Stacking spectral lines with multiplexed Bragg gratings in an acousto-optical tunable filter.

Volume Bragg gratings are a useful tool for spectral manipulation in a variety of settings. In a previous paper [Astron. & Astrophys. to be published, (2024)] we simulated an astronomical instrument that detects molecules on exoplanets by optically creating matched filters using multiplexed Bragg gratings, which optically stack spectral lines. Here, we confirm that we can freely modify and multiplex Bragg gratings, with an acousto-optical tunable filter (AOTF) and that we can stack spectral features in a lab setup using a commercially available AOTF. We find that we are able to multiplex an additional grating or modify an existing grating without altering other multiplexed gratings, so long as the bandpasses do not overlap. We can also successfully stack emission and absorption lines, producing comparable results when optically overlaying spectral lines and computationally summing images of separate lines.