{
  "annotation_id": "359c8a15-55ad-43c3-8d86-c762db24e772",
  "date_created": "2026-03-02T18:00:52.610000Z",
  "date_modified": "2026-03-02T18:00:52.610000Z",
  "file_hash": "b02a24774293b69157874a69cdf536b06ca42490f60d7cb6e0e5d43c983042d2",
  "private": false,
  "record": {
    "abstract": "A circularly polarized rotationally symmetric paraxial laser beams carries\nhbar angular momentum per photon as spin. Focussing the beam with a\nrotationally symmetric lens cannot change this angular momentum flux, yet the\nfocussed beam must have spin less than hbar per photon. The remainder of the\noriginal spin is converted to orbital angular momentum, manifesting itself as a\nlongitudinal optical vortex at the focus. This demonstrates that optical\norbital angular momentum can be generated by a rotationally symmetric optical\nsystem which preserves the total angular momentum of the beam.",
    "arxiv_id": "physics/0408080",
    "authors": [
      "Timo A. Nieminen",
      "Norman R. Heckenberg",
      "Halina Rubinsztein-Dunlop"
    ],
    "categories": [
      "physics.optics"
    ],
    "title": "Angular momentum of a strongly focussed Gaussian beam",
    "url": "https://arxiv.org/abs/physics/0408080"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "43f6c6e3-2fd2-477c-a740-0dbf80c10f22",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}