Efficient Anomalous Refraction of THz Beams Witha Multilayer Metal-Polymer Huygens' Metasurface

We describe design principles, fabrication techniques,and experimental testing for a Huygens' meta surface, which deflects a normally incident radiation beam atf approximate to 0.172 THz toward an angle of 52(degrees)in transmission. The meta surface is comprised of a cascade of five spatially-modulated aluminum impedance sheets photo lithographically patterned on 100-mu m-thick polypropylene substrates, stacked together via ultra thin adhesive layers. The physical geometries realizing the five-layer Huygens' meta-atoms are designed using a semi analytical model while the expected deflection, associated with negligible reflection and low diffractive losses, is verified by full-wave simulations and measurements.For the implemented deflector, with a work ingaperture diameter of 75 mm, the experimentally measured refraction efficiency reached 58%, with 20% and 22% losses attributed tospurious diffraction and absorption, respectively. Despite the sub-optimal performance, our results establish the proposed methods of synthesis and fabrication as promising for realizing quasi-opticalTHz components with unique characteristics, unattainable in this challenging regime with alternative approaches.