The High Efficiency and Resolution Multi Element Spectrograph (HERMES) for the Australian Astronomical Observatory (AAO) uses four large aperture, high angle of incidence volume phase holographic gratings (VPHG) for high resolution ‘Galactic archaeology’ spectroscopy. The large clear aperture, the high diffraction efficiency, the line frequency homogeneity, and mosaic alignment made manufacturing and testing challenging. We developed new metrology systems at the AAO to verify the performance of these VPH gratings. The measured diffraction efficiencies and line frequency of the VPH gratings received so far meet the vendor’s provided data. The wavefront quality for the Blue VPH grating is good but the Green and Red VPH gratings need to be post polishing.

Date Published: 7 September 2013
PDF: 11 pages
Proc. SPIE 8838, Optical Manufacturing and Testing X, 88380G (7 September 2013); doi: 10.1117/12.2024493

Published in SPIE Proceedings Vol. 8838:
Optical Manufacturing and Testing X
Oliver W. Fähnle; Ray Williamson; Dae Wook Kim, Editor(s)