Diamond turning of aluminum image slicers for astronomical applications

Image slicers have become a standard equipment in the field of astronomical spectroscopy. They are now widely used in most integral field spectrographs (IFSes) in order to detect and characterize distant galaxies or extra-solar planets. However, they are notoriously difficult to manufacture due to their multiple small tilted surfaces, but equipment such as that of AOFI (Advanced Optical Fabrication Infrastructure) of Universite Laval eases the process. In this regard, the team at AOFI has been tasked with the fabrication of the image slicer for the GIRMOS instrument. This paper presents the characterization of diamond turned RSA-6061 and AA-6061 T6 aluminum, and the definition of the different machining parameters, such as step size and tool radius, that could improve the surface quality of an aluminum image slicer. It also discusses the fabrication of the first prototypes at AOFI, that will eventually prove useful in the fabrication of the image slicer for GIRMOS, effectively lowering its risks.