Eigenmodes in random chiral metamaterial multilayers: Double-grid finite-difference frequency-domain analysis

Eigenmode analysis was conducted on disordered multilayer structures comprising chiral metamaterials and normal materials utilizing the double-grid finite-difference frequency-domain method. This study examined the suppression of wave localization under two distinct conditions. The first scenario involved ε near-zero (ENZ) or μ near-zero (MNZ) materials, whereas the second scenario considered conditions where the impedance of the metamaterial layers was matched to that of the normal material layer. The localization length significantly increased under impedance-matching conditions, as revealed by calculations performed with implicitly restarted Arnoldi methods with the shift-and-invert technique. Furthermore, when both permittivity and permeability were negative, two distinct branches were observed in the frequency dependence of the localization length. Conversely, no distinct suppression of localization was observed under the ENZ and MNZ conditions. The observed discrepancies between the present results and those reported in prior literature were systematically analyzed.