Multifunctional interleaved geometric-phase dielectric metasurfaces

Shared-aperture technology for multifunctional planar systems, performing several simultaneous tasks, was first introduced in the field of radar antennas. In photonics, effective control of the electromagnetic response can be achieved by a geometric-phase mechanism implemented within a metasurface, enabling spin-controlled phase modulation. The synthesis of the shared-aperture and geometric-phase concepts facilitates the generation of multifunctional metasurfaces. Here shared-aperture geometric-phase metasurfaces were realized via the interleaving of sparse antenna sub-arrays, forming Si-based devices consisting of multiplexed geometric-phase profiles. We study the performance limitations of interleaved nanoantenna arrays by means of a Wigner phase-space distribution to establish the ultimate information capacity of a metasurface-based photonic system. Within these limitations, we present multifunctional spin-dependent dielectric metasurfaces, and demonstrate multiple-beam technology for optical rotation sensing. We also demonstrate the possibility of achieving complete real-time control and measurement of the fundamental, intrinsic properties of light, including frequency, polarization and orbital angular momentum. Nanoantennas that alter the phase of optical signals using geometric parameters bring multiple light-shaping capabilities to a single device. Erez Hasman from the Technion — Israel Institute of Technology and co-workers patterned silicon surfaces into a two-dimensional array of interspersed nanorods to promote both geometric phase modulation and sharing of nanoantenna aperture space. While this approach enables control over photonic spin and wavefront generation, it also creates speckle noise that can affect performance. The team used Wigner distributions, a quantum-based signal analysis method, to determine the ultimate information capacities of channels within geometric phase metasurfaces. Their evaluations propose ways to combine data-carrying optical angular momentum (OAM) beams with swirling light vortices into a device that could simultaneously determine the frequency, polarization, and OAM of light at different wavelengths.