Anisotropic charge displacement supporting isolated photorefractive   optical needles
  The strong asymmetry in charge distribution supporting a single non-interacting spatial needle soliton in a paraelectric photorefractive is directly observed by means of electroholographic readout. Whereas in trapping conditions a quasi-circular wave is supported, the underlying double-dipolar structure can be made to support two distinct propagation modes. 
Eugenio DelRe (1), Alessandro Ciattoni (2), Aharon J. Agranat (3) ((1)   Pirelli Cavi e Sistemi, (2) Universita' dell'Aquila...