Cover story: Zhou YJ, Liu T, Dai CH et al. Functionality multiplexing in high-efficiency metasurfaces based on coherent wave interferences. Opto-Electron Adv 7, 240086 (2024).

With the growing developments in optical sciences and applications, there is an increasing demand on multifunctional optical devices capable of multiplexing as many as possible wave-control functionalities in one single ultra-compact system, yet conventional devices normally suffer bulky sizes and low degrees of freedom to manipulate light, thus are hard to multiplex multiple functionalities, being highly unfavourable for optical integration. Recently, scientists employ ultra-thin metamaterials composed of planar subwavelength microstructures, i.e., metasurfaces, to efficiently modulate light. However, most metadevices realized so far can only exhibit no more than two distinct wave-control functionalities, dictated by the number of independent incident polarizations. To solve the problem, Prof. Lei Zhou’s group from Fudan university propose an approach to design metadevices exhibiting (in principle) infinite number of wave-control functionalities based on coherent wave interferences tuned by continuously varying the polarization state of incident light, and experimentally verify the concept in the telecom wavelength regime (1550 nm). The experimentally realized meta-device can generate at least 5 different vectorial vortex beams carrying orbital angular momentum (OAM) with different topological charges and/or local polarization distributions (LPDs) continuously tuned by varying the incident polarization, far exceeding the limit in previous works.