Advances in Orbital Angular Momentum Lasers

As we celebrate 30 years since light's orbital angular momentum (OAM) was connected to its spatial structure, we reflect on the advances made in fundamental science and applications alike. A driving trend in recent times has been the creation of OAM directly from lasers, for potentially tuneable, compact and high-power sources of OAM light. In this tutorial style review we give a summary of the basics of OAM and its creation at the source, pointing to the seminal advances that have been made, the present state-of-the-art, and the open challenges that remain.