Abstract
The emerging fields of non-Hermitian optics and photonics are inspiring radically new, unconventional ways of mixing active and passive constituents to attain exotic light–matter interactions. Here, inspired by the concept of parity-time symmetry, we propose and explore a class of non-Hermitian multilayered metamaterials, featuring spatial modulation of gain and loss, which can exhibit extreme anisotropy in the epsilon-near-zero regime. Specifically, via analytic and numerical studies, we investigate the intriguing parameter tunability and wave-propagation effects that can occur in these media due to the delicate interplay between gain and loss. These include, for instance, field canalization, subdiffractive imaging, and reconfigurable waveguiding/radiation, and remarkably, they do not rely on the presence of metallic constituents. Moreover, we show that the extreme-parameter regime of interest is technologically feasible, e.g., in terms of material constituents based on dye-doped indium tin oxide at near-infrared wavelengths. Our outcomes bring about new, largely unexplored dimensionalities and possibilities in the tailoring of the effective properties of non-Hermitian metamaterials and open the door to a wealth of possible developments and applications in reconfigurable nanophotonics scenarios.