Figure 2: Optical eigensystem characteristics of the unidirectional converter region.

(a) Complex ξ trajectories for the forward (upper) and backward (lower) propagation cases. (b) Complex eigenvalue spectra and instantaneous eigenvalue trajectories on the complex ξ space. The wireframe surface and surface skin colour indicate real and imaginary parts, respectively. The instantaneous eigenvalue trajectories are calculated for the circular ξ(t) trajectory in a. Arrows on the trajectory curves indicate the direction of the parametric change with time t.