Effects of Substrate Phonon Absorption on the Resonance Properties of Ultrathin Metamaterials in the Terahertz Range

We have investigated effects of phonon absorption on the resonance spectra of ultrathin metal-insulator-metal (MIM) metamaterial absorbers (MMAs) in the terahertz (THz) frequency range. Top-incidence MIM MMAs show narrowband and large absorption. However, no resonant absorption is observed when the THz is incident from the backside of the GaAs substrate, due to strong acoustic phonon absorption in the GaAs substrate. 63% absorption peak is observed when the substrate is replaced with a high-resistivity Si, which is a good candidate for the integration with the recently proposed MEMS- based THz bolometer.