Control of the Scattering Properties of Complex Systems by Means of Tunable Metasurfaces

J. Erba, D. Shrekenhamerb, T. Sleasmanb, T.M. Antonsenc, d, S.M. Anlagea, d aQuantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA bJohns Hopkins University Applied Physics Laboratory, Laurel, MD, 20723, USA cDepartment of Physics, University of Maryland, College Park, Maryland 20742-4111, USA dDepartment of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742-3285, USA

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We demonstrate the ability to control the scattering properties of a two-dimensional wave-chaotic microwave billiard through the use of tunable metasurfaces located on the interior walls of the billiard. The complex reflection coefficient of the metasurfaces can be varied by applying a DC voltage bias to varactor diodes on the mushroom-shaped resonant patches, and this proves to be very effective at perturbing the eigenmodes of the cavity. Placing multiple metasurfaces inside the cavity allows us to engineer desired scattering conditions, such as coherent perfect absorption, by actively manipulating the poles and zeros of the scattering matrix through the application of multiple voltage biases. We demonstrate the ability to create on-demand coherent perfect absorption conditions at a specific frequency, and document the near-null of output power as a function of four independent parameters tuned through the coherent perfect absorption point. A remarkably low output-to-input power ratio Pout/Pin=3.71×10-8 is achieved near the coherent perfect absorption point at 8.54 GHz.

DOI:10.12693/APhysPolA.144.421 topics: coherent perfect absorption (CPA), tunable metasurfaces, scattering zeros and poles