The impulse response of a conductor-backed or air-backed lossy dielectric slab with frequency independent or dependent (Debye type) material parameters is evaluated analytically. It is shown that the impulse response consists of a specular reflection from the interface between free-space and the dielectric slab during the early-time period, and a natural mode series, which is a pure sum of damped sinusoids whose frequencies are determined by the poles of the complex s-plane reflection coefficient, during the late-time period. Time-domain responses using a truncated Gaussian pulse as an input with an arbitrary incident angle and with parallel or perpendicular polarization are compared to responses found by the inverse fast Fourier transform. The results may be applied to material characterization using the E-pulse method; and also give physical insight into the nature of transient scattering by a layered medium.
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