Two-octave supercontinuum generation in a water-filled photonic crystal fiber.

Supercontinuum generation in a water-filled photonic crystal fiber is reported. By only filling the central hollow core of this fiber with water, the fiber properties are changed such that the air cladding provides broadband guiding. Using a pump wavelength of 1200 nm and few-microjoule pump pulses, the generation of supercontinua with two-octave spectral coverage from 410 to 1640 nm is experimentally demonstrated. Numerical simulations confirm these results, revealing a transition from a soliton-induced mechanism to self-phase modulation dominated spectral broadening with increasing pump power. Compared to supercontinua generated in glass core photonic fibers, the liquid core supercontinua show a higher degree of coherence, and the larger mode field area and the higher damage threshold of the water core enable significantly higher pulse energies of the white light pulses, ranging up to 0.39microJ.