Information encoding with spin-dependent Bessel beams via metasurfaces

Abstract

Optical encryption plays an important role in information encryption. As an ultrathin optical elements, metasurfaces have the ability to precisely and fully control the incident light, which greatly promotes the development of optical information encryption. Here, we propose and demonstrate a method for optical encryption based on different spin-states of incident light via different intensity distributions generated by metasurface. The meta-devices with a numerical aperture (NA) of 0.6 and a diameter of 27 microns can independently encode two different binary numbers, where the light field distributions of the donut-shaped beam and the solid-shaped beam represent 0 and 1, respectively. On this basis, the optical encryption of information can be achieved through American Standard Code for Information Interchange (ASCII). The proposed method provides an ultracompact and highly secure platform for large-scale information encoding.