TABLE OF CONTENTS Chapter written by Alain DEREUX.
Today s performances of optical devices are limited by the restricted framework of the underlying fundamental concepts. These concepts rely exclusively on the notion of radiative electromagnetic eigenmodes sustained by large scale dielectric structures. The mathematical description of these modes includes at least an exponential of imaginary argument to account for propagation over distances much longer than the incident wavelength. Practically, such standard waveguides are rectilinear and feature transverse sections of several square micrometers.
Recently, researches on optical waveguides addressed the question of keeping a reasonable transmission level through a constriction whose width is smaller than the incident wavelength. Up to now, two research areas arise as being pertinent for the purpose of miniaturizing optical connections, namely: photonic crystals research and interface polaritons research.
At visible frequencies, interface polaritons are easily obtained at metal-dielectric interfaces : one speaks then of surface plasmon polaritons (SPP). This chapter will ignore all aspects dealing with photonic crystals (which is covered by other authors in this book) in order to bring to the fore the potential of sub-wavelength plasmonics devices as compared to high refraction index devices.
Whichever road map is followed, miniaturizing optical connections raises fundamental physical questions. A first set of questions deals with the basic concepts of non-radiative photonic transport through solid state mesoscopic and nanoscopic structures, including the practical problems of injection and detection in sub-wavelength structures. Characterizing the optical functionalities of such devices requires a coherent point of view on the issues...
