Full Complex-Amplitude Engineering by Orientation-Assisted Bilayer Metasurfaces

摘要

Optical complex-amplitude determines the propagation behavior of light infree space to the maximum extent. Precise control of complex-amplitude isthe key to generating user-defined light fields. Current attempts to controloptical complex-amplitude using metasurface, however, either have limitedamplitude/phase step numbers or lost high lateral resolution since amplitudeand phase are usually manipulated with size-varied nanostructures orseveral nanostructures integrated into a unit-pixel. Here, it is shown thatbilayer metasurface can readily decouple optical amplitude and phase, thusachieving arbitrary complex-amplitude modulation only by arranging the orientationangles of nanostructures. In this design, each unit-pixel in one layerhas only one nanostructure with the same size, thus significantly increasingthe lateral resolution of complex-amplitude modulation. More importantly,the approach of controlling optical complex-amplitude merely by changingnanostructure orientation can significantly simplify the metasurface designand aggrandize the fabrication tolerance, thus enhancing the robustness ofmetasurfaces toward practical applications.