Strong absorption and selective emission from engineered metals with dielectric coatings

We demonstrate strong-to-perfect absorption across a wide range of mid-infrared wavelengths (5-12μm) using a two-layer system consisting of heavily-doped silicon and a thin high-index germanium dielectric layer. We demonstrate spectral control of the absorption resonance by varying the thickness of the dielectric layer. The absorption resonance is shown to be largely polarization-independent and angle-invariant. Upon heating, we observe selective thermal emission from our materials. Experimental data is compared to an analytical model of our structures with strong agreement.