SIMPLIFIED DESCRIPTION OF MULTILAYER DIELECTRIC REFLECTORS

The absorptance minimum of a stack having much greater absorption in the high-index material occurs at omega greater than omega //c (band center). Operation at omega greater than omega //c could increase the damage resistance if the high-index material is easily damaged. At omega //c, E decays rapidly. As omega departs from omega //c in an infinite reflector, E penetrates deeper into the coating, with no decay at the band edges. The peak-to-peak distance in an infinite dielectric stack is constant for all frequencies in the band. By using the continuity of E and dE/dz, E can be obtained from E equals 0 at the metallic substrate or, in an infinite stack, from E equals 0 at the reflector surface for omega equals omega //c or E equals 0 in the center of the high- or low-index layer at the band edges. Simple closed-form approximations for the spectral absorptance and the phase of E are presented.