Improving the performance of the zoned fishnet metalens using the reference phase technique

The reference phase, first proposed for the design of Fresnel Zoned Plates Antennas with reduced side-lobe levels, is applied here in the design of zoned fishnet metamaterial lenses. Four different metalens designs at f = 56.7 GHz are presented with values of reference phase of 0, 0.7π, 1.4π and 2π. Numerical results demonstrate that the best focusing performance is obtained for the metalens design of 0.7π in terms of the focal length, power at the focal length, side lobe level and first null. This performance is experimentally validated by comparing the focusing properties of metalenses with (0.7π) and without reference phase (0). Experimental results demonstrate a good agreement with numerical ones with a reduction of side lobes of 2.5dB and first null of ~12dB for the design with reference phase.