Fig. 8
Color focusing imaging applications of metalenses. (a) Left panel: SEM image from a region of the metacorrector, made of TiO2 nanofins on a glass substrate. Scale bar: 500 nm. The inset shows an oblique view (scale bar: 200 nm). Middle panel: ray diagram at λ = 560 nm. The metacorrector with the diameter of 4 mm is placed at the entrance aperture of the objective. The objective consists of 14 lenses made of 7 different glasses. Right panel: a comparison of imaging under white light illumination with and without the metacorrector [81]. (b) Left panel: SEM image of a part of the fabricated metalens. Scale bar: 1 μm. Inset: a magnified view of the nanofins. Scale bar: 500 nm. Middle panel: the focal spot profile, with the top and bottom rows corresponding to the diode (monochromatic) and tunable broadband laser illumination, respectively. Scale bars: 2 μm. Right panel: imaging with the achromatic metalens. The pattern corresponding to number 6 has a linewidth of 8.77 μm [82]. Scale bars: 40 μm. (c) Left panel: schematic of a metasurface comprising an array of nanoposts. Middle panel: optical images of the singlet metasurface lens (upper raw) and the extended depth of focus device (lower raw). Right panel: imaging under white light [83]