Manipulating multiple scattering singularities in generic complex scattering systems with tunable parameters, Part I

The scattering S-matrix is an accessible quantity for experimental systems in many areas of research. This matrix contains a significant amount of information about the scattering processes of the system including a variety of singular events. These scattering singularities are related to many interesting phenomena that have exotic properties. These include the possibility of Coherent Perfect Absorption (CPA), exceptional points (EP), and others. CPA occurs when a specific eigenvector injected into a system is completely absorbed, nothing is transmitted or reflected (https://doi.org/10.12693/APhysPolA.144.421). EP’s are points in the parameter space of a non-Hermitian operator where its eigenvalues and associated eigenvectors coalesce and become degenerate. We can create conditions for both CPA’s and EP’s, experimentally and theoretically, by perturbing a system with tunable parameters, such as frequency and the applied bias voltage on a metasurface inside the system. In this talk, we experimentally demonstrate that by varying tunable metasurfaces inside a microwave cavity we can controllably manipulate the locations of the CPA’s and EP’s of the S-matrix.