  The propagation of bound optical waves along the surface of a one-dimensional
(1-D) photonic crystal (PC) structure is considered. A unified description of
the waves in 1-D PCs for both s- and p-polarizations is done via an impedance
approach. A general dispersion relation that is valid for optical surface waves
with both polarizations is obtained, and conditions are presented for
long-range propagation of plasmon-polariton waves in nanofilms (including lossy
ones) deposited on the top of the 1-D PC structure. A method is described for
designing 1-D PC structures to fulfill the conditions required for the
existence of the surface mode with a particular wavevector at a particular
wavelength. It is shown that the propagation length of the long-range surface
plasmon-polaritons can be maximized by wavelength tuning, which introduces a
slight asymmetry in the system.
