Classical theory of optical near field

Abstract

Themain purpose of this chapter is to present the quasi-static picture of an optical field in the vicinity of small-scale material. The quasi-static picture depends on the fact that the induced boundary charge density dominates the optical near field of a small-scale material via Coulomb’s law; therefore, such an optical near field is of a non-radiative or longitudinal nature. This simple physics leads to an intuitive understanding, even in complicated systems with magneto- and electro-optical effects. As prerequisites, the definitions of elementary concepts are given: “retardation effect,” “diffraction limit,” “near field,” and “far field.” Furthermore, two numerical methods are presented using the minimum degree of freedom of an electromagnetic field; one is described by the scalar potential adequate for a quasi-static system and the other by a dual vector potential for general optical systems. This chapter is restricted to linear optical effects and is a revised version of the article titled by “Classical Theory on Electromagnetic Near Field” in Progress in Nano-Electro-Optics II (Springer-VerlagBerlin Heidelberg, 2004).