Topological phases and edge states in a non-Hermitian trimerized optical lattice

TL;DR

This paper explores topological phases and edge states in a non-Hermitian, trimerized optical lattice, revealing how non-Hermiticity, boundary conditions, and gain/loss influence topological properties and enable robust optical diode functionalities.

Contribution

It introduces a non-Hermitian trimerized optical lattice model and analyzes its topological phases, edge states, and potential for unidirectional amplification.

Findings

Topological edge states depend on lattice size and boundary conditions.

Non-Hermiticity extends the topologically nontrivial region.

Unidirectional zero modes enable robust optical diode behavior.

Abstract

Topologically engineered optical materials support robust light transport. Herein, the investigated non-Hermitian lattice is trimerized and inhomogeneously coupled using uniform intracell coupling. The topological properties of the coupled waveguide lattice are evaluated, the PT-symmetric phase of a PT-symmetric lattice can have different topologies; the edge states depend on the lattice size, boundary configuration, and competition between the coupling and degree of non-Hermiticity. The topologically nontrivial region extends in the presence of periodic gain and loss. The nonzero geometric phases accumulated by the Bloch bands indicate the existence of topologically protected edge states between the band gaps. The unidirectional amplification and attenuation zero modes appear above a threshold degree of non-Hermiticity, which facilitate the development of a robust optical diode.