Three-Dimensional Electromagnetic Void Space

We report a realization of three-dimensional (3D) electromagnetic void space. Despite occupying finite volume space, such medium is optically equivalent to an infinitesimal point where waves experience no phase accumulation. The 3D space realized by constructing all-dielectric photonic crystals that the effective permittivity and permeability vanish simultaneously, forming six-fold Dirac-like with linear dispersions at center Brillouin Zone. demonstrate, both theoretically experimentally, exhibits unique properties rich functionalities absent in any other media, as boundary-control transmission switching perfect wave-steering mechanisms. Especially, contrary "doping" effect its two-dimensional counterpart, amazing property "impurity-immunity". Our work paves road towards can be manipulated unprecedented ways.