Tunable oriented mid-infrared wave based on metasurface with phase change material of GST

Abstract

Dynamically controlling the mid-infrared electromagnetic waves with tunable metasurfaces remains a challenging task. Phase change material of Ge2Sb2Te5 (GST) has shown tremendous advantages in constructing reconfigurable metasurface. In this work, we design a metasurface with GST to dynamically focus and deflect the beam at wavelength of 8.5 μm with a fixed structure. The designed metasurface is composed of GST nanocylinders on a Calcium Fluoride (CaF2) substrate. The focusing and deflection characteristics are manipulated by artificially controlling the value of crystalline fraction of each GST cylinder. In addition, we studied the diffraction pattern at a distance of 2 m for oriented deflection and its broadband performance. This method improves the degree of freedom of active modulation and provides a new route for tunable optical communication devices.