  Simultaneously increasing the spectral bandwidth and average output power of
mid-infrared supercontinuum sources remains a major challenge for their
practical application. We address this issue through experimental developments
of short tapered rods made from distinct glasses (silica, tellurite and
chalcogenide families) for covering distinct spectral regions by means of
supercontinuum generation in the femtosecond regime. We demonstrate that
ultra-broadband spectral broadenings over the entire glass transmission window
can be achieved in few-cm-long segments of tapered rods by a fine adjustment of
input modal excitation. As the most significant example, our simple
post-processing of glass rods unlocks the high-power regime for fiber-based
supercontinuum sources beyond the 10 micron waveband. By using a 5-cm-long
tapered Ge-Se-Te rod pumped at 6 micron, a supercontinuum spanning from 2 to 15
micron (3 to 14 micron) with an average output power of 93 mW (170 mW) is
obtained for 500-kHz (1-MHz) repetition rate. Spectral coverages from the
visible to 5 micron, and from the visible to 2.7 micron, are also reported with
tapered rods made of tellurite and silica glasses, respectively. Numerical
simulations are used to confirm the main contribution of the fundamental mode
in the ultrafast nonlinear dynamics, as well as the possible preservation of
coherence features. Our study opens a new route towards the power scaling of
high-repetition-rate fiber supercontinuum sources over the full molecular
fingerprint region.
