Extreme supercontinuum generation to the deep UV

We report the formation of an ultrabroad supercontinuum down to 280 nm in the deep UV by pumping sharply tapered (5–30 mm taper lengths) solid-core photonic crystal fibers with 130 fs, 2 nJ pulses at 800 nm. The taper moves the point of soliton fission to a position where the core is narrower, a process that requires normal dispersion at the input face of the fiber. We find that the generation of deep-UV radiation is limited by strong two-photon absorption in the silica.