Reduction of first side-lobe level (SLL) and nulls in artificial fishnet metalenses is accomplished here by applying the reference phase concept along with the zoning technique. Higher focusing efficiency is achieved for a specific reference phase when comparing numerically and experimentally four different designs. For such best design, an improvement of the first SLL (~2.4 dB), first null (~13 dB), and gain (~1.77 dB) is achieved experimentally compared to the design without reference phase.
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