Limiting Spectral Resolution of a Reflection Grating Made via Electron-beam Lithography

Gratings enable dispersive spectroscopy from the X-ray to the optical, and feature prominently in proposed flagships and SmallSats alike. The exacting performance requirements of these future missions necessitate assessing whether the present state-of-the-art in grating manufacture will limit spectrometer performance. In this work, we manufacture a 1.5 mm thick, 1000 nm period (1000 gr mm-1) flat grating using electron-beam lithography (EBL), a promising lithographic technique for patterning gratings for future astronomical observatories. We assess the limiting spectral resolution of this grating by interferometrically measuring the diffracted wavefronts produced in ± first order. Our measurements show this grating has a performance of at least R ∼ 14,600, and that our assessment is bounded by the error of our interferometric measurement. The impact of EBL stitching error on grating performance is quantified, and a path to measuring the period error of customized, curved gratings is presented.