The physical picture and the essential elements of the dynamical process for dispersive cloaking structures

We investigate the dynamical process of dispersive cloak by finite-difference time-domain numerical experiments. We find that there is a strong scattering process before achieving the stable state and its time length can be tuned by the dispersive strength. Poynting-vector directions show that the stable cloaking state is constructed locally while an intensity front sweeps through the cloak. Deeper studies demonstrate that the group velocity tangent component Vgθ is the dominant element in the process. This study is helpful not only for clear physical pictures but also for designing better cloaks to defend pulsive radars.