Asymmetric lasing at spectral singularities

TL;DR

This paper investigates spectral singularities in a PT-symmetric interferometer, revealing how synthetic magnetic flux influences asymmetric and unidirectional lasing, with implications for designing advanced laser devices.

Contribution

It introduces a PT-symmetric interferometer with synthetic magnetic flux, analyzing its spectral singularities and lasing behaviors, which is a novel approach in non-Hermitian photonics.

Findings

Spectral singularities lead to diverging scattering coefficients and laser solutions.

Synthetic magnetic flux preserves PT symmetry and controls lasing asymmetry.

Interplay between flux and non-Hermiticity induces asymmetric lasing.

Abstract

Scattering coefficients can diverge at spectral singularities. In such situation, the stationary solution becomes a laser solution with outgoing waves only. We explore a parity-time (PT)-symmetric non-Hermitian two-arm Aharonov-Bohm interferometer consisting of three coupled resonators enclosing synthetic magnetic flux. The synthetic magnetic flux does not break the PT symmetry, which protects the symmetric transmission. The features and conditions of symmetric, asymmetric, and unidirectional lasing at spectral singularities are discussed. We elucidate that lasing affected by the interference is asymmetric; asymmetric lasing is induced by the interplay between the synthetic magnetic flux and the system's non-Hermiticity. The product of the left and right transmissions is equal to that of the reflections. Our findings reveal that the synthetic magnetic flux affects light propagation, and the results can be applied in the design of lasing devices.