Picture of Optical Near Field Based on Electric Charges Induced on the Surface and Polarized Currents

Abstract

Although the self-consistent method of Chap. 6 can deal with a sample and probe with arbitrary shapes, it is not straightforward to obtain physically intuitive concepts and perspectives because it relies on numerical analyses with long computation times to derive quantitative results. In order to overcome this difficulty, the present chapter transforms the basic formulas of electromagnetism and presents a novel theoretical model by introducing a dual vector potential and a scalar potential. This model is useful for a systematic analysis of the three cases listed in Sect. 4.1. In order to demonstrate this advantage, Sect. 7.1 describes the case in which the near-field condition is met, i.e., the sizes of the material systems under study and their separation are sufficiently smaller than the wavelength of the incident light. Section 7.2 describes the case of the quasi-near-field condition, i.e., the near-field condition is not met with sufficiently high accuracy.