Fig. 4. Giant optical chirality.
(A and B) SEM images of (A) 2D and (B) 3D pinwheel array with periodicity of 1.45 μm. The height of the 3D pinwheels is about 380 nm. (C) Top-view SEM images of LH and RH 3D pinwheel arrays. Scale bars, 1 μm. (D) Measured CD in transmission [defined as CDT = (TL − TR)/(TL + TR)] versus wavelength for 2D LH, 3D LH, and 3D RH pinwheels, respectively. a.u., arbitrary units. (E) Measured (circular points) and calculated (solid lines) linear polarization rotation angle (θ) versus wavelength for 3D and 2D LH pinwheels, respectively. The unrealistic abrupt peaks around 1.45 μm in calculation are not shown for clearance because of the inaccurate retrieval of polarization states at nearly zero transmission at Wood’s anomaly (see full calculated data in fig. S9). Inset: Schematic of the linear polarization rotation. (F) Polar plot of (top) experimental and (bottom) calculated transmission versus detection polarization angle at specific wavelengths under x-polarized incidence for the 3D LH pinwheels. Nearly linearly polarized states are observed. In comparison, for wavelengths in the strong CD region (around 1.45 μm), the measured transmission of light exhibits elliptical polarization states (fig. S9H). Spectra are measured from 1.1 to 2 μm because of the restriction of the quarter-wave plate (see Materials and Methods).