Using PT-symmetry for switching applications
  This work introduces a new class of PT-symmetry grating assisted devices for switching or modulation applications. Their operation is based on a four-wave interaction, thus marking a step in the further development of PT-symmetry devices which currently are essentially based on two-wave interactions. A remarkable feature of the new device is that all their properties also hold for the case of imperfect PT-symmetry operation, corresponding to the important practical case of fixed losses. 
Anatole Lupu, Henri Benisty, Aloyse Degiron
physics.optics