TABLE OF CONTENTS Surface plasmons, also known as surface plasmon polaritons, play an important role in near-field microscopy, nanophotonics, and biomolecular sensor applications. [25] [27] Surface plasmon polaritons represent the interaction between electromagnetic waves and the oscillatory movement of free charges near the surface of metallic materials. When surface plasmons are confined to small structures, such as the tip of a scanning microscopic probe, quantum dots or nanoparticles, nanowires, or nanoapertures, they are referred to as localized plasmons. Surface plasmons usually occur in the electromagnetic wave spectrum in the visible or near-infrared region for highly conductive metals such as Ag, Al, and Au. In some polar dielectric materials, phonons or bound charges can also interact with the electromagnetic waves in the mid-infrared spectral region and cause resonance effects near the surface; these are called surface phonon polaritons, which have applications in tuning the thermal emission properties [28] and nanoscale nondestructive imaging [29] In the following, the basic mechanisms of surface polaritons will be presented, with discussions on some important applications. Emphasis is placed on the quantitative analysis of radiative properties for layered structures. In Sec. 10.4, the superlens concept will be introduced for imaging beyond the diffraction limit, and the energy streamline method will be presented for analyzing the energy propagation direction in the near-field regime.
Plasmons are quasiparticles associated with oscillations of plasma, which is a collection of charged particles such as electrons...
