Broadband Transreflective Metasurface for Multifunctional Dual-Band OAM Engineering

Shared-aperture dual-band transreflective metasurfaces enable independent manipulation of electromagnetic waves in both transmission and reflection across two separate frequency bands simultaneously. Nevertheless, dimensional constraints and unintended coupling limit the achievable bandwidth and phase coverage when the subcomponents are integrated in a compact area. This study presents a physics-based strategy to customize the resonant field and current distributions for the metasurface components, effectively suppressing inter-component coupling and expanding the phase range even within confined geometries. Using this proposed method, a shared-aperture dual-band transreflective metasurface with wideband operation and 2-bit phase discretization is designed. The efficacy of the meta-atom design strategy is demonstrated by a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40\times 40$ </tex-math></inline-formula> component prototype, which independently generates twisted orbital angular momentum (OAM) vortex beams in transmission at 14.5–20.7 GHz and in reflection at 30–40 GHz. The design strategy offers a novel approach for developing dual-band, wideband trans-reflection meta-atoms with potential applications in multifunctional wavefront shaping.