Radially oscillating and quasi-guided surface plasmon polaritons in cylindrical metallic nanostructures.

Abstract

We analytically propose radially oscillating and quasi-guided surface plasmon polaritons (SPPs) by designing the outer and core dielectric permittivities ε(a) and ε(c) of a cylindrical metallic nanotube. When the propagation constant satisfies √ε(a)<Re(k(z)/k(0))<√ε(c), the electromagnetic field propagates along the radial direction in the core region and decays outside the nanotube, forming a standing radially oscillating SPP. In contrast, when √ε(c)<Re(k(z)/k(0))<√ε(a), the electromagnetic field decays in the core region and propagates outside the nanotube, forming a quasi-guided SPP. The propagation length of both SPPs can reach tens of micrometers, in particular, the radially oscillating SPPs have an ultrastrong light confinement. Finally, we design position-flexible broadband plasmonic router based on quasi-guided SPPs, and we also discuss the advantages of a nanolaser based on radially oscillating SPPs.