  Complex non-local behavior makes designing high efficiency and
multifunctional metasurfaces a significant challenge. While using libraries of
meta-atoms provide a simple and fast implementation methodology, pillar to
pillar interaction often imposes performance limitations. On the other extreme,
inverse design based on topology optimization leverages non-local coupling to
achieve high efficiency, but leads to complex and difficult to fabricate
structures. In this paper, we demonstrate numerically and experimentally a
shape optimization method that enables high efficiency metasurfaces while
providing direct control of the structure complexity. The proposed method
provides a path towards manufacturability of inverse-designed high efficiency
metasurfaces.
