Realization of near-perfect absorption in the whole reststrahlen band of SiC

Abstract

Materials used for outdoor radiative cooling technologies need not only be transparent in the solar spectral region, but also need to have a broadband perfect absorption in the infrared atmospheric transparency window (infrared-ATW). Silicon carbide (SiC) has been thought to be a potential candidate for such materials. However, due to the near-perfect reflection of electromagnetic waves in the whole reststrahlen band (RB) of SiC, which is within the infrared-ATW, perfect absorption in the whole RB remains a challenge. Here by constructing a cone–pillar double-structure surface on SiC, a near-perfect absorption (>97%) of normally incident electromagnetic waves in the whole RB has been realized experimentally. Simulation results reveal that the dominant reason for the near-perfect absorption is the efficient coupling of incident electromagnetic waves into the bulk evanescent waves in the free-space wavelength range (10.33 μm, 10.55 μm) and the efficient coupling of incident electromagnetic waves into the surface phonon polaritons in the free-space wavelength range (10.55 μm, 12.6 μm). Our findings open up an avenue to enhance the absorption performance of SiC in infrared-ATW, and may lead to many new applications.