Optical performance of absorber structures for thermal detectors.

The concept of absorption by a metal-dielectric-metal structure is reexamined. The absorber system is modeled as a transparent medium between two absorbing films. We study the conditions for the parameters that ensure null reflectance and transmittance for a fixed wavelength of the incident radiation, and we present explicit expressions for the absorptance in each film. The absorption optimum conditions in a range of wavelengths are also analyzed.