Surface Plasmon Propagation in Nanostructured Metallic Waveguides

Visible frequencies of light can be routed on subwavelength scales with nanostructured, metallic waveguides by coupling optical energy to surface plasmon (SP) modes at a metal-insulator interface. Epitaxially-grown Ag nanowires and nanocoaxes provide a low-loss, ``model'' system to characterize the propagation of SP waves. We have studied these structures by electron, focused ion, scanning probe, and optical microscopies, and have observed propagation lengths exceeding 15$\lambda_{vac}$ with confinement on the order of $0.07(\lambda_{vac})^{2}$. Experimental efforts towards lithographically-fabricated metal-insulator-metal waveguides are discussed. Finally, an architecture for a nanocoax-based optical microscope,\footnote{K. Kempa, X. Wang, Z. F. Ren, and M. J. Naughton, \textit{Appl}. \textit{Phys}. \textit{Lett}. \textbf{92}, 043114 (2008)} which extracts near-field (evanescent) information and propagates it into the far-field, is presented.