Angewandte Naturwissenschaften und WirtschaftsingenieurwesenZeitschriftenartikel
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
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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 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
2008
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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
2008
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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.
Angewandte Naturwissenschaften und WirtschaftsingenieurwesenZeitschriftenartikel
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
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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 WirtschaftsingenieurwesenZeitschriftenartikel
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
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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 WirtschaftsingenieurwesenZeitschriftenartikel
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.
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