  We formulate a finite-difference time-domain (FDTD) approach to simulate
electromagnetic wave scattering from scatterers embedded in layered dielectric
or dispersive media. At the heart of our approach is a derivation of an
equivalent one-dimensional wave propagation equation for dispersive media
characterized by a linear sum of Debye-, Drude- and Lorentz-type poles. The
derivation is followed by a detailed discussion of the simulation setup and
numerical issues. The developed methodology is tested by comparison with
analytical reflection and transmission coefficients for scattering from a slab,
illustrating good convergence behavior. The case of scattering from a
sub-wavelength slit in a dispersive thin film is explored to demonstrate the
applicability of our formulation to time- and incident angle-dependent analysis
of surface waves generated by an obliquely incident plane wave.
