A Tunable Multigate Indium-Tin-Oxide-AssistedAll-Dielectric Metasurface

摘要

In this paper, an optically active reflective metasurface with tunable phaseperformance is designed which operates based on the excitation of both electricand magnetic resonances in a silicon-made nanoantenna element and theuse of layered indium tin oxide (ITO)–alumina under the influence of externalmultigate biasing. The capability of achieving robust control over the reflectioncharacteristics of two closely spaced electric and magnetic resonances isinvestigated. Adopting the multigate biasing enables relatively high reflectionamplitude of 0.4 over the entire phase-change coverage (≈180°) in thenear-infrared regime by exploiting the constructive interference between thegeometrical resonances. The physical mechanism behind this ITO-assistedmetal–insulator–semiconductor building block can be described as the strongconfinement of electromagnetic fields at the vicinity of ITO layers and thepossibility of modulating the carrier concentrations of the integrated activematerials by electrically varying the bias voltage. The uniformity of reflectionmagnitude for all reflection phase coverage, relatively high reflectivity,and electro-optical tunability is leveraged to design three multifunctionaldevices with step-by-step increase in complexity of biasing network includingultrathin reconfigurable linear/circular polarizer (simple identical biasing),dynamical beam steering platform (two-state biasing), and tunable metalenswith controllable on- and off-axes focusing pattern in real-time (advancedelement-by-element biasing).