Low‐Loss Epsilon‐Near‐Zero Metamaterials

Abstract

Abstract Different from the classical periodic‐resonator‐based metamaterials, epsilon‐near‐zero (ENZ) metamaterials provide a unique paradigm to achieve equivalent electromagnetic characteristics in deep subwavelength scales, exhibiting unprecedented impacts on a broad variety of extreme‐small‐volume applications. By doping regular dielectric rods in the ENZ host, the effective permeability µ eff of ENZ metamaterials is properly tuned for desired scattering properties and intrinsic impedance. However, losses in ENZ metamaterials severely limit the tuning range of the real part of µ eff and result in an undesired imaginary part. Here, to mitigate the loss issue of ENZ metamaterials, a dielectric‐free approach is theoretically studied and experimentally verified by substituting dielectric dopants with metal‐layer dopants to construct a low‐loss resonant cavity. Therefore, the largest tuning range of µ eff is achieved, which advances ENZ metamaterials from ideal cases to more extensive and practical applications. In addition to existing photonics and electronics applications of regular ENZ metamaterials, additional examples are studied to demonstrate the low‐loss benefits of layer‐type ENZ metamaterials, including integrated microfluidic switches and high‐sensitivity sensors with a sensitivity of 11.2% and quality factor of 2800. These examples reveal universal significance for wide‐range applications in extreme‐small‐volume devices and systems, such as integrated circuits, chips, and implanted devices.