View article

DOI: 10.1002/adma. 201600625 unchanged and altering the impedance. A remarkable example of this method is a nonmagnetic approximation, where only the relative permittivity is changed while the relative permeability remains at unity. Thus, an optical omnidirectional cloak can be achieved by embedding metal nanowires in a dielectric material.[20] Recently, a significant step toward a cloak with both preserved amplitude and phase has been made;[12] specifically, a metamaterial was designed to fully control both the refraction index and impedance, leading to the realization of a microwave unidirectional cloak based on transformation optics without any approximation for a special polarization. The great challenge of practical cloak design is that an invisibility cloak with perfect performance (ie, with both the phase and amplitude preserved) is difficult to achieve for full polarization, because from a transformation optics perspective, manipulating the phase and amplitude of light for full polarization requires the simultaneous control of six constitutive parameters, ie, εx, εy, εz, μx, μy, μz, in a Cartesian coordinate system, which is extremely complex to design and implement. The majority of experimental investigations of invisibility cloaks are restricted to special polarization,[2–5, 8–13, 21, 22] ie, transverse electric (TE) polarization or transverse magnetic (TM) polarization. To reduce the complexity, two remarkable efforts have been made to implement full-polarization 3D cloaks based on isotropic materials with the constitutive parameters designed based on quasiconformal mapping methods;[6, 7] however, the phase of the reflected wave is not …