Improving efficiency of supercontinuum generation in photonic crystal fibers by direct degenerate four-wave mixing

We numerically study supercontinuum generation in photonic crystal fibers pumped with low-power 30-ps pulses close to the zero dispersion wavelength. We show how the efficiency is significantly improved by designing the dispersion to allow widely separated spectral lines generated by degenerate four-wave mixing directly from the pump to broaden and merge, resulting in a 800-nm-wide supercontinuum. Full-vectorial plane-wave calculations show that a cobweb photonic-crystal-fiber structure can realize the dispersion profiles under consideration. The predicted efficient supercontinuum generation is more robust and survives fiber imperfections modeled as random fluctuations of the dispersion coefficients along the fiber.