An Idea of Implementing Photonic Space-Time Crystals Using Metasurfaces

Abstract: Photonic space time crystals (PSTCs) are emerging materials characterized by periodic variations in electromagnetic parameters with respect to both space and time. To date, research on PSTCs remains theoretical, with no practical realization reported. This article presents the practical realization of PSTCs through the design and simulation of a 2D metasurface-based photonic space-time crystal. It illustrates the characteristics of energy bandgaps, momentum bandgaps, and mixed energy momentum bandgap eigenmodes within the dispersion relation of these crystals. Additionally, the article details the properties of second order exceptional points that occur when two bandgaps overlap under specific conditions. The application of the metasurface based PSTC in 6G wireless communications is also demonstrated. This work aims to advance the understanding of PSTCs and their potential applications.