  We discuss the trapping of cold atoms within microscopic voids drilled
perpendicularly through the axis of an optical waveguide. The dimensions of the
voids considered are between 1 and 40 optical wavelengths. By simulating light
transmission across the voids, we find that appropriate shaping of the voids
can substantially reduce the associated loss of optical power. Our results
demonstrate that the formation of an optical cavity around such a void could
produce strong coupling between the atoms and the guided light. By bringing
multiple atoms into a single void and exploiting collective enhancement,
cooperativities ~400 or more should be achieveable. The simulations are carried
out using a finite difference time domain method. Methods for the production of
such a void and the trapping of cold atoms within it are also discussed.
