Screened electromagnetic propagators in nonlocal metal optics

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Abstract
A new type of screened Green’s function appropriate for studies of electromagnetic wave propagation in metals in the regime of nonlocal optics is constructed and discussed. The influence on the propagator characteristics of nonlocal screening effects caused by polariton, plasmon, and single-particle excitations is investigated. An eigenvector expansion of the dyadic propagator is used to study the near- and far-field parts of the propagator. In the near field the transverse and longitudinal parts of the propagator each have contributions from the two types of collective excitations. A nonlocal dyadic Green’s function associated with adjacent metal-vacuum half-spaces is introduced, and s- and p-polarized screening effects are discussed. The self-field part of the propagator and reflection effects at the boundary are investigated. It is indicated how the present formalism can be useful in studies of (i) selvedge responses in linear and nonlinear metal optics, and (ii) Brillouin scattering and rough-surface diffraction from solid-state plasmas. Finally, it is demonstrated that the present propagator formalism is adequate for the description of reflected and transmitted fields at sharp boundaries.