Rotational Multiplexing Method Based on Cascaded Metasurface Holography

Since the emergence of optical metasurfaces, their outstanding wavefront modulation ability and numerous degrees of freedom (DOFs) have motivated many multiplexing methods, and many unprecedented functionalities and impressive advances have been achieved. However, the number of DOFs of single-layer metasurfaces is intrinsically limited. To further explore the innovative multiplexing dimensions and application scenarios of metasurfaces, multilayer and cascaded metasurfaces are proposed. Inspired by the alignment sensitivity of cascaded metasurface holography, here the authors use the in-plane rotation between two cascaded metasurfaces as an additional design DOF to introduce the concept of the rotational multiplexing method. An iterative gradient optimization scheme based on a machine learning method is developed to obtain the phase profiles. Dual working modes can be achieved, and both single-layer and rotational cascaded holography can be reconstructed in the far-field. Such versatile configurations may provide promising solutions for optical encryption, data storage, and dynamic display.