Surface electromagnetic waves with damping. I. Isotropic media

Surface-electromagnetic-wave dispersion curves are usually calculated using a simple equation derived from Maxwell's equations and boundary conditions. When complex dielectric functions are used for the two media, the component of the propagation vector along the surface, kₓ, becomes infinite as the frequency approaches the surface polariton frequency ωₛ if ω is considered complex and kₓ is real. On the other hand, if kₓ is considered complex and ω real, the dispersion curves bend back toward smaller kₓ as ω approaches ωₛ. We have previously demonstrated that both types of behavior can be obtained from attenuated-total-reflection measurements of silver. We now extend this result to other materials and show that dispersion curves alone present an inadequate summary of the data.