Characterizing fabrication quality and UV performance of UV gratings

Ultraviolet (UV, 900−2000 Å) spectroscopy plays a vital role in studying exoplanets. Future UV spectrographs will require large-format, high-performance gratings (R > 10⁴). Unfortunately, measuring the UV performance of a large-format grating from 900−2000˚ Å is resource-intensive and requires large special vacuum facilities, hampering UV grating development. An efficient characterization process will save time and reduce costs, facilitating the development of blazed UV gratings for next-gen UV space telescopes. This work is part of an effort to determine if we can leverage trends found between measured UV grating performance (on small stamp-size gratings) and the grating’s intrinsic, fabricated characteristics to estimate the expected performance of large-format UV gratings. Here, we present a pilot study using an 855nm period grating. We characterize the grating’s fabrication quality via interferometry and single-point metrology. Finally, we describe measurements of the grating’s diffraction efficiency that will be conducted later this year.