Design And Investigation Of Single-Layer Polarization-Sensitive Phase-Gradient Metasurface

Metasurfaces have drawn increasing attention as the two-dimensional(2D)counterparts of three-dimensional(3D)metamaterials due to their simple structure and low profile.Among them,phase-gradient metasurface(PGMS)can provide specific transmission phases and further control the propagation wavefront artificially by adjusting the phase distributions on the metasurface.Therefore,it is possible to be applied in wireless communication or energy transfer systems.Specifically,polarization-sensitive PGMS has a wider application prospect because it can independently control the wavefronts for different polarized incident waves.However,multi-layer structures consited of several metallic layers and dielectric substrates were mainly used in the pervious PGMSs to increase the tranmission phase coverage or realize the integration of reflection and transmission functions,which also increased the complexity of structure and the difficulty of processing.To takle this problem,the improvement of dielectric structures on the phase-control coverage and polarization sensitivity of PGMS is investigated and studied.Further,three kinds of single-layer polarization-sensetive PGMSs are designed.The main work of this article is as follows:Firstly,a single-layer all-dielectric transmissive focusing metasurface with polarizationcontrollable focus is proposed.The element of metasurface is consisted of two orthogonally placed rectangular dielectric resonators.A polarization-controllable transmission phase coverage of about 330° with a high transmission magnitude of up to 0.95 can be obtained by adjusting the length of one of the two resonators;and morever,the polarization isolation effect can be obtained by carefully designing the widths of resonators.As a result,two orthogonal linearly-polarized(LP)waves can be focused on different preset positions by setting different phase distributions on the metasurface.Then,a single-layer polarization-dependent transmissive and reflective focusing metasurface is proposed.The element of metasurface is consisted of a cross-shaped dielectric unit and a couple of metallic strips/patches,which can transmit or reflect the LP incident wave according to its polarization(with a transmission/reflection magnitude of about 0.85/0.93)and provide a phase coverage of 360° respectively.By properly arranging the phase distributions,two foci or high gain beams can be obtained on the transmission or reflection sides for the orthogonally polarized waves respectively.Finally,a single-layer transmissive polarization-controllable focusing metasurface with small element size is proposed.Taking the advantages of hollow dielectric structure and simple metallic strips,the metasurface achieves a polarization-controllable transmission phase coverage of about 330° with a magnitude of above 0.8 by using small elements,and thus obtains a good focusing effect.Further,by setting different phase distributions on the metasurface,two orthogonal linearly-polarized(LP)waves can be focused on different positions.