Light dynamics in PT-symmetric multilayers: Phase transition, nonreciprocity, and propagation direction locking

Abstract

We report the numerical study of PT -symmetry breaking in one-dimensional structures with resonantly absorbing and amplifying layers described by the Maxwell-Bloch equations. Temporal dynamics of light interacting with such a structure is governed by strong field amplification and subsequent saturation of loss and gain above the exceptional point resulting in the lasing-like regime with powerful pulses generated both in reflection and transmission. In this regime, we predict and investigate the uniqueness of phase transition due to saturation, transmission nonreciprocity, and the direction locking of the transmitted and reflected radiation.