Fig. 3: Fabrication of ODLM-based CPL filters.
a Schematic illustration of major fabrication steps. b Scanning electron microscope (SEM) image of the nanograting before QWP metasurface integration. c SEM image of silicon QWP. d Cross section of grating covered by fused silica. The fringes on the surface of the SiOx spacer layer reflect the underlying grating thickness and duty cycle. e, f Atomic force microscope (AFM) images of the nanograting after PVD deposition of SiOx (~350 nm), indicating mitigated surface roughness (Ra = 11.5 nm). g Tilted-view SEM image of ODLM structure. The bright thin layer on top of each Si QWP pillar corresponds to residual SiOx mask. All the SEM scale bars are 1 µm, and the AFM scale bar is 0.5 µm
