Temporally Modulated Non-Hermitian Optical Systems Based on Epsilon-Near-Zero Media

Abstract

Non-Hermitian systems with judiciously designed loss and gain distributions have been shown to enable novel wave effects compared to their Hermitian counterparts. While this concept was recently extended to the temporal domain through time-varying material properties, a systematic investigation of dynamical open structures with time-varying radiation properties is still lacking, especially in the context of optical scattering. Here, we show that the radiation characteristics of a scattering system can be engineered in new ways using time-modulated epsilon-near-zero materials, leading to unique opportunities to overcome some of the limits and bounds of time-invariant system. Specifically, we demonstrate that such temporal modulations can enable novel wave effects, including unidirectional frequency transitions and bound states in the continuum that can be externally excited by broadband light sources.