High-performance astronomical gratings by Canon

Canon is developing wide variety of gratings that can be effective solutions for high precision spectroscopy for the next-generation ground-based and space telescopes. In this paper, we focus on our development of infrared immersion grating, which is one of the most demanding devices among various gratings. We use CdZnTe for mid-infrared (MIR) application and KRS5 for near-infrared (NIR) to MIR application. In particular, CdZnTe immersion grating is the key-device for the MIR high-resolution spectrograph for the space infrared telescope SPICA. Using our diamond cutting (planing) technique, grooves are shaped on the hypotenuse area (30 mm x 10 mm) of a CdZnTe prism with the spacing accuracy of < 5 nm (rms) and the surface roughness of < 5 nm (rms). We also performed cutting of KRS5 disk and confirmed that excellent grooves can be shaped on this material.