I used to make holographic diffraction gratings for use in the X ray region back in the early 1980s when the technique
was in its infancy. Interference patterns from re-combined laser beams were recorded in photo-resist spun-coated on
a plane or concave substrate. The angle of re-combination of the two beams defined the groove spacing and the groove profile
could be laminar or blazed depending on the recording geometry. The recorded profile was then ion – etched into the
substrate to form an X-ray resistant grating.
I can send more detail f you are interested