Optical metamaterials: Invisibility in visible and nonlinearities in reverse

Abstract

Recent experimental demonstrations of optical metamaterials opened up an entirely new branch of modern optics that can be described as "refractive index engineering" [1-20]. The refractive index of a material is the factor by which an electromagnetic wave is slowed down, compared with a vacuum, when it propagates inside the material. The material properties of conventional materials are largely controlled by the properties of their constituent components, viz., atoms and molecules. Their refractive indices can be modified to some degree by altering material chemical composition, using thermal or electrical tuning, or through nonlinear optical effects. Nevertheless, a majority of existing materials possesses positive, and typically greater than one, index of refraction. In contrast, meta-materials provide almost unlimited opportunities for designing the refractive index through a careful engineering of their constituent components, or meta-atoms. Several examples of engineered optical structures, including magnetic metamaterial and negative index metamaterials (NIMs), are shown in Fig. 13.1. Moreover, metamaterial properties can be tuned [21,22] and even controlled on a level of a single meta-atom [23]. Basic properties of optical metamaterials will be reviewed in Section 13.1. Additional design flexibility provided by metamaterials (discussed in Section 13.2) gives rise to new linear and nonlinear optical properties, functionalities, and applications unattainable with conventional materials. In this chapter, we discuss two examples of refractive index engineering in metamaterials that results in truly fascinating phenomena. © 2009 Springer-Verlag Berlin Heidelberg.