Fig. 5: Spectral broadening in the low power limit.

a, b Comparison of experimental spectra (points) and best fit of SPM model spectra (dotted lines) for two temperatures and several pulse energies. c, d Peak phase from the SPM fits in (b) and (a). Error bars give the uncertainty in peak phase obtained from the least-squares fitting procedure (±2 standard deviations). Solid lines show the linear best fit.