Nonlinear light control in optical couplers: Harnessing PPTT-symmetry for enhanced beam propagation.

This study explored the evolution of nonlinear eigenmodes in coupled optical systems supported by PT-symmetric Rosen-Morse complex potential, in which one channel is with gain and the other is with loss. We assessed that the threshold potential above which PT-symmetry breakdown occurs is enhanced by coupling constant, by examining low- and high-frequency eigenmodes of ground and first excited states. The stability of eigenmodes was verified by stability analysis using Bogoliubov-de-Gennes (BdG) equations and it was established that even though the Rosen-Morse potential-supported system can create eigenmodes, it cannot support stable soliton solutions for any potential values. The investigation was extended using the modified Rosen-Morse potential that is nearly PT-symmetric and deduced the conditions for better-defined thresholds, improved damping of growth of perturbation which destabilizes eigenmodes, and advanced control mechanisms to manage perturbations and potential interactions. Propagation dynamics of the eigenmodes and power switching between channels have been studied and the controlling mechanism has been discussed to use coupled systems as optical regulators to precisely direct light between multiple paths. We have explored the significance of couplers in signal-processing applications because they control the intensity of various frequency modes. Optical couplers can be used to develop devices that let light travel in one direction while restricting it in the other which find applications in optical sensing.