Spin angular momentum of photons and the associated polarization of light has been known for many years. However, it is only over the last decade or so that physically realizable laboratory light beams have been used to study the orbital angular momentum of light. In many respects, orbital and spin angular momentum behave in a similar manner, but they differ significantly in others. In particular, orbital angular momentum offers exciting new possibilities with respect to the optical manipulation of matter and to the study of the entanglement of photons.Bringing together 44 landmark papers, "Optical Angular Momentum" offers the first comprehensive overview of the subject as it has developed. It chronicles the first decade of this important subject and gives a definitive statement of the current status of all aspects of optical angular momentum. In each chapter, the editors include a concise introduction, putting the selected papers into context and outlining the key articles associated with this aspect of the subject.