Ultrafast Laser-Induced Metasurfaces for Geometric Phase Manipulation

Direct-write femtosecond laser nano-structuring of 300 nanometer thick a-Si:H films results in space-variant functional metasurfaces with form bire-fringence of up to Delta n approximate to -0.5. Engineering the orientation of local optical axis allows implementing continuous phase profiles of nearly any optical element including arrays of polarization micro-converters and microlenses, polarization gratings, and computer-generated holograms with continuous phase gradients of approximate to 1 rad mu m(-1).