Silver-filled carbon nanotubes used as spectroscopic enhancers

We analyze from a theoretical point of view the optical properties of arrays of carbon nanotubes filled with silver. Dependence of these properties on the different parameters involved is studied using a transfer matrix formalism able to work with tensorlike dielectric functions and including the full electromagnetic coupling between the nanotubes. We find that these structures exhibit very strong linear optical response and hence could be used as spectroscopic enhancers or chemical sensors in the visible range. Very localized surface plasmons, created by the electromagnetic interaction between the capped silver cylinders, are responsible for this enhancing ability. Enhancements of up to 10⁶ in the Raman signal of molecules absorbed on these arrays could be obtained.