Fig. 5. High-NA metalenses with methods relaxing the lattice constraints.

a The schematic of the a-Si metalens (NA ~0.99) achieved by asymmetric scattering of dimer nanoantennas, and its application in a confocal map of photoluminescence. Reproduced with permission⁴⁹. Copyright 2018, American Chemical Society. b The metalens (NA ~0.85) functionalized homemade two-photon direct laser lithography setup. Reproduced with permission⁵⁰. Copyright 2021, American Chemical Society. c Metalens-based (NA ~0.88) fiber tip for optically trapping. Reproduced with permission⁵². Copyright 2021, the Authors, published by Springer Nature