Localized modes and dark solitons sustained by nonlinear defects

Dark solitons and localized defect modes against periodic backgrounds are considered in arrays of waveguides with defocusing Kerr nonlinearity constituting a nonlinear lattice. Bright supported by local increase the nonlinearity, while dark decrease nonlinearity. exist for both types defect, although case weak they feature side bright humps making total energy propagating through system larger than transferred constant background. All found stable. characterized relatively narrow windows stability. Interactions unstable described.