  Solutions of the boundary-value problem for electromagnetic waves guided by a
layer of a homogeneous and isotropic (metal or dielectric) material sandwiched
between a structurally chiral material (SCM) and a periodically multi-layered
isotropic dielectric (PMLID) material were numerically obtained and analyzed.
If the sandwiched layer is sufficiently thick, the two bimaterial interfaces
decouple from each other, and each interface may guide one or more
electromagnetic surface waves (ESWs) by itself. Depending on the constitution
of the two materials that partner to form an interface, the ESWs can be
classified as surface-plasmon-polarition (SPP) waves, Tamm waves, Dyakonov-Tamm
waves, or Uller-Zenneck waves. When the sandwiched layer is sufficiently thin,
the ESWs for single bimaterial interfaces coalesce to form compound guided
waves (CGWs). The phase speeds, propagation distances, and spatial profiles of
the electromagnetic fields of CGWs are different from those of the ESWs. The
energy of a CGW is distributed in both the SCM and the PMLID material, if the
sandwiched layer is sufficiently thin. Some CGWs require the sandwiched layer
to have a minimum thickness. Indeed, the coupling between the two faces of the
sandwiched layer is affected by the ratio of the thickness of the sandwiched
layer to the skin depth in that material and the rates at which the fields of
the ESWs guided individually by the two interfaces decay away from their
respective guiding interfaces.
