  Nanofibre-based optical cavities are particularly useful for quantum optics
application, such as the development of integrated single-photon sources, and
for studying fundamental light-matter interactions in cavity quantum
electrodynamics (cQED). Although several techniques have been used to produce
nanofibre-based optical cavities, focussed ion beam (FIB) milling is becoming
popular; it can be used for the fabrication of complex structures directly in
the nanofibre. This technique uses a highly accelerated ion beam to remove
atoms from the target material with high resolution. However, it is challenging
to mill insulating materials with highly-curved structures and large aspect
ratios, such as silica nanofibres, due to charge accumulation in the material
that leads to mechanical vibrations and misalignment issues. In this article,
we highlight the main features of nanofibres and briefly review cQED with
nanofibre-based optical cavities. An overview of the milling process is given
with a summary of different FIB milled devices and their applications. Finally,
we present our technique to produce nanofibre cavities by FIB milling. To
overcome the aforementioned challenges, we present a specially designed base
plate with an indium tin oxide (ITO)-coated Si substrate and outline our
procedure, which improves stability during milling and increases repeatability.
