Metasurface virtual absorbers: unveiling operative conditions through
equivalent lumped circuit model
- Angelica Viola Marini ,
- Davide Ramaccia ,
- Alessandro Toscano ,
- Filiberto Bilotti
Abstract
Virtual absorption concept has been recently introduced as a new
phenomenon observed in electromagnetics and optics consisting of an
undefined energy accumulation within a finite volume of material without
dissipation. The anomalous behaviour is achieved by engaging the complex
zero scattering eigenmodes of the virtual absorbing system by
illuminating it with a proper complex frequency, whose value is strictly
determined by the system characteristics. In this paper, we investigate
on the position of the zero-pole scattering pairs in the complex
frequency plane as a function of the input impedance of the
metasurface-based lossless virtual absorber. We analytically derive the
conditions under which a properly modulated monochromatic plane wave can
be virtually absorbed by the system and stored within its volume. The
analysis is developed by modelling the propagation of a normally
impinging plane wave though its equivalent transmission line model
terminated on an arbitrary reactive load, which in turn models the input
impedance of the metasurface-based system under consideration. The study
allows to determine a priori whether the metasurface-based system can
support the virtual absorption or not by evaluating the time-constant
from its equivalent circuit.