Metalenses are two-dimensional planar metamaterial lenses, which have the advantages of high efficiency and easy integration. Based on the method of spatial multiplexing, a metalens with a wide working waveband is designed by arranging Ti O2 nanopillars under the resonance phase regulation. In addition, choosing an assistant metalens with optimized heights is effective to enhance metalens’ s focusing, which is also illustrated in this paper. The metalens, designed with numerical aperture(NA) of 0.72 and center working wavelength of 600 nm, achieves the working waveband of 550-660 nm, the focus point’s size of below 420 nm, and the focusing efficiency of more than 30%.
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