Theoretical investigation on the properties of polarization selection and asymmetric absorption for the ITO nanowire material

Abstract

In this paper, the features of the polarization selection and broadband asymmetric absorption based on the indium tin oxide (ITO) nanowire are studied theoretically. Only two layers of ITO material are introduced into our design, and such a structure is relatively simple. For a single-layer ITO nanowire structure, supposing the incident wave is the transverse electric (TE) wave, characteristics of high absorption can be found only in the case of epsilon-near-zero (ENZ). However, for the transverse magnetic (TM) wave, provided that the angle of incidence is greater than 10°, high absorption will be generated in the cases of ENZ and epsilon-near-pole. This also leads to the absorption bandwidth of the TM wave to be wider than that of the TE one. At some certain frequencies, the absorption rate for the TE wave is low, while for the TM wave, the absorption rate is very high, resulting in the polarization selection. For the presented double-layer structure of ITO material, the reasonable adjustment of the filling factors will produce obvious asymmetric absorption in forward and backward incidence for TE and TM waves, and the TE wave will always maintain a larger range of contrast D value higher than 0.9 than that of the TM one.