Multi-wavelength voltage-coded metasurface based on indium tin oxide: independently and dynamically controllable near-infrared multi-channels.

Abstract

In this paper, we present a design principle for achieving an electrically tunable, multi-wavelength device with multiple functionalities over a single metasurface platform with minimized footprint. This concept is realized based on the integration of four metal-insulator-metal (MIM) inclusions inside a unit cell, which is configured to support four independently controllable operating channels lying in near-infrared (NIR) regime. Incorporation of newly emerged, electrically tunable indium tin oxide (ITO) into such metasurface leads to a dynamical phase modulation over the reflected light. As a result, the phase tunability of almost 285°, 230°, 300°, and 280° are captured at T, O, C, and U optical communications bands, under applying external bias voltages. A digital coding strategy, consisting of "0" and "1" binary bits, is employed to represent the applied biasing configuration to the sub-units. Independently controlled, decoupled gap plasmon resonators, with the ability of eliminating the interference between channels, are enabled thanks to the geometry optimization and careful selection of materials. A meta-array configuration is implemented, in which electrically addressing the groups of MIM sub-units opens a pathway to the tunable applications, namely Airy beam generation, beam splitting, steering, and focusing.