Full Complex-Amplitude Engineering by Orientation-Assisted Bilayer Metasurfaces

摘要

Optical complex-amplitude determines the propagation behavior of light in free space to the maximum extent. Precise control of complex-amplitude is the key to generating user-defined light fields. Current attempts to control optical complex-amplitude using metasurface, however, either have limited amplitude/phase step numbers or lost high lateral resolution since amplitude and phase are usually manipulated with size-varied nanostructures or several nanostructures integrated into a unit-pixel. Here, it is shown that bilayer metasurface can readily decouple optical amplitude and phase, thus achieving arbitrary complex-amplitude modulation only by arranging the orientation angles of nanostructures. In this design, each unit-pixel in one layer has only one nanostructure with the same size, thus significantly increasing the lateral resolution of complex-amplitude modulation. More importantly, the approach of controlling optical complex-amplitude merely by changing nanostructure orientation can significantly simplify the metasurface design and aggrandize the fabrication tolerance, thus enhancing the robustness of metasurfaces toward practical applications.

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