Intermodal Cerenkov radiation in a higher-order-mode fiber

We demonstrate an intermodal Cerenkov radiation effect in a higher-order-mode (HOM) fiber with a mode crossing (i.e., two guided modes having the same propagation constant at the same wavelength). Lambda frequency-shifted soliton in the vicinity of the mode-crossing wavelength emits a phase-matched dispersive wave in a different propagation mode. We develop a theoretical explanation for this nonlinear optical effect and demonstrate that the mode crossing in HOM fibers can be utilized to achieve simultaneous wavelength and mode conversion; the strength of this intermodal nonlinear interaction can be tuned by controlled fiber bending. (C) 2012 Optical Society of America