Salisbury screen with lossy nonconducting materials: Way to increase spectral selectivity of absorption

We present a modified Salisbury screen design in which the thin absorbing metal layer is replaced with a layer of nonconducting lossy material. The conditions for total absorption in such a structure are explained using a simplified analytical model and rigorous numerical calculations. For the proof-of-principle experiments, germanium/silicon bilayers deposited on aluminium substrates are designed and manufactured. The structures demonstrate nearly perfect absorption in the near-IR spectral range. Compared to conventional Salisbury screens, a lossy semiconductor top layer exhibits increased spectral selectivity of absorption. The wavelength of nearly perfect absorption remains tunable by optimizing the thicknesses of the lossy and transparent layers.