Surface plasmon–polariton wave propagation guided by a metal slab in a sculptured nematic thin film

Surface plasmon–polariton (SPP) wave propagation guided by a metal slab in a periodically nonhomogeneous sculptured nematic thin film (SNTF) was studied theoretically. The morphologically significant planes of the SNTF on both sides of the metal slab could either be aligned or twisted with respect to each other. The canonical boundary-value problem was formulated, solved for SPP wave propagation, and examined to determine the effect of slab thickness on the multiplicity and the spatial profiles of SPP waves. Decrease in slab thickness was found to result in more intense coupling of two metal/SNTF interfaces. But when the metal slab becomes thicker, the coupling between the two interfaces reduces and eventually SPP waves localize to one of the two metal/SNTF interfaces. The greater the coupling between the two metal/SNTF interfaces, the smaller is the phase speed. Both the phase speed and the attenuation of an SPP wave also depend on the twist between the morphologically significant planes of the SNTF on the two sides of the metal slab