Figure 4. Broadband and wide-angle plasmonic metasurface-based quarter-wave plate.

(a) Tilted 3D view of the metasurface-based quarter-wave plate. A circularly-polarized wave incident from an angle of (θ_i, ϕ_i = 0°) is converted into a linearly-polarized wave upon reflection. Inset shows the polarization of the reflected and incident waves in the plane perpendicular to the wave vector. The angle between the electric field and the plane of incidence of the reflected light is 45°. (b) Unit cell configuration of the optimized quarter-wave plate. The dimensions are a_x = 180, a_y = 90, p_x = 240, p_y = 282, t_m = 40, t_d = 150, t_m2 = 100 (all in nm). (c) Top-view FESEM image of a portion of the fabricated nanostructure showing the nanorod array. Scale bar: 400 nm. The inset shows the magnified top view of two by three unit cells. Scale bar: 100 nm. (d) Theoretically predicted and experimentally measured polarization conversion ratio (PCR) and reflection magnitue (Refl. Mag.) as a function of wavelength at different angles of incidence (4°, 20°, 40°). (e) Theoretically predicted and experimentally measured polarization state in the plane perpendicular to the wave vector at 700, 900, and 1150 nm for different angles of incidence (4°, 20°, 40°).