Coding Metasurfaces with Reconfiguration Capabilities Based on Optical Activation of Phase-Change Materials for Terahertz Beam Manipulations

Ultrafast reconfigurable devices with high-speed responses, high-resolution capabilities, and ultracompact sizes will be essential for future real-time terahertz imaging, chemical detection, nondestructive biosensing, and communication systems. Multifunctional terahertz metasurfaces with active, programmable controls have enabled conspicuous functionalities of subwavelength planar devices and components for manipulating electromagnetic (EM) waves such as beam focusing, polarization modification, generation of exotic EM modes, or multibeam scanning applications. However, active metasurface technologies for EM beam manipulation, capable of dynamical topology change, or induced-phase reconfiguration are usually requiring various semiconductor-based controlling elements (e.g., PN diodes and transistors), which are difficult to implement in the high-frequency spectrum of terahertz waves. In this work, a coding metasurface is introduced integrating patterned GeTe phase-change materials as command elements, which allows the optical control of terahertz wave propagation. The suggested metasurface design brings plentiful of remarkable functionalities through different coding patterns and is highly effective to control beam tilting, directivity, and splitting of terahertz beams. The proposed concepts of coding metasurfaces integrating optically active phase-change materials are successfully confirmed by experimental demonstration and can be extended to more complex terahertz systems for imaging, tomography, sensing, and 6G communication applications.