Wideband metasurface absorber (metabsorber) using characteristic mode analysis

Area of Science:

• Electromagnetics
• Materials Science
• Metasurface Engineering

Background:

• Designing ultra-wideband (UWB) metasurface absorbers is complex due to inherent lossy characteristics affecting resonance behavior analysis.
• Existing methods often struggle to fully elucidate the absorption mechanisms in lossy metasurfaces.

Purpose of the Study:

• To develop a theoretical framework for analyzing and designing UWB metasurface absorbers.
• To extend the application of the theory of characteristic modes (TCM) to metabsorber design.
• To reveal the fundamental absorption mechanism of metasurface absorbers.

Main Methods:

• Formulated a framework extending the theory of characteristic modes (TCM) for metabsorber analysis.
• Compared modal behaviors of the lossy metabsorber with its lossless counterpart.
• Introduced 'absorption modes' to modify dual-band absorbers into UWB absorbers.

Main Results:

• The metabsorber and its lossless counterpart showed similar modal behaviors, clarifying the absorption mechanism.
• A dual-band metabsorber was successfully converted into an ultra-wideband absorber by introducing absorption modes.
• The proposed UWB metasurface absorber achieved a bandwidth of 5.51-36.56 GHz (6 octaves) with 90% absorptance, at a thickness of 1.99 times the Rozanov's limit.

Conclusions:

• The theory of characteristic modes provides an effective tool for understanding and designing UWB metasurface absorbers.
• The proposed absorption mode strategy enables the conversion of narrow-band absorbers into broadband devices.
• This research offers a pathway to highly efficient, ultra-wideband absorbers with potential applications in various electromagnetic fields.