Nanotechnology applied to silicon grism, for high-resolution infrared spectroscopy in astronomy

We present the results of our project for the design, construction and on-sky tests of silicon grisms. Silicon grisms are optical devices, that provide a medium-high resolution spectroscopic mode in imaging instruments, without introducing major changes in instrument configuration. After some critical phases during the experimentation, a silicon grism has been eventually fabricated and inserted in the filter wheel of the Near Infrared camera NICS, at the focal plane of the National Galileo Telescope (TNG), the 3.5 m Italian facility at the Canary Islands (E). The results of the main phases of the grism fabrication and the results of the on-sky tests are detailed reported.