Non-Hermitian skin effect and lasing of absorbing open-boundary modes in photonic crystals

TL;DR

This paper investigates absorbing open-boundary modes in non-Hermitian photonic crystals, revealing size-dependent spectra, their relation to the non-Hermitian skin effect, and their connection to lasing phenomena in systems with gain and topological properties.

Contribution

It introduces a new class of absorbing open-boundary modes in non-Hermitian photonic systems, demonstrating their size-dependent spectra and relation to lasing, expanding understanding of non-Hermitian topological photonics.

Findings

Modes exhibit a continuum spectrum in large systems.

Spectrum converges to non-Bloch-band dispersion with size.

Modes are related to poles of the S matrix and lasing.

Abstract

We explore absorbing open-boundary modes in non-Hermitian photonic systems. The modes have a continuum spectrum in the infinite system-size limit and can exhibit the non-Hermitian skin effect. In contrast to the conventional non-Hermitian skin modes under the fixed-end open-boundary condition, the modes concerned exhibit a strongly size-dependent spectrum that gradually converges to the non-Bloch-band dispersion. The modes correspond to the poles of the $S$ matrix, and are closely related to the lasing. We demonstrate these properties in a two-dimensional non-Hermitian photonic crystal with gain having a point-(pseudo)gap topology.