Review for optical metalens based on metasurfaces: fabrication and applications.

Metalens is the next generation of optical metasurfaces for compact imaging, sensing, and display applications that allow the phase, polarization, frequency, amplitude, angular momentum, etc. of the incident light to be designed with high degrees of freedom to meet the application requirements, which has attracted broad interest in the field of planar optics. One significant challenge in implementing applications for metalens is the efficient fabrication of large-scale nanostructures with high resolution, robustness and uniform patterning. In this review, we first introduced the manufacturing techniques compatible with metasurfaces fabrication in detail, including masked lithography, maskless lithography, and additive manufacturing, discussed the limitations and provided some insights. Next, we introduced the applications of metalens from the perspective of non-imaging and imaging optics fields. Metalens can enhance the illumination effect, shape beams, and improve the energy conversion efficiency in non-imaging optics. In imaging optics, the role of metalens in replacing traditional optical components in lithography, astronomical observation, microscopic and endoscopic systems is demonstrated. Finally, the challenges that the metalens facing on the road to commercial application are discussed, and the field's future development is prospected.