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A new method to design an ultra-thin high-gain circularly-polarized antenna system with high efficiency is proposed based on the geometrical phase gradient metasurface (GPGM). With an accuracy control of the transmission phase and also the high transmission amplitude, the GPGM is capable of manipulating an electromagnetic wave arbitrarily. A focusing transmission lens working at Ku band is well optimized with the F/D of 0.32. A good focusing effect is demonstrated clearly by theoretical calculation and electromagnetic simulation. For further application, an ultra-thin single-layer transmissive lens antenna based on the proposed focusing metasurface operating at 13 GHz is implemented and launched by an original patch antenna from the perspective of high integration, simple structure, and low cost. Numerical and experimental results coincide well, indicating the advantages of the antenna system, such as a high gain of 17.6 dB, the axis ratio better than 2 dB, a high aperture efficiency of 41%, and also a simple fabrication process based on the convenient print circuit board technology. The good performance of the proposed antenna indicates promising applications in portable communication systems.

High quality factor resonance with extremely narrow line‐width offers an important platform for terahertz (THz) sensing technology as it enables strong light‐matter interaction between THz waves and analyte materials. Lattice mode arising from the collective Rayleigh scattering of metamaterial periodic structures has the ability to strongly confine the electromagnetic waves on the surface that fails to radiate to the far‐field. Herein, for the first time, a strategy is experimentally demonstrated to design THz metasensors, which exhibit dual‐sensitivity of frequency and resonance intensity by coupling the first‐order lattice mode to the toroidal resonance. The frequency sensitivity mainly results from the localized field confinement, whereas the sensitivity of resonance intensity depends on the matching degree between toroidal resonance and lattice mode. It is found that both the frequency shift and resonance intensity show exponential growth with the increase in the analyte thickness. In addition, the sensing performance between toroidal and toroidal–lattice modes is compared to verify the superiority of the dual‐sensitivity property. This work would greatly improve the practical applications of THz sensing technology and open up new opportunities for the realization of slow light devices, multiband narrow filters, and nonlinear systems.

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