Fig. 3: Simulated results of metasurface with birefringent GaN nanopillars on sapphire substrate with dimension of P = 300 nm and h = 1 μm.
From: Broadband decoupling of intensity and polarization with vectorial Fourier metasurfaces
a Top view and b perspective view of one meta-structure. The numerical calculation is performed on unit cell of GaN nanopillar on sapphire substrate considering periodic boundary conditions on x and y. The width of the GaN nanopillar is fixed as Lv = 120 nm. c The simulated CP conversion by sweeping the length of the GaN nanopillar Lu from 150 to 260 nm in the wavelength range from 450 to 700 nm with zero rotation angle. The dash line represents the length of Lu = 210 nm. The purple star represents the wavelength at \(\lambda\) = 575 nm, which is the chosen point in d–f. d The simulated electric field distribution Ex at the plane of x = 0 and e Ey at the plane of y = 0. f By rotating the GaN nanopillars with an angle of δ from 0 to 180°, a near-unity CP conversion is shown in the black curve and a geometric phase from 0 to 360° is obtained. The simulated results are represented by the blue star, in very good agreement with the expected PB phase calculation (red curve).
