Terahertz Shielding Prediction of 1D-Periodic Nanolayered Coatings by an Effective Homogeneous Model

An innovative effective-medium model of ID-periodic multilayer coatings is developed by applying the transmission line method. Each period consisting of several layers with subwavelength thickness in the nanometer range is modelled as a homogeneous medium characterized by an effective complex conductivity and unit relative permeability. The resulting effective single layer (ESL), having the same total thickness of the multilayer laminate, is represented by a transfer matrix given by the product of the transmission matrices of the periods composing the structure. The effective homogeneous model is used to compute the shielding effectiveness of ID-periodic photonic-band-gap transparent coatings made by alternating layers of silver and zinc oxide films in the frequency range up to 10 THz. The good accuracy of the results obtained using the ESL is demonstrated by comparison with the results computed by means of the rigorous multilayer formulation.