Dispersive waves in fs cascaded second-harmonic generation

Optical solitons are nondispersive nonlinear waves that are supported through a balance between group-velocity dispersion (GVD) and nonlinearity. The so-called dispersive waves are linear waves phase-matched to these solitons, and are often found in supercontimuum generation [1, 2]. The dispersive wave wavelength can be predicted from a phase-matching condition to the solitonic wave [3]. This phase-matching point is often interpreted as being located where solitons are no longer supported, i.e. where the GVD changes sign. However, in reality the dispersive wave is found at the wavelength where the total dispersion of the generated soliton is changing sign.