Generation of optical vorticity from topological defects
  The propagation of an electromagnetic wave in a medium with a screw dislocation is studied. Adopting the formalism of differential forms, it is shown that torsion is responsible for quantized modes. Moreover, it is demonstrated that the modes thus obtained have well defined orbital angular momentum, opening the possibility to design liquid-crystal-based optical tweezers. 
S\'ebastien Fumeron, Erms Pereira and Fernando Moraes
cond-mat.soft cond-mat.other