Critical states embedded in the continuum

M. Koirala, A. Yamilov, A. Basiri, Y. Bromberg, H. Cao, T. Kottos

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


We introduce a class of critical states which are embedded in the continuum (CSC) of a one-dimensional optical waveguide array with one non-Hermitian defect. These states are on the verge of being fractal and have real propagation constants. They emerge at a phase transition which is driven by the imaginary refractive index of the defective 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 it they evolve to exponentially localized modes. An addition of a background gain or loss can turn these localized states into bound states in the continuum.

Original languageAmerican English
Article number013003
JournalNew Journal of Physics
StatePublished - 9 Jan 2015
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2015 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


  • bound states in the continuum
  • localization
  • optical waveguide array


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