Asymmetric Evolution of Interacting Solitons in Parity Time Symmetric Cells

We show the evolution of two fundamental bright solitons after being simultaneously launched into nonlinear triangular parity time (PT) symmetric waveguides, at mirrored transverse input positions. Numerical simulations show, whether below or above the phase transition, in general the retarded soliton propagating along the gain side and the advanced soliton evolving along the loss side of either waveguide interfere incoherently, within the interacting regime. In non-interacting regime, however, each soliton evolves as it has been launched individually. When beyond the phase transition, the unstable solitons become self-trapped after traversing relatively short distances. The incoherent interference alters the projectile of each soliton from that of the one launched individually at the same initial input position. The temporal dynamics of interacting solitons along PT symmetric waveguide, due to the interplay of nonlinearity and the active elements, are not periodic. This is in contrast to the interaction dynamics along the purely index guided cell. The results suggest that appropriately designed nonlinear PT symmetric waveguides, below or above the phase transition, can play the role of key elements in design and fabrication of optical gates, isolators, and switches.