Fleury, RomainSounas, Dimitrios L.Alù, Andrea2016-11-212016-11-212016-11-21201410.1103/PhysRevLett.113.023903https://infoscience.epfl.ch/handle/20.500.14299/131258We introduce a new mechanism to realize negative refraction and planar focusing using a pair of parity-time symmetric metasurfaces. In contrast to existing solutions that achieve these effects with negative-index metamaterials or phase conjugating surfaces, the proposed parity-time symmetric lens enables loss-free, all-angle negative refraction and planar focusing in free space, without relying on bulk metamaterials or nonlinear effects. This concept may represent a pivotal step towards loss-free negative refraction and highly efficient planar focusing by exploiting the largely uncharted scattering properties of parity-time symmetric systems.text::journal::journal article::research article