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Photonic gradient metasurfaces are ultrathin electromagnetic wave-molding metamaterials that provide a route for realizing flat optics. However, the up-to-date metasurface design, manifested by imprinting the required phase profile for a single, on-demand light manipulation functionality, is not compatible with the desired goal of multifunctional flat optics. Here, we report on a generic concept to control multifunctional optics by disordered (random) gradient metasurfaces with a custom-tailored geometric phase. This approach combines the peculiar ability of random patterns to support an extraordinary information capacity and the polarization helicity control in the geometric phase mechanism, simply implemented in a two-dimensional structured matter by imprinting optical antenna patterns. By manipulating the local orientations of the nanoantennas, we generate multiple wavefronts with different functionalities via mixed random antenna groups, where each group controls a different phase function. Disordered gradient metasurfaces broaden the applicability of flat optics, as they offer all-optical manipulation by multitask wavefront shaping via a single ultrathin nanoscale photonic device.
Veksler et al. (2015) studied this question.