Multilayer optical routing by means of vertical directional coupler with long range surface plasmons

We show that efficient multilayer optical routing is achievable with long range surface plasmon polaritons (LR-SPP) through an accurate design of vertical directional couplers (VDC). Our theoretical results suggest that by suitably tuning some geometrical parameters, in particular the path length and bend radius, it is possible to obtain a good control on the overall interaction, even in presence of fabrication non-idealities. We present a top-down fabrication process flow for LR-SPP multilayer optical circuits, obtained by stacking multiple ultrathin nanometric metal films within a polymeric dielectric background; the overall structure has a good degree of mechanical stability. By profiting from the topological advantage given by VDCs, as one of the useful applications of our work, we propose a new optical integrated circuit architecture scheme, capable of connecting two separate circuit paths without influencing the geometry or significantly promoting crosstalk with any other path in the middle. The possibility to develop vertically stacked optical integrated circuits upon electronic integrated circuits makes LR-SPPs a good technology for the production of inexpensive and high-density network systems.