When fiction becomes reality

Imagine the situation. An endless meeting, an awkward party… who can say that they have never dreamed of having the ability to suddenly vanish into thin air? From Greek mythology to J. K. Rowling's novels, humans have nourished the fantasy to turn invisible; the cap of Hades, Gyge's ring or Harry Potter's invisible cloak these are just a few examples of humans wandering imagination. In his novel of 1897, entitled The invisible man, H. G. Wells portrayed a scientist who theorized that if he could change the refractive index of his own body and if his body did not absorb or reflect light, then he would be invisible. Fiction or reality? Fiction of course… at that time.

A little over a century later, scientists are now capable of constructing devices that can ‘cloak’ objects. The secret lies in the ability to bend electromagnetic waves, such as light, around an object, so it appears the object is no longer there. The so called ‘cloaking structures’ are made of metamaterials. Metamaterials gain their properties from their structure rather than directly from their composition and show the peculiarity of having a negative index of refraction at optical frequencies, which effectively makes the light travel backwards.

This issue of Materials Today is entirely dedicated to metamaterials, fundamental concepts and practical applications. Christophe Caloz first presents a critical perspective of the field, to help the non-specialists find their way in this extremely active field of research. Resonator and transmission line type metamaterials are compared, exotic phenomena recently reported are briefly reviewed and practical applications are illustrated.

Pekka Alitalo and Sergei Tretyakov then stimulate our imagination by showing that cloaking and invisibility have become in recent years, fact instead of fiction. The authors investigate the different techniques available to obtain cloaking from electromagnetic or acoustic waves, their advantages and their drawbacks.

Finally, George Eleftheriades discusses the fundamentals of negative refractive index metamaterials synthesized using loaded transmission-line networks and their applications as lenses, that can overcome the diffraction limits, and small antennas for emerging wireless communication applications.

Such a rapidly evolving field of research could not simply be summarized by those three excellent review papers. We are therefore running a separate online special issue dedicated to metamaterials and following ‘Meta 2008’, the workshop held in Nanjing, China, November 9-12, 2008. This special issue will feature six additional review papers and will be available for download very soon. We will keep you posted!