Introductory remarks

The wide array of optical techniques and methods which are used for studying the electrodynamic properties of solids in the different spectral ranges of interest for condensed matter physics is covered by a large number of books and articles which focus on different aspects of this vast field of condensed matter physics. Here we take a broader view, but at the same time limit ourselves to the various principles of optical measurements and compromise on the details. Not only conventional optical methods are summarized here but also techniques which are employed below the traditional optical range of infrared, visible, and ultraviolet light. These techniques have become increasingly popular as attention has shifted from singleparticle to collective properties of the electron states of solids where the relevant energies are usually significantly smaller than the single-particle energies of metals and semiconductors.

We start with the definition of propagation and scattering of electromagnetic waves, the principles of propagation in the various spectral ranges, and summarize the main ideas behind the resonant and non-resonant structures which are utilized. This is followed by the summary of spectroscopic principles – frequency and time domain as well as Fourier transform spectroscopy. We conclude with the description of measurement configurations, single path, interferometric, and resonant methods where we also address the relative advantages and disadvantages of the various measurement configurations.