Generating in-Plane Optical Orbital Angular Momentum Beams With Silicon Waveguides

A simple on-chip integrated structure is proposed to generate optical orbital angular momentum (OAM) beams, where only silicon waveguides and couplers are involved. The operating principle is based on mode converting and proper controlling the phase shift of second-order propagating mode so that OAM modes with charge numbers of 1 or -1 can be selectively generated with mode purity > 90%. The proposed device is very compact with footprint of