  The excitation of multiple surface-plasmon-polariton (SPP) waves of different
linear polarization states and phase speeds by a surface-relief grating formed
by a metal and a rugate filter, both of finite thickness, was studied
theoretically, using rigorous coupled-wave-analysis. The incident plane wave
can be either p or s polarized. The excitation of SPP waves is indicated by the
presence of those peaks in the plots of absorbance vs. the incidence angle that
are independent of the thickness of the rugate filter. The absorbance peaks
representing the excitation of s-polarized SPP waves are narrower than those
representing p-polarized SPP waves. Two incident plane waves propagating in
different directions may excite the same SPP wave. A line source could excite
several SPP waves simultaneously.

Optics