  Metasurfaces enable precise control over the properties of light and hold
promise for commercial applications. However, fabricating visible metasurfaces
suitable for high-volume production is challenging and requires scalable
processes. Nanoimprint lithography is a cost-effective and high-throughput
technique that can meet this scalability requirement. This work presents a
mask-templating nanoimprint lithography process for fabricating metasurfaces
with varying fill factors and negligible wavefront aberrations using composite
stamps. As a proof-of-concept, a 6 mm diameter metalens formed of silicon
nitride nano-posts with a numerical aperture of 0.2 that operates at 550 nm is
demonstrated. The nanoimprinted metalens achieves a peak focusing efficiency of
($81\pm1$)%, comparable to the control metalens made with electron beam
lithography with a focusing efficiency of ($89\pm1$)%. Spatially resolved
deflection efficiency and wavefront data, which informs design and process
optimization, is also presented. These results highlight nanoimprint
lithography as a cost-effective, scalable method for visible metasurface
fabrication that has the potential for widespread adoption in consumer
electronics and imaging systems.
