  A simple metamaterial-based wide-angle plasmonic absorber is introduced,
fabricated, and experimentally characterized using angle-resolved infrared
spectroscopy. The metamaterials are prepared by nano-imprint lithography, an
attractive low-cost technology for making large-area samples. The matching of
the metamaterial's impedance to that of vacuum is responsible for the observed
spectrally selective "perfect" absorption of infrared light. The impedance is
theoretically calculated in the single-resonance approximation, and the
responsible resonance is identified as a short-range surface plasmon. The
spectral position of the absorption peak (which is as high as 95%) is
experimentally shown to be controlled by the metamaterial's dimensions. The
persistence of "perfect" absorption with variable metamaterial parameters is
theoretically explained. The wide-angle nature of the absorber can be utilized
for sub-diffraction-scale infrared pixels exhibiting spectrally selective
absorption/emissivity.
