Large-area optical metasurface fabrication using nanostencil lithography

We demonstrate a large-area fabrication process for optical metasurfaces utilizing reusable SiN on Si nanostencils. To improve the yield of the nanostencil fabrication, we partially etch the front-side SiN layer to transfer the metasurface pattern from the resist to the nanostencil membrane, preserving the integrity of the membrane during the subsequent potassium hydroxide etch. To enhance the reliability and resolution of metasurface fabrication using the nanostencil, we spin coat a sacrificial layer of resist to precisely determine the gap between the nanostencil and the metasurface substrate for the subsequent liftoff. 1.5 mm diameter PbTe meta-lenses on CaF2 fabricated using nanostencils show diffraction-limited focusing and focusing efficiencies of 42% for a 2 mm focal length lens and 53% for a 4 mm focal length lens. The nanostencils can also be cleaned using chemical cleaning methods for reuse. (C) 2021 Optical Society of America

Automated summary

This study demonstrates a large-area fabrication process for optical metasurfaces using reusable SiN on Si nanostencils, improving efficiency and reliability through methods such as partial etching of SiN layer and spin coating of sacrificial layer resist. The fabricated PbTe meta-lenses on CaF2 exhibit diffraction-limited focusing and high focusing efficiencies, showcasing the potential of nanostencils for metasurface fabrication.