2004/08/18 by Timo A. Nieminen, Norman R. Heckenberg, N. R. Heckenberg +5
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #FOS: Physical sciences #Laser-Matter Interactions and Applications #Optics (physics.optics) #Orbital Angular Momentum in Optics #Spectroscopy Techniques in Biomedical and Chemical Research #physics.optics
paper · pdf · doi:10.48550/arxiv.physics/0408080
4 pages, 3 figures
arxiv created 2004/08/18 · openalex publication_date 2004/08/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A circularly polarized rotationally symmetric paraxial laser beams carries hbar angular momentum per photon as spin. Focussing the beam with a rotationally symmetric lens cannot change this angular momentum flux, yet the focussed beam must have spin less than hbar per photon. The remainder of the original spin is converted to orbital angular momentum, manifesting itself as a longitudinal optical vortex at the focus. This demonstrates that optical orbital angular momentum can be generated by a rotationally symmetric optical system which preserves the total angular momentum of the beam.