From Planar to 3D Nanophotonic Lenses: Advancing Design, Fabrication, and Applications

Abstract

ABSTRACT Nanophotonic lenses are transformative optical elements for nanoscale light manipulation and miniaturized optical systems. For a given material platform, the finite thickness of a planar metalens limits the phase and group‐delay response available for simultaneously achieving high numerical aperture, broad bandwidth, and high focusing efficiency. This Review examines the transition from planar to three‐dimensional (3D) nanophotonic lenses for imaging and how added degrees of freedom expand the available optical design space. State‐of‐the‐art fabrication methods, with emphasis on two‐photon lithography, are discussed together with computational design strategies including topology optimization, evolutionary algorithms, and machine learning. Recent demonstrations show that this enlarged design space can support broadband focusing, aberration correction, depth‐of‐field control, and multichannel imaging. Key challenges in scalable fabrication, material development, and large‐scale inverse design are summarized as a roadmap for future 3D nanophotonic lenses.