Abstract
Multimode waveguides can be used as multichannel devices to push the transmission bandwidth of optical signals to its limits, provided demultiplexing can be correctly performed, e.g., by selecting a given mode from the rest of the modes. This simple task is usually accomplished by Fourier filtering and requires long interaction distances; here we propose a possibly more compact alternative by using parity-time () symmetry in a periodic fashion in the transverse direction, laying out stripes with gain and losses across the guide width. We first describe the evolution of the system as the level of gain and losses varies and then provide a perturbation analysis of the waveguide mode eigenvalues that clarifies this behavior. We next show that this stripe pattern results in a configuration of eigenvalues that can select a narrow subset of modes. We outline the close relationship between a simplified tight-binding model for an array of coupled single-mode waveguides and a genuine broad multimode dielectric waveguide, showing the advantage of the simplified model for quick studies exploring the complex landscape of symmetry in multimode waveguides.
1 More- Received 16 February 2015
DOI:https://doi.org/10.1103/PhysRevA.91.053825
©2015 American Physical Society