Propagative oscillations in co-directional polariton waveguide couplers

We report on novel exciton-polariton routing devices created to study and purposely guide light-matter particles in their condensate phase. In a co-directional coupling device, two waveguides are connected by a partially etched section which facilitates tunable coupling of the adjacent channels. This evanescent coupling of the two macroscopic wavefunctions in each waveguide reveals itself in real space oscillations of the condensate. This Josephson-like oscillation has only been observed in coupled polariton traps so far. Here, we report on a similar coupling behavior in a controllable, propagative waveguide-based design. By controlling the gap width, channel length or the propagation energy, the exit port of the polariton flow can be chosen. This co-directional polariton device is a passive and scalable coupler element that can serve in compact, next generation logic architectures.