Supercontinuum generation from intense partially coherent laser beams in optical fibers

Abstract

This paper analyses the advantageous features of supercontinuum (SC) generated from continuous-wave (CW) excitation. It has been shown that both the generation mechanisms and the temporal and spectral properties of supercontinuum produced with CW pump lasers are different from those of generated by means of pulsed excitation, in particular the remarkable smoothness of CW-SC spectra. We show that these unique spectral features stem from the fission of the partially coherent CW input beam into a train of subpicosecond pulses induced by the modulation instability (MI). These subpicosecond pulses lead to the formation of optical solitons with inherently random parameters, which self-frequency shift differently depending on their characteristics. The resulting supercontinuum spectrum is hence the average of many different soliton spectra, which have suffered different frequency shifts. Different experimental setups used in our lab are presented and the dependence of the SC generation on the coherence of the fiber laser and the fiber dispersion profile are shown.