Near-field imaging of spin-locked edge states in all-dielectric topological metasurfaces

Abstract

A new class of phenomena stemming from topological states of quantum matter has recently found a variety of analogies in classical systems. Spin-locking and one-way propagation have been shown to drastically alter scattering of electromagnetic waves, thus offering an unprecedented robustness to defects and disorder. Despite these successes, bringing these new ideas to practical grounds meets a number of serious limitations. In photonics, when it is crucial to implement topological photonic devices on a chip, two major challenges are associated with electromagnetic dissipation into heat and out-of-plane radiation into free space. Both these mechanisms may destroy the topological state and seriously affect the device performance. Here, we demonstrate experimentally that the topological order for light can be implemented in all-dielectric on-chip prototype metasurfaces, which mitigate the effect of Ohmic losses by using exclusively structured dielectric materials, and we reveal that coupling of the system to the radiative continuum does not affect topological properties. We demonstrate the spin-Hall effect of light for spin-polarized topological edge states through near-field spectroscopy measurements.