  Metalenses, artificially engineered subwavelength nanostructures to focus
light within ultrathin thickness, promise potential for a paradigm shift of
conventional optical devices. However, the aperture sizes of metalenses are
usually bound within hundreds of micrometers by the commonly-used
scanning-based fabrication methods, limiting their usage on practical optical
devices like telescopes. Here, for the first time, we demonstrate a
high-efficiency, single-lens, refractive metalens telescope. We developed a
mass production-friendly workflow for fabricating wafer-scale (80-mm aperture)
metalenses using deep-ultraviolet (DUV) photolithography and a multi-exposure
process involving reticle rotation and pattern stitching to leverage the radial
symmetry of metalenses. Our metalens works in the near-infrared region (1200 -
1600 nm) with diffraction-limited performance and a high peak focusing
efficiency of 80.84% at 1450 nm experimentally. Based on the metalens, we built
a single-lens telescope and acquired images of the lunar surface, revealing its
geographical structures. We believe our demonstration of the metalens telescope
proves the exciting potential lying in the metasurfaces and could bring new
possibilities for areas involving large optical systems, including geosciences,
planetary observation, and astrophysical science.
