Designing black mirrors

Black mirrors, or total absorbers, are related to neutral density (ND) filters. ND filters are primarily concerned with transmittance, whereas a black mirror has no transmittance and endeavors to reduce the reflectance to zero in the wavelength band of interest by absorbing all the light. Metal layers must be used for the absorptance capabilities and dielectric layers to create the interference phases, which maximize the electric field at the absorbing layers. Very thin metal layers, whose indices of refraction vary with the thickness and require special software handling in the design process, are required. The procedures and an additional viewpoint on designing black mirrors are discussed here.