Phase-Transition and Phase Change Materials Integration for Reconfigurable mm-Waves and THz (Meta)Devices

We present our research on integration of phase transition and phase change materials (VO2 and W:doped VO2 composites, GeTe…) as agile elements in frequency reconfigurable antennas, modulators and metasurfaces or polarizers with broadband responses and very good performance at mm-wave and THz frequencies. We are indicating several approaches enabling fast, reversible optical control over large areas of the two different states of GeTe and evaluate the phase change performance of these thin-films in the THz domain using Time Domain Spectroscopy (THz-TDS). The excellent contrast in THz properties of GeTe between the two amorphous and crystalline states was used to demonstrate sub-THz reconfigurable spatially coded metasurfaces (in transmission or reflection geometries) allowing beam direction of propagation control or lensing with variable focus. This versatile and flexible approach based on non-volatile, optically controlled and multi-operational devices incorporating chalcogenide PCMs is expected to generate exciting developments in the mm-wave and THz domains and anticipates novel programmable devices with multifunctional capabilities for electromagnetic wave manipulation and sensing.