title: Observation of bandgap guidance of optical vortices in a tunable negative defect.
abstract: We experimentally demonstrate linear bandgap guidance of optical vortices as high-gap defect modes (DMs) in two-dimensional induced photonic lattices. We show that donut-shaped vortex beams can be guided in a tunable negative (lower-index) defect, provided that the defect strength is set at an appropriate level. Such vortex DMs have fine features in the "tails" associated with the lattice anisotropy and can be considered as a superposition of dipole DMs. Our numerical results find good agreement with experimental observations.
authors.affiliation: Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education and TEDA Applied Physics School, Nankai University, Tianjin 300457, China.
authors.forename: Daohong
authors.initials: D
authors.lastname: Song
authors.forename: Xiaosheng
authors.initials: X
authors.lastname: Wang
authors.forename: Daniel
authors.initials: D
authors.lastname: Shuldman
authors.forename: Jiandong
authors.initials: J
authors.lastname: Wang
authors.forename: Liqin
authors.initials: L
authors.lastname: Tang
authors.forename: Cibo
authors.initials: C
authors.lastname: Lou
authors.forename: Jingjun
authors.initials: J
authors.lastname: Xu
authors.forename: Jianke
authors.initials: J
authors.lastname: Yang
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Chen