Populating and probing protected edge states through topology-entailed trivial states

TL;DR

This paper introduces topology-entailed trivial (TET) states that enable access and manipulation of topological edge states without losing their protection, facilitating practical photonic applications.

Contribution

The authors demonstrate that TET states, arising from hybridized interface states, allow selective light injection, extraction, and long-range coherence in topological photonic systems.

Findings

Successful selective injection and extraction of light into topological states

Long-range coherent light exchange between separated topological channels

TET states enable protection-preserving manipulation of light flow

Abstract

Topological insulators enable non-reciprocal light propagation that is insensitive to disorder and imperfections. Yet, despite considerable attention from the photonics community and beyond, the very feature that has inspired numerous proposals for applications of topological transport also turns out to be one of the main stumbling blocks for practical implementations: Accessing topologically protected states is generally assumed to require their protection to be lifted. We overcome this limitation by topology-entailed trivial (TET) states that arise from the hybridization of counter-propagating interface states. We demonstrate selective injection and extraction of light into topological states as well as long-range coherent light exchange between spatially separated topological channels. Our results highlight the potential of TET states as protection-preserving paradigm to manipulate the flow of light in topological platforms.