Supercontinuum generation through cascaded four-wave mixing in photonic-crystal fibers: When picoseconds do it better

By numerically solving the generalized nonlinear Schrödinger equation, we provide a comparative analysis of spectral and temporal transformations of pico and femtosecond laser pulses in a guided mode with a generic dispersion profile typical of a photonic-crystal fiber. We demonstrate that with an appropriate choice of the input laser pulse parameters, picosecond pulses are efficiently transformed into a supercontinuum emission through a cascade of phase-matched four-wave mixing (FWM) processes. For femtosecond pulses, soliton frequency-shifting phenomena tend to arrest such FWM cascades. In this regime, picosecond pulses can provide much higher efficiencies of supercontinuum generation, as well as much broader and much smoother spectra of output radiation compared to femtosecond pulses with the same peak power.