Angewandte Naturwissenschaften und WirtschaftsingenieurwesenZeitschriftenartikel
K. O'Holleran, Florian Flossmann, M. Padgett, M. Dennis
Fractality of light's darkness
Physical Review Letters - moving physics forward, vol. 100, no. 053902
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Natural light fields are threaded by lines of darkness. For monochromatic light, the phenomenon is familiar in laser speckle, i.e., the black points that appear in the scattered light. These black points are optical vortices that extend as lines throughout the volume of the field. We establish by numerical simulations, supported by experiments, that these vortex lines have the fractal properties of a Brownian random walk. Approximately 73% of the lines percolate through the optical beam, the remainder forming closed loops. Our statistical results are similar to those of vortices in random discrete lattice models of cosmic strings, implying that the statistics of singularities in random optical fields exhibit universal behavior.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenZeitschriftenartikel
Florian Flossmann, K. O'Holleran, M. Padgett, M. Dennis
Polarization Singularities in 2D and 3D Speckle Fields
Physical Review Letters - moving physics forward, vol. 100, no. 203902
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The 3D structure of randomly polarized light fields is exemplified by its polarization singularities: lines along which the polarization is purely circular (C lines) and surfaces on which the polarization is linear (L surfaces). We visualize these polarization singularities experimentally in vector laser speckle fields, and in numerical simulations of random wave superpositions. Our results confirm previous analytical predictions [M. R. Dennis, Opt. Commun. 213, 201 (2002)] regarding the statistical distribution of types of C points and relate their 2D properties to their 3D structure.