filter that uses the resonant properties of certain materials to selectively reflect or transmit light of specific wavelengths. This type of filter is often used in astronomy to isolate specific spectral lines, such as the hydrogen alpha line, for further study.
Stardust resonant filters are typically made from a thin layer of material that is deposited on a substrate. The material is chosen to have a resonant frequency that corresponds to the wavelength of light that is to be filtered. When light of this wavelength strikes the filter, it is absorbed by the material and then re-emitted in a specific direction. This allows the filter to selectively reflect or transmit light of a specific wavelength.