This book has its origins in a set of lecture notes, assembled at UCLA for a graduate course on the optical studies of solids. In preparing the course it soon became apparent that a modern, up to date summary of the field is not available. More than a quarter of a century has elapsed since the book by Wooten: Optical Properties of Solids – and also several monographs – appeared in print. The progress in optical studies of materials, in methodology, experiments and theory has been substantial, and optical studies (often in combination with other methods) have made definite contributions to and their marks in several areas of solid state physics. There appeared to be a clear need for a summary of the state of affairs – even if with a somewhat limited scope.

Our intention was to summarize those aspects of the optical studies which have by now earned their well deserved place in various fields of condensed matter physics, and, at the same time, to bring forth those areas of research which are at the focus of current attention, where unresolved issues abound. Prepared by experimentalists, the rigors of formalism are avoided. Instead, the aim was to reflect upon the fact that the subject matter is much like other fields of solid state physics where progress is made by consulting both theory and experiment, and invariably by choosing the technique which is most appropriate.