“…Following these theoretical suggestions, Rüter et al [4] have demonstrated the first experimental vindication of PT -symmetry in a configuration of linearly coupled waveguides. Since then, the study of PT -symmetry has been extended in diverse domains and phenomena, which include the onset of chaotic dynamics in optomechanical systems [5], modulational instability in complex media [6], soliton switch [7], active LRC circuits [8], optical oligomers [9][10][11][12][13][14][15][16], multilayered structures [17,18], unidirectional reflection-less transmission resonance in Bragg periodic structures [19,20], wireless power transfer [21], plasmonics [22,23] and so forth.…”