Topologically protected midgap states in complex photonic lattices

TL;DR

This paper demonstrates the creation of topologically protected midgap states in complex photonic lattices with gain and loss, enabling robust, tunable amplification for applications in beam dynamics and lasing.

Contribution

It introduces a method to engineer topologically protected states in photonic systems with gain and loss, expanding the design possibilities for robust photonic devices.

Findings

Topologically protected midgap states can be realized with spatially distributed gain and loss.

These states maintain protection and gain tunability under suitable arrangements.

Applications include enhanced beam control and tunable laser operation.

Abstract

One of the principal goals in the design of photonic crystals is the engineering of band gaps and defect states. Drawing on the concepts of band-structure topology, I here describe the formation of exponentially localized, topologically protected midgap states in photonic systems with spatially distributed gain and loss. When gain and loss are suitably arranged these states maintain their topological protection and then acquire a selectively tunable amplification rate. This finds applications in the beam dynamics along a photonic lattice and in the lasing of quasi-one-dimensional photonic crystals.