{
  "annotation_id": "7788cda3-1aa4-428d-bd51-4138d8f136fe",
  "date_created": "2026-03-02T18:01:14.694000Z",
  "date_modified": "2026-03-02T18:01:14.694000Z",
  "file_hash": "a90e9ff6c9017f237c4ae464201365b2e008b09f000edcd036653761fd52118b",
  "private": false,
  "record": {
    "abstract": "This dissertation is concerned with understanding and analyzing some of the\neffects of diffraction in the near field. The contributions of homogeneous and\nof evanescent waves to two-dimensional near-field diffraction patterns of\nscalar fields are examined in detail. Exact relations are obtained for\ncalculating these contributions for arbitrary propagation distances, along with\napproximate expressions for the near field. The behavior of the two\ncontributions is illustrated for the case of a plane wave diffracted by a slit\nin an opaque screen. The finite-difference time-domain (FD-TD) method is used\nexamine the influence of exact boundary values on the near field for the case\nof a slit in a thin perfectly conducting screen. The FD-TD numerical results\nare displayed in color images that illustrate the intricate behavior of the\namplitude and the phase of the field in the vicinity of the slit. These\nnumerical results are compared with the predictions of approximate theories.\nSome new methods for determining near-fields in rigorous diffraction problems\ninvolving thin screens are discussed. Specifically, new approximate theories of\ndiffraction are introduced for both scalar and electromagnetic fields and an\niterative Fourier-based algorithm is proposed for solving the rigorous boundary\nvalue problem. In order to understand the effects of an optical vortex on\ndiffraction, the field emerging from a spiral phase plate illuminated by a\nGaussian beam is examined. It is shown that the amplitude profile of the\nemerging field changes appreciably over propagation distances that are much\nsmaller than the Rayleigh range.",
    "arxiv_id": "physics/0610191",
    "authors": [
      "Marek W. Kowarz"
    ],
    "categories": [
      "physics.optics",
      "physics.comp-ph"
    ],
    "title": "Diffraction Effects in the Near Field",
    "url": "https://arxiv.org/abs/physics/0610191"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "49955268-db60-4df2-9586-716677c1a8c4",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}