Light propagation in square law media with random imperfections

This paper investigates the deformation of the field transmitted through a square law medium waveguide. We consider the situation where the center of the waveguide randomly oscillates around the optical axis or the radius of the waveguide randomly pulsates. The random perturbations are small, but th e waveguide is long, which gives rise to a macroscopic effect of the inhomo geneities. This effect is characterized by coupling mechanisms between opti cal modes, which tend to strengthen high order modes. Precise expressions f or the transmitted wave are derived which exhibit remarkable regimes, where behaviors such as shift, spreading or even focusing of the field can be ob served. Numerical simulations are in good agreement with the theoretical re sults. (C) 2000 Elsevier Science B.V. All rights reserved.