Interaction of edge exciton polaritons with engineered defects in the hyperbolic material Bi2Se3

Hyperbolic materials exhibit unique properties that enable intriguing applications in nanophotonics. The topological insulator Bi 2 Se 3 represents a natural hyperbolic optical medium, both in the THz and visible range. Here, using cathodoluminescence spectroscopy and electron energy-loss spectroscopy, we demonstrate that Bi 2 Se 3 supports room-temperature exciton polaritons and explore the behavior of hyperbolic edge exciton polaritons, which are hybrid modes resulting from the coupling of the polaritons bound to the upper and lower edges of Bi 2 Se 3 nanoplatelets. We compare Fabry-Pérot-like resonances emerging in edge polariton propagation along pristine and artificially structured edges and experimentally demonstrate the possibility to steer edge polaritons by means of grooves and nanocavities. The observed scattering of edge polaritons by defect structures is found to be in good agreement with finite-difference time-domain simulations. Our findings reveal the extraordinary capability of hyperbolic polariton propagation to cope with the presence of defects, providing an excellent basis for applications such as nanooptical circuitry, nanoscale cloaking and nanoscopic quantum technology. Hyperbolic materials have unique optical properties such as negative refraction and highly directional polaritons, relevant in super-resolution imaging. Here, the topological insulator Bi 2 Se 3 is shown to host hyperbolic edge-confined exciton polaritons that can be steered via engineered edge defects.