In one aspect, a multi-layer absorber is disclosed, which comprises a proximal layer having a radiation-receiving surface adapted for receiving electromagnetic radiation, and a distal layer disposed adjacent the proximal layer to receive at least a portion of the received radiation, if any, transmitted through said proximal layer, wherein said proximal layer exhibits an index of refraction having a real part that is less than the real part of an index of refraction of the said distal layer for at least one frequency of the electromagnetic radiation in a range of about 1 GHz to about 110 GHz.