Speckle-based 3D sub-diffraction imaging of sparse samples through a multimode fiber

Resolving structural misalignments on the nanoscale is of utmost importance in areas such as semiconductor device manufacturing. Metaphotonics provides a powerful toolbox to efficiently transduce information on the nanoscale into measurable far-field observables. In this work, we propose and demonstrate a novel interlaced displacement sensing platform based on diffractive anisotropic metasurfaces combined with polarimetric Fourier microscopy capable of resolving a few nanometer displacements within a device layer. We show that the sensing mechanism relies on an interplay of Pancharatnam-Berry and detour phase shifts and argue how nanoscale displacements are transduced into specific polarization signatures in the diffraction orders. We discuss efficient measurement protocols suitable for high-speed metrology applications and lay out optimization strategies for maximal sensing responsivity. Finally, we show that the proposed platform is capable of resolving arbitrary two-dimensional displacements on a device.