  We generalize the geometrical model of transformation optics to Rieman-Cartan
space with torsion by introducing topological defects in physical space. By
relaxing the integrable condition, we show explicitly that the generalized
equivalent medium are bi-anisotropic where the magnetoelectric coupling
parameters emergent as the dislocation density. We also show the generation of
orbital angular momentum of light. Our theory may open intriguing venues for
controlling the vectorial degree of freedom of light with metamaterials.
