Topological funneling of light.
Sebastian WeidemannMark KremerTobias HelbigTobias HofmannAlexander StegmaierMartin GreiterRonny ThomaleAlexander SzameitPublished in: Science (New York, N.Y.) (2020)
Dissipation is a general feature of non-Hermitian systems. But rather than being an unavoidable nuisance, non-Hermiticity can be precisely controlled and hence used for sophisticated applications, such as optical sensors with enhanced sensitivity. In our work, we implement a non-Hermitian photonic mesh lattice by tailoring the anisotropy of the nearest-neighbor coupling. The appearance of an interface results in a complete collapse of the entire eigenmode spectrum, leading to an exponential localization of all modes at the interface. As a consequence, any light field within the lattice travels toward this interface, irrespective of its shape and input position. On the basis of this topological phenomenon, called the "non-Hermitian skin effect," we demonstrate a highly efficient funnel for light.