Realization of time-reversal invariant photonic topological Anderson insulators

TL;DR

This paper demonstrates the realization of a time-reversal invariant photonic topological Anderson insulator, showing disorder-induced topological phase transitions and robust edge state transport without breaking time-reversal symmetry.

Contribution

It introduces and experimentally confirms a novel photonic topological Anderson insulator that preserves time-reversal symmetry, expanding the understanding of disorder-induced topological phases.

Findings

Disorder induces a topological phase transition in photonic systems.

Robust unidirectional edge modes are observed in the presence of disorder.

Disorder enables beam steering, offering new control over light propagation.

Abstract

Disorder, which is ubiquitous in nature, has been extensively explored in photonics for understanding the fundamental principles of light diffusion and localization, as well as for applications in functional resonators and random lasers. Recently, the investigation of disorder in topological photonics has led to the realization of topological Anderson insulators characterized by an unexpected disorder-induced phase transition. However, the observed photonic topological Anderson insulators so far are limited to the time-reversal symmetry breaking systems. Here, we propose and realize a photonic quantum spin Hall topological Anderson insulator without breaking time-reversal symmetry. The disorder-induced topological phase transition is comprehensively confirmed through the theoretical effective Dirac Hamiltonian, numerical analysis of bulk transmission, and experimental examination of bulk and edge transmissions. We present the convincing evidence for the unidirectional propagation and robust transport of helical edge modes, which are the key features of nontrivial time-reversal invariant topological Anderson insulators. Furthermore, we demonstrate disorder-induced beam steering, highlighting the potential of disorder as a new degree of freedom to manipulate light propagation in magnetic-free systems. Our work not only paves the way for observing unique topological photonic phases but also suggests potential device applications through the utilization of disorder.