Miniature Magneto-Optical Trap Enabled by Integrated Nanophotonic Metasurfaces and Gratings

Cold and ultracold atoms are premier platforms for quantum-enhanced sensing, timing, and navigation; however, traditional magneto-optical traps (MOTs) rely on bulky assemblies of beam splitters, polarizers, and waveplates, which hinder their miniaturization. We aim to demonstrate a compact nanophotonic–atomic platform that integrates a diffractive grating MOT (GMOT) with multifunctional metasurfaces to efficiently cool and trap ⁸⁷Rb atoms in a centimeter-scale volume. A crystalline-silicon metasurface simultaneously functions as a quarter-wave plate and beam expander, achieving high polarization purity and near-unity transmission. The metasurface-manipulated beam illuminates a 2D diffraction grating, forming a five-beam GMOT with 24% first-order diffraction efficiency and 99.7% correct circular handedness. We expect this integrated architecture to support atom-loading rates above 10⁶ atoms/s and ~200 μK temperatures –performance comparable to bulk MOTs but in a package over 100× smaller. This on-chip integration eliminates the need for complex optical alignments, paving the way for scalable cold-atom arrays and hybrid photonic–atomic architectures. The resulting cold-atom ensemble provides a path toward chip-scale quantum sensors, optical lattices, and single atom trapping and manipulation.