Resonance-free deep ultraviolet to near infrared supercontinuum generation in a hollow-core antiresonant fibre

Supercontinuum generation in the ultraviolet (UV) spectral region is challenging in solid-core optical fibres due to solarisation and photodarkening. Antiresonant hollow-core fibres have overcome this limitation and have been shown to guide UV light at sufficient intensity for UV spectral broadening through nonlinear optics in the filling gas. However, their UV guidance is usually limited by discontinuities caused by the presence of high-loss resonance bands. In this paper, we report on resonance-free supercontinuum generation spanning from the deep UV to the near infrared achieved through modulation instability in an argon-filled antiresonant hollow-core fibre. The fibre was directly fabricated using the stack-and-draw method with a wall thickness of approximately 90 nm, enabling continuous spectral coverage from the deep UV to the near infrared. We also report numerical simulations to investigate the supercontinuum bandwidth and the factors limiting it, finding that the overall dispersion landscape, and associated group-velocity matching of cross-phase modulation interactions, is the dominant constraint on spectral extension.