Scattering-free pulse propagation through invisible non-Hermitian media

Abstract

We demonstrate a design principle for unidirectionally invisible non-Hermitian structures that are invisible not only for one specific wavelength but rather for a broad frequency range. Our idea is based on the concept of constant-intensity waves, which can propagate even through highly disordered media without backscattering or intensity variations. In contrast to already existing invisibility studies, our design principle requires neither a specific symmetry (like $\mathcal{PT}$ symmetry) nor periodicity and can thus be applied in a much wider context. This generality combined with broadband frequency stability allows a pulse to propagate through a disordered medium as if the medium were entirely uniform.