Compact planar meta-lenses for nondiffracting surface wave deflection

A novel planar lens structure is proposed by using metasurfaces to convert cylindrical-like surface wave to inclined nondiffracting wave with a deflection angle. Based on the geometric optics, the refractive index distribution of the surface wave lens is derived. A square metal ring-shaped metasurface cell is used for realizing small refractive index whilst two opposite E-shaped metal patches are used to form the meta-cell with large refractive index. By adjusting the size of meta-cells, the desired refractive index distribution is obtained after optimization. Measured results show that the inclined nondiffractive surface wave can be achieved with the maximum propagation distance of 99.72 mm at the tilted angle of 26.8°, which are consistent with the full-wave simulation and numerical calculation results. The proposed meta-lens achieves compact size, large titled angle, and long nondiffraction propagation distance, therefore could be well utilized in surface wave communication and nondestructive detection of surface defects.