Can Fano profile for a plasmonic material could be obtained using it's absorption spectra? I have seen lots of papers using some astonishing line shapes and linewidth, how these are being calculated?
Yes, You can! what you need to do is use a material which has sharp absorption profile and close to plasmon absorption band. Moreover, in order to have a Fano absorption profile, you need to couple a broad spectral profile(Plasmon band) to a very sharp profile. Just like scattering case! For more info see attachment!