Reverberation-Induced Non-Locality: Implications for RIS-Based Communications and Opportunities for Scattering Singularity Control

In this talk, I will discuss origin, implications and opportunities arising from reverberation-induced non-local effects when programmable metasurfaces are deployed in complex scattering systems rather than free space. Based on a discrete-dipole approximation, I will show how long-range coupling between meta-atoms arises due to rays encountering multiple meta-atoms as they bounce around in the complex scattering system. This implies a non-linear dependence of the linear transfer function on the metasurface configuration. For RIS-assisted wireless communications, common models tacitly assume a linear dependence and their predictions are hence questionable. For extreme scattering control, reverberation-induced non-locality strongly increases the ability of a programmable metasurface to finely tune the location of poles and zeros of the overall system’s transfer function. I will show applications to analog differentiation and reflectionless signal routing.