title: Anisotropic reflection oscillation in periodic multilayer structures of parity-time symmetry.
abstract: We show that periodic multilayer structures with parity-time (PT) symmetries imposed by a balanced arrangement of gain and loss can exhibit anisotropic reflection oscillation patterns as the number of unit-cells is increasing. At the minima of reflection oscillation patterns, the PT symmetric medium exhibits bidirectional transparency with the eigenvalues of the scattering matrix degenerated, where the PT symmetric set-up can still render directional responses due to the one-way field localization inside the system. With certain number of unit-cells, the PT symmetric crystal is unidirectionally invisible. More complicated reflection/transmission oscillations can be observed by segregating neighboring unit-cells with a uniform dielectric layer. Our results may pave the way towards a new class of functional optical devices with intriguing and unexpected directional responses.
authors.forename: Xue-Feng
authors.initials: XF
authors.lastname: Zhu
authors.forename: Yu-Gui
authors.initials: YG
authors.lastname: Peng
authors.forename: De-Gang
authors.initials: DG
authors.lastname: Zhao