Controlling scattering of light through topological transitions in all-dielectric metasurfaces

TL;DR

This paper demonstrates control over light scattering in all-dielectric metasurfaces through topological phase transitions, enabling tunable resonances and a method to extract topological properties from far-field scattering data.

Contribution

It introduces a technique to control and tune scattering properties via topological phase transitions and retrieves topological invariants from far-field measurements.

Findings

Topological phase transitions induce switching of resonance quality factors.

Far-field spectra can be used to extract topological invariants.

The method enables design of metasurfaces with controllable scattering characteristics.

Abstract

Topological phase transitions in condensed matter systems have shown extremely rich physics, unveiling such exotic states of matter as topological insulators, superconductors and superfluids. Photonic topological systems open a whole new realm of research exhibiting a number of important distinctions from their condensed matter counterparts. Photonic modes can couple to the continuum of free space modes which makes it feasible to control and manipulate scattering properties of the photonic structure via topology. At the same time, the direct connection of scattering and topological properties of the photonic states allows their probing by spectroscopic means via Fano resonances. Here we demonstrate that the radiative coupling of modes supported by an all-dielectric metasurface can be controlled and tuned under topological phase transitions due to band inversion, correspondingly inducing a distinct switching of the quality factors of the resonances associated with the bands. In addition, we develop a technique to retrieve the topological properties of all-dielectric metasurfaces from the measured far-field scattering characteristics. The collected angle-resolved transmission and reflection spectra allow extracting the momentum-dependent frequencies and lifetimes of the photonic modes. This enables retrieval of the effective photonic Hamiltonian, including the effects of a synthetic gauge field, and topological invariants~-- pseudo-spin Chern numbers. Our results thus open a new avenue to design a new class of metasurfaces with unique scattering characteristics controlled via topological effects. This work also demonstrates how topological states of open systems can be explored via far-field measurements.