Designing and characterizing UV gratings for exoplanet habitability studies

Ultraviolet (UV, 900−2000 Å) astrophysics plays a vital role in studying exoplanets and evaluating their potential habitability. One approach to understanding exoplanetary habitability is through the study of their absorption spectra, which can reveal not only the chemical composition and physical properties (e.g., mass-loss rate) of their atmosphere but also the UV environment around the host star. Using grating simulation software, we explored a grating-parameter space (blaze angle, grating period) to optimize the design parameters of a UV grating designed for observing key spectral features (e.g., H i, O i, C ii, etc.) in exoplanetary atmospheres. We use interferometric measurements to determine the grating's groove placement accuracy, groove uniformity, and limiting resolution; and other metrology techniques to characterize the surface roughness. We quantify the expected performance of our UV gratings using these measurements. This work is part of an effort to leverage trends found between measured UV grating performance and the grating's intrinsic, fabricated characteristics to estimate the expected performance of UV gratings as we fabricate larger gratings.