We introduce a novel concept of the pseudo-parity-time (pseudo-$\mathcal{P}\mathcal{T}$) symmetry in periodically modulated optical systems with balanced gain and loss. We demonstrate that whether or not the original system is $\mathcal{P}\mathcal{T}$ symmetric, we can manipulate the property of the $\mathcal{P}\mathcal{T}$ symmetry by applying a periodic modulation in such a way that the effective system derived by the high-frequency Floquet method is $\mathcal{P}\mathcal{T}$ symmetric. If the original system is non-$\mathcal{P}\mathcal{T}$ symmetric, the $\mathcal{P}\mathcal{T}$ symmetry in the effective system will lead to quasistationary propagation that can be associated with the pseudo-$\mathcal{P}\mathcal{T}$ symmetry. Our results provide a promising approach for manipulating the $\mathcal{P}\mathcal{T}$ symmetry of realistic systems.

• Received 5 February 2013

DOI:https://doi.org/10.1103/PhysRevLett.110.243902