Ionization-induced asymmetric self-phase modulation and universal   modulational instability in gas-filled hollow-core photonic crystal fibers
  We study theoretically the propagation of relatively long pulses with ionizing intensities in a hollow-core photonic crystal fiber filled with a Raman-inactive gas. Due to photoionization, previously unknown types of asymmetric self-phase modulation and `universal' modulational instabilities existing in both normal and anomalous dispersion regions appear. We also show that it is possible to spontaneously generate a plasma-induced continuum of blueshifting solitons, opening up new possibilities for pushing supercontinuum generation towards shorter and shorter wavelengths. 
Mohammed F. Saleh, Wonkeun Chang, John C. Travers, Philip St.J.   Russell, and Fabio Biancalana
physics.optics