  Unravelling superradiance, also known as superfluorescence, relies on an
ensemble of phase-matched dipole oscillators and the suppression of
inhomogeneous broadening. Here we report on a novel superradiance platform that
combines an optical lattice free from the ac Stark shift and a hollow-core
photonic crystal fibre, enabling an extended atom-light interaction over $2
\mathrm{mm}$ free from the Doppler effect. This system allows controlling the
atom spatial distribution and spectral homogeneity whilst efficiently coupling
the radiation field to an optical fibre. The experimentally-observed and
theoretically-corroborated temporal, spectral and spatial dynamic behaviours of
the superradiance, e.g., superradiance ringing and density-dependent frequency
shift, demonstrate a unique interplay between the trapped atoms and the
fibre-guided field with multiple transverse modes. Our theory indicates the
resulting temporal evolution of the guided light shows a minimal beam radius of
$3.1 \mathrm{\mu m}$ that is three times smaller than that of the lowest-loss
fibre mode.
