Spatiotemporal Vortex Pulses: Angular Momenta and Spin-Orbit Interaction

Recently, spatiotemporal optical vortex pulses carrying a purely transverse intrinsic orbital angular momentum were generated experimentally [{\it Optica} {\bf 6}, 1547 (2019); {\it Nat. Photon.} {\bf 14}, 350 (2020)]. However, an accurate theoretical analysis of such states and their angular-momentum properties remains elusive. Here we provide such analysis, including scalar and vector spatiotemporal Bessel-type solutions as well as descrption of their propagational, polarization, and angular-momentum properties. Most importantly, we calculate both local densities and integral values of the spin and orbital angular momenta, and predict observable spin-orbit interaction phenomena related to the coupling between the trasnverse spin and orbital angular momentum. Our analysis is readily extended to spatiotemporal vortex pulses of other natures (e.g., acoustic).