Non-Hermiticity-Induced Wave Confinement and Guiding in Loss-Gain-Loss Three-Layer Systems

Abstract: Following up on previous studies on parity-time-symmetric gain-loss bi-layers, and inspired by formal analogies with plasmonic waveguides, we study non-Hermiticity-induced wave confinement and guiding phenomena that can occur in loss-gain-loss three-layers. By revisiting previous well-established "gain-guiding" concepts, we investigate analytically and numerically the dispersion and confinement properties of guided modes that can be supported by this type of structures, by assuming realistic dispersion models and parameters for the material constituents. As key outcomes, we identify certain modes with specific polarization and symmetry that exhibit particularly desirable characteristics, in terms of quasi-real propagation constant and sub-wavelength confinement. Moreover, we elucidate the effects of material dispersion and parameters, and highlight the potential advantages by comparison with the previously studied gain-loss bi-layer configurations. Our results provide additional perspectives on light control in non-Hermitian optical systems, and may find potentially intriguing applicability to reconfigurable nanophotonic platforms.