Beam refraction with an isotropic and ultrathin Huygens´ metasurface

We propose an isotropic and ultrathin Huygens´ metasurface that can refract normally incident electromagnetic waves efficiently to a predefined angle at 25 GHz. The phase gradient of the surface is controlled by five subwavelength (with dimensions of 0.5λ₀ × 0.5λ₀, λ₀ is the free-space wavelength at 25 GHz) non-resonant spatial phase shifters, which have metallic structures etched on both sides of an ultrathin dielectric substrate (with the thickness of 0.07λ₀). The peak value of the transmission efficiency of the device approaches 60%. The proposed metasurface may find applications in designing various electromagnetic lenses, or beam-steerable devices.