Guided-mode-excited nonlocal metasurfaces: Engineering angular response for stable beam steering in terahertz leaky-wave antennas

초록

This work proposes a nonlocal terahertz metasurface that suppresses the gain degradation intrinsic to local-metasurface-aided leaky-wave antennas by maintaining a stable scattering response as the angle at which the guided mode impinges on the metasurface varies with the scanning frequency. This angular insensitivity is realized by engineering the spatial dispersion (i.e., nonlocality) provided by four surface susceptibilities: tangential electric and magnetic, normal magnetic, and magnetoelectric coupling susceptibilities. We analyze the theoretical degrees of freedom available for angular-response control on the basis of these four susceptibilities within a reciprocal, lossless, dipolar framework in an asymmetric environment. On the basis of this analysis, an optimization-based synthesis method is applied to obtain the required susceptibilities, which yield a close approximation of the desired angle-independent scattering behavior. Additionally, an iterative truncation method is introduced to bridge the gap between abstract susceptibility design and physically realizable structures. Full-wave simulations demonstrate a beam-scanning range of nearly 50° across the 1.9–2.6 THz band, representing an approximately 2.6-fold expansion in continuous, well-formed scanning coverage compared with a local-metasurface counterpart designed under otherwise identical conditions. © 2026 American Physical Society.