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Suche nach „[U.] [Schwarz]“ hat 5 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

    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

    Propagation dynamics of optical vortices in Laguerre-Gaussian beams

    Optics Communications, vol. 250, no. 4-6, pp. 218-230

    2005

    DOI: 10.1016/j.optcom.2005.02.032

    Abstract anzeigen

    We have calculated the propagation dynamics of an initial off-axis vortex with topological charge 1 in Laguerre–Gaussian background beams View the MathML source(LG10andLG70), which are examples of background beams with non-generic dislocation surfaces, on which the real and imaginary parts of the light field are zero. When initially a vortex with broad core (e.g., r-vortex) is embedded in the background beam, the dislocation surfaces are destroyed during propagation and two vortices with opposite charge are created per dislocation surface in planes perpendicular to the propagation direction. For a vortex with narrow core (e.g., point vortex) diffraction is important and leads to the birth of more than two vortices per dislocation surface. These results are also valid for other background beams with dislocation surfaces, e.g., Hermite–Gaussian and Ince–Gaussian beams. We investigated experimentally the spatial evolution of the intensity distribution of an initial off-axis vortex with narrow core and topological charge 1 in View the MathML sourceLG10andLG70 background beams. The experimental results are in good agreement with the calculated intensity distributions.

    Angewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Florian Flossmann, U. Schwarz, M. Maier

    Optical Vortices in a Laguerre-Gaussian LG10 beam

    Journal of Modern Optics, vol. 52, no. 1009

    2005

    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.