A High Efficiency Metasurface And Application In Microwave Lens

Arbitrary control of the wavefront of electromagnetic waves has always been a hot topic in the field of electromagnetism. Traditional devices used to manipulate electromagnetic waves depend on gradual phase changes accumulated along the optical path, which also means bulky volume and high loss. In contrast, the limit of volume could be broken by introducing abrupt phase changes through metasurface. In this research, transmition-type metasurfaces are designed based on PancharatnamBerry phase to efficiently control the transmitted phase of electromagnetic wave, which could provide an alternative for control of wavefront of transmitted wave.Firstly, the research was focused on the study of unit cells with high efficiency. Here the efficiency means the ratio of energy of the transmitted cross-polarized wave to that of the incident wave. Based on single-layer metal structure, the ability of polarization reversing of single-layered metallic line structure, "Gong"-shaped structure and U-shaped structure were studied. Comparison was made between singlelayered metallic structure and double-layered structure, which verified the method of designing unit cells with high efficiency. Then gradient changed phase was obtained through double-layered metallic line structure, splited resonant ring(SRR) structure and ring-shaped structure according to P-B phase principle. Measurement of transmission coeffiencient and phase were conducted on fabricated samples with double-layered SRR structure, which showed good agreement with simulation results and theoretical values.Secondly, metalens were designed based on unit cells with metallic line structure, SRR structure and ring structure. Combined with spatial distribution of abrupt phase change, anomalous refraction were obtained under normal incidence of circularly polarized wave. The experimetal results agreed with theretical calculation quite well. On the other hand, the phase profile of the axicon were reproduced based on P-B phase pricinple and designed unit cells with abrupt phase. And then a microwave metalens with converging function were obtained.In this thesis, both the efficiency of cross-polarization conversion and the ultrathin property with respect to wavelength were satisfied, which makes the metalens with abrupt phase changes more suitable for practical applications.