An Ultrathin, Fast-Response, Large-Scale Liquid-Crystal-Facilitated Multi-Functional Reconfigurable Metasurface for Comprehensive Wavefront Modulation.

The rapid advancement of prevailing communication and sensing technologies necessitates cost-effective millimeter-wave arrays equipped with a massive number of phase-shifting cells to perform complicated beamforming tasks. Conventional approaches employing semiconductor switch/varactor components or tunable materials encounter obstacles such as quantization loss, high cost, high complexity, and limited adaptability for realizing large-scale arrays and operating at millimeter-wave frequencies. Here, we report a low-cost, ultrathin, fast-response, and large-scale solution relying on advanced metasurface (i.e., the 2D version of a bulk 3D metamaterial) concepts combined together with ultrathin liquid crystal (LC) materials requiring a layer thickness of only 5 μm. Rather than immersing resonant structures in LCs, a joint material-circuit-based strategy is devised, via integrating deep-subwavelength-thick nematic LCs into slow-wave structures, to achieve constitutive metacells (i.e., artificial atoms or meta-atoms) with continuous phase shifting and stable reflectivity. A LC-facilitated reconfigurable metasurface system containing more than 2300 metacells is realized with its unprecedented comprehensive wavefront manipulation capacity validated through three diverse beamforming functions, including beam focusing/steering, reconfigurable OAM-carrying beams, and tunable holograms, demonstrating a milli-second-level function-switching speed. The proposed methodology offers a paradigm shift for modulating electromagnetic waves in a non-resonating broadband fashion with fast-response and low-cost properties by exploiting functionalized LC-enabled metasurfaces. Moreover, it is expected that this extremely agile metasurface-enabled antenna technology will facilitate a transformative impact on communication/sensing systems and empower new possibilities for wavefront engineering and diffractive wave calculation/inference. This article is protected by copyright. All rights reserved.