Recording high-dispersion spherical holographic gratings in a modified Rowland mounting by use of a multimode deformable mirror

Abstract

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.

Varied line spacing plane holographic grating recorded by using uniform line spacing plane gratings

“…9 (ii) The second method uses multimode deformable mirrors (MDMs). Duban studied the theory, 10,11 discussed the realization, 12 and simulated the performance in the cosmic origins spectrograph (COS) gratings. 13,14 The main difficulty of this mounting comes from the fabrication of the MDMs.…”