Light-Like Group Velocities and Long Lifetimes for Leaky Surface Plasmon Polaritons in Noble Metal Nanostripes



Propagating surface plasmon polaritons (PSPPs) are electron motions at the surfaces of conductors that have a definite momentum. For metal nanostructures on a glass substrate, two types of PSPP modes exist: bound modes where the field is localized at the metal−glass interface and leaky modes at the metal−air interface. In this paper, the leaky PSPP modes of Ag and Au nanostripes created by photolithography were examined by a combination of real space and Fourier space (back focal plane) imaging measurements and finite element simulations. The back focal plane images provide information about the wavevector k SPP of the leaky mode, and the real space images yield the propagation length L SPP. The measured wavevectors and propagation lengths are in good agreement with the finite element simulations for the Au nanostripes, but not for Ag. This is attributed to surface contamination of the Ag nanostructures. Performing the back focal plane experiments over a range of excitation frequencies generates ω versus k dispersion curves, which can be used to determine the PSPP group velocities via v g = ∂ω/∂k. The group velocities are very high, ∼90% of the speed of light. Combining the propagation length and group velocity measurements allows an estimate of the lifetime of the PSPP modes by L SPP /v g. The results of this analysis show that the leaky PSPP modes have lifetimes that are an order of magnitude longer than those for the localized surface plasmon resonances of metal nanoparticles. The experiments show that the lifetimes decrease as the width of the stripes decreases. This is attributed to increased radiation damping for the thinner nanostripes.


Attribute NameValues
  • Tuphan Devkota

  • Gregory Hartland

Journal or Work Title
  • The Journal of Physical Chemistry

  • 123

First Page
  • 15729

Last Page
  • 15737

  • 19327455

Publication Date
  • 2019-06

  • Magellan SEM

  • American Chemical Society

Date Created
  • 2019-10-09

  • English

Departments and Units
Record Visibility Public
Content License
  • All rights reserved

Digital Object Identifier


This DOI is the best way to cite this article.