Generation of multiple VUV dispersive waves in tapered gas-filled hollow-core anti-resonant fibers

In this work, we numerically investigate an experimentally feasible design of a tapered Ar-filled hollow-core anti-resonant fiber and we report the generation of multiple dispersive waves (DWs) in the vacuum ultra-violet (VUV) region. The fiber is pumped at 800 nm with only 7 $\mu$J pulse energy and we show, for the first time to the best of our knowledge, that optimization of the taper structure can allow the generation of multiple DWs at wavelengths as short as ~128 nm with a record maximum relative power spectral density (PSD) of -37 dB/nm. We also observed a coherent supercontinuum spanning 128-800 nm. The effect of various sections of the fiber taper on PSD in the VUV is also investigated. The proposed fiber taper structure provides a new way to generate light in the VUV spectral range using low gas pressure and relatively low pulse energy.