Published online by Cambridge University Press: 03 May 2011
The recent development of artificially structured optical materials—termed optical metamaterials—has led to a variety of interesting optical effects that cannot be observed in naturally occurring materials. Indeed, the prefix “meta” means “beyond” in the Greek language, and thus a metamaterial is a material with properties beyond those of naturally occurring materials. Examples of the novel optical phenomena made possible by the advent of metamaterials include optical magnetism [1, 2], negative refractive index [3, 4], and hyperbolic dispersion [5, 6]. Metamaterials constitute a 21st-century area of engineering science that is not only expanding fundamental knowledge about electromagnetic wave propagation but is also providing new solutions to complex problems in a wide range of disciplines, from data networking to biological imaging. Although metamaterials have attracted public attention, most people see them only in devices such as Harry Potter's cloak of invisibility, or machines like StarCraft's Arbiter, with the ability to make things invisible. Indeed, the research on metamaterials indicates that the invisibility cloak is a real possibility, and might find applications in advanced defence technologies. However, it is worth mentioning other opportunities where such advanced materials can find practical applications. A very important one is the transformation of evanescent waves into propagating waves, enabling one to view subwavelength-scale objects with an optical microscope, thereby surpassing the diffraction limit [7–9].