Design criteria for band rejection filters made from multilayers of dielectric and ultrathin metal films

Narrowband rejection filters can be constructed from multilayers of dielectric and ultrathin metal films operating in the anomalous skin effect region constrained by the optical size effect. The wavelength of the main reflecting spectrum is wholly determined by the dielectric thickness, and the bandwidth can be reduced by increasing the total number of layers and selecting the dielectric film with high refractive index while diminishing the thickness of the metal film.