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Metasurface optics for full-color computational imaging

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Science Advances  09 Feb 2018:
Vol. 4, no. 2, eaar2114
DOI: 10.1126/sciadv.aar2114
  • Fig. 1 Design, simulation, and fabrication of imaging metasurfaces.

    (A) The metasurfaces are made up of silicon nitride nanoposts, where the thickness T, lattice constant p, and diameter d are the design parameters. (B) Schematic of a metasurface comprising an array of nanoposts. (C) Simulation of the nanoposts’ transmission amplitude and phase via RCWA. Simulated intensity along the optical axis of the singlet metasurface lens (D) and EDOF metasurface (E), where, going from top to bottom in each panel, 400, 550, and 700 nm wavelengths are used. The dashed lines indicate the desired focal plane where the sensor will be placed. Optical images of the singlet metasurface lens (F) and the EDOF device (G). Scale bars, 25 μm.

  • Fig. 2 Characterization of the imaging metasurfaces.

    The PSFs of the singlet metalens (top row) and EDOF lens (bottom row) were measured under blue (A and E), green (B and F), and red (C and G) illumination conditions. Scale bars, 25 μm. The MTFs were also calculated for both designs (D and H). In both (D) and (H), a normalized frequency of 1 corresponds to the same cutoff frequency of 579 cycles/mm.

  • Fig. 3 Imaging at discrete wavelengths.

    The appropriately cropped original object patterns used for imaging are shown in (A) and (B). Images were captured of the 1951 Air Force resolution chart with the singlet metalens (C) and the EDOF lens without (D) and with deconvolution (E). Images were also taken of a binary Mona Lisa pattern with the singlet metalens (F) and the EDOF device without (G) and with deconvolution (H). Scale bars, 20 μm.

  • Fig. 4 Imaging with white light.

    Images were taken under white light illumination of color printed RGB (A) and ROYGBIV (B) text, a colored rainbow pattern (C), and picture of a landscape (D) with a blue sky, green leaves, and multicolor flowers. The appropriately cropped original object patterns used for imaging are shown in the left column. Scale bars, 20 μm.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/2/eaar2114/DC1

    section 1. Effect of the cubic phase strength α on image quality

    section 2. Image comparison for different deconvolution methods

    section 3. Assessing chromatic invariance by SSIM of images

    section 4. Comparison of theoretical and experimental MTFs with nonzero source bandwidth

    section 5. Off-axis metalens performance

    fig. S1. Transmission amplitude and phase of the nanoposts as a function of diameter.

    fig. S2. Transmission amplitude and phase of the nanoposts as a function of lattice constant and diameter.

    fig. S3. Scanning electron micrographs of the fabricated metasurfaces.

    fig. S4. Experimental setup for characterizing the focal plane.

    fig. S5. Experimental setup for imaging with metasurfaces.

    fig. S6. Images captured with systems of different cubic phase strength.

    fig. S7. Image quality comparison for different deconvolution methods.

    fig. S8. Comparison of theoretical and experimental MTFs with nonzero source bandwidth.

    fig. S9. Simulated off-axis performance of the singlet and EDOF metalenses.

    fig. S10. Efficiencies of the singlet and EDOF metalenses.

    Reference (40)

  • Supplementary Materials

    This PDF file includes:

    • section 1. Effect of the cubic phase strength α on image quality
    • section 2. Image comparison for different deconvolution methods
    • section 3. Assessing chromatic invariance by SSIM of images
    • section 4. Comparison of theoretical and experimental MTFs with nonzero source bandwidth
    • section 5. Off-axis metalens performance
    • fig. S1. Transmission amplitude and phase of the nanoposts as a function of diameter.
    • fig. S2. Transmission amplitude and phase of the nanoposts as a function of lattice constant and diameter.
    • fig. S3. Scanning electron micrographs of the fabricated metasurfaces.
    • fig. S4. Experimental setup for characterizing the focal plane.
    • fig. S5. Experimental setup for imaging with metasurfaces.
    • fig. S6. Images captured with systems of different cubic phase strength.
    • fig. S7. Image quality comparison for different deconvolution methods.
    • fig. S8. Comparison of theoretical and experimental MTFs with nonzero source bandwidth.
    • fig. S9. Simulated off-axis performance of the singlet and EDOF metalenses.
    • fig. S10. Efficiencies of the singlet and EDOF metalenses.
    • Reference (40)

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