Transition between superluminal and subluminal light propagation in photorefractive Bi12SiO20 crystals Bo, Fang ; Zhang, Guoquan ; Xu, Jingjun Abstract Publication: Optics Express Pub Date: October 2005 DOI: 10.1364/OPEX.13.008198 Bibcode: 2005OExpr..13.8198B