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We demonstrate a wireless security application to protect the weakest link in phone-to-phone communication, using a terahertz metasurface. To our knowledge, this is the first example of an eavesdropping countermeasure in which the attacker is actively misled. 

Abstract Integration of nanoscale photonic and plasmonic components on Si substrates is a critical step toward Si‐based integrated nanophotonic devices. In this work, a set of unique complex 3D metamaterials with intercalated nanolayered and nanopillar structures with tunable plasmonic and optical properties on Si substrates is designed. More specifically, the 3D metamaterials combine metal (Au) nanopillars and alternating metal‐nitride (Au‐TiN and Au‐TaN) nanolayers, epitaxially grown on Si substrates. The ultrafine Au nanopillars (d≈ 3 nm) continuously grow throughout all the nanolayers with high epitaxial quality. Novel optical properties, such as highly anisotropic optical property, high absorbance covering the entire visible spectrum regime, and hyperbolic property in the visible regime, are demonstrated. Furthermore, a waveguide based on a silicon nitride (Si₃N₄) ridge with a multilayer structure is successfully fabricated. The demonstration of 3D nanoscale metamaterial design integrated on Si opens up a new route toward tunable metamaterials nanostructure designs with versatile material selection for various optical components in Si integrated photonics. 

Abstract Key challenges limiting the adoption of metallic plasmonic nanostructures for practical devices include structural stability and the ease of large‐scale fabrication. Overcoming these issues may require novel metamaterial fabrication with potentials for improved durability under extreme conditions. Here, a self‐assembled growth of a hybrid plasmonic metamaterial in thin‐film form is reported, with epitaxial Ag nanopillars embedded in TiN, a mechanically strong and chemically inert matrix. One of the key achievements lies in the successful control of the tilt angle of the Ag nanopillars (from 0° to 50°), which is attributed to the interplay between the growth kinetics and thermodynamics during deposition. Such an anisotropic nature offered by the tilted Ag nanopillars in TiN matrix is crucial for achieving broadband, asymmetric optical selectivity. Optical spectra coupled with numerical simulations demonstrate strong plasmonic resonance, as well as angular selectivity in a broad UV–vis to near‐infrared regime. The nanostructured metamaterials in this work, which consist of highly conductive metallic nanopillars in a durable nitride matrix, have the potential to serve as a novel hybrid material platform for highly tailorable nanoscale metamaterial designs, suitable for high temperature optical applications.