Quantitative index metrology for 3D voxelated structures in photopolymer

Thanks to recent advances in two-stage photopolymers, it is now possible to dictate arbitrary 3D voxelated refractive index structures within a continuous volume of polymer, with dynamic range Δn in excess of 0.01 and with micron-scale spatial resolution. However, quantitative metrology for such structures remains an under-explored challenge. Here we demonstrate that TIE-based phase imaging, in conjunction with scanning confocal reflection microscopy, can achieve unambiguous quantitative characterization of arbitrary voxelated index structures. This characterization then guides the design, fabrication, and validation of novel optical components, including flexible gradient-index lenses for in situ medical imaging.