A reinterpretation of the metamaterial perfect absorber
  We develop a simple treatment of a metamaterial perfect absorber (MPA) based on grating theory. We analytically prove that the condition of MPA requires the existence of two currents, which are nearly out of phase and have almost identical amplitude, akin to a magnetic dipole. Furthermore, we show that non-zero-order Bragg modes within the MPA may consume electromagnetic energy significantly. 
Yong Zeng, Hou-Tong Chen, and Diego A. R. Dalvit
physics.optics