Nonlinear dynamics in photonic systems with Parity-Time symmetry

We review our recent progress in the study of nonlinear photonic systems with balanced gain and loss described by the models with parity-time (PT) symmetry. We discuss the nonlinear dynamics in optical waveguide couplers and show that for intensities below a threshold, the field oscillates between the waveguides, whereas above the threshold the symmetry breaking is observed. This nonlinearity-induced effect can be generalized to other systems, as well as can be observed experimentally. We then move to the systems with continuous variables and study the soliton dynamics and soliton scattering in the systems with PT -symmetric potentials. In particular, we demonstrate that both single and multiple soliton scattering can exhibit almost perfect unidirectional flows associated with an energy exchange between the soliton center of mass and its internal mode.