Fig. 2: Transmittance of radial gratings and spiral-like structures (SLSs) with sinusoidal amplitude profiles.

a Sinusoidal amplitude radial grating and SLSs with m = 10, b sinusoidal amplitude structures with m = 30, for various values of L. i corresponds to radial gratings, while ii–iv correspond to SLSs. Additional examples, including binary profiles and further variations of L, are provided in Fig. S1.