Ultraprecision micro-grinding of germanium immersion grating element for mid-infrared super dispersion spectrograph

The design of a mid-infrared high dispersion spectrograph with a resolution of 200,000 at 10 mum employing germanium immersion grating elements is required for the 'SUBARU' large space telescope. The authors applied an ultraprecision micro-grinding technique using fine-diamond grinding tools whose edges have been sharpened by electrical and mechanical processes to fabricate the element, and successfully obtained the required element with a sharp and smooth V-faced grating structure using germanium. The successful fabrication of this element is expected to contribute to the production of a compact and efficient high dispersion spectrograph in the development of the most advanced image analyzer.