Parity-time-symmetric plasmonic metamaterials

We theoretically investigate the optical properties of parity-time (PT)-symmetric three-dimensional metamaterials composed of strongly coupled planar plasmonicwaveguides. By tuning the loss-gain balance, we showhow the initially isotropic material becomes both asymmetric and unidirectional. Investigation of the band structure near the material's exceptional point reveals several interesting optical properties, including double negative refraction, Bloch power oscillations, unidirectional invisibility, and reflection and transmission coefficients that are simultaneously equal to or greater than unity. The highly tunable optical dispersion of PT-symmetric metamaterials provides a foundation for designing an unconventional class of three-dimensional bulk synthetic media, with applications ranging from lossless subdiffraction-limited optical lenses to nonreciprocal nanophotonic devices.