Virtual perfect absorption in resonant media and their PT-symmetric generalizations

TL;DR

This paper explores virtual perfect absorption (VPA) in resonant media, revealing its dependence on medium density and demonstrating near-ideal VPA in PT-symmetric structures, along with the emergence of quasilasing pulses.

Contribution

It provides a theoretical analysis of VPA in resonant media and introduces the behavior of VPA and quasilasing in PT-symmetric bilayers.

Findings

VPA critically depends on medium density and deteriorates at high densities.

Almost ideal VPA persists in PT-symmetric loss-gain bilayers.

High gain leads to symmetric quasilasing pulses in the structures.

Abstract

Virtual perfect absorption (VPA) is an effect simulating real absorption of light by using excitation at a complex frequency corresponding to a scattering zero. We theoretically study VPA in resonantly absorbing and amplifying media irradiated by two counterpropagating waves with exponentially growing amplitudes. We show that VPA critically depends on the medium density (i.e., level of loss or gain) deteriorating in the high-density limit. In contrast, almost ideal VPA persists in the PT-symmetric loss-gain bilayer. For high enough gain, powerful quasilasing pulses are observed at later times symmetrically (single amplifying layer) or symmetrically (PT-symmetric structure) generated in both propagation directions.