“…Compared with the time-harmonic scattering problems, mathematical studies are much less done for the time-domain counterparts due to the challenge of the temporal dependence. The analysis can be found in [15,25,26,27,28,33] for the time-domain acoustic, elastic, and electromagnetic scattering problems in different structures including bounded obstacles, open cavities, and unbounded rough surfaces. In these works, the idea was to utilize the Laplace transform as a bridge between the time-domain and the frequency domain.…”