Optical mesh lattices with PT symmetry

We investigate a class of optical mesh periodic structures that are discretized in both the transverse and longitudinal directions. These networks are composed of waveguide arrays that are discretely coupled, while phase elements are also inserted to discretely control their effective potentials and can be realized both in the temporal and the spatial domain. Their band structure and impulse response are studied in both the passive and parity-time (PT)-symmetric regime. The possibility of band merging and the emergence of exceptional points, along with the associated optical dynamics, are considered in detail both above and below the PT-symmetry breaking point. Finally, unidirectional invisibility in PT-synthetic mesh lattices is also examined, along with possible superluminal light transport dynamics.