Symmetry in the equations of nonlinear dynamics of semiconductor laser   subject to delayed optical feedback
  Delayed feedback laser dynamics is described by means of Lang-Kobayashi equation model. Since a lot of initial states asymptotically approach to periodic attractor in the phase space, only periodic steady-state regimes have been studied here. Lyapunov transformation allows us to reduce problem to the differential equation of the first order whereas the spectrum of laser oscillation is governed by the appropriate eigen value problem. Using the symmetry proves that there is the dual laser system with anticipated feedback which has the same dynamic characteristics as laser with delayed feedback. 
Anatoly P. Napartovich and Alexander G. Sukharev
nlin.CD physics.optics