Suppressing meta-holographic artifacts by laser coherence tuning

摘要

a Scanning electron microscope (SEM) image of a part of a meta-hologram comprised of 128 × 128 unit cells, each having 2 × 2 silicon nanopillars of the same diameter D. The spatial phase modulation is achieved by varying D from 142 to 366 nm. Inset: magnified view of the silicon nanopillars revealing surface roughness which causes unwanted scattering and interference of light. b (left) Designed phase map φH of a small meta-hologram comprised of 8 × 8 unit cells, based on the calculated phase response of individual nanopillars with different diameters. b (right) Actual phase response φA from a numerical simulation of the entire metasurface, showing a significant deviation from the designed one due to near-field interactions among neighboring nanopillars. c, d Holographic images of a star object generated by two fabricated meta-holograms with the same design shown in (a). Their intensity fluctuations are nearly identical, indicating that the fluctuations result mainly from deterministic interactions among meta-atoms. Optical vortices are already eliminated from the computer-generated hologram. The illumination source is a monochromatic laser at wavelength λ = 1064 nm, which has a high spatial and temporal coherence