We introduce a model for two coupled waves propagating in a hollow-core fiber: a linear dispersionless core mode and a dispersive nonlinear surface mode. The linear coupling between them may open a bandgap through the mechanism of avoidance of crossing between dispersion curves. The third-order dispersion of the surface mode is necessary for the existence of the gap. Numerical investigation reveals that the entire bandgap is filled with solitons, and they are stable in direct simulations. The gap-soliton (GS) family includes stable pulses moving relative to the given reference frame up to limit values of the corresponding boost delta, beyond which they do not exist. The limit values are asymmetric for delta lesser or greater than 0. Recently observed solitons in hollow-core photonic crystal fibers may belong to this GS family.
© 2005 Optical Society of America
(060.5530) Fiber optics and optical communications : Pulse propagation and temporal solitons
(190.4370) Nonlinear optics : Nonlinear optics, fibers
(190.5530) Nonlinear optics : Pulse propagation and temporal solitons
(230.4320) Optical devices : Nonlinear optical devices
I. M. Merhasin and Boris A. Malomed, "Gap solitons in a model of a hollow optical fiber," Opt. Lett. 30, 1105-1107 (2005)