Photonic Crystal Slab Metalens

We report a highly efficient broadband metalens design based on an amorphous silicon photonic crystal slab structure with a center wavelength of 940 nm. The structure is an ideal candidate for large area phase manipulation with compact, reliable, and low aspect ratio patterning on a thin film. Simulation results show continuous 2π transmission phase control by tuning the air hole filling size near the degenerate band edge, and the metalens structure is achieved with efficiency above 80% and the operation wavelength over 100 nm.