Miguel A. Porras ,Upper Bound to the Orbital Angular Momentum Carried by an Ultrashort Pulse. PHYSICAL REVIEW LETTERS 122, 0-5 (2019). DOI: 10.1103/PhysRevLett.122.123904
https://doi.org/10.1103/PhysRevLett.122.123904
https://doi.org/10.1103/PhysRevLett.122.123904
https://doi.org/10.1142/S0129626419500105
https://doi.org/10.1016/j.physa.2019.122116