  We revisit scattering of electromagnetic waves from metallic and
semiconducting cylinders in the framework of complex angular momentum
techniques. We prove that "resonant surface polariton modes" are generated by a
unique surface wave, i.e. a surface polariton, propagating close to the
cylinder surface. This surface polariton corresponds to a particular Regge pole
of the $S$-matrix of the cylinder. From the associated Regge trajectory we can
construct semiclassically the spectrum of the complex frequencies of the
resonant surface polariton modes which can be considered as Breit-Wigner-type
resonances. Furthermore, by taking into account Stokes' phenomenon, we derive
an asymptotic expression for the position in the complex angular momentum plane
of the surface polariton Regge pole. We then describe semiclassically the
surface polariton and provide analytical expressions for its the dispersion
relation and its damping. All these features allow us to consider the
photon-cylinder system as a kind of artificial atom where the photon plays the
role of the electron. Finally, we briefly discuss the implication of our
results for two-dimensional photonic crystals.
