Tunable ultraviolet dispersive-wave emission driven directly by 40-fs Ti:sapphire laser pulses in a hollow capillary fiber

We demonstrate that by using a 1-m-long gas-filled hollow capillary fiber (HCF) with a core diameter of 100 μm, tunable ultraviolet (UV) dispersive-wave (DW) pulses can be generated in a compact, single-stage setup driven directly by 40-fs Ti:sapphire laser pulses. By adjusting the gas type and pressure inside the HCF, the central wavelength of the UV DW can be continuously tuned from 185 nm to ∼450 nm. In the experiment, we found that for ∼320-450 nm DW generation, Raman-active gas filled in the HCF can efficiently suppress the pulse fission effect of the high-order soliton due to the Raman-induced pulse energy dissipation, leading to the high-quality DW generation at these wavelengths with smooth, single-peak spectra. These results provide some useful insights for designing compact, wavelength-tunable ultrafast UV light sources with microjoule-level pulse energies.