Electromagnetic oscillations in periodic mediums outside the passbands
  It was usually assumed that the resonator based on a waveguide has the eigen oscillations that are formed by interference of two waves which propagate in different directions and have equal amplitudes. These patterns are usually called standing waves. We have shown that the eigen oscillations of a resonator which is filled by a layered dielectric can be base on the evanescent (non-propagating) waves. In some cases we need only one eigen wave to compose the eigen oscillation of a closed cavity. 
Mikola I. Ayzatsky