Retrieval of the complex-valued refractive index of germanium near the M-4,M-5 absorption edge

Publication date
DOI http://dx.doi.org/10.1364/JOSAB.36.001716
Reference C.J. Kaplan, P.M. Kraus, E.M. Gullikson, L.J. Borja, S.K. Cushing, M. Zuerch, H.T. Chang, D.M. Neumark and S.R. Leone, Retrieval of the complex-valued refractive index of germanium near the M-4,M-5 absorption edge, J. Opt. Soc. Am. B 36, 6: 1716-1720 (2019)

The complex-valued index of refraction of germanium in the extreme ultraviolet (XUV) is measured by multi-angle reflectance of synchrotron radiation. The resulting index of refraction is higher resolution than previously measured values. It reveals new structures attributed to transitions from the 3d-core orbitals to the Σ5,2 and the 5,2 conduction bands. Additionally, it is shown that the problem of total external reflection, which renders multi-angle reflectance measurements insensitive to the complex-valued refractive index at grazing incidence, can be overcome by employing measurements at angles of incidence away from the critical angle.