Spectrographs with holographic gratings on freeform surfaces: design approach and application for the LUVOIR mission

TL;DR

This paper presents a novel design approach using holographic gratings on freeform surfaces for advanced spectrographs, demonstrating high spectral resolution and feasibility for space missions like LUVOIR.

Contribution

It introduces a new method for integrating holographic gratings on freeform surfaces in spectrograph design, achieving high resolution and practical feasibility.

Findings

Spectrographs with holographic gratings on freeform surfaces achieve spectral resolution of 126,359-133,106.

The approach enables a dual-function grating acting as a cross-disperser and camera mirror.

Feasibility of the gratings with current technology is demonstrated.

Abstract

In the present paper we demonstrate the approach to use a holographic grating on a freeform surface for advanced spectrographs design. On the example POLLUX spectropolarimeter medium-UV channel we chow that such a grating can operate as a cross-disperser and a camera mirror at the same time. It provides the image quality high enough to reach the spectral resolving power of 126 359-133 106 between 11.5 and 195 nm, which is higher than the requirement. Also we show a possibility to use a similar element working in transmission to build an unobscured double-Schmidt spectrograph. The spectral resolving power reaches 2750 for a long slit. It is also shown that the parameters of both the gratings are feasible with the current technologies.