Manufacturing silicon immersion gratings on 150mm material

Silicon immersion gratings will allow the Giant Magellan Telescope Near-IR Spectrograph (GMTNIRS) to achieve continuous coverage over the entire J, H, K, L and M photometric bands with resolution R similar to 65,000 at J, H and K and R similar to 80,000 at L and M. Gratings for J, H and K will be blazed at R3, while the L and M gratings will be blazed at R4 to achieve the desired resolution. The higher blaze angle of the L and M gratings requires that we use 150mm diameter substrates rather than the 100mm substrates that our standard process was built for. In order to accommodate the larger substrates we have constructed a custom UV exposure system for contact printing of grating lines, and constructed fixtures for coating and etching of the larger substrates. These updates to our process have resulted in the successful production of a grating for the GMTNIRS M-band.