Optically tunable broadband reflective metasurfaces for dynamic terahertz wave modulation

Abstract

Terahertz metasurfaces have potential applications in areas such as high-resolution imaging, wireless communications, and security detection. However, most of the previously reported metasurfaces are either static or tunable metasurfaces with limited overlap bandwidth, which hinders their application prospects. Here, a dynamically tuned terahertz metasurface was proposed based on the Pancharatnam–Berry phase principle. The insulator-to-metal phase transition of the photoconductive silicon allows the design of two independent resonators combined in a single unit structure and switched reflection phase shift under pump light illumination. Based on the multiple resonance theory, two resonators are carefully designed to achieve an overlapping bandwidth operating in the ultra-broadband range of 0.9–1.5 TH z. Consequently, a broadband vortex beam generator with switchable topological charges l = 2 and l = 1 was proposed. In addition, a broadband holographic memory also was demonstrated, allowing switching between different holograms. The propose broadband tunable metasurface not only has promising applications in vortex beam generation and holographic memory, but also provides a broad application prospect for the miniaturisation of future terahertz devices and increasing the capacity of communication systems.