  Multiple p- and s-polarized compound surface plasmon-polariton (SPP) waves at
a fixed frequency can be guided by a structure consisting of a metal layer
sandwiched between a homogeneous isotropic dielectric (HID) material and a
periodic multilayered isotropic dielectric (PMLID) material. For any thickness
of the metal layer, at least one compound SPP wave must exist. It possesses the
p-polarization state, is strongly bound to the metal/HID interface when the
metal thickness is large but to both metal/dielectric interfaces when the metal
thickness is small. When the metal layer vanishes, this compound SPP wave
transmutes into a Tamm wave. Additional compound SPP waves exist, depending on
the thickness of the metal layer, the relative permittivity of the HID
material, and the period and the composition of the PMLID material. Some of
these are p polarized, the others being s polarized. All of them differ in
phase speed, attenuation rate, and field profile, even though all are excitable
at the same frequency. The multiplicity and the dependence of the number of
compound SPP waves on the relative permittivity of the HID material when the
metal layer is thin could be useful for optical sensing applications.
