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