Reconfigurable Metasurface Cloak for Dynamical Electromagnetic Illusions

Considerable attentions have been focused on the realization of carpet cloaks in the past decade. Most of the current carpet cloaks can perform only one electromagnetic (EM) shape for concealing inside objects, and dynamical control of arbitrary EM virtual shapes remains a significant challenge. Here, a desirable method is proposed to construct a reconfigurable carpet cloak using tunable metasurface technology. By controlling the active elements loaded on the metasurface, the surface phase distribution can be dynamically changed to make the cloak generate the predesigned scattering field. This reconfigurable metasurface cloak is experimentally realized at the microwave frequency, which demonstrates that it can not only reduce unwanted scattering for imitating the reflection of a flat metallic plane, but also mimic other different EM virtual shapes by reconfiguring the phase distribution. To the best of our knowledge, this is the first carpet cloak that achieves dynamical illusions by switching the EM shapes without changing its physical shape. The proposed technology could be also extended to the terahertz and even optical domain

Merging Geometric Phase and Plasmon Retardation Phase in Continuously Shaped Metasurfaces for Arbitrary Orbital Angular Momentum Generation

Traditional technologies to generate and manipulate the orbital angular momentum (OAM) suffer from bulky size and do not lend themselves to nanophotonic systems. An ultrathin metasurface based on abrupt phase shift has recently been proposed as an alternative method. Nevertheless, gradient phase was generally approximated by multiple meta-atom/molecules with discrete levels of abrupt phase shift, which not only increases the design and fabrication complexity but also causes difficulties in obtaining simultaneous electrical and optical functionality. Furthermore, a discontinuous phase profile would introduce phase noise to the scattering fields and deteriorate the purity of the OAM beams. Here, we propose a wavefront engineering mechanism by virtue of the spin–orbit interaction in continuously shaped plasmonic metasurfaces, which offers a new approach to generate OAM modes of high purity. Equally important, a method producing arbitrary OAM topological charge, integral and fractional, is demonstrated by merging the plasmon retardation phase with the geometric phase in the proposed continuously shaped metasurfaces. The proposed approach is well supported by full-wave numerical simulations and experimental characterization of the fabricated structure in the visible regime