  We report the fabrication of single mode buried channel waveguides for the
whole mid-infrared transparency range of chalcogenide sulphide glasses by means
of direct laser writing. We have explored the potential of this technology by
fabricating a prototype three-dimensional three-beam combiner for future
application in stellar interferometry, which delivers a monochromatic
interference visibility of 99.89% at 10.6 \mum, and an ultrahigh bandwidth
(3-11 \mum) interference visibility of 21.3%. These results demonstrate that it
is possible to harness the whole transparency range offered by chalcogenide
glasses on a single on-chip instrument by means of direct laser writing, a
finding that may be of key significance in future technologies such as
astrophotonics and biochemical sensing.
