Verifying the Drude response

In commemoration of the inventor – Paul Karl Ludwig Drude – examples of contemporary interest in the vivid field of ellipsometry are presented. More than 100 years after his provision of the general concept and the first experimental application, ellipsometry has matured as tool-of-excellence in almost all materials research areas. This contribution reviews selected applications in solid-state materials physics and engineering addressing state-of-the-art ellipsometry concepts. Particular emphasis is placed on the generalized ellipsometry framework. Infrared ellipsometry and magnetooptic infrared ellipsometry provide access to yet another important achievement of Paul Drude in optical physics: The free electron model in conductors, but also clearly reveal deviations from thereof within charge-correlated systems, exemplified here by the observation of Landau level splitting in two-dimensional electron gases using synchrotron light source ellipsometry at terahertz frequencies.