Anderson localization in Bragg-guiding arrays with negative defects
  We show that Anderson localization is possible in waveguide arrays with periodically-spaced defect waveguides having lower refractive index. Such localization is mediated by Bragg reflection, and it takes place even if diagonal or off-diagonal disorder affects only defect waveguides. For off-diagonal disorder the localization degree of the intensity distributions monotonically grows with increasing disorder. In contrast, under appropriate conditions, increasing diagonal disorder may result in weaker localization. 
Valery E. Lobanov, Yaroslav V. Kartashov, Victor A. Vysloukh, and   Lluis Torner
physics.optics nlin.PS