Effects of Using Lossy Materials on the Metal-Insulator-Metal Nanostructure Absorption Spectrum

Metal-insulator-metal metasurfaces (MIM-M) structures can achieve near-unity absorptance at sub-wavelength volumes. A conventional approach to tune the absorption wavelength and the bandwidth of MIM-Ms is to change the geometrical parameters of the structure. In this research, we investigate numerically a new approach to achieve enhanced absorption in MIM-Ms in the mid-infrared spectral region by using both lossy metals and a lossy dielectric. The absorption in the dielectric spacer layer is attributed to the Berreman and epsilon near-zero modes in combination with the dielectric intrinsic loss. The simulations have revealed the presence of additional absorption peaks compared with the case of lossless dielectrics. In particular, the effects of the dielectric thickness and the radiation incident angle on the absorption spectra of the proposed MIM-M structures have been investigated.