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M2.7: Fourier spectroscopy

Fourier spectroscopy is a powerful tool for the investigation of the optical properties of materials in the far infra-red(FIR) and mid infra-red(MID). First of all, we are going to understand the technique by looking at the effect of some parameters of the Fourier transformation on the absorption spectrum of water vapor. Then we are going to measure the reflectance of a single crystal of BeO. The signature of the phonon modes in the reflectivity is studied as a function of the polarization of the light. Then the reflectivity of stainless steel is measured to see the response of the free electrons. You are going to learn how to model the reflectivity using a Drude-Lorentz model. The parameters of the model are obtained by fitting the data with the software RefFIT.