ABSTRACT
We have touched briefly on the optical properties of materials in the early chapters, but here we must bring together the concepts of electron structure and the known optical properties of materials. This is done by identifying the allowed energy transitions which determine the main features of the optical spectrum. This means that we need to connect measured optical properties with the allowed electron energy levels. The major classification of electron transitions is here between transitions within the same band (intraband) and transitions between different bands (interband). The former are lower-energy transitions which lead to the high reflectivity of metals in the visible spectrum. The latter are higher-energy transitions which can lead to specific colours in materials. Various methods for measuring the optical properties are discussed including both conventional static optical measurements and differential techniques under external modulation of field, temperature or stress. Finally, the specialized topics of photoluminescence, and electroluminescence are discussed.
