Gap solitons in inhomogeneous high-index photonic bandgap fibers

Microstructured optical fibers based on As₂Se₃ glass may be designed to have an in-plane photonic bandgap, and thereby support modes with zero propagation constant and zero group velocity. It has been shown that such structures will support gap solitons which by way of Raman scattering will be driven towards the zero velocity state. An important question in connection with slow-light propagation is the influence of waveguide imperfections, which typically leads to a strong scattering of the slow light as the group velocity tends to zero. Theoretical investigations of this subject have so far focused on the experimentally realized case of planar photonic bandgap waveguides, where the imperfections are present on a subwavelength scale given by the lattice periodicity. In microstructured fibers, however, the deformation spectrum can be expected to be of an entirely different nature, with long-period perturbations playing a dominant role. The purpose of this work is to investigate how such long-period perturbations will affect the propagation of slow-mode optical solitons.