Figure 1 | Establishment of the thickness bound. (IMAGE)
Caption
a, Schematic of a metalens with a hyperbolic phase profile. It can have subwavelength thickness and produces a diffraction-limited focal spot at normal incidence but suffers from strong aberrations at oblique incidence. b, Schematic of a diffraction-limited lens system with a wide FOV. It achieves diffraction-limited focusing over a wide range of incident angles but requires a larger thickness h. c, Examples of systems that realize wide-FOV diffraction-limited focusing. The transmission matrix (d) in angular basis and (e) in spatial basis, for a hyperbolic metalens. This basis conversion can be realized through Fourier transform and inverse Fourier transform. f, Intensity profile inside the metalens given a localized input at the center of the metalens, corresponding to the middle column of the spatial transmission matrix. The lateral spreading is the difference between the output width and the input width. The output width is also the vertical width of the near-diagonal elements of the spatial transmission matrix. Transmission matrices of ideal lens systems with (g) small FOV and (h) large FOV. Increasing the FOV increases the lateral spreading, which requires a larger thickness to achieve it.
Credit
by Shiyu Li and Chia Wei Hsu
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CC BY