Volumetric Meta-Optics for Sorting Light By Color, Polarization and Angle of Incidence

Three-dimensional elements, with refractive index distribution structured at subwavelength scale, provide an expansive optical design space that can be harnessed for demonstrating multifunctional free-space optical devices. We present three dimensional dielectric elements, designed to be placed on top of the pixels of image sensors that provide multiple functionalities like sorting and focusing of light based on its color, polarization and incidence angle. The devices are designed via iterative gradient-based optimization to account for multiple target functions while ensuring compatibility with existing nanofabrication processes. This approach combines arbitrary functions into a single compact element, even where there is no known equivalent in bulk optics, enabling novel integrated photonic applications. We analyze how the device behaves for input parameters that it was not designed for and investigate how the arrangement of the pixels in the image plane affects the device performance. We present preliminary experimental data in the mid infrared.