  We report generation of an ultrafast supercontinuum extending into the mid-
infrared in gas-filled single-ring hollow-core photonic crystal fiber (SR-PCF)
pumped by 1.7 $\mu$m light from an optical parametric amplifier. The simple
fiber structure offers shallow dispersion and flat transmission in the near and
mid-infrared, enabling the generation of broadband spectra extending from 300
nm to 3.1 $\mu$m, with a total energy of a few $\mu$J. In addition, we report
the emission of ultraviolet dispersive waves whose frequency can be tuned
simply by adjusting the pump wavelength. SR-PCF also provides an effective
means of compressing and delivering tunable ultrafast pulses in the near and
mid-infrared spectral regions.
