Fig. 1. Schematic illustration of the broadband high-efficiency metalens composed of quasi-continuous nanostrips.

Fig. 2. (a) The structure and phase distribution of the designed metalens. The inset shown in the low panel is the phase distribution along the white dotted line. (b) The higher magnified image of the quasi-continuous metalens and the correlative scale bar is 3 μm. (c) SEM image of part of the fabricated metalens sample. scale bar: 3 μm.

Fig. 3. (a) Experimental setup for measuring the quasi-continuous metalens. Abbreviations for the optical components: LP, linear polarizer; QWP, quarter waveplate; CCD, charge coupled device. (b) Measured cross-polarized intensity distributions along the propagation direction at the wavelength of 632.8 nm. The up and down panels correspond to x-z plane and y-z plane, respectively. (c–i) The intensity profiles on the focal plane for different wavelengths incidence. The position of the focal plane and the incident wavelengths have been marked. The curves on the upper and right sides depict the intensity distributions along x-axis and y-axis, respectively. All intensities have been normalized.

Fig. 4. (a) The phase distribution and the designed quasi-continuous structure of the superoscillatory lens. (b) The lens phase profile (up panel) and binary super-oscillation phase (down panel) along the radial direction. π-phase-jump at positions r₁=0.175R, r₂=0.406R and r₃=0.645R. (c) The SEM image of the fabricated superoscillatory lens. (d) The measured cross-polarized intensity distributions along z-axis at the wavelength of 632.8 nm. (e–k) The intensity distributions on the focus plane for different wavelengths incidence. The curves on the upper and right sides represent the intensity distributions along x-axis and y-axis, respectively. The incident wavelengths and the measured focus plane are labelled in the figures.

Fig. 5. The power efficiency in the simulation and experiments. The simulated results for P (period) [the distance between adjacent nanostrips] changing from 160 nm to 300 nm are shown in the blue region. The red diamonds and the black squares are the experimental efficiencies for metalens and superoscillatory lens, respectively, which have been marked in the figure.