Broadband Electromagnetic Absorber Based on 3D Conical Helix Metamaterials

Metamaterials, artificial structures that enable various electromagnetic (EM) responses not observable in natural materials, are paid attention owing to their arbitrary responsibility comes from their design. Metamaterial electromagnetic absorbers(1) are widely explored as alternatives of conventional ferromagnetic materials for high frequency (&gt;1 GHz). However, resonant absorption mechanism affords only narrow absorption bandwidth and metamaterial absorbers need to be complex structure with multiple resonances in order to gain broadband absorptive band.<br/>In this work, we report 3D conical helix metamaterials with broadband absorption in GHz region, inspired by similar design for optical region(2). Less than 30% fractional absorption band was demonstrated in numerical simulation and experiment. Geometric parameters of conical helix to obtain both high absorption intensity and broad bandwidth are clarified.<br/><br/>(1) Landy N. I., Sajuyigbe S., Mock J. J., Smith D. R. and Padilla W. <i>Phys. Rev. Lett.</i> <b>2008</b>, <i>100</i>, 207402.<br/>(2) Mudachathi R. and Tanaka T. <i>Opt. Exp.</i> <b>2019</b>, <i>27</i>, 26369.