Generation of spectrally unmodulated and broad pulses through non-linear propagation with elliptical polarization

Abstract A fiber-based spectral broadening technique is reported which improves the temporal quality of ultrashort pulses by generating a wide, smooth spectrum from a sub-picosecond laser. The experimental results are confirmed by numerical simulations. It is demonstrated that the interplay between third order nonlinear effects such as cross-phase modulation and nonlinear elliptical polarization rotation have an important role in birefringent fibers and this is an appealing alternative to highly modulated spectrum caused by self-phase modulation. The theoretical model predicts the efficient generation of smooth, wide spectra with compensable phase and shows that proper polarization control is also crucial. An additional model is proposed which allows the determination of the proper set of parameters for the highest efficiency.