Figure 5. Chromatic aberration of metasurface doublet lens and its correction.

(a) Illustration of focusing of wideband light by a metasurface doublet lens. The spectrum of the incident light (shown at the bottom) is assumed as a Gaussian function centred at the design wavelength of the doublet lens (850 nm). Simulated focal plane intensity for the metasurface doublet lens as a function of incident light's bandwidth for incident angles of 0° and 15° are shown on the right. Scale bar, 2 μm. (b) On-axis modulation transfer function (MTF) of the metasurface doublet lens for different bandwidth of incident light. The MTF is computed using the simulation results shown in a. (c) Image formed by the metasurface doublet lens with unfiltered LED illumination (40 nm FWHM bandwidth) and (d) with filtered LED illumination (10 nm FWHM bandwidth). Scale bar, 100 μm. See Supplementary Fig. 3 for the spectra. The images are captured using the setup shown in Fig. 4a but with a higher magnification objective ( × 20, 0.4 NA). (e) Result of chromatic aberration correction for the image shown in d. Scale bar, 100 μm. The insets in c–e show zoomed-in views of the images at the locations indicated by the rectangles with the same outline colours corresponding to viewing angles of 0° (red border) and 15° (green border), and the scale bars shown in the insets represent 10 μm. FWHM, full width at half maximum.