14 research outputs found
Wave-vector and polarization dependence of conical refraction
We experimentally address the wave-vector and polarization dependence of the
internal conical refraction phenomenon by demonstrating that an input light
beam of elliptical transverse profile refracts into two beams after passing
along one of the optic axes of a biaxial crystal, i.e. it exhibits double
refraction instead of refracting conically. Such double refraction is
investigated by the independent rotation of a linear polarizer and a
cylindrical lens. Expressions to describe the position and the intensity
pattern of the refracted beams are presented and applied to predict the
intensity pattern for an axicon beam propagating along the optic axis of a
biaxial crystal
Polarization tailored novel vector beams based on conical refraction
Coherent vector beams with involved states of polarization (SOP) are
widespread in the literature, having applications in laser processing,
super-resolution imaging and particle trapping. We report novel vector beams
obtained by transforming a Gaussian beam passing through a biaxial crystal, by
means of the conical refraction phenomenon. We analyze both experimentally and
theoretically the SOP of the different vector beams generated and demonstrate
that the SOP of the input beam can be used to control both the shape and the
SOP of the transformed beam. We also identify polarization singularities of
such beams for the first time and demonstrate their control by the SOP of an
input beam
On the dual-cone nature of the conical refraction phenomenon
In conical refraction (CR), a focused Gaussian input beam passing through a biaxial crystal and parallel to one of the optic axes is transformed into a pair of concentric bright rings split by a dark (Poggendorff) ring at the focal plane. Here, we show the generation of a CR transverse pattern that does not present the Poggendorff fine splitting at the focal plane, i.e., it forms a single light ring. This light ring is generated from a nonhomogeneously polarized input light beam obtained by using a spatially inhomogeneous polarizer that mimics the characteristic CR polarization distribution. This polarizer allows modulating the relative intensity between the two CR light cones in accordance with the recently proposed dual-cone model of the CR phenomenon. We show that the absence of interfering rings at the focal plane is caused by the selection of one of the two CR cones. (C) 2015 Optical Society of Americ
Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction
We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a 87Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results
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Originally published in Optics Express on 09 March 2015 (oe-23-5-5704
Media 5: Polarization tailored novel vector beams based on conical refraction
Originally published in Optics Express on 09 March 2015 (oe-23-5-5704