Pump wave coherence, modulation instability and their effect on continuous-wave supercontinua

The effect of pump coherence on the evolution of continuous-wave (CW) supercontinua is explored within the framework of the generalised nonlinear Schrödinger equation. Recent results of experimental studies, using an amplified spontaneous emission (ASE) based CW pump source, with a selectable coherence time, confirm the trend observed numerically [1]: an optimum degree of partial pump coherence generates the broadest spanning continuum. The effect of third order dispersion on continuum expansion is discussed in the context of an optimum degree of pump coherence. Finally, a design guideline for CW pumped supercontinuum light sources is suggested, relating the optimum pump bandwidth to the modulation instability period.

► The dynamics of continuous-wave supercontinuum are reviewed. ► A numerical model to describe intensity fluctuations in CW fibre lasers is developed. ► Pump coherence in the evolution towards a Raman soliton continuum is analysed. ► An optimum criterion is given: τc,optimum ≈ 3TMI.