Letter | Published:

Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides


Achieving control of light-material interactions for photonic device applications at nanoscale dimensions will require structures that guide electromagnetic energy with a lateral mode confinement below the diffraction limit of light. This cannot be achieved by using conventional waveguides1 or photonic crystals2. It has been suggested that electromagnetic energy can be guided below the diffraction limit along chains of closely spaced metal nanoparticles3,4 that convert the optical mode into non-radiating surface plasmons5. A variety of methods such as electron beam lithography6 and self-assembly7 have been used to construct metal nanoparticle plasmon waveguides. However, all investigations of the optical properties of these waveguides have so far been confined to collective excitations8,9,10, and direct experimental evidence for energy transport along plasmon waveguides has proved elusive. Here we present observations of electromagnetic energy transport from a localized subwavelength source to a localized detector over distances of about 0.5 μm in plasmon waveguides consisting of closely spaced silver rods. The waveguides are excited by the tip of a near-field scanning optical microscope, and energy transport is probed by using fluorescent nanospheres.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Saleh, B.E.A. & Teich, M.C. Fundamentals of Photonics (Wiley, New York, 1991).

  2. 2

    Mekis, A. et al. High transmission through sharp bends in photonic crystal waveguides. Phys. Rev. Lett. 77, 3787–3790 (1996).

  3. 3

    Quinten, M., Leitner, A., Krenn, J.R. & Aussenegg, F.R. Electromagnetic energy transport via linear chains of silver nanoparticles. Opt. Lett. 23, 1331–1333 (1998).

  4. 4

    Brongersma, M.L., Hartman, J.W. & Atwater, H.A. Electromagnetic energy transfer and switching in nanoparticle chain arrays below the diffraction limit. Phys. Rev. B 62, R16356 (2000).

  5. 5

    Kreibig, U. & Vollmer, M. Optical Properties of Metal Clusters (Springer, Berlin, 1995).

  6. 6

    Maier, S.A. et al. Plasmonics – a route to nanoscale optical devices. Adv. Mater. 13, 1501–1505 (2001).

  7. 7

    McMillan, R.A. et al. Ordered nanoparticle arrays formed on engineered chaperonin protein templates. Nature Mater. 1, 247–252 (2002).

  8. 8

    Krenn, J.R. et al. Squeezing the optical near-field zone by plasmon coupling of metallic nanoparticles. Phys. Rev. Lett. 82, 2590–2593 (1999).

  9. 9

    Maier, S.A., Brongersma, M.L., Kik, P.G. & Atwater, H.A. Observation of near-field coupling in metal nanoparticle chains using far-field polarization spectroscopy. Phys. Rev. B 65, 193408 (2002).

  10. 10

    Maier, S.A., Kik, P.G. & Atwater, H.A. Observation of coupled plasmon–polariton modes in Au nanoparticle chain waveguides of different lengths: Estimation of waveguide loss. Appl. Phys. Lett. 81, 1714–1716 (2002).

  11. 11

    Maier, S.A., Brongersma, M.L. & Atwater, H.A. Electromagnetic energy transport along arrays of closely spaced metal rods as an analogue to plasmonic devices. Appl. Phys. Lett. 78, 16–18 (2001).

  12. 12

    Maier, S.A. et al. Optical-pulse propagation in metal nanoparticle chain waveguides. Phys. Rev. Lett. (submitted).

  13. 13

    Lamprecht, B. et al. Metal nanoparticle gratings: influence of dipolar particle interaction on the plasmon resonance. Phys. Rev. Lett. 84, 4721–4724 (2000).

  14. 14

    Salerno, M., Felidj, N., Krenn, J.R., Leitner, A. & Aussenegg, F.R. Near-field optical response of a two-dimensional grating of gold nanoparticles. Phys. Rev. B 63, 165422 (2001).

  15. 15

    Schider, G. et al. Optical properties of Ag and Au nanowire gratings. J. Appl. Phys. 90, 3825–3830 (2001).

  16. 16

    Quinten, M. & Kreibig, U. Absorption and elastic scattering of light by particle aggregates. Appl. Opt. 32, 6173–6182 (1993).

  17. 17

    Lieberman, K., Ben-Ami, N. & Lewis, A. A fully integrated near-field optical, far-field optical, and normal-force scanned probe microscopy. Rev. Sci. Instrum. 67, 3567–3572 (1996).

  18. 18

    Fujihira, M. et al. Scanning near-field optical microscopy of fluorescent polystyrene spheres with a combined SNOM and AFM. Ultramicroscopy 61, 271–277 (1995).

Download references


The authors are grateful to Richard Muller, Paul Maker, and Pierre Echternach of the Jet Propulsion Laboratory in Pasadena for professional help with electron beam lithography. This work was sponsored by the Air Force Office of Scientific Research and also partly by the NSF grants ECS0103543, EIA-98-71775 and DMI-02-09678 and the Center for Science and Engineering of Materials at Caltech.

Author information

Competing interests

The authors declare no competing financial interests.

Correspondence to Stefan A. Maier.

Rights and permissions

Reprints and Permissions

About this article

Further reading

Figure 1: Far-field extinction spectrum of Ag nanoparticle chains and single particles.
Figure 2: Excitation and detection of energy transport in plasmon waveguides by near-field optical microscopy.
Figure 3: Evidence for energy transport in plasmon waveguides by the width of the intensity of fluorescent nanospheres.