Supercontinuum generation is shown for the first time in a tapered triangular structure photonic crystal fiber with two closely spaced zero dispersion wavelengths where dispersion becomes normal for all guided wavelengths at a certain distance along the taper. The numerical calculation shows an increased bandwidth and a reduced depletion of the pump source when the photonic crystal fiber is tapered. We simulate the propagation of 15 femtosecond pulse with a peak power of 80 kW centered at 808 nm. Both fiber and pump source are commercially available and the improved light source can be used for measuring techniques such as optical coherence tomography and spectroscopy.
Supercontinuum generation in photonic crystal fibers with two zero dispersion wavelengths (ZDWs) is investigated numerically. The role of the second ZDW is examined for 5 fiber designs where the higher ZDW differs while the lower ZDW is almost the same for all fibers. We find that tapering can arrest pump depletion, thereby improving the flatness and bandwidth of the supercontinuum. Pumping with low-power picosecond pulses is also investigated; we find that the low peak power leads to a broad four-wave mixing gain bandwidth, resulting in a supercontinuum that is extremely flat over almost 500 nm.