Narrowband mirrors tuned at the desired far UV spectral lines

The far ultraviolet (FUV, 100-200 nm wavelengths) contains plenty of spectral lines for key targets of the astrophysics, solar physics, and atmospheric physics communities. Imaging at spectral lines like O VI (103.2, 103.8 nm), H Lyman a (121.6 nm), N V (123.8, 124.2 nm), O I (130.4, 135.6 nm), C IV (155 nm), etc., will enable address important targets for the above communities, which is reinforced by the very limited access to such imaging so far. Hence LUMOS instrument of LUVOIR (Large Ultraviolet Optical Infrared Surveyor, large space telescope concept) proposed imaging emission features, such as outer planet auroras at H-2 Werner bands to map CH4 absorption, for which LUMOS would use a FUV imaging channel operating with narrow- and medium- band filters. The GOLD group has been investigating narrowband mirrors that are tuned at the desired FUV spectral line(s) as candidate coatings for imaging space instrumentation. It developed Al/LiF/SiC/LiF coatings that can be tuned at the shortest end of the FUV, 100 nm, which enables mirrors peaked at H Lyman. (102.6 nm) or at the O VI doublet. Furthermore, such coatings can be designed to reject the ubiquitous H Lyman a, where they can be made to reflect below 1%. The group is also investigating on narrowband mirrors based on multilayers that alternate two fluorides, such as AlF3/LaF3. These coatings can be tuned at the desired FUV wavelength longer than 120 nm. The proceeding presents a summary of the main results on these two sorts of coatings, which can cover the full FUV with narrowband MLs.