PRINCIPLES OF NEAR-FIELD OPTICAL MAPPING

Abstract

Before the emergence of the actual interest for the potential applications of nanophotonics, a generation of surface physicists worked on the development of a new class of instruments known today as near-field optical microscopes. Many fundamental phenomena discovered in this context are directly relevant for the development of miniaturized optical devices. As time passed and as we will show in this chapter, it was recognized that one main practical feature of near-field optical microscopes is the ability to map the electromagnetic fields associated with optical waves. Today, this functionality provides an essential way of characterizing miniaturized optical devices, such as, but not limited to, plasmonic devices. In such devices, where the sizes of the objects are of the order of the wavelength λ or smaller, phenomena involving evanescent electromagnetic waves, i.e. decaying within a range given by λ, dominate. To fully exploit the potential of optical nanodevices, it is clear that signal detection or any signal conversion process should be controlled at the subwavelength scale. Therefore, the development of nanophotonics demands a clear understanding of the fundamental issue of the detection of optical fields at the subwavelength scale.