Holographic gratings for the Far Ultraviolet Spectroscopic Explorer: Development, imaging, and efficiency tests of two prototypes

We report on a study and test of two 6000-groove/mm prototype holographic gratings for NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) mission. The first grating was designed and developed on the basis of the FUSE requirements as specified at the end of the first study in 1992. This design relies on an ellipsoidal grating, recorded with aberrated wave fronts to correct sagittal coma. The second grating corresponds to the new design adopted after the complete mission was restructured in 1993. With this solution a new family of spherical holographic gratings recorded with stigmatic sources was permitted to increase the aperture size while simplifying the figuring and recording of the blank. The design, fabrication, and testing of each prototype are described, and we show that the challenging requirement of a 30,000 resolving power at 1000 Angstrom, with a 25% groove efficiency is reached. (C) 1996 Optical Society of America