Lossless tensor surface electromagnetic cloaking for large objects in free space

Electromagnetic cloaking for large objects in free space using a lossless impenetrable tensor impedance surface is proposed. The key enabling feature is enforcement of the pointwise lossless condition via introduction and optimization of surface waves that carry power along the curved bounding surface of the cloaked region. In a pointwise lossless and reciprocal manner, the cloaking surface converts the incident plane wave into surface waves on the lit side, carries the power along the surface into the shadow side, and continuously releases a propagating wave to reconstruct the incident field behind the object. Overcoming the difficulties associated with currently available active and passive metasurface cloaks, the proposed cloaks may be realized entirely using passive constituents and they are effective for electrically large free-standing objects that cast shadows. The surface cloaks may be realized as subwavelength-thin passive tensor gradient metasurfaces.