Infrared epsilon-near-zero absorption excited by magnetic dipole resonance

Abstract

In natural or artificial Epsilon-near-zero (ENZ) materials, excitation of the absorption at ENZ point requires large incident-angle or polarization dependence, and thus become limited in practical applications. In this paper, the magnetic dipole resonance in a metal-ENZ-insulator–metal structure breaks such restrictions on ENZ absorption, by providing a critical longitudinal electric field to the embedded ENZ material. In numerical and corresponding experimental realizations, a thin SiO2 film in the metal-ENZ-insulator–metal structure serves as the ENZ layer at mid-infrared and holds the ENZ absorption at both TE and TM polarizations under normal incidence. The cooperation of ENZ absorption, magnetic dipole mode and the loss of SiO2film further results in infrared absorption enhancement and band-width broadening.