Machining metre-sized gratings with nanometre accuracy

 We aim to make large diffraction gratings

Grating requirements

• Up to 1.6m x 0.3m in size
• Random error in groove position < 15nm
• Cyclic errors < 1nm

Based on wet-etching of silicon

Overall concept

Concept sketch

System requirements

• X-direction position of head ~ 10nm relative accuracy across ~200mm (<1nm cyclic error)
• X-direction stability of Y-"saddle" ~ 100 micron across travel, no fast vibrations
• Tilt motion of Y-saddle in roll/yaw ~ 1 arcminute (0.3 milliradian)
• Y-direction speed 100mm/s +-1%
• Z-direction position stability of head wrt substrate ~ 20 microns