Optimization of THz absorption in thin films

In this paper, we report on experimentally verified models, which assist in the design and fabrication of either thin metal films, with high broad-band absorption in the 3-5 THz spectral region, or thin metatamaterial structures of nearly 100% absorption at a specific, resonant, THz frequency. The THz absorption properties of the structures were modeled using COMSOL finite element modeling software. Optimized thin metal films and thin metamaterial structures were fabricated using standard microfabrication processes on Si substrates. The THz spectral characteristics of the structures were probed using FTIR spectrometer in the reflection mode. The measured THz reflection, from thin film of both broad-band and resonant metamaterial structures, exhibit excellent agreement with their respective models. Both types of absorbers can be incorporated in the fabrication of MEMS-based THz thermal sensors operating in active mode with quantum cascade laser (QCL) sources.