Nonlinearly induced escape from a defect state in waveguide arrays

We experimentally investigate the linear and nonlinear optical properties of a nonuniform waveguide array. By reducing the width of a single waveguide, we decrease its effective index and induce waveguiding along the defect. Due to the positive nonlinearity, the index difference is reduced for increasing power levels with the result that the field escapes. Waveguiding is suppressed by the action of the nonlinearity.