Ultra-thin optical vortex phase plate based on the L-shaped nanoantenna for both linear and circular polarized incidences

• We have designed a VPP suitable for both CP and LP incidence simultaneously.
• The phase and amplitude can be decided by the length and width of the the L-shaped nanoantenna unit.
• The "SAM-to-OAM conversion" can be achieved for the VPP with the topological number of ll=±2 under the incidence of CP lights.
• The VPP shows a superior broadband characteristic.

Based on the L-shaped gold nanoantennas, the ultra-thin optical vortex phase plates (VPPs) have been designed to generate the optical vortex beams with different topological charges, which are independent of the incident polarization states and suitable for both X/Y linear and circular polarization incidences simultaneously. The phase and amplitude of transmitted cross-polarization light can be simultaneously manipulated by changing two degrees of freedom (the length and the width) in the L-shaped nanoantenna unit. Evolution properties of the generated vortex beam are demonstrated and analyzed. The different interactions of angular momentums between light and the VPP in the different incident polarization states have also been investigated fully. The designed VPP shows a superior broadband characteristics in near-infrared wavelength ranging from 750 nm to 1200 nm, which enable a potential implication for integrated optics and vortex optics.