Broadband absorption phenomena in temporal metamaterials with modulation of the refractive index.

This study investigates the broadband absorption of electromagnetic (EM) waves in temporal metamaterials (TEMLs). These materials are temporal multilayer structures with a time-varying refractive index, n(t), and have attracted significant attention in recent years. While considerable progress has been made in TEML research, the broadband absorption phenomenon still requires further investigation. The transmission matrix method (TMM) was used to analyze the transmission characteristics of EM waves in TEMLs, focusing on the broadband absorption phenomenon. This broadband absorption is based on the frequency conversion properties of the temporal interface. Due to the isotropic nature of TEMLs, their absorption characteristics remain consistent across all incident angles, demonstrating complete polarization insensitivity. The unique temporal properties of TEMLs overcome the limitations of time-harmonic materials and enable the tunability of EM properties. This study advances the technology for controlling EM waves in the time domain and offers new, to our knowledge, strategies for designing novel, to the best of our knowledge, devices.