Transverse orbital angular momentum: setting the record straight

Abstract: The nature of the transverse orbital angular momentum (tOAM) associated with spatiotemporal optical vortex (STOV) pulses has been the subject of recent debate. We demonstrate that the approaches to tOAM presented in several papers are incorrect and lead to unphysical results, including erroneous claims of zero total tOAM. We emphasize the importance of calculating the OAM of any extended physical object at a common instant of time, and reemphasize the special status of the centre of energy as a reference point for all OAM calculations. The theory presented in [Phys. Rev. Lett. 127, 193901 (2021)] is the only correct classical field-based framework that both agrees with experiments and provides a self consistent understanding of transverse OAM in spatiotemporal light fields.