  The resonance band in hollow-core photonic crystal fiber (HC-PCF), while
leading to high-loss region in the fiber transmission spectrum, has been
successfully used for generating phase-matched dispersive wave (DW). Here, we
report that the spectral width of the resonance-induced DW can be largely
broadened due to plasma-driven blueshifting soliton. In the experiment, we
observed that in a short length of Ar-filled single-ring HC-PCF the soliton
self-compression and photoionization effects caused a strong spectral blueshift
of the pump pulse, changing the phase-matching condition of the DW emission
process. Therefore, broadening of DW spectrum to the longer-wavelength side was
obtained with several spectral peaks, which correspond to the generation of DW
at different positions along the fiber. In the simulation, we used super-Gauss
windows with different central wavelengths to filter out these DW spectral
peaks, and studied the time-domain characteristics of these peaks respectively
using Fourier transform method. The simulation results verified that these
multiple-peaks on the DW spectrum have different delays in the time domain,
agreeing well with our theoretical prediction. Remarkably, we found that the
whole time-domain DW trace can be compressed to ~29 fs using proper chirp
compensation. The experimental and numerical results reported here provide some
insight into the resonance-induced DW generation process in gas-filled HC-PCFs,
they could also pave the way to ultrafast pulse generation using DW-emission
mechanism.
