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

TL;DR

This paper demonstrates the fabrication of a high-resolution reflection grating using electron-beam lithography and evaluates its spectral resolution, showing it can achieve a resolution of at least 14,600, relevant for future astronomical spectroscopy.

Contribution

It introduces a method to manufacture and assess high-resolution gratings via EBL, including quantifying stitching errors and measurement bounds for spectral performance.

Findings

Achieved a spectral resolution of at least R ~ 14,600.

Quantified the impact of EBL stitching errors on grating performance.

Presented a method for measuring period errors in curved gratings.

Abstract

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 at 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 +/-1st 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 quantifed, and a path to measuring the period error of customized, curved gratings is presented.