Exceptional points (EPs) are non-Hermitian degeneracies that can enable various intriguing applications such as enhanced sensing and asymmetric mode switching. Here, we theoretically propose the design of a 1 × 2 terahertz switch by employing the topological structure of the energy surfaces (i.e., eigenvalue distributions in a two-variable parameter space) near an EP. The switch consists of a pair of terahertz waveguides, one of which has a monolayer graphene laid on the bottom. The wave transmission through the system can be understood by considering an adiabatic trajectory on self-intersecting Riemann sheets due to the existence of an EP. The trajectory can be tuned by changing the chemical potential of graphene, and as a result, we can choose in which waveguide the power exits to achieve the switching functionality. The physics behind the switch lies in the fact that the trajectories on different sides of the EP lead to different final states due to the unique topological structure of energy surfaces near the EP. We perform numerical simulations to optimize the performance of the terahertz switch.

• Received 20 March 2018
• Revised 11 June 2018

DOI:https://doi.org/10.1103/PhysRevApplied.10.034045