Realization of Epsilon-Near-Zero Metamaterial Stack Based on Dielectric-Semiconductor-Metal Multilayers

Abstract

The epsilon-near-zero (ENZ) metamaterials are designed theoretically based on multilayer nanostructure stack with three sublayers (in each period) in the visible range for transverse magnetic mode at normal and transverse electric mode at oblique incident lights. The sublayers can be either metal, dielectric, or semiconductor materials. The effective permittivities of the multilayer metamaterial stacks are derived based on the optical nonlocality analysis that expand via the Bloch theory and transfer matrix method. Multilayer metamaterials based on dielectric-semiconductor-metal (DSM) including Al2O3 − Ge − Ag triple layers are considered to study their unique optical properties and determine the ENZ wavelengths at visible frequencies. Furthermore, the propagation properties of terahertz (THz) waves passing through the DSM multilayer stacks have been theoretically investigated by calculating transmission, reflection, and absorption spectra at different angles of incidence. The electric field distribution and absorption results show that the optical loss can be reduced and kept under control in multilayer metamaterial stacks. The result of reflection and transmission indicate that the DSM multilayer stacks can be introduced as a band-pass filter, and various conditions are considered for optimal filtering. In addition, it is shown that the number of depth in reflection spectra (peak in transmission spectra) increases by increasing the number of triple layers in the structures which perfectly matches with the frequencies that satisfy the Bragg’s law. All analytical results are in good agreement with the results obtained from numerical simulations.