Femtosecond soliton supercontinuum generation in anisotropic microstructure fibre

The polarization anisotropy of microstructure fibre may be introduced especially to provide more possibilities to control the supercontinuum production. Thus polarization degree of freedom should be incorporated to the numerical model. In this paper we analyze numerically the supercontinuum generation in the microstructure fibres with periodically modulated holes ellipticity. Femtosecond pulse propagation in single mode microstructure fibre was described by NSE-type equation, including Raman delayed response. Propagation constant of fundamental mode was calculated by a full vector numerical model based on the plane-wave method. The holes ellipticity was assumed to be periodically modulated along the fibre with the period near 10 mm. The results are the next: ellipticity (no modulation) leads to spectrum splitting which decrease when ellipticity goes to 1. The splitting is about 15 THz for ellipticity 0.5. The pulses in both polarizations were split into solitonic part (un-shifted) and two delayed Raman solitons (also un-shifted). For larger ellipticity the solitonic and Raman soliton pulses acquire temporal shift up to 7000 fs. Modulation of the ellipticity leads to spectral broadening and disappearing of the spectral gaps between spectrum of solitonic part and dispersion wave. Controlling the fibre anisotropy allows to generate the pulses with different polarization having control temporal and spectral shift.