Optical cloaking with metamaterials

Artificially structured metamaterials have enabled unprecedented flexibility in manipulating electromagnetic waves and producing new functionalities, including the cloak of invisibility based on coordinate transformation. Unlike other cloaking approaches4–6, which are typically limited to subwavelength objects, the transformation method allows the design of cloaking devices that render a macroscopic object invisible. In addition, the design is not sensitive to the object that is being cloaked. The first experimental demonstration of such a cloak at microwave frequencies was recently reported7. We note, however, that that design cannot be implemented for an optical cloak, which is certainly of particular interest because optical frequencies are where the word ‘invisibility’ is conventionally defined. Here we present the design of a non-magnetic cloak operating at optical frequencies. The principle and structure of the proposed cylindrical cloak are analysed, and the general recipe for the implementation of such a device is provided. The coordinate transformation used in the proposed nonmagnetic optical cloak of cylindrical geometry is similar to that in ref. 7, by which a cylindrical region r , b is compressed into a concentric cylindrical shell a , r , b as shown in Fig. 1a. This transformation results in the following requirements for anisotropic permittivity and permeability in the cloaking shell: