Coherent perfect absorber and laser in purely imaginary conjugate metamaterials

TL;DR

This paper introduces a novel approach using purely imaginary conjugate metamaterials to realize both coherent perfect absorption and lasing modes, expanding the understanding of wave control in complex conjugate media.

Contribution

It proposes a new mechanism for achieving CPA and laser modes in purely imaginary conjugate metamaterials, including conditions for their simultaneous occurrence.

Findings

Perfect absorption achieved in a sub-unity index slab for air incident waves.

Conditions for simultaneous CPA and laser modes are analytically derived.

Purely imaginary conjugate metamaterials enable dual wave control functionalities.

Abstract

Conjugate metamaterials, in which the permittivity and the permeability are complex conjugates of each other, possess the elements of loss and gain simultaneously. By employing a conjugate metamaterial with a purely imaginary form, we propose a mechanism for realizing both coherent perfect absorber (CPA) and laser modes, which have been widely investigated in parity-time symmetric systems. Moreover, the general conditions for obtaining CPA and laser modes, including obtaining them simultaneously, are revealed by analyzing the wave scattering properties of a slab made of purely imaginary conjugate metamaterials. Specifically, in a purely imaginary conjugate metamaterial slab with a sub-unity effective refractive index, perfect absorption can be realized for the incident wave from air.