Full-Space Spin-Controlled Four-Channel Metalens With Equal Power Distribution and Broad Bandwidth

Abstract

A novel method is proposed to achieve a multifunctional full-space metalens supporting high power efficiency, broadband operation and large design flexibility for four spin-controlled output channels. A full-space meta-atom comprising an ultra-thin printed circuit board layer and a low-cost 3D-printed dielectric block are introduced. This meta-atom combines the geometric and propagation phase phenomena to divide an incident circularly-polarized wave into four equi-powered output channels (left- and right-polarized reflected waves and left- and right-polarized transmitted waves). The output waveforms can be stipulated with large flexibility by tuning the meta-atoms. The usage of non-resonant phase-tuning mechanisms allows the resultant metalenses to be broadband and power efficient. Two full-space metalenses are demonstrated using this unit cell, where the four output channels carry different combinations of orbital angular momenta and focal lengths. Simulation and experimental results show that, over a broad bandwidth of 50–70 GHz (33$\%$), all channels realize the pre-designed functionalities with high mode purities and achieve an average power efficiency of 90$\%$. Compared to previous multifunctional metalenses, these metalenses offer the simultaneous achievement of full-space operation, spin-decoupled manipulation, high-efficiency and a broad working bandwidth, opening new opportunities for millimeter-wave imaging and communication systems.