Ultrafast solitonic nonlinear directional couplers utilizing multicomponent glass dual-core photonic crystal fibres

We present experimental and numerical progress in the development of nonlinear directional couplers based on multicomponent glass photonic crystal fibre. The first part of the paper reports a multi-wavelength nonlinear switch, operating in ultralong wavelength optical communication band, based on a special square lattice dual-core photonic crystal fibre excited with femtosecond pulses. The soliton-fission process in this coupler resulting in switching possibilities of spectrally separated solitons shifted away from the excitation wavelength. Due to the fibre birefringence the switching wavelength can be tuned by rotating the polarization of the excitation field. Motivated by the experimental results, the numerical studies were focused on single fundamental soliton switching that exhibits high extinction ratios. After numerical optimization of the photonic crystal fibre structure, the resultant coupler design was further analysed from the aspect of nonlinear propagation based on coupled nonlinear Schrödinger equations. The simulated nonlinear directional coupler indicates the possibility to realize a high-extinction-ratio switch of sub-nJ 100 fs pulses which are simultaneously compressed below 15 fs.