Asymmetric hologram with a single-size nanostructured metasurface.

Geometric metasurfaces, governed by PB phase, have shown their strong polarization sensitivity and can generate opposite phase delay when the handedness of incident circularly-polarized (CP) light is opposite. Here, we show this interesting characteristic can be employed to generate asymmetric forward and backward propagation with the same incident left- or right-handed CP light, which is hard to achieve with conventional optical elements and devices. Specifically, with the modified holographic design algorithm to consider both forward and backward CP light, an asymmetric meta-hologram is designed, which can project two different holographic images in the forward and backward directions, respectively. We demonstrate this concept by fabricating an asymmetric hologram with a single-size nanostructured metasurface, and the experimentally obtained holographic images in both directions have shown their advantages of high fidelity, broadband response and low crosstalk. The proposed asymmetric metasurface can play an important role in data storages, anti-counterfeitings, optical communications, displays and many other related fields.