  The physics and applications of fiber-based supercontinuum (SC) sources have
been a subject of intense interest over the last decade, with significant
impact on both basic science and industry. New uses for SC sources are also
constantly emerging due to their unique properties that combine high
brightness, multi-octave frequency bandwidth, fiber delivery, and single-mode
output. The last few years have seen significant research efforts focused on
extending the wavelength coverage of SC sources towards the 2 to 20 $\mu$m
molecular fingerprint mid-infrared (MIR) region and in the ultraviolet (UV)
down to 100 nm, while also improving stability, noise and coherence, output
power, and polarization properties. Here we review a selection of recent
advances in SC generation in a range of specialty optical fibers, including
fluoride, chalcogenide, telluride, and silicon-core fibers for the MIR;
UV-grade silica fibers and gas-filled hollow-core fibers for the UV range; and
all-normal dispersion fibers for ultralow-noise coherent SC generation.
