Line Waves Existing at Junctions of Dual-Impedance Metasurfaces

Abstract

Line waves (LWs) are special electromagnetic modes supported on junctions of different metasurfaces that enforce a duality condition, such as capacitive and inductive metasurfaces. These edge modes are tightly confined to the interface and can propagate along arbitrary one-dimensional paths with high efficiency. Such attractive characteristics show potential applications for robust waveguides. Here, we introduce a compact dual-impedance metasurface platform to explore the properties of LWs. We explore intrinsic properties of LWs including dispersion, confinement, and spin-momentum locking. It is found that broadband LWs can be supported by metasurfaces with varied surface wave momentum, and the dispersion of LWs can be tailored by tuning either their capacitive or inductive properties. The equivalent impedances of metasurfaces are extracted to establish a simplified semianalytical model to study their spin-momentum locking properties. Unidirectional propagation can be excited via a chiral point source placed near the junction. We further implement a parallel plate waveguide consisting of four metasurfaces arranged with a duality symmetry. Experiments validate the analysis and indicate the existence of highly robust transmissions even when the waveguide is longitudinally warped, providing an enticing option for applying LWs in the field of wearable wireless channels and flexible electronics.

Experimental Verification of Backscattering Protection in PTD-Symmetric Bifilar Edge Waveguides

“…In particular, the WG introduced in [10] consists of a junction between two planar surfaces characterized by complementary impedance BCs (capacitive and inductive). This structure supports an edge mode, whose field is tightly confined in the proximity of the junction; such a mode exhibits highly efficient propagation also along nonrectilinear paths, as experimentally demonstrated in [12]. However, the structures in [10] and [12] are open; as a consequence, their Green's functions are characterized by a continuous spectrum of modes, and therefore, even if there is no backscattering at PTD-symmetric discontinuities, there can be radiation losses.…”

Near-field chiral excitation of universal spin-momentum locking transport of edge waves in microwave metamaterials

“…5(c), and the equivalent surface reactance can be extracted from the phase constant. 29 The authors proposed and analyzed the structures recently, 29 but related experiments to visualize the spin-momentum locking are challenging and have been solved in this work. 26,27,29,48 We set up the experimental environment as shown in Fig.…”

“…Spoof SPPs and LWs are slow waves, while the closed PTIs waveguides can support both slow and fast waves without leakage. From the perspective of assembly process, people can use flexible substrates, such as polyimide, to guide the spoof SPPs and LWs along curved surfaces, 18,23,29 indicating the potential applications in wearable networks. 54 PTIs usually exist in solid hole-slab or pillars, losing the flexibility.…”

“…1(c). LWs have been experimentally observed by linearly polarized feedings; 29,30 however, unidirectional coupling stays in the simulation stage, 28,29 where related experiments are still lacking. Therefore, the second part of this work is to visualize the spin-momentum locking of LWs.…”

Loss‐induced phase transition in mid‐infrared plasmonic metamaterials for ultrasensitive vibrational spectroscopy

“…Great efforts have been invested to break through the above limitations. In terms of design constraints, the metamaterials, that is, artificial materials, can be engineered to achieve desired properties 44–49 . Approaches report that design constraint limitations can be bypassed by metamaterial structure optimization 50,51 .…”