Inverse design of arbitrary optical helicity patterns

Superposing multiple plane waves can generate helicity lattices, in which the optical helicity varies regularly in space. Here we propose an inverse design method for constructing arbitrary helicity structures based on placing a digital structure of dielectric inclusions in three-dimensional space. We apply the method to design structures that reproduce two-dimensional lattices embedded within a three-dimensional region using only a single plane wave as an input. In order to demonstrate the power and flexibility of our method, we go beyond the paradigm of a regular lattice and propose structures which can create arbitrary images consisting of regions of varying helicity, again using only a single plane wave as an input.