19 research outputs found
Spectroscopic observation of the rotational Doppler effect
We report on the first spectroscopic observation of the rotational Doppler
shift associated with light beams carrying orbital angular momentum. The effect
is evidenced as the broadening of a Hanle/EIT coherence resonance on Rb vapor
when the two incident Laguerre-Gaussian laser beams have opposite topological
charges. The observations closely agree with theoretical predictions.Comment: Submited to Physical Review Lette
Optical Generation of Vortices in trapped Bose-Einstein Condensates
We demonstrate numerically the efficient generation of vortices in
Bose-Einstein condensates (BEC) by using a ``phase imprinting'' method. The
method consist of passing a far off resonant laser pulse through an absorption
plate with azimuthally dependent absorption coefficient, imaging the laser beam
onto a BEC, and thus creating the corresponding non-dissipative Stark shift
potential and condensate phase shift. In our calculations we take into account
experimental imperfections. We also propose an interference method to detect
vortices by coherently pushing part of the condensate using optically induced
Bragg scattering.Comment: 8 pages, 4 figure
Dynamics of field dislocations and disclinations in a few-mode waveguide: II. Pure types of singularities
Vortex knots in light
Optical vortices generically arise when optical beams are combined. Recently, we reported how several laser beams containing optical vortices could be combined to form optical vortex loops, links and knots embedded in a light beam (Leach et al 2004 Nature 432 165). Here, we describe in detail the experiments in which vortex loops form these structures. The experimental construction follows a theoretical model originally proposed by Berry and Dennis, and the beams are synthesized using a programmable spatial light modulator and imaged using a CCD camera