Influence of counter-running wave interference on operation of the PT-symmetric structures

Abstract

This work provides a theoretical investigation of how counter-propagating wave interference, together with gain and loss saturation, affects the output intensities of PT-symmetric structures. A modified transfer matrix approach is employed, enabling a simultaneous examination of the impact of these nonlinear effects on the longitudinal field distribution. The resulting output intensity, reflectance, and transmittance characteristics are presented as functions of the input intensity for two cases in which the field distribution intensity is analyzed without and with taking into account the interference of counter-propagating waves, for different structure lengths, numbers of primitive cells, and saturation intensity levels. The results demonstrate that interference between counter-propagating waves significantly alters the output intensity, reflectance, and transmittance characteristics within the intermediate range of incident wave intensities, particularly for structures with small primitive cell sizes. Moreover, it modifies the bistability effect, causing the hysteresis loop to widen. Furthermore, in some configurations, this interference suppresses the unidirectional invisibility that would otherwise occur due to gain/loss saturation.