Non-hermitian optical waveguide couplers

Abstract

We discuss the PT symmetry effects in non-Hermitian waveguiding geometries starting from a classical example of a two-core coupler with gain and loss. We demonstrate that a nonlinear response can break the PT symmetry in a coupler, and discuss the regimes of parametric amplification and nonlocality associated with such systems. Then, we analyse non-Hermitical trimers and also a PT-symmetric system embedded into an array of waveguides. Finally, we demonstrate the existence of nontrivial modes in non-Hermitian waveguiding structures with asymmetric layers of gain and loss.