Nonlinear inter-core coupling in triple-core photonic crystal fibers.

We have developed a coupled-mode theory to describe light propagation in triple-core photonic crystal fibers (PCFs) in the nonlinear regime. The propagation equations including nonlinearities have been solved analytically. The nonlinear coupling for symmetric and asymmetric fibers is modeled for different coupling and nonlinear parameters. We investigate nonlinear inter-core coupling experimentally with a single high intensity pump beam. Optical switching of a signal beam in the presence of a control pump beam at a different wavelength is also demonstrated. The self-phase modulation (SPM) parameter gamma in the triple-core PCF studied is determined.