Hybrid Wavefront-Resonance Representation for Transient Scattering by an Open Cavity Part II: Numerical Results and Interpretation

In this second part in a three part sequence, the hybrid wavefront-resonance scheme developed in Part I is applied and explored numerically for the transient field scattered by a plane parallel waveguide cavity configuration. Emphasis is on validating the effectiveness of this representation and on explaining the observed features in the scattered signal at early, intermediate, and at late observation times. Utilizing results reported earlier for the complex resonances [3], it is shown that the late-time observables carry the signature of a cluster of high-Q internal resonances that occurs near modal cutoff frequency, in the form of a slowly decaying typical waveform which is independent of the incident angle or the excitation pulse but is related to the cavity dimensions. The early-time field is expressed as a rapidly decaying series of external wavefront interactions, while at intermediate times the internal resonances synthesize the dispersive guided mode return. The convergence of the resonance series, and its role in establishing the early-time causal wavefront are explored. By properly selecting the incident angle and pulse-shape, one may de-emphasize the early-time contributions and enhance the magnitude of the late time typical waveform.