Broadband and High-Efficiency Manipulation of Transmitted Vortex Beams via Ultra-Thin Multi-Bit Transmission Type Coding Metasurfaces

A transmission-type digital coding metasurface with features of ultrathin thickness and high efficiency over a wide operating bandwidth is proposed. The proposed metasurface is composed of low profile cascaded meta-atoms that can control the cross-polarized transmitted waves in the broad spectrum of K-band. The effectiveness of the proposed method based on the predesigned coding sequences is demonstrated by realizing various vortex beams (VB) that carry higher-order orbital angular momentum (OAM) under normal and oblique incidences. VB with flexible feature and multiple VBs from the same aperture are also realized by using the convolution operation. Two samples with 3-bit and 2-bit resolutions are fabricated to experimentally demonstrate the simulated results with single and multiple VBs. The proposed design can be easily extended to other frequency regimes to realize similar functionalities. We believe that the proposed design will find potential applications in the transmission-type optical devices.