METAMATERIALS

Broadband achromatic lens

Light Sci. Appl. 7, 85 (2018)

Polarization-independent, achromatic metalenses that operate across a broad window in the near-infrared have been developed and tested by Sajan Shrestha and co-workers from Columbia University and Brookhaven National Laboratory in the USA. The key innovation behind the design of the lenses is the use of suitable meta-units — the building blocks of metasurfaces — to provide diverse phase dispersions. As a proof-of-principle demonstration, a dielectric metasurface platform of amorphous silicon nanostructures on a quartz substrate was employed. Based on the numerical simulation of the phase dispersion for each meta-unit, metalenses composed of the three meta-units, singular pillers, annular pillars and concentric pillars with a height of 1,400 nm, were built. The lenses were experimentally characterized by passing a tunable beam from a supercontinuum laser source through a monochrometer and to the metalens. The three-dimensional intensity distribution around the focal point was then measured by acquiring a stack of two-dimensional images at different distances from the metalens. A focused beam diameter of 200 μm was consistently obtained at a focal distance of 800 μm (numerical aperture of about 0.13) over the wavelength range of 1,200–1,650 nm. The beam diameter was nearly diffraction-limited with no obvious distortion.

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Correspondence to Noriaki Horiuchi.

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Horiuchi, N. Broadband achromatic lens. Nature Photon 13, 72 (2019). https://doi.org/10.1038/s41566-019-0352-3

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