Fig. 3: Focusing characterization of different lens designs.
From: Diffraction-limited imaging with monolayer 2D material-based ultrathin flat lenses
a Images of foci of lenses with different numbers of rings (N = 3–8). b Plot of the peak intensity of the focus versus N. c Resolution of the focus versus N. d Focal length versus N. e Focal length versus a1. f Resolution versus first ring radius a1
