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Suche nach „[M.] [Dennis]“ hat 6 Publikationen gefunden
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    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    U. Schwarz, Florian Flossmann, M. Dennis

    Topology of Generic Polarization Singularities in Birefringent Crystals

    Topologica, vol. 2, no. 006-1

    2009

    DOI: 10.3731/topologica.2.006

    Abstract anzeigen

    An optical vortex incident on a birefringent crystal unfolds into a complex topological structure of lines of circular polarization (C–lines) and surfaces of linear polarization (L–surfaces). The incident beam splits into two or-thogonally polarized beams of ordinary and extraordinary polarization. Ex-traordinary refraction causes a shift of the extraordinarily polarized beam even under normal incidence. This shift together with the different phase velocities of both beams is the origin of an intriguing pattern of polarization singularities. We measure spatially resolved the full set of Stokes parameters after the beam passed the crystal to determine experimentally the spatial structure of the polarization singularities in three dimensions, two spatial directions (x, y) and one (Λ) corresponding to the relative phase retarda-tion between ordinary and extraordinary beam. The observed unfolding of the initial phase singularity is the most generic case of the generation of polarization singularities in uniaxial or biaxial birefringent crystals. It can be describe in a very general way in terms of Stokes parameters where the polarization singularities arise naturally from the zeros of the Stokes param-eters.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    K. O'Holleran, Florian Flossmann, M. Dennis, M. Padgett

    Methodology for imaging the 3D structure of singularities in scalar and vector optical fields

    Journal of Optics, vol. 11, no. 0094020

    2009

    DOI: 10.1088/1464-4258/11/9/094020

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    K. O'Holleran, Florian Flossmann, M. Padgett, M. Dennis

    Fractality of light's darkness

    Physical Review Letters - moving physics forward, vol. 100, no. 053902

    2008

    Abstract anzeigen

    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 Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    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

    2008

    Abstract anzeigen

    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.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Florian Flossmann, U. Schwarz, M. Maier, M. Dennis

    Stokes parameters in the unfolding of an optical vortex through a birefringent crystal

    Optics Express, vol. 14, no. 23, pp. 11402-11411

    2006

    Abstract anzeigen

    Following our earlier work (F. Flossmann et al., Phys. Rev. Lett. 95 253901 (2005)), we describe the fine polarization structure of a beam containing optical vortices propagating through a birefringent crystal, both experimentally and theoretically.We emphasize here the zero surfaces of the Stokes parameters in three-dimensional space, two transverse dimensions and the third corresponding to optical path length in the crystal. We find that the complicated network of polarization singularities reported earlier – lines of circular polarization (C lines) and surfaces of linear polarization (L surfaces) – can be understood naturally in terms of the zeros of the Stokes parameters.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Florian Flossmann, U. Schwarz, M. Maier, M. Dennis

    Polarization Singularities from Unfolding an Optical Vortex through a Birefringent Crystal

    Physical Review Letters - moving physics forward, vol. 95, no. 1009

    2005

    DOI: 10.1103/PhysRevLett.95.253901

    Abstract anzeigen

    Optical vortices (nodal lines and phase singularities) are the generic singularities of scalar optics but are unstable in vector optics. We investigate experimentally and theoretically the unfolding of a uniformly polarized optical vortex beam on propagation through a birefringent crystal and characterize the output field in terms of polarization singularities (C lines and points of circular polarization; L surfaces and lines of linear polarization). The field is described both in the 2-dimensional transverse plane, and in three dimensions, where the third is abstract, representing an optical path length propagated through the crystal. Many phenomena of singular optics, such as topological charge conservation and singularity reconnections, occur naturally in the description.