A Multilevel Amplitude Reconfigurable Metasurface via Laser-Induced Phase Change of GeTe

Abstract

This letter proposes a nonvolatile, multilevel amplitude-reconfigurable phase-change metasurface array that operates without bias networks or integrated heating electrodes. The metasurface unit cell adopts an H-shaped metallic structure composed of three patches with different dimensions, where the central gap is filled with a germanium telluride (GeTe) thin film. By applying multiple laser pulses, different local crystallization ratios are induced in the GeTe layer. To characterize the electromagnetic response under this nonuniform phase-transition state, an equivalent impedance model is established and validated. Simulation and measurement results demonstrate that the laser-induced metasurface exhibits multiple controllable impedance states, enabling multilevel amplitude reconfiguration. In the X band, simulations show that the reflection coefficient $|S_{11}|$ can be tuned from −0.31 dB to −19.6 dB, while three representative laser-induced states are experimentally characterized to achieve three reflection levels of −8.2 dB, −4.5 dB, and −1.08 dB at 11.2 GHz. Benefiting from the nonvolatile phase-change behavior of GeTe and the laser-writing mechanism, the proposed metasurface requires no static power to maintain its reconfigured states and provides a promising platform for reconfigurable radar applications, including radar signature manipulation and false-target generation.