Tunable Perfect Absorption of Microwave Radiation via Dielectric Slabs in Irregular Arrangements: A Non-Hermitian Approach

Abstract

This study introduces a novel passive approach for achieving tunable perfect absorption of microwave radiation, employing non-Hermitian physics to manipulate electromagnetic waves without conductive elements. By utilizing common dielectric slabs in irregular configurations within a rectangular waveguide, we can completely absorb electromagnetic energy, distinctively retaining it within the electromagnetic field instead of converting it into heat. This method contrasts with traditional metamaterials that rely on conductive components to absorb energy. Employing the transfer matrix method and Sequential Quadratic Programming for optimization, our research identifies specific non-uniform placements of FR4 slabs that maximize absorption within targeted microwave bands. Experimental validation, executed in a standard WR90 waveguide connected to a vector network analyzer, confirms the theoretical and finite element simulation results, underscoring the effectiveness of our passive strategy. This work advances our understanding of non-Hermitian systems in electromagnetic wave control and offers significant potential for applications in reducing electromagnetic pollution and enhancing secure communications, all while aligning with ecological preservation objectives.