  We experimentally demonstrate the efficient generation of circularly
polarized pulses tunable from the vacuum to deep ultraviolet (160-380 nm)
through resonant dispersive wave emission from optical solitons in a gas-filled
hollow capillary fiber. In the deep ultraviolet we measure up to 13 microjoule
of pulse energy, and from numerical simulations, we estimate the shortest
output pulse duration to be 8.5 fs. We also experimentally verify that simply
scaling the pulse energy by 3/2 between linearly and circularly polarized
pumping closely reproduces the soliton and dispersive wave dynamics. Based on
previous results with linearly polarized self-compression and resonant
dispersive wave emission, we expect our technique to be extended to produce
circularly polarized few-fs pulses further into the vacuum ultraviolet, and few
to sub-fs circularly polarized pulses in the near-infrared.
