Tunable VUV-to-VIS ultrafast pulses generation in hollow capillary fibers with 15.7% dispersive-wave efficiency at 320 nm

We report a compact hollow-capillary-fiber (HCF) system that generates tunable dispersive-wave (DW) pulses spanning the vacuum ultraviolet (VUV) to visible (VIS) spectral regions. Through optimization of the HCF and gas parameters, we demonstrate continuously tunable DW generation with a wider tuning range (147-520 nm) than previously reported in similar compact systems (200-380 nm). Using a 140-μm-core, 1-m-long helium-filled HCF, we enhance deep-UV pulse generation efficiency via spectral blue-shifting of the DW at a relatively high soliton order, achieving a record 15.7% conversion efficiency at 320 nm. This work provides key insights for developing compact, tunable, and microjoule-level ultrafast VUV-to-VIS laser systems based on DW emission.