Generation of Orbital Angular Momentum by a Point Defect in Photonic Crystals

Being able to generate orbital angular momentum (OAM) of light enables infinite communication channels for either classical or quantum optical communication, in principle, but this neat trick is held back by technical challenges when integrated with other designs. The authors present a physical mechanism to produce OAM-carrying vortex waves via a point defect in a three-dimensional photonic crystal, plus an interesting scheme to convert guided waves in a line defect to localized waves in a point defect, and then to radiated vortex waves in free space. This approach will impact engineering solutions for scalable, on-chip OAM generation.