Introduction—A historical overview

The rapid development of picosecond technology has allowed us to examine fundamental processes in materials. The following chapters will review these developments. Here we shall first investigate some historical concepts that underly the measurement of rapid phenomena. We shall see that some concepts are very old and that many are included in present technology, although in a most sophisticated form. We shall also attempt to discover why investigators have been interested in rapid phenomena in the past, and how some of their motivations and procedures differ from those of today. We shall try to answer the question why picosecond light pulses have become so attractive in such a short period of time, what some of the main research directions are, and what we can expect in the future. We hope to succeed in this general overview in our attempt of outlining the objectives and providing perspective into picosecond studies, although we shall only briefly survey that field; the new concepts are discussed in great detail in subsequent chapters.