Coherent Chiral-Selective Absorption and Wavefront Manipulation in Single-Layer Metasurfaces

Recently, chiral metasurfaces have drawn enormous attentions due to their flexibility in realizing nearly arbitrary chiral effect with designable strength. One intriguing direction in this field is chiral-selective absorption. However, previous studies mostly require multilayer design and meanwhile often work in a passive way. Here, for the first time to the authors' knowledge, a chiral-selective metasurface absorber is experimentally demonstrated with a single-layer free-standing metasurface using coherent control method, where the strength of the chiral-selective behavior can be actively tuned with a 100% modulation depth by simply changing the phase difference between the two coherent inputs. Specifically, under coherent symmetric illumination, near unity absorption is achieved for one circularly polarized incidence, while high-efficiency cross-polarization conversion is obtained for the other circularly polarized incidence. Such chiral-selective absorption property is quite suitable for achieving coherent chiral-selective wavefront control for the unabsorbed circularly polarized incidence. Three coherent chiral metagratings are designed and experimentally characterized by further employing Pancharatnam-Berry phase method and multiplexed method, where very good performances are achieved. The proposed approach on coherent control can enrich the functionalities and also improve the performances of the conventional single-layer metasurfaces, which can find extending applications in various practical cases.

Automated summary

This study demonstrates a chiral-selective metasurface absorber using a single-layer free-standing metasurface and coherent control method, actively tuning the strength of chiral-selective behavior by changing the phase difference between two coherent inputs. It achieves near unity absorption for one circularly polarized incidence and high-efficiency cross-polarization conversion for the other circularly polarized incidence. This approach enriches functionalities and improves the performance of conventional single-layer metasurfaces, with potential applications in various practical cases.