Nonlinear propagation of a-few-optical-cycle pulses in a photonic crystal fiber-experimental and theoretical studies beyond the slowly varyingenvelope approximation

The evolution of spectral and temporal profiles of 4.5 optical-cycle pulses propagating near zero-dispersion wavelength (ZDW) in a photonic crystal fiber is investigated experimentally and theoretically beyond the slowly varyingenvelope approximation. The excellent agreement between the experimental an theoretical results suggests that the observed gap in the spectral profile, the most distinctive feature, originates from the self-steepening effect. This effect intensifies the spectral component shorter than the ZDW with the decay of higher order solitons and consequently induces the intrapulse four-wave mixing (FWM). As a result, the anti-Stokes and Stokes components produced by the FWM enables us to generate a supercontinuum from 480 to 1020 nm.