Broadband absorption enhancement in anisotropic metamaterials by mirror reflections

Nonresonant anisotropic metamaterials (AMMs), such as nanotube arrays, can be applied to achieve broadband absorption of electromagnetic (EM) waves. However, the AMMs should be very thick (similar to 1000 wavelengths) to attain high absorption. Here, we propose that using a slanted or corrugated metallic mirror, a thin AMM (similar to 3 wavelengths) is sufficient to obtain high absorption in a wide wavelength range (absorption >87% for wavelengths of 0.5-3 mu m) and over a wide angular range. Unlike common absorptions, EM waves in an ambient medium (air) is first coupled with a propagating wave in the AMM and is then converted into a lossy wave by mirror reflections.