Diffraction by volume gratings with imaginary potentials

  title={Diffraction by volume gratings with imaginary potentials},
  author={Michael V. Berry and D H J O’Dell},
  journal={Journal of Physics A},
A medium described by an imaginary potential (or imaginary (refractive index) 2 ), that varies sinusoidally in one direction, acts as a volume grating for plane waves incident on it obliquely or normally. Two peculiar features are identified. First, if the potential is weak, so that there are only two significant diffracted beams near the Bragg angle, and three for normal incidence, diffraction is strongly affected by degeneracies of the non-Hermitian matrix generating the 'Bloch waves' in the… 

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