Nonlinear self-flipping of polarization states in asymmetric waveguides
  Waveguides of subwavelength dimensions with asymmetric geometries, such as rib waveguides, can display nonlinear polarization effects in which the nonlinear phase difference dominates the linear contribution, provided the birefringence is sufficiently small. We demonstrate that self-flipping polarization states can appear in such rib waveguides at low (mW) power levels. We describe an optical power limiting device with optimized rib waveguide parameters that can operate at low powers with switching properties. 
Wen Qi Zhang, M. A. Lohe, Tanya M. Monro and V. Shahraam Afshar
physics.optics