Invited Paper
Photonic Transport Control by Spin-Optical Gradient Metasurface

Photonic gradient metasurfaces are ultrathin electromagnetic wave-molding metamaterials that provide a route for realizing flat optics. Recently, we reported on a novel class of metasurfaces – spinoptical metamaterials – which gives rise to a spin-controlled dispersion due to the optical Rashba effect. The optical spin as an additional degree of freedom offers controlled manipulation of spontaneous emission, absorption, scattering, and surface-wave excitation. Spin-symmetry breaking in nanoscale structures caused by spin-orbit interaction, leading to a new branch in optics – spinoptics is presented. The spin-based effects offer an unprecedented ability to control light and its polarization state in nanometer-scale optical devices, thereby facilitating a variety of applications related to nano-photonics. 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 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.

mehasman@technion.ac.il