Fig. 5

Fabrication of the one-dimensional inhomogeneous sample and experimental setup. a Cutting off an isosceles right-triangle part from the original rectangular plate consisting of 2 × 91 × 182 unit cells. The real (blue line) and imaginary (red line) parts of the inhomogeneous permittivity of the cut part satisfy the designed Kramers–Kronig (K–K) profile along the x direction. b Reassembling of four identical cut plates into a larger symmetric square plate. Seen from the origin, the real (blue lines) and imaginary (red lines) parts of the inhomogeneous permittivity satisfy the same K–K profile along the x, y, –x, and –y directions, respectively. This plate is then sandwiched by two parallel copper-plated boards so that only a transverse electromagnetic mode can exist in the plate. Both boards are slightly larger than the plate. c Full-wave simulation of the sample shown in b at 2.4 GHz when the radiative source is placed in the center of the square plate. In the model, a free space boundary was used at the cutting edge, and a perfectly matched layer (PML) boundary was used to enclose the entire simulation region. d Photograph of the actual experimental setup. A small monopole probe with omnidirectional radiation is placed at the center of the square plate. Another identical monopole is sequentially placed in each cell to measure the amplitude and phase of the electric field