Critical States Embedded in the Continuum
  We introduce a class of critical states which are embedded in the continuum (CSC) of one-dimensional optical waveguide array with one non-Hermitian defect. These states are at the verge of being fractal and have real propagation constant. They emerge at a phase transition which is driven by the imaginary refractive index of the defect waveguide and it is accompanied by a mode segregation which reveals analogies with the Dicke super -radiance. Below this point the states are extended while above they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states to bound states in the continuum. 
M. Koirala (1), A. Yamilov (1), A. Basiri (2), Y. Bromberg (3), H. Cao   (3), T. Kottos (2) ((1) Missouri University of Scie...
cond-mat.dis-nn cond-mat.mes-hall physics.optics