Non-hermitian photonics in polarization space with terahertz metasurfaces

Abstract

Non-Hermitan degeneracies, also known as exceptional points (EPs) have been the center of much interestdue to its unique branch point topology and defective eigenspace. However, despite much interestingphenomena with EPs, not much work has been done yet in a controllable manner. Here, we demonstrateelectrical access to the EP in only single non-Hermitian metasurface via asymmetric control of loss inthe comprising SRR modes. Electrostatically tuned graphene is utilized to provide a perturbation to theSRR modes resulting in changes in the dissipation rate. By mapping out the eigentransmission surfaceas a function of frequency and graphene Fermi energy, a branch point singularity corresponding to theEP is observed. Furthermore, the coalescence of eigenstates at the EP is veried by plotting the transmissioneigenstates on a Poincare sphere. Our results provide various applications such as asymmetrictransmission and EP-locked sensor for terahertz conductive materials.