Recording high-dispersion spherical holographic gratings in a modified Rowland mounting by use of a multimode deformable mirror.
To reduce the uncorrected higher-order aberrations for holographic gratings requiring an extreme dispersion, we have modified the Rowland mounting by moving the recording laser sources away from the grating. Then, with a multimode deformable plane mirror to record the grating, the correction of all the aberrations up to the fourth order inclusive is found sufficient to obtain a high-quality image. Applied to the FUSE-LYMAN grating, with a groove density of as much as 5740 grooves/mm, for which a resolution of 30,000 was required, this new recording device produces a resolution from 139,000 to 222,000 over the spectral range.
Duban
M
M
Institut Gassendi, Laboratoire d'Astronomie Spatiale, Centre National de la Recherche Scientifique, BP 8, F-13376 Marseille Cedex 12, France. michel.duban@astrsp-mrs.fr