Fig. 6

Fiber- and waveguide-integrated metalenses. Fiber-integrated metalenses: a Schematic of a high-NA metafiber system. (inset) Measured focal plane in water (scale bar = 500 nm). b SEM image of integrated metalens (scale bar = 25 μm). (a) and (b) are reproduced with permission [76] (Copyright 2021, Springer Nature). c (top) Optical and (bottom) SEM images of achromatic metafiber. (d) SEM image of fabricated metalens on fiber end face. (e) Measured transverse FWHM and axial focal positions at different wavelengths. c-e are reproduced with permission [80] (Copyright 2022, Springer Nature). Waveguide-integrated metalenses: f Waveguide-integrated one-dimensional resonance-phase-based metalens. g Experimental intensity distribution of metalens. Field-emission SEM image of waveguide and metalens (inset). f and g are reproduced with permission [86] (Copyright 2020, American Association for the Advancement of Science). h Waveguide-integrated two-dimensional metalens. (inset) SEM image of metalens (scale bar = 500 nm). Reproduced with permission [88] (Copyright 2022, American Chemical Society). i Waveguide-integrated metalens based on geometric phase. j Simulated intensity distribution above one-dimensional metalens with (left) resonant phase and (right) geometric phase. i and j are reproduced with permission [87] (Copyright 2021, De Gruyter)