Fig. 22.1 — Plasmonic response of metal nanostructures

Chapter 22 — Plasmonics

The exploitation of the plasmonic response of metals for optical trapping applications may be divided into two broad categories. The first is to use the (LSPs) supported by metallic nanoparticles, which we have discussed in Section 3.9, to enhance their mechanical reaction to the fields and thereby enable optical trapping. The second is to use the (SPPs) supported by nanostructures on a substrate to generate enhanced fields over a small volume, where particles can be more effectively trapped, as we have seen in Subsection 12.4.4. The distinction between SPPs and LSPs is illustrated in Fig. 22.1. SPPs are the propagating electromagnetic surface waves arising from the excitation of a collective oscillation of the free electrons in a thin metal film, i.e., a quasi two-dimensional metallic structure that is nanoscale in one dimension only; since a SPP is an evanescent mode, it must be excited by an evanescent electric field, which is typically achieved using the Kretschmann geometry. LSPs, instead, are associated with excitations of oscillations in the bound electrons of metallic nanoparticles, or nanovoids within a metallic substrate, and can be directly excited with a propagating field. In this Chapter we review a number of optical trapping and manipulation experiments in which plasmonic force enhancement plays a crucial role.

22.1  Plasmonic nanoparticles

22.2  Plasmonic substrates

22.3  Plasmonic apertures

22.4  Further reading


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