Advancements in space-based NUV spectrography: precision fabrication and evaluation of an optical slit using optical lithography and deep reactive ion etching

This article describes the development of a space-based near-Ultraviolet (NUV) spectrograph, focusing on the intricate fabrication and meticulous evaluation of an optical slit employing advanced techniques such as optical lithography and deep reactive ion etching (DRIE). The fabrication process entails a precise definition of the slit pattern on silicon wafer substrates through optical lithography, followed by the transfer of the pattern into the substrate material using DRIE. The resultant optical slit boasts sub-angstrom surface roughness and nanometer-scale slit width uniformity, essential for achieving superior spectrographic performance. Through comprehensive evaluation methodologies, including interferometry and spectrophotometry, the optical slit’s spectral resolution, throughput, and stray light rejection are rigorously examined. These breakthroughs promise to elevate the sensitivity, resolution, and dependability of space-based NUV spectrographic instruments, enabling deeper exploration of celestial phenomena and cosmic evolution.