Near-perfect absorber of infrared radiation based on Au nanorod arrays

A polarization-independent metamaterial near-perfect absorber is numerically studied in the infrared range in a two-perpendicular-nanorod design. It is shown that the absorptance and the peak wavelength associated with magnetic resonance are sensitive to the nanorod length, the thickness, and the refractive index of the spacer, while only being slightly affected by the period and the distance between neighboring nanorods. This design shows two absorption peaks with absorptance values of 89% and 83% at the wavelengths of 1.24 and 1.46  μm, respectively. Furthermore, the absorptance and the peak wavelength associated with magnetic resonance show negligible dependence on the polarization angle. These properties are advantageous for applications, including thermal sensing and selective emitters in thermophotovoltaics.