Kramers-Kronig analysis of modulated reflectance data investigation of errors

The errors introduced in Δε2 spectra by Kramers-Krönig analysis of modulated reflectivity data are investigated using an analytical model. It is found that the energy position of singularities is always reproduced with good accuracy even if the experimental spectrum of ΔR/R is cut barely above the last structure of interest. This procedure is instead completely insufficient when a quantitative line shape analysis is required. In such cases data up to very high energy are required for a meaningful analysis. Errors due to other sources, like baseline shifts or inaccurate static optical constants, are also investigated