Fig. 1. (a) Schematic diagram of the wide-angle metalens, which focuses the beam from the angle of θ to the focal point with lateral shift of f·tan θ; (b) evolution of the target value (focal spot peak intensity) with the number of optimization iterations for the wide-angle and narrow-angle metalenses; (c) 3D printed narrow-angle metalens (left) and wide-angle metalens (right).

Fig. 2. (a), (b) Simulated intensity distribution in the x–y plane for (a) the narrow-angle metalens and (b) the wide-angle metalens at incident angles of 0°, 10°, and 20°; (c), (d) measured intensity distribution in the x–y plane for (c) the narrow-angle metalens and (d) the wide-angle metalens at incident angles of 0°, 10°, and 20°; (e) schematic diagram of the experimental setup.

Fig. 3. (a) Focusing efficiency of two metalenses at different incident angles; (b) FWHM of two metalenses; MTF curves of (c) the narrow-angle metalens and (d) the wide-angle metalens.

Fig. 4. (a) Experimental setup for testing the object-image relation of the metalens; (b) details of the definition of the object distance and image distance for the point-to-point focusing; (c) on-axis ideal Gaussian object-image relation and the simulated and measured ones for the two metalenses.

Fig. 5. (a) Schematic diagram of off-axis point-to-point focusing; variation of (b) the image height x₂ and (c) the image distance y₂ for different x₁ and y₁.

Fig. 6. (a) Experimental setup for practical object imaging with a close look at the object; image of the object by the narrow-angle metalens in (b) simulation and (c) experiment; image of the object by the wide-angle metalens in (d) simulation and (e) experiment.