Fig. 2. Numerical simulation of the metasurfaces.
(A) Top view and (B) perspective view of one metastructure. P = 300 nm and h = 1000 nm. (C) Simulated results of the polarization conversion efficiency a(λ) (red and black lines) and propagation phase φ(λ) (blue and green lines) with two different sizes of GaN nanopillars. Red and blue curves: Lu1 = 170 nm and Lv1 = 70 nm. Black and green curves: Lu2 = 220 nm and Lv2 = 120 nm. (D) Calculated azimuth angle and ellipticity angle of the output polarization and (E) the corresponding SoP on Poincaré sphere as a function of incident wavelength from 475 to 675 nm with dispersive superposition consisting of two different sizes of GaN nanopillars with zero SOA, indicating that the traditional linear superposition of opposite polarization leads to dispersive polarization response. (F) Calculated azimuth and ellipticity angles of the output polarization and (G) the corresponding SoP on Poincaré sphere as a function of incident wavelength from 475 to 675 nm with the proposed nondispersive superposition consisting of a uniform size of GaN nanopillars with Lu2 = 220 nm, Lv2 = 120 nm, δL1 = 0°, δR1 = 22.5°, and δR2 = 22.5°, indicating that an assembly of a generic building block could realize broadband polarization-maintaining behavior with unlimited bandwidth.