  Optical metasurfaces, consisting of subwavelength-scale meta-atom arrays,
hold great promise to overcome fundamental limitations of conventional optics.
Scalable nanomanufacturing of metasurfaces with high uniformity and
reproducibility is key to transferring technology from laboratory
demonstrations to commercialization. Recently, nanoimprint lithography (NIL)
has attracted increasing interests for metasurface fabrication because of its
superior nanometer resolution, rapid prototyping and large-area manufacturing
capability. Despite NIL demonstrations of single-layer metasurface, scalable
fabrication of double- and multi-layer metasurfaces remains challenging. Here
we leverage the nanometer-scale resolution and 3D pattern transfer capability
of NIL to fabricate multi-layered metasurfaces for on-chip polarimetric imaging
devices. Our process achieved sub-100 nm nanostructures, high alignment
accuracy (translational error <200 nm; rotational error <0.02{\deg}), and good
uniformity (<4 nm linewidth deviation) over >20 mm2. This NIL-based, low-cost
and high-throughput nanomanufacturing approach paves the way toward scalable
production of a plethora of metasurface structures for ultra-compact optic and
optoelectronic devices and systems.
