Energy flux in a surface-plasmon-polariton wave bound to the planar interface of a metal and a structurally chiral material.

The spatial profile of the energy flux in a surface-plasmon-polariton (SPP) wave bound to the planar interface of a metal and a structurally chiral material (SCM) shows strong dependencies on the pitch of the SCM. More than one SPP-wave mode at the same frequency (or free-space wavelength) being possible for the chosen interface, the energy-flux profiles of different modes are different. Although the energy flux on the metal side of the interface decays exponentially with distance from the interface, the profile on the SCM side exhibits oscillations as a function of distance from the interface and decay rates, which are highly variable. Because of the periodic nature of the SCM, the Floquet-Lyapunov theorem may be invoked to explain this behavior.