Wave-Medium Interactions in Dynamic Matter and Modulation Systems

Space-time modulation systems have recently garnered significant attention due to their resemblance to moving-matter systems, unique properties, and promising applications. Unlike conventional moving-matter systems, modulation systems do not involve any net motion of matter and are therefore easier to implement and capable to attain relativistic and superluminal velocities. However, the fundamental wave-medium interaction aspects in such media, such as scattering and energy-momentum relations, have been essentially unexplored to date. In this article, we fill this gap, considering three dynamic systems: moving-matter blocs, moving-perturbation interfaces, and moving-perturbation truncated periodic structures, and provide corresponding general formulations along with comparisons. Our investigation reveals significant roles played by the “pushing” and “pulling” effects of the moving interface onto the wave in such systems. Moreover, it describes different energy and momentum transfers between moving media and homogenized moving-perturbation structures that result from conventional and reverse Fresnel-Fizeau drag effects.