Complex intensity modulation transfer function for supercontinuum generation in microstructure fibers

We investigated the complex intensity modulation transfer function for supercontinuum generation in microstructure fibers (MSF). We measured the relative intensity and phase modulations in the output spectrum of the MSF with spectral resolution of one and ten nanometers, respectively. For small intensity modulation indices (~ 1 %) we found power modulation gain factors as large as 100 in certain spectral areas of the super continuum. In all spectral regions the phase modulation coefficient was found not to exceed 40 rad per percent of pulse power change. Consequences for applications of phase-coherent supercontinua, such as frequency metrology, pulse synthesis, heterodyne coherent anti-Stokes Raman scattering (CARS) are discussed.