CPA-lasing associated with the quasibound states in the continuum in asymmetric non-Hermitian structures

TL;DR

This paper investigates how asymmetry in non-Hermitian layered photonic structures enables the transition from quasibound states in the continuum to simultaneous coherent perfect absorption and lasing, revealing unique behaviors and potential applications.

Contribution

It introduces a novel mechanism linking quasibound states to CPA-lasing in asymmetric non-Hermitian media, analyzed through scattering matrix techniques.

Findings

Linear dependence of quality factor on inverse asymmetry parameter

Identification of loss-induced lasing-like behavior at CPA-lasing point

Analysis of geometric and non-Hermitian asymmetries in ENZ media

Abstract

Non-Hermitian photonic systems with loss and gain attract much attention due to their exceptional abilities in molding the flow of light. Introducing asymmetry to the $\mathcal{PT}$-symmetric system with perfectly balanced loss and gain, we reveal the mechanism of transition from the quasibound state in the continuum (quasi-BIC) to the simultaneous coherent perfect absorption (CPA) and lasing in a layered structure comprising epsilon-near-zero (ENZ) media. Two types of asymmetry (geometric and non-Hermitian) are analyzed with the scattering matrix technique. The effect of the CPA-lasing associated with the quasi-BIC is characterized with the unusual linear dependence of the quality factor on the inverse of asymmetry parameter. Moreover, the counter-intuitive loss-induced-lasing-like behavior is found at the CPA-lasing point under the non-Hermitian asymmetry. The reported features of non-Hermitian structures are perspective for sensing and lasing applications.