摘要： A major challenge in supercontinuum (SC) generation is to overcome the shortcomings of existing fibre-based SC sources in the ultraviolet (UV) wavelength range below 400 nm. There is particular need for broadband sources of UV light in applications such as multi-photon fluorescence microscopy for simultaneous coherent excitation of multiple fluorophores. However, UV generation in conventional silica-core fibres is extremely difficult because of factors such as material absorption, large normal dispersion, glass stability, power handling, and aging, and this has motivated much recent interest in the use of alternative approaches. Although these results show great promise, compatibility with the ubiquitous silica platform remains a problem, and there is thus intense current interest in generating UV-light using modified UV-resistant silica glasses. In this paper, we report the design and fabrication of small-core highly nonlinear UV-grade photonic crystal fiber (PCF) drawn from Heraeus F110 UV-resistant silica glass, and its application to broadband UV generation over 260-400 nm. The few mode PCF is shown in Fig. 1(a) and was designed with: core diameter ~4.24 μm, hole diameter d = 3.5 μm, pitch Λ =3.88 μm, and was designed to support five LP modes in a scalar approximation. The calculated dispersion coefficients and mode profiles are shown in Figs 1(b) and (c). Figure 1(d) and (e) show experimental results pumping with picosecond laser pulses at 355 nm. For a 1m length of the PCF, we observe intermodal four-wave mixing (FWM) peaks with Fig. 1(d) showing a series of spectra as the output power varies from 0.1 – 0.2 mW. The FWM peaks are generated over the range 350-370 nm and the peak positions are in good agreement with calculations based on the fibre modal characteristics. For a longer 3 m fibre length, intermodal FWM is not observed, but rather we see cascaded Raman scattering out to 6th-order over the range 355-395 nm. The UV-emission was observed to have stable 0.3 mW output power without any detrimental photo-darkening. In this paper, we have reported the fabrication of highly nonlinear photonic crystal fiber from UV-grade glass and experimentally demonstrate nonlinear frequency conversion over 350-395 nm by pumping at 355 nm with picosecond laser pulses. These results represent an important step towards efficient UV supercontinuum generation in an all-silica fiber platform.