  CUBES is the Cassegrain U-Band Efficient Spectrograph, a high-efficiency
instrument operating in the UV spectral range between 300nm and 400nm with a
resolution not less than 20000. CUBES is to be installed at a Cassegrain focus
of the Very Large Telescope of the European Southern Observatory. The paper
briefly reviews various types of devices used as dispersing elements in
astronomical spectrographs to achieve high resolution, before identifying
binary transmission gratings produced by microlithography as the best candidate
technology for the CUBES instrument. We describe the lithographic fabrication
technology in general, two different design considerations to achieve the
required high-resolution transmission grating, its prototyping by a
direct-write lithographic fabrication technology, and the characterization of
the achieved optical performance. An outlook to the realization of the grating
for the final instrument, taking the most recent developments of lithographic
writing capabilities into consideration is given.
