Absorption and Scattering by a Temporally Switched Lossy Layer: Going beyond the Rozanov Bound

In this paper we study the electromagnetic scattering, absorption, and performance bounds for short time modulated pulses that impinge on a time-varying lossy layer that is sandwiched between vacuum and a perfect electric conductor. The electric characteristics of the layer, namely, the conductivity, permittivity, and permeability, are assumed to change abruptly or gradually in time. We demonstrate numerically that a time-varying absorbing layer that undergoes temporal switching of its permittivity and conductance can absorb the power of a modulated, ultrawideband, as well as a quasimonochromatic, pulsed wave beyond what is dictated by the time-invariant Rozanov bound when integrating over the whole frequency spectrum. We suggest and simulate a practical metamaterial realization that is constructed as a three-dimensional array of resistor loaded dipoles. By switching only the dipole's load resistance, desired effective media properties are obtained. Furthermore, we show that Rozanov's bound can be bypassed with abrupt and a more practical gradual, soft, switching, thus overcoming some possible causality issues in abrupt switching.

Automated summary

This paper investigates the electromagnetic scattering, absorption, and performance bounds of short time modulated pulses on a time-varying lossy layer. Numerical simulations show that a time-varying absorbing layer with switching permittivity and conductance can absorb more power from modulated, ultrawideband, and quasimonochromatic pulsed waves than the time-invariant Rozanov bound. A practical metamaterial design using resistor-loaded dipoles is suggested and simulated to achieve desired effective media properties. Furthermore, the study demonstrates that abrupt and gradual switching can bypass the Rozanov bound and overcome potential causality issues.