Guided-wave devices with fixed losses inspired by PT-symmetry and their spectrum singularity

Abstract : Guided-wave devices with plasmonic-type fixed losses can be adapted to exploit the singular point behavior well known for exact PT symmetric guides. Coupled guides having fixed losses and variable gain fail to exhibit a singular point in their eigenvalues if the guides! effective indices coincide. We show how to "heal# this situation and restore singularity by detuning among the guides. We also present a frame inspired by Kogelnik!s representations of alternate 'E couplers to usefully account for several configurations.