Reconfigurable vortex beam generator based on the Fourier transformation principle

A method to generate the optical vortex beam with arbitrary superposition of orbital angular momentum (OAM) on photonic chip is proposed. The components of different OAMs can be controlled by the phases of incident light based on the Fourier transformation principle. A typical device composed of nine Fourier holographic gratings is illustrated, where the OAMs of the generated optical vortex beam can be controlled on-demand from -2nd to 2nd and the working bandwidth is about 80 nm. Our work provides a feasible method to manipulate the vortex beam or detect arbitrary superposition of OAMs in the integrated photonics.