Loss Compensation and Superresolution in Metamaterials with Excitations at Complex Frequencies

Abstract

Metamaterials, from optics to radio frequencies and acoustics, have attracted significant attention over the last few decades, with promising applications in a wide range of technological areas. However, it has been recognized that their performance is often hindered by ubiquitous material loss and nonlocal phenomena. A canonical problem consists in imaging through metamaterial superlenses, which hold the promise of superresolution but which are, in practice, limited by material loss as we attempt to image deeply subwavelength details. Active metamaterials have been explored to compensate for loss; however, material gain introduces other obstacles, e.g., instabilities, nonlinearity, and noise. Here, we demonstrate that the temporal excitation of passive metamaterials using signals oscillating at complex frequencies can effectively compensate material loss, leading to resolution enhancement when applied to metamaterial superlenses. More broadly, our results demonstrate that virtual gain stemming from tailored forms of excitation can tackle the impact of loss in metamaterials, opening promising avenues for a broad range of applications from acoustic to photonic technologies.