Janus-like metasurface acts according to the direction of light​

https://news.kaist.ac.kr/newsen/html/news/?mode=V&mng_no=40370

"overcomes metasurface limitations using thin, light Janus metasurface precisely controlling asymmetric light transmission through nanometer-sized artificial structures... enhances security by only decoding information under specific conditions... performing different functions in both directions: lens or hologram depending on incidence direction, selectively controlling intensity, phase, polarization... AR, holographic displays, LiDAR, quantum communication"