The theory of absorption of infrared radiation based on the formation of antiparallel surface current in a metamaterial absorber appears to be invalid when the thickness of the dielectric material in the structure is increased by an integral multiple of a half-wavelength. The absorption characteristics repeat themselves with an increase of each integral multiple of a half-wavelength, despite the fact that the surface current components for an odd value of integers are parallel to each other. This contradicts the theory of absorption based on the formation of antiparallel surface current. The reason for this uncertainty in surface current has been well explored in this paper, wherein we demonstrate theoretically the principle of absorption in a metamaterial structure based on the principle of multiple reflection and the interference model. For validation of the occurrence of the multiple reflection phenomena involved in absorption, time-domain analyses of metamaterial absorbers under normal as well as oblique incidence have been simultaneously analyzed. The time of occurrence of each reflection obtained numerically using the inverse chirp-Z transform is found to be in good agreement with the results obtained analytically.
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